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CFR Final Rule
 Federal Register Information
Federal Register: August 6, 1993 (Volume 58, Number 150)]
[Page 42136]
Header Information
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 23
[Docket No. 26269; Amendment No. 23-45]
RIN: 2120-AD20
Small Airplane Airworthiness Review Program Amendment No. 4
Preamble Information
AGENCY: Federal Aviation Administration, DOT
ACTION: Final rule
SUMMARY: This amendment changes airframe and flight airworthiness standards for normal, utility, acrobatic, and commuter category airplanes. The changes are based on a number of recommendations discussed at the Small Airplane Airworthiness Review Conference held on October 22-26, 1984, in St. Louis, Missouri. These updated safety standards will continue to provide an acceptable level of safety in the design requirements for small airplanes used in both private and commercial operations. Some of the changes provide design requirements applicable to advancements in technology being incorporated in current designs. This amendment will also reduce the regulatory burden in showing compliance with some requirements while maintaining an acceptable level of safety.
EFFECTIVE DATE: September 7, 1993.
FOR FURTHER INFORMATION CONTACT: Kenneth W. Payauys, Aerospace Engineer, Standards Office (ACE-110), Small Airplane Directorate, Federal Aviation Administration, 601 East 12th Street, Kansas City, Missouri 64106, telephone (816) 426-5688.
SUPPLEMENTARY INFORMATION:
Background
On June 15, 1990, the FAA issued a notice of proposed rulemaking (NPRM) that proposed changes to the airframe and flight airworthiness standards for normal, utility, acrobatic, and commuter category airplanes (Notice No. 90-18, 55 FR 26534, June 28, 1990). The FAA based the proposed changes on the Small Airplane Airworthiness Review Program and on the conference that resulted in recommendations based on review proposals.
History
To encourage public participation in improving and updating the airworthiness standards applicable to small airplanes, the FAA announced the Small Airplane Airworthiness Review Program on January 31, 1983, and invited all interested persons to submit proposals for changes to part 23.
By the close of the proposal period on May 3, 1984, the FAA had received more than 560 proposals. On October 22-26, 1984, the FAA held the Small Airplane Airworthiness Review Program Conference in St. Louis, Missouri. The conference was attended by over 300 persons representing all aspects of the U.S. small airplane industry as well as many international representatives. A copy of the transcripts of all discussions held during the conference is filed in FAA Regulatory Docket 23494.
After reviewing the proposals and the public comments received at the conference, the FAA issued a number of rulemaking documents. These include:
(1) A notice proposing to upgrade cabin safety and occupant protection standards during emergency landing conditions (Notice 86-19, 51 FR 44878, December 12, 1986), which led to amendment 23-36 (53 FR 30802; August 15, 1988).
(2) A notice proposing airworthiness standards for advanced technology in current airplane design (Notice 89-5, 54 FR 9276, March 6, 1989), which led to amendment 23-42 (56 FR 344, January 3, 1991).
(3) A notice proposing airworthiness standards for complex systems critical for safety in small airplanes (Notice 89-6, 54 FR 9338, March 6, 1989), which led to amendment 23-41 (55 FR 43306, October 26, 1990).
(4) A notice of proposed airworthiness standards for powerplant and equipment not included in the above three notices (Notice 90-23, 55 FR 40598, October 3, 1990), which led to Amendment 23-43 entitled Small Airplane Airworthiness Review Program Amendment No. 3 (58 FR 18958, April 9, 1993). The review program and conference also led to the proposal for this rulemaking action, which updates the airframe and flight airworthiness standards for small airplanes.
The FAA is participating in an important international effort to harmonize part 23 of the Federal Aviation Regulations (FAR) with the Joint Aviation Requirements (JAR) developed by representatives of the Joint Aviation Authorities (JAA). This final rule is a significant step in the harmonization effort, which is being encouraged and supported by the aviation community worldwide.
Discussion of Comments
General
Interested persons were invited to participate in the development of this final rule by submitting written data, views, or arguments to the regulatory docket. Eight commenters responded to Notice No. 90-18. Commenters represent U.S. manufacturers of small aircraft (General Aviation Manufacturers Association, GAMA), Joint Aviation Authorities, JAA, individual airworthiness authorities (United Kingdom, Australia, Transport Canada), the Air Line Pilots Association (ALPA), a representative of the Association of Europeene des Constructeures des Material Aerospatial (AECMA), and one private individual. Most commenters either endorse other comments or comment on only a few of the proposed changes. GAMA comments on a significant number of the proposed changes and JAA comments on virtually every proposed change. AECMA submitted a one-sentence comment endorsing the GAMA comment.
One commenter (ALPA), while supporting "the fundamental intent" of the NPRM and applauding "the FAA for the work and progress" from the 1984 conference, also states a belief that there is a need for a "single regulation to prescribe that all part 25 certification aircraft are used by scheduled commercial airlines."
In general, the commenters agree with the proposed changes and one commenter (GAMA) urges the FAA to issue a final rule as expeditiously as possible.
In the NPRM, the FAA specifically solicited comments on the following subjects:
Conference Proposal 2, Section 23.3, Permit installation of turbojet engines on commuter category airplanes.
Conference Proposal 7, Section 23.65, Require performance limitations based on weight, altitude and temperature.
Conference Proposal 10, Section 23.145, Establish control force limits for reduced pilot strength, and
Conference Proposal 29, Section 23.307, Require material correction factors during structural tests.
The first two subjects listed above are subjects on which the FAA solicited comments for future rulemaking. No final action is taken in this rulemaking on these two subjects. The discussion of comments on these two subjects follows the proposal-by-proposal discussion at the end of the supplementary information section of this preamble. The second two subjects relate to rulemaking proposal number 10 (Section 23.145) and rulemaking proposal 29 (Section 23.307). Discussion of comments for these subjects is contained in the proposal-by-proposal discussion.
Discussion of Comments on Specific Sections of Part 23
As stated above, the majority of the specific comments were received from the GAMA and the JAA. In the following proposal-by-proposal discussion, the basic intent of each proposed change is summarized and substantive comments are addressed individually. Comments and changes of an editorial nature are generally omitted from the discussion.
In this final rule, the FAA has withdrawn a total of three proposals from the NPRM and is amending (for clarification) two sections for which changes were not proposed in the NPRM. The withdrawal of some proposed amendments and the addition of amendments that were not proposed has created a mismatch between the proposal numbers as discussed in this preamble and the amendment numbers included in the amendatory portion of this final rule. The following table provides the necessary cross reference:
Proposal No. | Amendment No. |
| 1-28 | 1-28 |
| 29 | Not Adopted |
| 30-47 | 29-46 |
| No proposal | 47 & 48 |
| 48-67 | 49-68 |
| 68 | Not Adopted |
| 69-72 | 69-72 |
| 73 | Not Adopted |
| 74-83 | 73-82 |
Proposal 1
This proposal contained the authority citation for part 23, for which there was no change.
Proposal 2
The FAA proposed a change to Section 23.23 that specified the limits for load distribution for weight and balance considerations. The one comment (JAA) received generally agreed with the proposed change but does not agree that the specific reference to lateral center of gravity (c.g.) range limits should be deleted. Also, the JAA does not believe (1) that the proposal treats lateral c.g. consistently and (2) that there is a need for all of the required flight test evaluation with displaced lateral c.g. limits. The JAA notes that requiring all testing to be repeated with fuel asymmetry is unnecessary and impractical but that it would be appropriate to take fuel asymmetry into account for some tests such as minimum control speeds, stall handling, and lateral stability.
The FAA agrees that deleting specific references to lateral c.g. limits may not be appropriate and has revised Section 23.23(a) to retain lateral load limits in the regulations. The FAA disagrees that the proposal treats lateral c.g. limits inconsistently. Repeating all testing with fuel asymmetry is unnecessary to find compliance. Accordingly, the FAA adopts Section 23.23 with the change discussed above.
Proposal 3
The FAA proposed a change to Section 23.25 to clarify the criteria used for assuming occupant weights in normal, commuter, utility, and acrobatic category airplanes. The proposed change would no longer permit the certification of normal category airplanes with seats placarded for occupants of less than 170 pounds. Seats limited to some lower weight by the placard installation will be referred to as "child seats" in the remainder of this discussion.
The GAMA and JAA commented on this proposal. The GAMA opposes deleting the provision that allows for the installation of child seats. The GAMA notes that existing provisions of Section 23.25 allow the manufacturer to install child seats and establish proper loading provisions for the airplane. GAMA believes that deleting this provision would operationally limit future airplanes. The GAMA also notes that several unacceptable alternatives could result from the proposed deletion, such as carrying less fuel, installing fewer seats, and carrying less safety equipment. The GAMA feels that child seats in airplanes fulfill a consumer need. The GAMA does not agree with the FAA's statement in the NPRM that the lack of specific standards for child seats is appropriate justification for disallowing placarding of child seats. The GAMA states that seat rules can be changed to certify fixed child seats at selected weight limits.
The JAA states that it does not understand the FAA's reasoning for disallowing child seats in normal category airplanes.
The FAA reconsidered this proposal, based on these comments, and agrees that eliminating the approval of child seats in normal category airplanes is inappropriate. However, the FAA points out that future rulemaking to provide safe standards for child seats will be needed in view of changes to Section 23.562 made by amendment 23-36 (53 FR 30802, August 15, 1988), which established a safety level for occupants with a nominal weight of 170 pounds.
Although the FAA will allow the installation of child seats, placarding pilot seats for occupants weighing less than 170 pounds or 190 pounds, depending upon airplane category, will not be allowed because there is no reason to do so. Accordingly, a revision to Section 23.25(a)(2) ensures that pilot seats are not placarded for a reduced weight.
The GAMA also pointed out that the minimum fuel requirement of "at least one-half hour" in Section 23.25(a)(2)(i), which is a part of the requirement for computing the minimum or maximum weight, is inconsistent with the fuel requirements of part 91. Section 91.151, Fuel requirements for flight in VFR conditions, requires 30 minutes of fuel reserve for day operations and 45 minutes of fuel reserve for night operations. Also, Section 91.167, Fuel requirements for flight in IFR conditions, requires the airplane to have enough fuel to: (1) reach its intended destination; (2) fly to an alternate destination, if required; and (3) allow 45 minutes of further flight at normal cruising speed.
Section 23.25(a)(2)(i) requires the pilot to have all seats occupied, engine oil at full capacity, and enough fuel for continued flight and a safe landing. The 45-minute fuel reserve, required by the operating rules, exceeds the Section 23.25(a)(2)(i) fuel requirement of "at least one-half hour." Proposed Section 23.25(a)(2)(i) is, therefore, revised to "at least 45 minutes for night VFR and IFR approved airplanes." The FAA adopts Section 23.25 with the changes discussed above.
Proposal 4
The FAA proposed to change Section 23.33 by adding propeller speed and pitch limits for turbine engine/propeller combinations and other requirements applicable to turbopropeller-powered airplanes not covered by the present rule.
The FAA received comments from the JAA and the GAMA. Both commenters questioned the need to add requirements for turbopropeller-powered airplanes (proposed paragraphs (b)(1)(ii) and (b)(2)(ii)) since it is unlikely that a fixed-pitch propeller will be used on a turbine-powered engine.
The FAA has re-examined these proposals and determined that proposed paragraphs (b)(1)(ii) and (b)(2)(ii) are not necessary.
The GAMA states that the proposal for Section 23.33(d)(2)(ii) will allow a 2,700 r.p.m. engine to operate at 2,940 r.p.m., or higher, if the governor should fail and that this change does not appear to be in the interest of safety. The FAA is not making any change to the proposed requirement because the information contained in the comment is insufficient. The NPRM documents that there are usually two governors in an engine/propeller system, one controlling the propeller rotational speed and one controlling the overspeed of the turbine engine. This explanation notes that if the propeller governor fails, the overspeed limit will be established by the turbine governor and probably will be 106 to 108 percent. The condition identified by the GAMA is nearly the same as the condition identified in the notice (2,940 r.p.m. is a 108.9 percent overspeed of 2,700 r.p.m.). The GAMA appears to support proposed Section 23.33(d)(2)(ii) that would have required a means to limit the engine overspeed to 99 percent of the approved engine overspeed.
The FAA recognizes that a fuel control governor usually controls turbine engine overspeed. Any required margin (such as the proposed 1 percent) would be considered during the establishment of the approved overspeed. Accordingly, it burdens the applicant to require an additional device that arbitrarily limits overspeed to 99 percent. By removing the 99 percent requirement, Section 23.33(d)(2)(ii) allows full approved overspeed. The FAA adopts Section 23.33 with the changes discussed above.
Proposal 5
The FAA proposed to clarify the performance data requirements of Section 23.45 and to combine the requirements for reciprocating and turbine-engine-powered airplanes. Since the one comment received from the JAA agreed with the proposed change, the FAA amends Section 23.45 as proposed.
Proposal 6
The FAA proposed to change Section 23.53 to introduce a rotation speed, VR, for multiengine airplanes and to eliminate reference to VX (speed for the best angle of climb) for airspeeds at 50 feet. The FAA received comments on this proposal from the JAA and the GAMA.
The JAA notes that the reference to 1.3 V sub S1 (stalling speed or minimum steady flight speed in a specific configuration) in proposed Section 23.53(b)(1)(ii) and (b)(2)(ii) is unnecessary and suggests clearer wording for the proposed change. The proposed language that states, "not less than 1.2 VS1," establishes the minimum VS1 speed that must be reached by a height of 50 feet above the takeoff surface. The JAA recommends revising the language to read, "1.2 VS1, or any other speed shown to be safe * * *." The FAA rejects this suggestion because it would allow the use of a speed below 1.2 VS1, which the FAA considers the minimum acceptable margin above the stall speed at the 50 foot point.
The GAMA recommends deleting the words "including turbulence" in proposed Section 23.53(b)(1)(ii) and (b)(2)(ii). The GAMA believes that considering turbulence deviates from the intent of the general requirement of Section 23.45 that requires still air performance corrections in a standard atmosphere.
The commenter is partly correct. Most of the performance testing can be done in still air under standard atmospheric conditions, but some tests need to be done under other conditions. Thus, Section 23.53 requires turbulent conditions for some, but not all, testing to find safe minimum takeoff speeds. Accordingly, these words are not being deleted from Section 23.53(b)(1)(ii) and (b)(2)(ii).
The GAMA also asks why turbulence is considered for normal, utility, and acrobatic category airplanes and not for commuter category airplanes.
The GAMA is correct that the takeoff speed requirements in Section 23.53(c) for commuter category do not specifically address turbulence. However, other requirements applicable to commuter category, such as Section 23.45(f)(3), that, in part, address critical-engine-inoperative takeoff performance require this performance to be determined according to the procedures established by the applicant for the operation in service, including turbulence conditions. Therefore, since turbulence for commuter category airplanes is otherwise addressed it has not been nor does it need to be included in Section 23.53.
In addition, the FAA has noted that the proposed paragraph Section 23.53(a) was not clear in distinguishing between the proposed VR speed and the VR speed established by Section 23.53(c)(4) for commuter category airplanes. An editorial change to Section 23.53(a) clarifies that Section 23.53(a) applies only to normal, utility, and acrobatic category airplanes, not to commuter category airplanes. The FAA adopts Section 23.53 with the changes discussed above.
Proposal 7
The FAA proposed to delete from Section 23.65 the current rate-of-climb requirements and to specify a minimum speed at which the angle-of-climb criteria must be met. The FAA received comments on this proposal from the JAA, GAMA, and ALPA. As previously discussed, the portion of the JAA, GAMA, and ALPA comments that address the subject of weight, altitude, and temperature (WAT) requirements for part 23 airplanes is discussed following this proposal-by-proposal discussion.
The GAMA states that the FAA has not justified the proposed change to Section 23.65(a)(1) for a minimum all-engine-climb speed of 1.2 VS1 and that this restriction appears unnecessary because VX is usually greater than 1.2 VS1. GAMA notes that, if VX is lower, any questions resulting from attitude and engine failure can easily be dealt with in the flying quality rules.
The JAA believes that the proposed minimum climb speed of 1.2 VS1 (stall speed or minimum steady flight speed obtained in a specific configuration) offers an inadequate stall speed margin for an everyday all-engines-operating case and recommends not less than 1.2 VMC (minimum control speed with critical engine inoperative) or 1.3 VS1. The GAMA states that the FAA has not justified the proposed minimum all-engine-climb speed of 1.2 VS1. As presented in the NPRM, the FAA finds that 1.2 VS1 is an improvement in the minimum performance standards. Deleting climb rate requires considering a minimum speed to ensure an adequate margin between stall speed VS and the selected climb speed. If VX is usually greater than 1.2 VS1, as the GAMA states, then rule compliance is not a burden. If VX is lower than 1.2 VS1, then VX provides an insufficient margin with stall speed which cannot be dealt with in the flying quality rules. This position is supported by another commenter. The FAA concludes that 1.2 VS1 is adequate and that a VMC based requirement is unnecessary. The FAA adopts Section 23.65 as proposed.
Proposal 8
The FAA proposed to change Section 23.141 to clarify the general requirements for flight characteristics.
The one commenter (JAA) agrees with the proposal but suggests some changes for the paragraph. The first is to insert the phrase "at all practical loading conditions" so that the section will read "through Section 23.253 at all practical loading conditions, at all practical operating altitudes."
The FAA notes that the current evaluation of an airplane's flight characteristics must consider all practical loading conditions in accordance with Section 23.21. This addition does not add a requirement to flight characteristic testing and does clarify the requirement. The final rule paragraph adds this phrase.
The other suggested change proposes to add a phrase between "under Section 23.1527" and "without exceptional piloting skill," which reads, "for which certification has been requested." The FAA agrees and has added the phrase to the final rule. The phrase clarifies that the loading condition and altitudes, checked during the flight characteristics evaluation, are those conditions and altitudes requested by the applicant for approval. The FAA adopts Section 23.141 with the changes discussed above.
Proposal 9
The FAA proposed to change Section 23.143 by replacing the word "Dive" with the word "Descent" because descent more accurately reflects the total phase of flight. No one commented on this proposed change, and the FAA adopts the change to Section 23.143 as proposed.
Some comments received on Section 23.145 resulted in revisions to the table in Section 23.143(c). These comments are discussed in the discussion of Section 23.145.
Proposal 10
The FAA proposed to change Section 23.145 to correct an error created by amendment 23-21 and to correct the trim speeds and procedures.
Although the FAA received no comments on paragraph (a) of Section 23.145, the FAA notes that "the airplane as nearly as possible in trim at 1.3 VS1" is a condition specified for both maximum continuous power and power off in Section 23.145(a)(1) and (a)(2). To eliminate redundancy, the FAA moved these words in the final rule to the introductory text of Section 23.145(a).
The JAA and the GAMA commented on Section 23.145(b), (c), and (d). The GAMA believes that the one-hand control force of 50 pounds in proposed Section 23.145(b) is too stringent but does not provide any further recommendations. The NPRM proposal discusses the reasons for selecting the particular control force and the control force is retained as proposed.
The GAMA also suggested deleting the 50-pound control force in Section 23.145(b) or moving it to the table in Section 23.143(c). The FAA agrees with the suggestion that the one-hand control force for the wheel should be located in the table in Section 23.143(c). This table contains other forces for the control wheel, stick, and rudder pedals. It is appropriate to add this one-hand control force to the table.
The JAA provides extensive comments on Section 23.145(b). First, the JAA asks to what the 50-pound control force limit of Section 23.145(b) applies. The JAA believes that this force should include any initial out-of-trim force and the change of control force that occurs during the variations in flight conditions. As proposed by the FAA, this requirement does not determine the total control force on the airplane during the maneuvers specified in Section 23.145, paragraphs (b)(1) through (b)(5). The one-hand control force test verifies that the changing control forces, during the maneuver, do not become higher than the pilot can safely control. The FAA specifies a one-hand control force because, during the maneuvers, the pilot is using one hand to change the power settings or flap positions. Only one hand will be available to correct the resulting control force changes. Accordingly, the requirement for the airplane control force is not limited to a total of 50 pounds, as the JAA advocates. The requirement allows force to be the sum of the initial out-of-trim force plus the allowed 50 pounds to correct the maneuver. In practice, the total control force on the airplane depends upon the direction of the pilot force and the direction of the initial out-of-trim force. The out-of-trim forces may add (or subtract) to the 50-pound control force limit.
The JAA also recommends deleting the words "the gear extended" from Section 23.145(b) since the demonstration required by paragraphs (b)(3) and (b)(4) are with gear retracted.
The FAA re-examined these requirements and agrees that the gear position requirements of Section 23.145(b) conflict with Section 23.145, paragraphs (b)(3) and (b)(4). But, the FAA does not agree that the gear position requirement of Section 23.145(b) should be deleted. It is necessary to specify the needed gear position in the maneuvers in Section 23.145, paragraphs (b)(1) through (b)(5). To correct these requirements, the FAA removes the words "with the landing gear extended" from Section 23.145(b) and adds this phrase to Section 23.145, paragraphs (b)(1) and (b)(2).
The JAA also believes that proposed Section 23.145(b)(2)(i) fails to address properly a normal balked landing demonstration. First, the JAA notes that the proposed initial trim speed of 1.2 VSO (stalling speed or minimum steady flight speed in landing configuration) is below the final approach speed of 1.3 VSO. Second, mishandled balked landings are covered in Section 23.145(b)(2)(ii). Third, it is incorrect to require speed abuse for the normal demonstration requirements.
The JAA also disagrees with the proposal to require the airplane to maintain the speed used to show compliance with Section 23.77. The JAA's reasons for disagreeing are that Section 23.77 provides requirements for the balked landing climb case, and it is inappropriate to correlate this climb condition to those for the balked landing demonstration of Section 23.145(b)(2)(i), which recommends go-around settings. To support not using the speed of Section 23.77, the JAA notes that it could be as low as 1.1 VSO, which is not a realistic go-around speed with flaps partly retracted. The JAA recommends a speed of 1.3 VSO.
Finally, the JAA disagrees with the reference to Section 23.145(b)(1)(i) in proposed Section 23.145(b)(2)(iii) because there should be no flap gate positions between fully extended and go-around flaps. The JAA agrees with giving credit for the flap gate positions in the mishandled balked landing requirements of Section 23.145(b)(2)(ii), but questions the need to maintain a speed of 1.1 VSO. The JAA believes that it is acceptable to retrim between each gate stage of flap retraction and that it should be acceptable to allow the airplane to accelerate to 1.1 VS1, where VS1 is the selected flap setting configuration.
The FAA has reviewed the proposal in light of the comments received on Section 23.145(b) concerning airplane trim at 1.2 VSO or 1.3 VSO and agrees that an abuse speed of 1.2 VSO for a normal balked landing is inappropriate. The final rule allows an abuse speed of 1.3 VSO for a normal balked landing. However, the FAA considers an abuse speed of 1.2 VSO appropriate for a mishandled balked landing.
The FAA does not agree that it is inappropriate to correlate the balked landing climb in Section 23.77 to the balked landing of Section 23.145(b)(2)(i). The FAA has evaluated this and determined that a speed showing compliance with the balked landing climb is also safe for a wings level go-around flight. Changes to Section 23.77 clarify that the balked landing speed is the minimum speed that must be maintained.
The last item related to Section 23.145(b) is the comment on the credit given for gated flap positions. Upon re-examination of proposed Section 23.145(b)(2)(iii), the FAA agrees with this comment. There should not be a flap gate position between the flap fully extended position and the go-around position. If on is provided, it should be bypassed so the go-around setting can be quickly attained. Permitting a gated position conflicts with Section 23.145(b)(2)(i) in a normal balked landing. Section 23.145(b)(2)(i) requires the flaps to be retracted as quickly as possible to the go-around position. Section 23.145(b)(2)(iii) omits the provision for flap gate credit from the final rule.
As proposed, Section 23.145(b)(2)(ii) would allow the use of flap gate positions for the mishandled balked landing demonstration requirements. The FAA agrees; therefore, it is acceptable to accelerate the airplane to 1.1 times the minimum steady flight speed. The final rule includes this provision.
The JAA concurs with Section 23.145, paragraphs (b)(3), (b)(4), and (b)(5), and suggests moving Section 23.145(b)(5) to Section 23.175 and combining it with Section 23.175(d). The FAA reviewed the possibility of combining these two sections, which would require revisions in both. This could create unintended meanings, and since the recommended changes are beyond the scope of the notice, the FAA will consider this proposal for future rulemaking.
Both the GAMA and the JAA offer comments on proposed Section 23.145(c). The GAMA notes that this requirement would require a demonstration of an elevated load factor, and suggests that, for reasons of safety, this should be an extrapolation of lower speed data or an analytical finding. The JAA states that the JAA is unclear on the relationship of this proposal to present Section 23.335(b)(4)(i) and suggests a paragraph revision that would reference Section 23.335(b)(4)(i).
Proposed Section 23.145(c) requires a demonstration of 1.5 g pitch maneuver capability up to VD/MD (design dive speed/design dive Mach number). The demonstration is necessary and should not be extrapolated from a lower speed test. Calculations may be used to show compliance with Section 23.335(b)(4)(i). It is inappropriate to combine the design airspeed with the proposed Section 23.145(c) flight demonstration. Also, showing compliance with Section 23.335(b)(4)(i) by flight demonstration fails to explore the pitch maneuver capabilities close to VD/MD. The FAA adopts Section 23.145(c) as proposed.
The JAA questions the need for the c.g. conditions contained in Section 23.145, paragraphs (d)(1) and (d)(2). Section 23.21 covers these conditions. The FAA's review shows that the specific reference to the c.g. position is unnecessary, and deletes it. The FAA adopts Section 23.145 with the changes discussed above.
Proposal 11
The FAA proposed changing Section 23.147 to delete the existing Section 23.147(a), to renumber the remaining requirements, and to delete references to center of gravity.
Since the only comment, from the JAA, agrees with the proposed change, the FAA adopts Section 23.147, as proposed.
Proposal 12
The FAA proposed to define airworthiness standards for determining the minimum control speed and to reword particular portions of Section 23.149 for clarity.
The FAA received comments from the JAA and the GAMA, on Section 23.149. Only the JAA addressed the proposed revised definition of VMC in Section 23.149(b)(2). The JAA objected to the proposal to change the words "recovering control" to "maintaining control." The FAA intended this proposed revision to eliminate any implication that control is lost when the engine fails. The JAA feels the proposed change is "ill-advised" because the demonstration of VMC results in an airplane handling excursion, in all three axes, followed by a recovery. The JAA identifies the continued use of the word "recovery" in the stall requirements to support this position.
The FAA considered the JAA's comments, and the conference discussion, and concludes that the term "recovering" should not be used. Though excursions may occur in all three axes, those excursions do not mean that complete loss of control of the airplane has occurred. "Maintaining control" includes the action needed to correct these excursions and to continue to fly the airplane with one engine inoperative. It is appropriate for use in this definition. This revision in the VMC definition should not be considered for extension to the stall requirements. Control is lost in a stall; therefore, the term "recovery" is appropriate for the stall requirements.
The JAA also states that the NPRM phrase, "with a yaw of not more than 20 degrees," in the proposed definition of VMC is confusing since heading excursions are limited to 20 degrees in unchanged Section 23.149(d).
The FAA has reviewed this proposed change, along with the text of Section 23.149(d), and agrees that the proposed revision does not provide the intended improvements. Accordingly, it is removed in this final rule. The JAA also comments on proposed Section 23.149(b)(5), which would require that in determining minimum control speed the airplane must be in the most critical takeoff configuration. The JAA states that JAR 23.149(b)(5) requires that the propeller controls should remain in the recommended take-off setting throughout.
To clarify this requirement and ensure that the proper propeller control setting will be used, final rule Section 23.149(b)(5) includes a statement on the propeller control setting consistent with JAR 23.149(b)(5).
The FAA received comments from the GAMA and the JAA on the proposed change to Section 23.149(c) to establish an operational limitation for a minimum speed to intentionally render the critical engine inoperative. This proposal for a safe, intentional, one-engine-inoperative speed, VSSE, includes language that defines a maximum and a minimum value for this speed. The GAMA opposes the maximum and minimum values proposed and believes that these limits are so small that they defeat the purpose. The JAA does not agree with the establishment of VSSE as a limitation.
The FAA has considered these comments and agrees with the expressed position that VSSE should not be established as a limitation. The FAA is aware of the benefits resulting from informing the pilot of the speed that provides an additional safety margin above VMC. This is especially important in a training environment. Accordingly, Section 23.149(c) is revised to require that VSSE must be established and a new Section 23.1585(c)(6) requires that this information must be put in the AFM. By establishing this requirement, information recommended by GAMA's Specification No. 1 can be included in the AFM. The FAA adopts Section 23.149 with the changes discussed above.
Proposal 13
The FAA proposed changes to the landing control requirements in Section 23.153. The FAA received comments from the JAA and the GAMA on this proposal.
The GAMA believes that the FAA may have overlooked the effect that the proposed change would have on airplanes weighing 6,000 pounds or less which are not required to meet Section 23.153. For these airplanes the GAMA believes that the speed for control during landing should be set in a different way than using the speed used for the demonstration of landing under Section 23.75, minus 5 knots.
The FAA disagrees. The FAA considered all airplane weights in the NPRM. Existing Section 23.75 does not differentiate landing speed by weight.
The GAMA states that Section 23.153(b) adds the steepest approach gradient for landing control. The GAMA believes that the approach gradient is inappropriate because there is no practical way for a pilot to determine the gradient.
The FAA notes that part 23 already requires a pilot to determine the gradient. Section 23.75(a), as amended by amendment 23-42, requires landing distance to be determined for all airplanes. The section also requires that the distances be based on a descent gradient of 5.2 percent at not less than a 1.3 VS1 speed. Additionally, an applicant may show a steeper approach gradient if a means is available to display gradient to the pilot.
The JAA states that the proposed changes to Section 23.153 bring the requirement substantially into line with JAR 23.153. JAA also concurs with the inclusion of all airplanes and with the inclusion of proposed paragraphs (b) and (c). The JAA states that it is "disturbed that the cross-reference to Section 23.143(c) could allow the use of a (two-handed) elevator control force as high as 75 pounds in a landing maneuver."
The FAA agrees with the JAA. To clarify the FAA's intent, final rule Section 23.153 specifies a one-handed force. The FAA adopts proposed Section 23.153, with this change.
Proposal 14
The FAA proposed to change Section 23.155 to clarify the conditions used to prove elevator control force.
The JAA submitted the only comment on this proposal, stating its preference for existing Section 23.155(b)(2). Also, the JAA states that, if the FAA retains Section 23.155(b)(1) as proposed, the words "for level flight" should be changed to "for wings level flight."
The FAA agrees that "for wings level flight" clarifies "level flight condition" and has, therefore, changed the final rule accordingly. In evaluating the suggestion to add the word "wings", the FAA notes that the current Section 23.155(b)(2), which this proposal is replacing, uses the words "with wings level." Adding the word "wings" will retain the previously used language. Since the proposals for Section 23.155(b)(1) and (b)(2) also contain the words "level flight," the suggested change is also made to these paragraphs. The FAA adopts Section 23.155, with the changes discussed above.
Proposal 15
The FAA proposed to add a ten-second limit to the equation in Section 23.157(a)(2) and a seven-second limit to the equation in Section 23.157(c)(2). These proposed limits would restrict all airplanes above 12,500 pounds to a minimum rate of roll, correcting an inadvertent oversight introduced by adding the commuter category in amendment 23-34.
The JAA stated that the proposed change would align Section 23.157 with JAR 23.157. The GAMA believes that proposed Section 23.157(b)(4) is not clear and suggests reversing the words "and" and "or."
The FAA agrees that it would not be possible to trim the airplane to the greater of "1.2 VS1 and 1.1 VMC." Accordingly, "and" has been changed to "or" in the final rule.
The FAA adopts Section 23.157 with the change discussed.
Proposal 16
The FAA proposed to revise the engine power requirements of Section 23.175 for the climb conditions.
The comment from the JAA agrees with the proposed change to the required power for reciprocating engines. However, the JAA does not believe that the phrase "or the maximum power or thrust selected by the applicant as an operating limitation for use during cruise * * * " is appropriate. The JAA believes that this limitation can be abused and asks how it should be interpreted in comparison with, for example, maximum continuous power or thrust, if the latter is greater. The JAA notes it is considered unreasonable to "get around" the requirement by declaring a "limitation" while claiming credit for a higher maximum continuous limit under other circumstances. Also, the JAA notes other requirements in part 23 using similar words referring to limits for cruise or climb operations.
The first item addressed by the JAA is that this limitation can be abused; the FAA agrees. This is true of most limitations placed on an airplane. Engine power or thrust limitations are no more likely to be abused than any other limitation. An important aspect of safety in the aviation community is the training of pilots and their understanding that limitations are established to avoid possible unsafe conditions. The FAA does not find the JAA's reasons adequate to change the proposed requirements that would permit the establishment of limitations.
The other JAA position, that limitations are established to allow the holders of a type certificate to "get around" certain other provisions of the requirements, is not valid. There are circumstances, such as where an airframe manufacturer needs to replace the engine on a particular airplane model and the only engine available produces more horsepower than the engine that was originally approved for that airframe. By using the higher powered engine, and establishing limitations, it may be possible to obtain approval without incurring the additional expenses of redesign and testing that would otherwise be needed for using a higher power engine. The regulations permitting the establishment of limitations benefit the public by reducing costs. No known adverse affects on safety have resulted from these provisions.
The JAA also noted that the present Section 23.175(d)(3) contains a reference to Section 23.161(c)(4), which does not exist. A review of the regulations shows that some publications do reference Section 23.161(c)(4) while other publications correctly reference Section 23.161(c)(2).
To verify the correct paragraph that should be referenced in Section 23.175(d)(3), the FAA reviewed the history of both Sections 23.161 and 23.175. Before the adoption of amendment 23-21 on March 1, 1978, Section 23.161 requirements for power approaches were contained in Section 23.161(c)(4), and Section 23.175(d)(3) correctly referenced in Section 23.161(c)(4). When the FAA adopted amendment 23-21, it revised the trim requirements and moved the power approach requirements to Section 23.161(c)(2). Amendment 23-21 also revised Section 23.175(d)(3) to correctly reference Section 23.161(c)(2). This error needs to be corrected in the current publications and, while not included in the NPRM, is included in this final rule.
The FAA adopts Section 23.175 with the change discussed above.
Proposal 17
The FAA proposed to revise Section 23.177(a) to require that static directional stability and lateral stability be shown under more realistic operating conditions expected in service. Changes proposed to Section 23.177(a)(1) revise the approach configuration to be used to evaluate the static directional stability. Instead of the maximum continuous power previously required, the engine power necessary to maintain a three degree angle of descent is now specified. Proposed revisions to Section 23.177(a)(2) require static lateral stability in the landing configuration at the engine power necessary to maintain a three degree angle of descent. Presently, 75 percent maximum continuous power is used. In addition, the proposal would have deleted the current rule requiring a bank angle of 10 degrees or more.
The JAA and the GAMA address Section 23.177(a)(1). The JAA states, "We do not agree with the proposed relaxations in minimum speed (in configurations other than takeoff) and maximum power in the landing configuration for demonstrating positive directional stability." The JAA believes that directional instability is an undesirable characteristic and should not be permitted within, or outside, the normal flight envelope, and that 1.2 VS1 is a reasonable lower speed for all configurations. The JAA also states that power settings above that needed for approach are reasonable in the landing configuration, for example, during the initiation of a go-around. The JAA recommends retaining the existing criteria for airspeed and power. Further, the JAA states that the NPRM explanation that the relaxation in minimum airspeed is taken from Conference Proposal 130 "is not valid for directional stability as the proposed relaxation was only applicable to lateral stability demonstrations."
The FAA reviewed Conference Proposal 130 and agrees with the JAA that speed range relaxation was not applicable to directional stability. The FAA also agrees that 1.2 VS1 is a reasonable lower speed for all configurations and revises Section 23.177(a)(1) accordingly. The FAA disagrees with requiring directional stability in the landing configuration at maximum continuous power, since go-around is a transitory condition and the pilot normally changes the airplane configuration promptly. The power required for the three degree angle of descent is retained.
The GAMA states that Section 23.177(a)(1) needs to be clarified. The GAMA states that the proposed language calls for a demonstration at 1.2 VS1 for the takeoff configuration and at 1.3 VS1 for climb, cruise, and approach configurations in the same sentence. The GAMA states that the next sentence addresses the "landing configuration" normally a power-off case) as having power to maintain a three degree angle of descent (usually the approach case). The GAMA asks whether the word "landing" should be replaced with the word "approach" for the latter demonstration.
The FAA has determined that, contrary to the GAMA assumption, "landing" is the correct word and as the rule states some power is required in the landing configuration to maintain a three-degree angle of descent. This agrees with the configuration and power in proposed Section 23.75.
The GAMA notes that the NPRM proposes showing directional stability "at speeds from 1.2 VS1 in the takeoff configuration and 1.3 VS1 in other configurations * * *. " The GAMA states that rudder force reversal (in the same paragraph) is prohibited "from VS1" with no configuration distinction and asks if these are compatible.
The FAA agrees that the rule, as proposed, gave speed ranges that were not compatible. As noted earlier, Section 23.177(a) adopts the speed of 1.2 VS1 as the lowest for all configurations and this change eliminates the incompatibility. The FAA adopts Section 23.177(a)(1) with the changes discussed.
The JAA comment on proposed Section 23.177(a)(2), states "we see merit in retaining the existing 10° bank criterion, to define slip angle, provided that a rudder force of 150 lbs. is not exceeded." Section 23.177(a)(2) is adopted as proposed.
However, the JAA also believes that the proposed relaxation in power for the landing configuration demonstration is ill-advised and that the airplane could be laterally unstable in a go-around.
The FAA agrees that relaxation of the engine power requirements could result in lateral instability in a go-around. However, since go-around is a transitory condition where the pilot normally makes prompt changes to the airplane configuration, there is no need for the regulations to address higher engine power in the landing configuration.
Concerning the proposed Section 23.177(a)(3), the JAA questions two points. First, in the sentence, "At larger slip angles up to the angle at which full rudder and aileron control is used * * *," the JAA believes that the wording should read "full rudder or aileron." The JAA also believes it is unlikely that rudder and aileron limits would be reached together in a steady sideslip maneuver. Second, the JAA questions the meaning of the sentence, "Enough bank must accompany the sideslip to hold a constant heading." The JAA believes clarification is necessary.
The FAA agrees that the word "or" between the words "rudder" and "aileron" clarifies Section 23.177(a)(3). Concerning the second point, the FAA has applied this rule for several years without any questions about its intent or manner of performing the maneuver. The FAA adopts Section 23.177(a), with the changes discussed above.
Proposal 18
The FAA proposed to remove Section 23.179, Instrumented stick force measurements. Since the FAA received only one comment from JAA, which agrees with the proposed change, the FAA is deleting Section 23.179, as proposed.
Proposal 19
The FAA proposed to revise Section 23.181 to account for installed stability augmentation systems, and to require an evaluation of the airplane for phugoid-type oscillations. The FAA received comments on this proposal from the JAA and the GAMA.
The JAA notes that part 25 requires stability and augmentation systems and Section 25.181 "does not include the relaxation in stick fixed dynamic stability demonstrations offered by the proposed change to FAR 23.181". JAA apparently bases this conclusion on the phrase "except when compliance with Section 23.672 is shown."
The FAA did not intend for this phrase (proposed for Section 23.181(a)(2) and (b)(2)) to relax the dynamic stability requirements. If a stability and augmentation system is installed, that system will move the primary controls. Since the JAA comment shows that the proposed wording could be misunderstood, the FAA has removed this wording from the final rule and has added a new Section 23.181(c) to replace it. Proposed paragraph (c) of Section 23.1891 is paragraph (d) in the final rule.
The JAA and the GAMA each comment on proposed Section 23.181(c). The JAA states that it will propose the same requirement for JAR 23. The GAMA notes the phugoid oscillation requirement of proposed Section 23.181(c) requires the development of guidance material (phugoid is an oscillation in pitch). The FAA recognizes the need for guidance and is revising Advisory Circular 23-8A, Flight Test Guide for the Certification of Part 23 Airplanes. The FAA adopts Section 23.181 with the changes discussed above.
Proposal 20
The FAA proposed to clarify the requirements of Section 23.201(c) by stating the time that the elevator control must be held against the stop to consider the airplane in a stall condition. The FAA recognizes the use of artificial stall barrier systems, such as a stick pusher, as an acceptable means of defining stall. When the system activates, the airplane is in a stall condition. The FAA received comments on this proposal from the GAMA and the JAA.
The GAMA questions the FAA's justification for the proposed requirement for a two-second delay after the control reaches the aft stop during stall determination.
The wording proposed by the FAA would replace the current definition, which reads, "or until the control reaches the stop." Several airplanes have been tested where the elevator has been pulled back to achieve the required speed reduction, but a nose pitch down motion and stall did not occur. Instead, the speed reduction continued until the elevator control reached the mechanical stop and the speed reduction simply stopped. In each of these tests, lengthy discussions between the FAA and the manufacturer have occurred on how long the elevator control needs to be held against the stop before this flight condition can be called a stall. This proposed change defines the stall condition. The FAA chose the two-second interval based on conference discussions and testing experience. The FAA adopts this proposal as presented. The GAMA also suggests that the last line of Section 23.201(c) more appropriately belongs in Section 3.201(d)(2). Section 23.201(d)(2) addresses the power application procedure to be used, if required during stall recovery, and is similar to Section 23.201(c). The requirements of Section 23.201(c) define when the stall evaluation is completed and assure that engine power is not applied too quickly. To clarify the two different statements on the application of power at the completion of the stall, the requirements of Section 23.201(c) are adopted as proposed, and Section 23.201(d)(2) is revised to use similar wording.
The JAA notes on Section 23.201(f) that it is the power loading and not the weight of the airplane that produces the extremely high nose-up attitudes at 75 percent maximum continuous power; therefore, the proposed relaxation for airplanes of over 6,000 pounds should be extended to all weights of airplanes. The JAA believes that the power-on stall problem should be addressed more directly by placing an upper limit of 30 degrees on the pitch attitude.
The FAA does not agree with the recommendation to place an upper limit of 30 degrees on the pitch attitude. An attitude limit would require extensive and costly flight tests to evaluate various airplane configurations and flight attitudes without a corresponding increase in safety.
The FAA agrees with the JAA's position that the relief proposed for airplanes of more than 6,000 pounds should be extended to airplanes of all weights. When these proposals were developed, the FAA was unaware of any airplanes of 6,000 pounds or less that would have engine power-to-weight ratios capable of producing the extremely nose-high stall characteristics experienced in heavier airplanes. Following the development of these proposals, several airplanes of 6,000 pounds or less maximum weight have been developed with similar power-to-weight ratios. There is a need to allow those airplanes to use the same test procedures proposed for airplanes of more than 6,000 pounds. The FAA has re-examined the stall test procedures and notes that airplanes of all weights have been successfully tested at the current 75 percent maximum continuous power requirement. Therefore, there is a need to consider various power-to-weight ratios likely to occur for airplanes of any weight. Accordingly, the final rule language is revised to allow manufacturers to continue testing at 75 percent maximum continuous power for airplanes at any weight. If this test shows undesirable stall characteristics at extremely nose-high attitudes, the testing may be done in accordance with the power and configuration proposed in the notice for airplanes of more than 6,000 pounds. The final rule provides relief for airplanes that encounter extremely nose-high attitudes and undesirable stall characteristics. The FAA revises proposed Section 23.201(f)(4) to allow testing airplanes of any weight for the power requirements discussed. The FAA adopts Section 23.201 with the changes discussed above.
Proposal 21
The FAA proposed to change the Section 23.203 roll excursion requirements to clarify the permissible limits for both turning stalls and accelerated stalls. The FAA received two comments on this proposal.
The GAMA asks FAA "to clarify how one can regain level flight * * * without increasing power (Section 23.203(b)) with the power off at the maneuver entry requirement of Section 23.203(c)(4)(i)."
The FAA has clarified the requirement by revising Section 23.203(b) to read "wings level flight" rather than "level flight."
The GAMA also states that the "FAA has not provided sufficient data to justify the reduction in allowable roll excursion requirements for turning flight stalls" and requests more justification.
As stated in the NPRM, 60 degrees of roll in turning flight stalls would permit a roll to go to 90 degrees, which the FAA considers to be hazardous. The FAA adopts the proposal for Section 23.203(b)(4) as proposed.
The JAA concurs with the proposed changes to Section 23.203 but notes that the two comments offered on Section 23.201(f) relating to power apply equally here.
As discussed in the response to comment on Section 23.201(f)(4), the FAA disagrees with the recommendation to place an upper limit of 30 degrees on pitch attitude. An attitude limit would require many tests to evaluate various airplane configurations and flight attitudes without a corresponding increase in safety. Since the NPRM did not address a specific pitch limit, the suggested limit is beyond the scope of the notice and would require additional rulemaking. Also, as previously indicated, the FAA agrees with the JAA recommendation that the relief proposed for airplane weights greater than 6,000 pounds should be applied to all airplane weights. The FAA revises Section 23.203(c)(4) to read like Section 23.201(f)(4).
The JAA also states that to advocate "normal use of flight controls" in the special circumstances of stall recovery is potentially misleading.
The FAA does not agree. The phrase "normal use of flight controls" has been successfully applied in Section 23.202(e) for many years without problems. For example, if ailerons remain effective during the stall, then regaining level flight by using them is appropriate. The FAA adopts Section 23.203 with the change discussed above.
Proposal 22
The FAA proposed to revise the critical-engine-inoperative stall requirements of Section 23.205 to require that critical-engine-inoperative stalls be evaluated with the wing flaps in the climb position.
The comment received, from the JAA, expresses serious reservations about keeping the initial-engine-inoperative stall requirement. The JAA asserts that the real life one-engine-inoperative stall is not represented by limiting power to 75 percent, by maintaining wings level at the stall, and by utilizing a reduced throttle recovery. Conversely, the JAA states that requiring high asymmetric power to be held down to the stall and throughout the recovery would create an unreasonable risk of spinning. The JAA questions whether this requirement can be of significance in ensuring adequate one-engine-inoperative low speed characteristics in service. The JAA observed that the Transport Category Directorate deleted the equivalent part 25 requirement through amendment 25-72.
Since this issue was not addressed in the NPRM, the FAA is not taking any action at this time. The FAA adopts proposed Section 23.205 as proposed.
Proposal 23
The FAA proposed to change Section 23.207 to require the current stall warning margins to be applicable to straight stalls, as set forth in Section 23.201(c). It also proposed requirements for turning flight and accelerated stalls in a new Section 23.207(d). The intent is to ensure that an adequate margin above the stalling speed exists in these two stall conditions.
The FAA received comments from the JAA and the GAMA on this proposal. The GAMA states that the upper stall warning margin should apply to power-off stalls only. The GAMA believes the lead-in of proposed Section 23.207(c) should be rewritten to read, "For the power-off stall tests required by 23.201(c) * * *." According to the GAMA, applying Section 23.207(c) to the power-on stall conditions of Section 23.201(c) would result in very high deck angles for airplanes with high thrust-to-weight ratios. With a stall warning greater than the 10 knot limit, or 15 percent of the stalling speed limit, the commenter feels that the pilot will be alerted sooner and, thus, avoid excessively high deck angles. The GAMA notes that multiengine airplanes at maximum weight, aft c.g., and high power can fly at airspeeds below VMC. If the difference between VMC and the stall speed is greater than 10 knots, or 15 percent of the stall speed, the GAMA believes the airplane could be difficult to recover if the critical engine fails. According to the GAMA, a stall warning greater than 10 knots, or 15 percent of the stall speed, reduces the time the airplane will be below VMC without a stall warning. The GAMA states that an equivalent level of safety can be established for a stall warning in excess of 10 knots, or 15 percent of the stall speed, if there are no nuisance warnings during normal takeoff, climb, approach to landing flare, go-around, or during the emergency procedures of single-engine takeoff and climb, approach, and landing.
The GAMA's suggested changes are beyond the scope of this notice. The proposed revision of Section 23.201 would preclude very high deck angle stalls in the power-on condition. Further, the stalls required by Section 23.201(c) are one knot/second decelerations and the 10 knot, or 15 percent of the stalling speed, warning is appropriate for this flight condition. New Section 23.207(d) addresses higher decelerations; therefore, Section 23.207(d) is adopted as proposed.
The JAA concurs with the proposed amendments. However, the JAA is concerned with the FAA's explanation for rejecting conference proposal 160 concerning the audibility of a stall warning when wearing headsets. The JAA believes that regulating the use of headsets, regarded as personal instead of airplane equipment, would be difficult. The JAA states that it would be unusual to see an AFM prohibition on the use of certain types of headsets and questions whether such a limitation would be observed. The JAA states it is therefore essential to ensure that all audio warnings remain adequately audible with any standard of headset that is likely to be used in service. The JAA states that the following words are being considered for JAR 23.1431(d): "If provision is made for the use of headsets, it must be demonstrated that all aural warnings are effective, with all permitted types of such equipment in use under the most adverse conditions." The JAA concludes that the FAA apparently does not intend to regulate this subject.
The FAA discussed this issue in the NPRM but did not make a specific proposal. This issue is under consideration for a future rulemaking.
After publishing the NPRM, the FAA recognized that the second sentence of the proposed Section 23.207(d) prohibits a stall warning occurrence when a stall is imminent. The intent of the proposal was to preclude nuisance stall warnings. Revised Section 23.207(d) clarifies that stall warnings should not occur when utilizing AFM procedures. The FAA adopts Section 23-207 with the change discussed above.
Proposal 24
First, the FAA proposed to clarify Section 23.233(a) by specifying that the crosswind requirements must be demonstrated. Second, it proposed to revise Section 23.233(b) to make the rudder effective at half the touchdown speed. Third, it proposed seaplane directional stability and control requirements to ensure better handling during water operations up to the maximum crosswind velocity of 0.2 VSO.
The FAA received comments on this proposal from the JAA and from a private individual. The JAA believes that it is necessary to establish the maximum crosswind conditions under which safe operation has been demonstrated and to publish this information in the AFM. The JAA suggests that, with the addition of the word "taxiing," the words currently proposed for JAR 23.233(a) are preferable. They are: "(a) A 90o cross-component of wind velocity, demonstrated to be safe for taxying, take-off and landing, must be established and must not be less than 0.2 V ." The FAA concurs with this suggestion and revises Section 23.233(a) to agree with the JAR wording.
The other commenter states: "Paragraph 23.233 as proposed is unclear and grossly unrealistic. It is not clear that 23.233(a) applies during landing or takeoff as well as taxiing. Moreover, 0.2 VSO is inadequate for normal operation of small airplanes. That velocity is less than seven knots for airplanes offered currently. Small airplanes are routinely operated in crosswinds several times as great." The commenter believes that Section 23.233(a) should be revised to read: "(a) It must be demonstrated that there is no uncontrollable ground or water looping tendency in 90o crosswinds, up to a wind velocity of 0.5 VSO, but not less than 15 knots, at any speed at which the airplane may be expected to be operated on the ground or water during landing or takeoff." The commenter also notes that many small airports have single runways that are subject to crosswinds substantially exceeding the demonstrated crosswind components of existing airplanes but that operations proceed regularly in these conditions. The commenter concludes, "The regulations should agree with the clear public need."
In response to this commenter, the FAA notes that the change to Section 23.233, made in response to the JAA comments, clarifies that Section 23.233(a) includes landing, takeoff, and taxiing. Since the FAA did not propose crosswinds above 0.2 VSO in the NPRM, it is inappropriate to apply a more stringent crosswind criterion in the final rule.
The JAA also states that there is no need to address seaplanes separately in a proposed new Section 23.233(d), which refers to Section 23.233(a). The FAA disagrees. Seaplanes need to be addressed separately. As stated in the NPRM, seaplane step taxi and step turns are conditions that need separate investigation; therefore, Section 23.233(d) is adopted as proposed. The FAA adopts Section 23.233 with the change discussed above.
Proposal 25
The FAA proposed changing the requirements of Section 23.235 to require an airplane evaluation during taxi, takeoff, and landing on the roughest surface expected in service. Also, the FAA proposed to require water handling information and information on allowable sea conditions for small airplanes that may be operated from water.
The FAA received comments from the GAMA and the JAA on this proposal. The JAA believes that Section 23.235(a) should address the characteristics of the whole airplane, not just the shock absorbers. The commenter recommends the wording of proposed JAR 23.235: "The airplane shall be demonstrated to have satisfactory characteristics and the shock-absorbing mechanism must not damage the structure of the aeroplane, when the aeroplane is taxied on the roughest ground that may reasonably be expected in normal operation and when takeoffs and landings are performed on unpaved runways having the roughest surface that may reasonably be expected in normal operation."
The FAA concurs and changes Section 23.235(a) for clarification. The GAMA mentions that Section 23.235(a) proposes to cover rough field takeoffs and landings, but the title of the existing rule limits its content to taxi operations. The FAA agrees and has revised the section title.
The GAMA states that the means of compliance is unclear and asks whether takeoffs and landings on rough ground must be demonstrated. The clarification of Section 23.235(a) discussed above resolves this issue.
The GAMA also notes that Section 23.235(b) proposes inclusion of "allowable" sea conditions for floatplanes in the AFM. The GAMA believes that this establishes an inappropriate limitation of little use to a pilot contemplating a landing. At most, the GAMA states, a statement of demonstrated wave height for operations should be included in the AFM. The FAA concurs with the GAMA's view and Section 23.235(b) is revised as suggested.
The JAA wants AFM information to appear in subject G, not subpart B, and suggests transferring the intent of proposed Section 23.235(b) to Sections 23.1583 and 23.1585. The FAA concurs and moves the AFM portion of Section 23.235(b) to Section 23.1585. Sea conditions are not an intended limitation so it is inappropriate to move the AFM portion to Section 23.1583. The FAA adopts Section 23.235 with the changes discussed above.
Proposal 26
The FAA proposed clarifying in Section 23.251 that buffeting must not cause structural damage anywhere in the flight envelope and specifying a single value of design dive/mach speed, VD/MD, rather than the minimum value of design dive speed, VD, permitted in the structural requirements. Since the only comment from the JAA agrees with the proposed change, the FAA adopts Section 23.251 as proposed.
Proposal 27
The FAA proposed to change Section 23.253 to expand the trim condition in Section 23.253(a) from "any likely cruise speed" to "any likely speed," which encompasses the descent trim condition. Since the only comment from the JAA agrees with the proposed change, the FAA adopts Section 23.253 as proposed.
Proposal 28
The FAA proposed to revise Section 23.305 to clarify the meaning of failure during static ultimate load test.
The one commenter, the JAA, questions why the "liberal interpretation" mentioned in the NPRM occurs in applications of part 23 regulations and not in part 25. The FAA addressed this issue in the FAR part 23 Airframe Airworthiness Review, which identified inconsistent definitions of failure during ultimate load testing. Advisory Circular 23-6, which resulted from that meeting, addresses this commenter's concerns. The Transport Airplane Directorate, which is responsible for part 25, is aware of the part 23 regulatory action.
The FAA adopts Section 23.305 as proposed.
Proposal 29
The FAA proposed a new requirement to correct structural test results for material correction factors in Section 23.307. The FAA received comments on this proposal from the GAMA, the JAA, and from Transport Canada.
The GAMA states that the proposed amendment is impractical and, perhaps, impossible to meet. The GAMA notes that under current regulations a factor of safety of 1.5 times limit load covers variations in material mechanical properties, construction dimensions, and load predictions. Also, the GAMA notes that the 1.5 factor has proven satisfactory for ultimate strength for more than 60 years. The GAMA recommends withdrawing the proposal.
Transport Canada notes difficulties when accounting for material and dimensional variations of the many subcomponents, determining their effect on the strength tests, and justifying a material correction factor of a singular value. Transport Canada proposes a "practical alternative" for low budget manufacturers of requiring the test specimen to be of lower strength than production articles.
The JAA suggests that this topic should more properly be addressed in FAR part 21 since the topic applies to all products.
No comments addressed composite materials which is a specific issue of this proposal.
Considering the validity of the comments, the complexities of the "practical alternative," and the lack of attention to the composite material issue, the FAA has decided to withdraw the proposed change to Section 23.307.
Proposal 30
The FAA proposed to amend Section 23.321 so the effects of compressibility on flight loads will be considered at each speed within the flight envelope.
The GAMA recommends that Section 23.321(b) be rewritten to require consideration of compressibility effects above Mach 0.6. The GAMA argues that the effects of compressibility below Mach 0.6 are insignificant on flight loads. The JAA argues that compressibility needs to be taken into account only if significant and that compressibility is unlikely to be significant if the airplane Mach number is less than 0.5.
The FAA has reviewed the NPRM proposal and the comments received. To simplify certification procedures of lower performance airplanes, small compressibility effects may be neglected below a design dive speed of Mach (MD) 0.40. At Mach numbers above zero, theoretical compressibility effects cause an increase in an airfoil lift curve slope. This increase is proportional to the Prandtl-Glauert factor, 1/ü(1-M2), where M is the free stream Mach number. This theory correlates very well with wind tunnel tests of airfoils and wings.
Wind tunnel tests provide low speed airfoil data between Mach 0.2 and 0.4. The experimental data contains the theoretical effects of speed between zero and the test Mach number. Taking 0.30 as an average test Mach number, then, according to theory, the lift curve slope will increase by 4 and 10 percent, respectively, at 0.40 and 0.50 Mach numbers. The FAA considers the latter figure to be a significant increase.
Considering this problem, the FAA reviewed the design dive speeds for some light airplanes certificated under Civil Air Regulation (CAR), part 3. It calculated an MD somewhat less than 0.4 at 15,000 feet in the standard atmosphere. One of the airplanes examined, a turbocharged version, had a maximum operating altitude of 24,000 feet and an MD somewhat greater than 0.5.
The FAA has decided that the effects of compressibility must be considered by the applicant. Compressibility threshold significance varies due to wind tunnel data and testing methods, altitudes, and airplane design. For these reasons, the FAA establishes no design dive speed Mach number compliance threshold. The original proposal would have revised paragraph (b) of Section 23.321 to provide for the effects of compressibility. Upon re-evaluation, the FAA has concluded that it would be clearer to add this requirement in a new paragraph (c). The FAA adopts Section 23.321 with the changes discussed above.
Proposal 31
The FAA proposed to correct an error in Section 23.361 introduced by amendment 23-26. The error significantly reduced the structural design torque levels required for flight conditions at takeoff power. The intent is that the torque factors of Section 23.361(c) apply to all Section 23.361(a) conditions.
Since the only comment received, from the JAA, agrees with the proposed change, the FAA adopts Section 23.361 as proposed.
Proposal 32
The FAA proposed to change the heading of Section 23.369 by eliminating the phrase "Special conditions for" at the beginning of the heading. The content of Section 23.369 remains unchanged.
The one commenter, the JAA, agrees with the editorial change and asks whether this is the only part of the structure needing special consideration in reversed airflow conditions. The FAA is not aware of any additional need for special consideration based on 30 years of service history. The FAA adopts Section 23.369 as proposed.
Proposal 33
The FAA proposed to include aerodynamic loads in the design of the engine mount with the gyroscopic loads required by Section 23.371. The one commenter, the JAA, suggests adding the word "combined" so the introductory statement reads "designed for the combined gyroscopic and aerodynamic loads * * *." The FAA agrees and revises the introductory statement. The proposed Section 23.371 is adopted with the change discussed above.
Proposal 34
The FAA proposed to increase the minimum rudder force, from 130 pounds to 150 pounds, in the last line of the table of Section 23.397(b) to make it compatible with the "strength of pilots" limits shown in Section 23.143. Since the only comment received, from the JAA, agrees with the proposed change, Section 23.397(b) is adopted as proposed.
Proposal 35
The FAA proposed to revise Section 23.415 to add requirements defining airplane tie-down loads and to include design criteria for attachment fittings and surrounding structure.
The one commenter, the JAA, submits a recommended "more comprehensive" regulatory paragraph for consideration, and interpretative material based on JAR 23.415(c). The JAA proposes considering all weights between the empty weight and the maximum weight declared for tie-down limit load conditions. The JAA believes the following areas should be included in the consideration: tie-down points stated in the appropriate manual, surrounding structure, control system surfaces, and associated gust locks.
The FAA agrees that all weights should be considered for tie-down points and that structure surrounding the tie-down points should be substantiated for adequate strength. The recommendation to consider these weights is beyond the scope of the notice. The recommendation is retained for a future rulemaking notice. The FAA adopts Section 23.415 as proposed.
Proposal 36
The FAA proposed to clarify when Section 23.473(f) requires a ground load energy absorption test. The FAA received one comment on this proposal. The commenter proposed a wording change that would revise Section 23.473(f) and would change the meaning of this requirement. Since the FAA considers the commenter's proposed change beyond the scope of the notice, the FAA adopts Section 23.473(f) as proposed.
Proposal 37
The FAA proposed to revise Section 23.479(c) to add a new requirement for landing gear spring-back loads. Additionally, this proposal allows for loads development based on testing or rational analyses other than that referenced in appendix D. This proposal also restricts the minimum values of the drag component when using the method referenced in appendix D. Since the only comment received, from the JAA, agrees with the proposed change, Section 23.479(c) is adopted as proposed.
Proposal 38
The FAA proposed to clarify the location and combination of loads in Section 23.485. Since the only comment received, from the JAA, agrees with the proposed change, the FAA is amending Section 23.485, as proposed.
Proposals 39-47
The FAA proposed to amend Section 23.521 and to add new Section 23.523, 23.525, 23.527, 23.529, 23.531, 23.533, 23.535, 23.537, and a new appendix H, to provide a complete new set of water load requirements. Present part 23 refers to Air Force-Navy-Civil (ANC-3) and incorporates by reference the water loads sections of part 25. Since the one comment received, from the JAA, agrees with the proposal, the proposed amendment, new sections and appendix H are adopted as proposed.
Proposal 48
The FAA proposed to add a new Sections 23.573, applicable to composite structure, which would require the applicant to apply a damage tolerance evaluation. It also proposed optional damage tolerance requirements for metallic structures.
The proposed optional damage tolerance requirements caused confusion, so in this final rule the FAA has referenced this optional provision in new Sections 23.571(c) and 23.572(a)(3). Further, in Sections 23.573, the FAA added a lead sentence informing the applicant that composite structure must be evaluated using Section 23.573. Now, when the applicant reads these three sections, it should be clearer that damage tolerance is mandatory for composite structures and optional for metallic structures.
The FAA received substantive comments on this proposal from the GAMA, the JAA, the CAA-Australia, and Transport Canada. The CAA-Australia's views on fiber reinforced plastics (FRP) are:
1. They exhibit very complex failure mechanisms.
2. Fatigue failures usually show multiple defects throughout the specimen; for metallic structures, a single crack is frequently observed.
3. Four basic damage modes occur. These are matrix cracking, delamination, fiber fracture, and interfacial debonding. These damage modes may occur singly, or in combination, and interact with each other.
Based on these views, the CAA-Australia believes that: (1) primary structure that has undetectable damage must carry design ultimate load; (2) that this structure must also carry design limit loads if the damage is detectable; and (3) when detectable damage occurs, the airplane must be removed from service unless it can be shown that the structure will always carry ultimate load with that damage.
The CAA-Australia believes that FRP structures should be designed to carry the ultimate load when manufacturing or service damage exists that is not immediately obvious. This position is based on the lack of knowledge about actual damage initiation, propagation rates, inspection difficulties, and material that is vulnerable to invisible accidental damage. The CAA-Australia offers the following additional comments on proposed Section 23.573.
1. We are concerned that the damage tolerance approach will be used even where it is not practicable simply to circumvent the consequences of large scatter factors needed in the safe life approach. We believe that with appropriate scatter factors the safe life approach remains acceptable, and perhaps desirable, for FRP in these classes of airplanes.
2. Proposed paragraphs (b) and (k) should not be limited to impact damage because other sources of damage exist.
3. Damaged structure ultimate load capability should also apply to metallic structure despite whether it is damage tolerant. Damaged structure should be removed from service if its strength falls below ultimate load capacity.
4. The proposal is interpreted to require analyses, or proof testing, of production bonded joints in metallic structures, regardless of whether they have been evaluated as safe life or damage tolerant.
5. The words "and/or" in the introductory text of the proposal should be revised to read "and" to clarify that both the wing and pressurized cabin must be evaluated.
6. The primary structure should be inspected even when a "no growth (zero growth)" crack exists. Also, visual inspections may be misleading. The intent of part 25, and the proposal for part 23, is to maintain safety by inspection given uncertainties in the design process, and errors in manufacturing, maintenance, and operation.
7. The term "barely visible damage" should be avoided. Certain non-destructive inspection (NDI) techniques are believed to "find" defects, to "see" defects. Considering NDI, "visible" is no longer a word associated only with human vision. Also, the commenter notes that, if the unaided eye visual inspection is accepted as a threshold for detecting damage, explicit inspection procedures should be provided. It is not acceptable to use maintenance procedures or the pilot's preflight inspection as the means of accomplishing visual inspection.
The GAMA comments on this proposal:
1. The NPRM heading "Water Loads" for Section 23.573 is a typographical error.
2. The proposal would add a requirement that makes the damage tolerance evaluation a requirement for composite structure and an option for metallic structure.
3. Many requirements for composite structure are not appropriate for metallic structure.
4. The proposal contains detailed acceptable means of compliance that should be removed and placed in an Advisory Circular.
Based on the above stated positions, the GAMA submitted a proposed complete revision of Section 23.573 that would more clearly present the criteria for composite and metallic structure.
The JAA comment states that the proposed provisions of JAR 23 relating to composites are also based on recently issued FAA special conditions and is therefore largely technically harmonized with the proposed new Section 23.573. However, the JAA notes several concerns:
1. Unlike previously issued special conditions, the proposal only addressed pressurized cabin structure and omitted critical fuselage structure.
2. The proposal for Section 23.573(k) for structures, where damage tolerance methods are shown to be impractical fails to require previously issued special conditions. These special conditions required a residual strength test to ultimate load after completion of the fatigue test. The JAA recommends inserting this provision because the operator would be unaware of any reduction in strength capability.
3. The editorial layout of proposed Section 23.573 is potentially misleading as to its applicability to metallic and composite structures.
The FAA reviewed the above comments and, in general, concurs. Special conditions issued earlier for composite airplanes were used as the basis for this proposed new section. Many of these special conditions were prepared and issued before AC 20-107 was issued. Therefore, there was no guidance available for composite structures and it was appropriate for those special conditions to include acceptable means of compliance. The regulations should be limited to minimum airworthiness standards to be met by an applicant for a type certificate and the acceptable means of compliance should be included in advisory circulars. The FAA finds that AC 20-107 contains much of the guidance needed for compliance with the requirement in proposed Section 23.573. If there is a need, the FAA will develop and issue additional guidance. Based on the comments, the FAA has carefully reviewed the proposal and has deleted the redundant material and the guidance material from the final rule.
The FAA agrees with and generally accepts the complete rewrite of proposed Section 23.573 submitted by the GAMA. The GAMA rewrite clearly presents mandatory requirements for composite materials, Section 23.573(a); optional damage tolerance design standards for metallic structures, Section 23.573(b); and inspection provisions, Section 23.573(c).
The following paragraphs should assist the reader's understanding of the transition from NPRM to this final rule:
1. Section 23.573(a) of the final rule contains the provisions included in the introductory text in the NPRM. The last sentence of this paragraph comes from proposed Section 23.573(j) in the notice. Proposed Section 23.573(j) contained general requirements applicable to all composite structures. It also should have been included in the general requirements of the introductory text in the notice. The words "material variability and environmental conditions" in Section 23.573(j) cover the list of conditions, such as temperature and humidity, that were spelled out in the proposal and that are removed from the final rule. AC 20-107 contains information about this topic.
2. Section 23.573(a)(1) of the final rule contains the text of the first sentence of proposed Section 23.573(b). The FAA guidance material in the second sentence of proposed Section 23.573(b) is included in AC 20-107.
3. Section 23.573(a)(2) comes from proposed Section 23.573(c). Certain explanatory words were removed from this paragraph. Section 23.573(a)(3) is a combination of Section 23.573(g) and (h), in the proposal. Section 23.573(g), for pressurized cabins, and Section 23.573(h), for other parts of the airplane, contained common testing requirements that have been combined. The structural items, such as the wing, identified in proposed Section 23.573(h) appear in final rule Section 23.573(a) and are not repeated in Section 23.573(a)(3). The special consideration for pressurized cabin structure in proposed Section 23.573(g)(1) and (g)(2), is now included in final rule Section 23.573(a)(3)(i) and (a)(3)(ii).
4. Section 23.573(a)(4) is the same as Section 23.573(d) in the NPRM. Section 23.573(a)(5) is the same as Section 23.573(i) in the NPRM. Verifying the strength of bonded joints by non-destructive testing is added to this paragraph to provide a third acceptable means of approval.
5. Section 23.573(a)(6) comes from Section 23.573(k) in the NPRM. This paragraph is rewritten for consistency with the other paragraphs in this section.
6. Instead of the composite damage tolerance requirements proposed for metallic structures by Section 23.573(a) in the NPRM, the final rule provides these requirements in Section 23.573(b).
7. Section 23.573(c) combines the proposed requirements of Section 23.573, paragraphs (e) and (l), from the NPRM and makes this a requirement applicable to composite structures. Those inspection requirements also apply to metallic structures subject to the optional damage tolerance provisions of final rule Section 23.573(b).
8. Proposed Section 23.573(f) is deleted in the final rule. This paragraph described load spectra, load truncation, and types of damage that must be considered in the damage tolerance evaluation. It contained advisory material on testing methods and did not contain any testing requirements. Though this paragraph is removed, the topics identified must be considered and documented in any damage tolerance evaluation.
The FAA adopts Section 23.573, with the changes discussed above and includes revisions to Section 23.571 and 23.572.
Proposal 49
The FAA proposed to revise Section 23.613 to place into part 23 the probability basis used for establishing material allowables. The probability basis appears in MIL-HDBK-5 and is duplicated in Section 23.613 and 23.615.
The FAA received comments on this proposal from the GAMA, the JAA, and Transport Canada. The JAA agrees with the proposals because they significantly harmonize with JAR 23.
The GAMA believes that Section 23.613(c) should continue to list the various strength authority documents (MIL-HDBK-5 and others) to make it clear that these references continue to be acceptable. The FAA agrees that these references are still acceptable and concludes that since this material is advisory, it is more appropriate that it be included in an advisory circular.
Transport Canada suggests substitution of the word "design" for the word "strength" in proposed Section 23.613(d) on the ground that a "design detail may have high static strength but still be a poor design from the point of view of fatigue." The FAA agrees and has amended the paragraph accordingly. The proposed Section 23.613 is adopted with the changes discussed above.
Proposal 50
The FAA proposed to remove Section 23.615 since it is no longer needed in view of the changes to Section 23.613. The two commenters, the GAMA and the JAA, agree with the proposal. Section 23.613 is removed as proposed.
Proposal 51
The FAA proposed to provide relief from non-destructive testing requirements for critical castings and to define non-structural casting requirements in Section 23.621.
One commenter, the JAA, believes the intent of proposed Section 23.621(c)(1)(i) is: "* * * 100 percent inspection by visual, radiographic and either magnetic particle, penetrant or other approved equivalent non-destructive inspection method." The FAA agrees and revises Section 23.621(c)(1)(i) accordingly.
The JAA states that it is sympathetic to the FAA's proposed revision to Section 23.621(c)(1)(ii) but requests the sharing of FAA's experience concerning the adequacy of a factor of 2.0. All available experience was shared in discussions at the Airworthiness Review Conference; in conference proposals 240, 241, and 242; and in the explanation information contained in the NPRM. The FAA adopts proposed Section 23.621(c)(1)(ii) as proposed.
The JAA also states that Section 23.621(e), regarding non-structural castings, is redundant since present Section 23.621(a) already excludes non-structural castings.
After further review, the FAA has concluded that 23.621(a) refers to "non-structural" fluid systems castings only. Section 23.621(e) includes those fluid systems castings addressed by Section 23.621(a), but it is not limited to them. Section 23.621(e) is adopted as proposed and any redundancy between Section 23.621, paragraphs (a) and (e), will be addressed by future rulemaking. The FAA adopts Section 23.621 with the changes discussed above.
Proposal 52
The FAA proposed to define the dive speed, VD, to reduce the Mach number from 0.6 to 0.5, and to introduce flutter criteria for damaged structure in Section 23.629. The FAA received comments on this proposal from the GAMA and from the JAA.
The GAMA recommends that the proposed changes to Section 23.629(d)(1) not be made. This commenter recommends that the Mach cut-off references remain at 0.6 and 260 knots (EAS) and that the reference to altitude be eliminated. The JAA states that since "260 kt EAS at 14,000 feet is M=0.5, this has been proposed for JAR 23. "
The FAA has determined that the Mach number 0.5 is technically more appropriate (and the JAA agrees) to the 260 knot (EAS) requirement and causes no significant flutter certification problem. After further review, the FAA has decided that the reference to altitude, although technically correct, is irrelevant; therefore, it is removed.
The GAMA proposes that VD/MD would be more appropriate than VD alone. The FAA agrees and changes the proposal accordingly.
The GAMA also asks the FAA to revise Section 23.629(g) and (h) to clarify that the phrase "analysis only" is the regulatory requirement.
The FAA disagrees. As proposed, Section 23.629(g) and (h) require an analysis and permit certification by testing. An "analysis only" requirement would effectively discourage and prohibit other certification substantiation. The words "by analysis or test" replace the words "by analysis" in paragraphs (g) and (h). By this change, the applicant is required to show that the airplane is free from flutter up to VD/MD, but is permitted to use analysis or other means that are appropriate for the design.
Finally, the GAMA proposes that the analytical flutter clearance factor of 1.2 VD in Section 23.629(b) be changed to 1.15 VD. Changes to Section 23.629(b) are outside the scope of this NPRM. The FAA will consider this in future rulemaking projects.
The JAA observes that VD is not explicitly stated in proposed Section 23.629(h) although it is in proposed Section 23.629(g). The FAA agrees that both paragraphs should address VD, and final rule Section 23.629(h) is revised accordingly. The FAA adopts Section 23.629 with the changes discussed above.
Proposal 53
The FAA proposed to extend the installation requirements in Section 23.655, currently applicable only to the tail surfaces, to include all control surfaces.
Since the only comment, received from the JAA, agrees with the proposed change, the FAA adopts Section 23.655 as proposed.
Proposal 54
The FAA proposed to add a new Section 23.672 that provides criteria for approval of certain stability augmentation devices, and automatic and power-operated systems.
The FAA received comments on this proposal from the GAMA, the JAA, and the ALPA. The ALPA strongly supports the proposed change. The JAA states that the adoption of proposed FAR 23.672 for JAR 23 is under discussion.
The GAMA recommends that the FAA make it clear that this requirement would not apply to a simple downspring or a bobweight stability device. The FAA agrees with the GAMA that new Section 23.672 would not apply to devices such as downsprings and bobweights since they are not "systems" as addressed in this requirement. Since Section 23.672 is virtually identical to Section 25.672, and since there have been no problems interpreting that section consistent with this position, the FAA concludes that no changes are needed. The FAA adopts Section 23.672 as proposed.
Proposal 55
The FAA proposed to revise Section 23.679 by adding provisions for an automatic-disengage control lock system. The proposal would also add requirements for the locks to be installed so they limit operation of the controls and thereby provide the pilot with an unmistakable warning that the controls are locked at the start of the takeoff roll.
The FAA received comments on this proposal from the GAMA, the JAA, and the ALPA. The ALPA strongly supported the proposed change.
The GAMA believes that the proposal would add to the cost and complexity of the control lock system without a commensurate benefit. The GAMA is unaware of any adverse service history resulting from installed control locks and believes that the current rule provides an adequate level of safety. In support of this position, the GAMA includes an estimated cost of $250,000 to develop a fully automatic gust lock system for a type certificated airplane model.
To evaluate and resolve the GAMA comments, the FAA has reviewed the original conference proposals, numbers 252, 253, and 254. It has also reviewed the record of the public meeting. In response to the GAMA comment concerning any adverse service history, this review shows that the original conference proposals were submitted because accidents were occurring because of control locks that remained installed during takeoff. The economic analysis of the proposals in the notice also identified this accident service history and showed severe airplane damage, pilot injuries, and possible fatalities.
The FAA is aware that an automatically released control lock system would be costly. The proposal did not mandate the installation of an automatic system, but would add an optional provision that would show the acceptance of such systems.
The JAA stated its assumption that the proposed requirement would not be applicable to external locks. Based on the comments received, the FAA has re-examined the proposal. Since the proposal would have eliminated the current Section 23.679(a), external systems that use the red warning ribbons as a means of warning the pilot that the locks are in place would no longer be acceptable. The FAA has determined that there is a need to retain the provision of current Section 23.679(a), so that presently used locks and their warning systems remain acceptable. The added provision of Section 23.679(a)(2) will make it clear that systems that automatically disengage the locks are also acceptable but not mandatory.
The proposal to limit the operation of the airplane when the locks are engaged is being restated since control locks and their warnings can be overlooked and automatic disengage systems will fail. The FAA believes an additional safeguard is required. By requiring a system that will ensure that airplane operation is limited, the pilot will receive a pre-takeoff warning and thus a hazardous takeoff will not be attempted.
In summary, the FAA has considered the comments and has revised the proposed rule language by retaining the current provisions of Section 23.679(a) and Section 23.679(a)(1), and by adding the provision for accepting automatically disengaged locking systems as an option. The language in proposed Section 23.679(a)(2) to require the control surfaces to be locked so the pilot receives an unmistakable warning at the start of the takeoff if the locks have not been removed is retained as Section 23.679(b). The unmistakable warning required by this paragraph may be a tactile warning that the pilot receives by the feel of the controls. Finally, proposed Section 23.679(b) is retained as paragraph (c).
The FAA has determined that these changes are not substantive and will clarify this requirement by providing relief from the provisions identified by the commenters. The FAA adopts Section 23.679 with the changes discussed above.
Proposal 56
The FAA proposed to revise Section 23.729, paragraphs (f)(1) and (f)(2), by changing the power and flap settings necessary to warn the pilot that the landing gear is not fully extended and locked.
The FAA received two comments on this proposal from the JAA and the ALPA. The ALPA strongly supported the proposed change.
The JAA generally agrees with the proposal. However, the JAA notes that these requirements are liable to produce nuisance warnings when the throttles are closed for descent from a high altitude or when one throttle is pulled back following an engine failure. The JAA suggests that the FAA consider an approach for part 23 gear warning requirements similar to the approaches proposed for part 25 in Notice No. 89-20 (54 FR 34116, August 17, 1989).
The revision of the landing gear warning requirements proposed for part 25 is beyond the scope of this rulemaking. While no action will be taken on this suggestion now, the FAA will consider this suggestion for future rulemaking.
Nuisance warnings concern the FAA, and the language changes proposed in the NPRM should reduce them. Proposed Section 23.729(f)(2) would have required a landing gear warning when the flaps are extended beyond the approach setting. That change would eliminate the nuisance warnings occurring when flaps are set "to" the approach flap position. Subsequent to the issuance of the notice it has come to FAA attention that many airplanes have more than one approach flap setting and that the proposal would be unclear as to which approach flap setting should be used as the threshold for the gear warning. Also, if the lower approach flap setting is used, nuisance warnings could occur because that setting is also frequently used for takeoff flaps. To clarify this requirement, the proposal has been revised to require the gear warning when the flaps are extended beyond the maximum approach flap position. The FAA adopts Section 23.729 with the changes discussed above.
Proposal 57
The FAA proposed to remove Section 23.731(a), which contains a requirement that each main and nose wheel must be approved. Since there is a basic requirement to approve the complete airplane, including all components, parts, and appliances, Section 23.731(a) is unnecessary. No comments were received on this proposal, and the FAA adopts Section 23.731, as proposed.
Proposal 58
The FAA proposed to remove the current Section 23.733 reference to the tire rating assigned by the Tire and Rim Association. This would be accomplished by:
1. Stating that tire ratings must be approved.
2. Requiring that static and dynamic ratings be established.
3. Defining the conditions where those ratings are to be used.
The FAA received comments on this proposal from the GAMA and the JAA. The JAA asks the FAA to explain the undiscussed change in the drag reaction from 0.21W to 0.31W.
At least one publication of part 23 regulations contains a typing error that gave this reaction as 0.21W. The FAA has reviewed the history of this requirement and verified that the value of 0.31W that is in Section 23.733(a)(2), as published in the Code of Federal Regulations, is correct.
The GAMA questions the removal of the reference to the Tire and Rim Association and recommends its retention. In the NPRM, the FAA identifies the existence of other organizations whose appropriate rating also would be considered. The FAA adopts Section 23.733 as proposed.
Proposal 59
The FAA proposed to remove the first sentence of Section 23.737 that states that each ski must be approved. Since the only commenter, the JAA, agrees with the proposed change, the FAA adopts Section 23.737 as proposed.
Proposal 60
The FAA proposed to revise Section 23.751 to clarify the buoyancy requirements for the main floats of seaplanes. Since the only commenter, the JAA, agrees with the proposed change, the FAA adopts Section 23.751 as proposed.
Proposal 61
The FAA proposed to remove the words "must be approved" from the main float design requirements in Section 23.753. Since the only commenter, the JAA, agrees with the proposed change, the FAA adopts Section 23.753 without change.
Proposal 62
The FAA proposed to add wording to the hull requirements for seaplanes in Section 23.755 to clarify that airplanes must be kept afloat without capsizing. Since the only commenter, the JAA, agrees with the proposed change, the FAA adopts Section 23.755(a), introductory text, as proposed.
Proposal 63
The FAA proposed to revise the 23.773 requirements for the pilot compartment view to address the environment expected in all the operations requested for certification.
The JAA states that it will consider this change for JAR 23 but that it proposes to retain present paragraph (b) relating to night flight tests. The GAMA contends that the words "must be shown in all operations for which certification is requested," could be interpreted to mean that the same view must be provided for all operations.
The FAA does not agree with the GAMA interpretation. Section 23.773(a) and (a)(1) require the pilot compartment view to be sufficiently extensive, clear, and undistorted to allow the pilot to perform the various functions identified in this proposal. The word "sufficiently" is included because the FAA recognizes that the view needed for one operation may differ from the view needed for another. The intent is also shown by the words "sufficiently large" used in Section 23.773(b). The FAA adopts Section 23.773 as proposed.
Proposal 64
The FAA proposed to clarify the Section 23.775 criteria to be used for determining the cleared windshield area that is necessary to ensure safe operation for icing conditions. The proposed new Section 23.775 would require that a probable single failure of a transparency heating system may not adversely affect the integrity of the airplane cabin. The FAA received comments on this proposal from the GAMA and the JAA.
The JAA does not find the proposal for Section 23.775(f) acceptable for inclusion into JAR 23. The JAA does not provide any suggested changes.
In reviewing this comment, the FAA notes that the proposal for Section 23.773 identifies the need for a clear and undistorted view for these same four operations and the ability to "perform any maneuver within the operating limitations of the airplane." If the airplane is approved for operation in known or forecast icing conditions, the requirements of Section 23.773 will be applicable. Section 23.775(f) should be the same as Section 23.773. Accordingly, Section 23.775(f) is revised to be the same as Section 23.773.
The JAA also believes that transparency heating systems covered by proposed Section 23.775(g), should be certificated under the principles of Section 23.1309. The FAA notes that Section 23.1309 applies to all systems, as defined by Section 23.1309(f) and would apply to transparency heating systems. The provisions of the proposal for Section 23.775(g) identify specific hazards that could occur. These specific hazards would have catastrophic consequences and must be avoided through the use of appropriate designs.
The other commenter, GAMA, notes that its comments on proposal 63 also apply to this proposal to clarify criteria for determining cleared windshield areas. The FAA addresses the concern about the amount of cleared windshield under proposal 63. The response is also applicable to the cleared area needed for the operations identified in this proposal. The FAA adopts Section 23.775 with the change discussed above.
Proposal 65
The FAA proposed that Section 23.851 be revised to require a hand fire extinguisher to be located in the pilot's compartment of all airplane categories. This proposal would also add minimum standards for hand held fire extinguishers. The FAA received comments on this proposal from the JAA and the GAMA.
One commenter, JAA, believes the requirement in current Section 23.851, paragraphs (a) and (b), is more appropriate for the operating rules.
The FAA does not agree with this commenter's position. It is incorrect to allow an airplane to be certificated and not include the equipment required for the airplane to be placed in operation. When this occurs, the new owner/operator must then install the required equipment. Such an installation would not only need to meet the operating rules but also would need to meet the requirements of Sections 23.851 and 23.561(b)(3). Because the operator may not have the structural design data for the airplane, finding a suitable location to install a fire extinguisher meeting the load factors of Section 23.561 could be difficult. Such installations are more easily accomplished by the airframe manufacturer. The requirements of current Section 23.851(a) and (b) will be retained.
The JAA also notes that proposed Section 23.851(c)(2) does not ban extinguishers that use toxic agents. The JAA believes that such agents should be banned. The FAA does not agree with this position. The first consideration in evaluating the use of a hand fire extinguisher is its effectiveness in putting out any in-flight fire. If the best agent for the type of fire that may occur causes toxic gas, the concentration of that gas that would result from a completely discharged extinguisher and its hazard to the occupants must be evaluated. If the concentration would be hazardous, it may still be possible to use the extinguisher if the gas can be vented from the area in a short time, and if there would be no adverse affect upon the occupants. To ban such fire extinguishers could lower the level of safety of the airplane by reducing the chance that in-flight fires can be extinguished. The FAA plans no action to ban the use of such fire extinguishing agents at this time.
The other commenter, GAMA, believes the proposal for Section 23.851(a), requiring a hand fire extinguisher to be located conveniently in the pilot's compartment, is too restrictive. The GAMA points out that the pilot's compartment is usually small, therefore, it is frequently difficult to find suitable space for a fire extinguisher. The GAMA recommends revising Section 23.851(a) to read, "There must be at least one hand fire extinguisher located within easy access of the pilot while seated."
The FAA agrees that the recommended revision would require the same pilot access to the fire extinguisher as intended by the proposal. Because this revision allows the fire extinguisher to be located in the cabin, where the pilot can reach it, it could be confused with the extinguisher required for the cabin. To identify the applicable extinguisher, the proposal is revised to read, "There must be at least one hand fire extinguisher for use in the pilot compartment that is located within easy access of the pilot while seated."
The GAMA also recommends that the FAA develop more explicit guidance criteria concerning the acceptable size, agent, etc., than is now contained in the operating rules in Section 91.513. The FAA agrees that better guidance needs to be developed, and will consider future advisory material to develop such guidance.
The FAA observes that Section 91.513(c)(3) requires at least one hand fire extinguisher located in the passenger compartment of each airplane accommodating more than six passengers. Accordingly, this operating rule and the NPRM are not compatible. If the requirements in the notice were adopted as proposed, normal category airplanes that accommodate more than six passengers could be certificated without a passenger compartment fire extinguisher. Then, operators of those airplanes would be required to have an extinguisher installed.
The FAA discussed, in the NPRM, the burden that would fall on the operator if that operator needed to install a new fire extinguisher that also must meet other current airworthiness requirements. For consistency with Section 91.513(c)(3), the final rule Section 23.851 has been revised to require a fire extinguisher in the cabin of airplanes that accommodate more than six passengers. The FAA adopts Section 23.851 with the changes discussed above.
Proposal 66
The FAA proposed to clarify the existing requirement of Section 23.865 by excluding those portions of the engine mount certificated with the engine and by addressing the allowable damage expected on engine isolators. Since the only commenter, JAA, agrees with this proposal, the FAA adopts Section 23.865 as proposed.
Proposal 67
The FAA proposed a change to Section 23.1507 to establish an operating maneuvering speed (VO) different from the design maneuvering speed (VA) established by Section 23.335(c). VO is the maximum speed where, at any given weight, the pilot may apply full control excursion without exceeding the design limit load factor.
The one commenter, the JAA, believes that this new concept of VO needs further discussion. The JAA also notes that, while proposed Section 23.1507(a), establishing an operating limitation, is correctly located, Section 23.1507(b), which defines VO, should be moved to become Section 23.335(d) while retaining the existing definition of VA, design maneuvering speed, at Section 23.335(c).
The FAA disagrees with moving the VO definition to Section 23.335, since it would put an operational definition in the design section of part 23. The VO definition in Section 23.1507 is consistent with the requirements of Sections 23.1505 and 23.1511, namely, that the relationships between "operating" speeds and "design" speeds are established. The comment has caused the FAA to re-examine and reword proposed Section 23.1507. The revised wording deletes the definitions of computed stall speed (VS) and the limit maneuvering load factor (n) and utilizes those already contained in Section 23.335. The final rule section heading includes the word "operating" to maintain a distinction from the design maneuvering speed of Section 23.335. The FAA adopts Section 23.1507 with the change discussed above.
Proposal 68
The FAA proposed to add a new Section 23.1516 that establishes an intentional one-engine-inoperative speed for pilot training.
The one commenter, the JAA, refers to its comments on proposed Section 23.149. The FAA agrees that VSSE should not be established as a limitation; therefore, it deletes the proposed Section 23.1516.
Proposal 69
The FAA proposed to change Section 23.1521 to ensure that powerplant limitations established for airplane certification do not exceed those established during the certification of the engine or the propeller, and are in accord with limitations used in determining compliance with this part.
The one commenter on this proposal, JAA, notes that examples from FAA experience would be useful in the preparation of interpretations. The FAA's principal experience involves derated engines and some turbopropeller engine installations that have a higher maximum power at cruise than at takeoff. The FAA adopts Section 23.1521 as proposed.
Proposal 70
The FAA proposed to add a new Section 23.1522 that specifies auxiliary power unit (APU) limitations in the operating limitation section of the AFM.
The one commenter, JAA, believes that, without requirements addressing APU's in subpart E of part 23, the introduction of this proposal on operating limitations is premature.
The FAA points out that APU's have been addressed in Section 23.901 as amended in Small Airplane Airworthiness Review Program Amendment No. 3, Amendment 23-43 (58 FR 18958, April 9, 1993). The FAA adopts Section 23.1522 as proposed.
Proposal 71
The FAA proposed to change Section 23.1525 to clarify the existing rule which is vague and brief, by requiring the establishment and inclusion of kinds of operations authorized in the AFM, as specified by Section 23.1583(h).
The one commenter, JAA, notes that existing Section 23.1525 and proposed JAR 23.1525 are statements rather than requirements. The JAA believes that what is needed is a requirement that establishes the kinds of operations authorized and the resulting airplane operational limitations. The JAA suggests a slightly modified version of proposed JAR 23.1525, as follows: "The kinds of operation authorized (such as VFR, IFR, day or night) and the meteorological conditions (such as icing) and the category in which the aeroplane is eligible for certification, appropriate to the installed equipment, must be established." The JAA believes that the requirement to furnish this information in the AFM belongs in Section 23.1583(h) and that a cross-reference, as proposed in Section 23.1525, is unnecessary.
The FAA concurs with the JAA's comment and the final rule language is changed to closely follow the JAA's suggested version. The FAA adopts Section 23.1525 with the change discussed above.
Proposal 72
The FAA proposed to change Section 23.1527 to clarify that the maximum operating altitude allowed for any part 23 airplane must be established based on those limitations determined by flight, structural, powerplant, functional, or equipment characteristics.
The one commenter, JAA, suggests reversing the order of Section 23.1527(a) and (b) for clarity. The FAA concurs and adopts Section 23.1527 with this change.
Proposal 73
The FAA proposed to change Section 23.1545 by deleting current paragraph Section 23.1545(b)(6) which requires a red radial mark on the airspeed indicator. This mark identifies the minimum control speed with the critical engine inoperative, VMC, on multiengine airplanes.
The one commenter on this proposal, JAA, states that the red radial line on the airspeed indicator at VMC offers useful guidance to the pilot for this class of airplane and should be retained.
For the reasons given by the JAA, the FAA agrees that the red radial should be retained. The proposed amendment to Section 23.1545 is withdrawn.
Proposal 74
The FAA proposed to change Section 23.1549 to expand the current powerplant instrument requirements to include auxiliary power units (APU).
The one comment from JAA on this proposed change refers to the JAA's comments on proposed changes to Section 23.1522 in which the JAA opposed referencing APU in the absence of requirements addressing APU in subpart C.
As previously stated, since the Small Airplane Airworthiness Review Program Amendment No. 3, Amendment 23-43 (58 FR 18958, April 9, 1993) addresses APU, Section 23.1549 is adopted as proposed.
Proposal 75
The FAA proposed to change Section 23.1557 to clarify the marking requirements for filler openings and to require a marking for the coolant filler opening similar to the requirements for fuel and oil. The FAA also proposed deleting Section 23.1557(f) because the AFM and fuel quantity indicator provide this information to the pilot.
The one commenter, JAA, concurs with the proposed changes, except that the JAA believes that Section 1557(c)(2), which contains marking requirements for oil filter openings, should end with the words "and the permissible oil designations." While the FAA agrees, after further review, the FAA has determined that, as with fuel filler marking, the oil filler marking should permit reference to the AFM as an alternative. The proposed Section 23.1557 is adopted with the change discussed above.
Proposal 76
The FAA proposed to change Section 23.1563(a) by substituting VO for VA in conjunction with the change to Section 23.1507.
The one commenter, JAA, states that VO should be further considered later, in the light of discussions on proposed Section 23.1507. The concept of VO was discussed under proposal 67 relating to Section 23.1507, and for the reasons stated there the FAA adopts Section 23.1563(a) as proposed.
Proposal 77
The FAA proposed to change Section 23.1581(f) to establish a new requirement for providing a means to record updates to the AFM.
The FAA received comments on this proposal from the ALPA and the JAA. The ALPA strongly supports the proposed change.
The JAA agrees with a requirement for a means of recording the amendment status of the AFM, but believes that a "log of revisions" is only one acceptable means of compliance and that a list of effective pages is equally acceptable.
The FAA agrees with the commenter and has determined that the rule text permits the suggested alternative. A change in the heading to read "Revisions and amendments" clarifies this point. The proposed Section 23.1581(f) is adopted with the change discussed above.
Proposal 78
The FAA proposed an introductory sentence to Section 23.1583. During the type certification process, there are limitations required other than those specified by this section. The FAA proposed to expand Section 23.1583(h) to identify the kinds of operation that were type certificated, such as icing. Also, the section was proposed to be revised to identify installed equipment that must be operable for aircraft operation in icing conditions. The NPRM also proposed a new Section 23.1583(m). Although Section 23.1523, Load distribution limits, generally covers it, the effects of an asymmetric fuel load are not emphasized. The effects of lateral fuel imbalance are not usually addressed although the lateral center of gravity limits must be furnished in the AFM.
The FAA received comments on this proposal from the GAMA and the JAA. The commenters on the proposal for Section 23.149, which would establish a safe, intentional, one-engine-inoperative speed, VSSE, as a limitation in Section 23.1583, oppose the inclusion of VSSE in Section 23.1583(a)(2). In response to these comments, the FAA agrees that this speed should not be established as a limitation and VSSE is removed from Section 23.1583(a)(2). Revisions to Sections 23.149 and 23.1585 require manufacturers to determine a safe one-engine-inoperative speed and provide this information in the AFM.
The JAA also notes that the words "of each airplane" in the introductory statement are not necessary and should be removed. The FAA concurs. While reviewing comments on Section 23.1583(a)(2), the FAA noted that since VA is removed as an airspeed limitation in Section 23.1507, VA should also be removed from Section 23.1583(a)(2).
The JAA states that, having established the kinds of operation authorized under Section 23.1525 (VFR, IFR, day, night, and others), Section 23.1583(h) is merely to require that this information be made available in the AFM. The JAA suggests words based on JAR 23.1583, as follows:
"The Aeroplane Flight Manual must contain:
* * * * *
(h) Kinds of operation. A list of the kinds of operation to which the aeroplane is limited under Section 23.1525 for which approval has been given."
If the FAA retains proposed Section 23.1583 as proposed, the JAA suggests replacing "is requested" with "has been given." The JAA also notes the need to identify the required operational status of installed equipment, where this may affect operation limitations, will be proposed as an extension to JAR 23.1583(i).
The GAMA states that "The last sentence of proposed Section 23.1583(h) is confusing and subject to multiple interpretations. Certain equipment, such as deicing equipment, might be appropriately included in a listing that affects operating limitations (flight into known icing in this example) but, reference to the kinds of operation for which approval is requested may lead to confusion and continue the argument that has been going on for more than ten years with respect to minimum equipment lists versus what is required (required equipment lists) for a particular operation. Most operators of part 23 airplanes, including operators of single-engine personal use airplane, have traditionally equipped their airplanes according to their personal operational requirements and preferences. This will become even more true in the near future as alternate sole source navigational systems are approved. The proposed wording of the last sentence of paragraph Section 23.1583(h) appears to require that a detailed minimum equipment list be included in the limitations section of the AFM. This in turn requires a supplemental type certificate for any variation from the manufacturer's standard installed equipment list. Such a list might well be appropriate as a 'required' equipment list for various kinds of operations and may be interpreted to provide operational authority for such operations. However, it is more likely that it will perpetuate the confusion of what must be operative and what may be inoperative during a particular flight. This item needs further review."
The FAA agrees that a reference in Section 23.1583(h) to the kinds of operation within Section 23.1525 is appropriate instead of repeating examples of kinds of operations. This change and the other change suggested by the JAA are made in the final Section 23.1583(h).
The FAA does not agree with the GAMA that the last sentence in Section 23.1583(h) is confusing and subject to multiple interpretation. A Kind of Equipment List (KOEL) has been part of the limitations for many years. A Minimum Equipment List (MEL) is an operational requirement covered by part 91 and the relationship between a KOEL and an MEL is well established and in use by the public.
Except for editorial changes, suggested by the JAA, and minor clarifying editorial changes, Section 23.1583(h) is adopted as proposed.
Proposal 79
The FAA proposed to change Section 23.1585 to revise flight procedures and scheduled speeds that are essential for the safe operation of the airplane and the achievement of the scheduled performance. Additionally, the procedures for starting engines in flight are considered necessary for all multi-engine airplanes; therefore, the FAA proposed to eliminate the reference to commuter category and to turbine engines.
The FAA received comments on this proposal from the JAA and the CAA-UK. The CAA-UK comment addresses conference proposals that the FAA rejected and, as previously stated, this preamble does not address comments on rejected conference proposals. The JAA notes that the proposed changes align closely with JAR 23.
The JAA believes that GAMA Specification No. 1 is acceptable and fears that certain of the proposed changes may conflict with it. The FAA recognizes that GAMA Specification No. 1 may need to be revised.
Also, the JAA states that it is "unclear from what the operating procedures 'must be * * * segregated" in the AFM.
With the addition of abnormal procedures to normal and emergency procedures covered under the present rule, the FAA's intent is that the AFM be organized so that abnormal procedures are clearly separated from normal procedures, etc.
The JAA notes that procedures for maintaining and recovering control following engine failure above or below VMC are still required in spite of the NPRM explanation that these are within the scope of basic airmanship. The FAA concurs with the JAA that the explanation in the NPRM shows that recovering of control above and below VMC is within the scope of basic airmanship. These procedures were inadvertently left in the text of the proposed rule as Section 23.1585(c)(5); therefore, proposed paragraph (c)(5) is omitted from the final rule.
The JAA states: "In spite of the explanation, FAR 23.1585(d) through (g) appear to remain unchanged although (f), not required for JAR 23, requires for all aeroplanes that a restart envelope must be established. In Section 23.1585, however, the operating procedures for restarting of the engine(s) must be furnished for multi-engined aeroplanes only. This inconsistency will lead to confusion."
The JAA comment on Section 23.1585(d) through (g) indicates that the text of the NPRM explanation may have been misunderstood. The NPRM explanation noted that non-flight items were considered for the NPRM but not addressed as the NPRM was aimed at flight items. Thus, the FAA did not intend to change Section 23.1585(d) through (g).
The FAA does not understand the JAA's reference to Section 23.1585(f) with respect to an engine restart envelope for all airplanes, since Section 23.1585(f) concerns unusable fuel and indicator marking. Nor does the FAA understand the inconsistency suggested by the JAA since the proposed restart procedures are in paragraph (c) which only applies to multiengine airplanes.
In response to comments on proposed Section 23.235, as discussed under that section, the FAA is amending Section 23.1585(a) to add a requirement for seaplane handling procedures and demonstrated wave height.
Also as discussed in proposal 12, the FAA decided that VSSE should not be a limitation; therefore, a new Section 23.1585(c)(6) is added to require that VSSE be furnished to the pilot in the AFM. The FAA adopts Section 23.1585 with the changes discussed above.
Proposal 80
The FAA proposed to reorganize and simplify Section 23.1587, which specifies the performance information that must be provided in the AFM.
The one commenter, JAA, states that while the proposed changes move considerably towards the proposed text of JAR 23.1587, the JAA has already decided that "the calculated approximate effect" on performance of altitude and temperature is unacceptable.
The JAA states that the maximum temperature at which compliance with the cooling requirements has been shown is wrongly located in the AFM and that it should appear as a limitation in Section 23.1521(e), as in proposed JAR 23. Unlike proposed JAR 23.1587, the JAA notes that there is no proposal to address the effect of factored winds, runway slope, or grass surfaces on takeoff and landing distances or to schedule a flight-over-water speed. The JAA believes data are necessary for meaningful compliance with even the simplest performance operating rules.
Since none of these items were proposed in the NPRM, it is inappropriate for the FAA to include them in the final rule and the proposed Section 23.1587 is adopted as proposed.
Proposal 81
The FAA proposed to amend Section 23.1589(a) to publish the weight and location of each item of equipment that can be easily removed, relocated, or replaced.
Since the only comment received, from the JAA, agrees with the proposed change, the FAA adopts Section 23.1589, as proposed.
Proposal 82
The FAA proposed to amend appendix D by adding a new paragraph (c), which supports a new requirement in Section 23.479(c) concerning dynamic spring-back of the landing gear.
Since the only comment received, from the JAA, agrees with the proposed change, appendix D is adopted as proposed.
Proposal 83
The FAA proposed to add a new appendix H that supports amended Section 23.521.
Since the only comment received, from the JAA, agrees with the proposed change, appendix H is adopted as proposed.
Turbojet Engines
While not proposing any rule change in the NPRM, the FAA requested and received comments about changing part 23 to allow the use of turbojet engines on commuter category airplanes. Comments were received from the ALPA and from the JAA. The ALPA opposes the use of turbojet engines and believes that the certification of turbojet airplanes should remain under part 25 requirements.
The JAA states that since basic FAR/JAR 23 includes turbojets, "there is no fundamental reason for excluding them from commuter category" airplanes. The JAA believes that turbojets provide enhanced reliability compared to reciprocating engines. The JAA also believes that turbojet engines provide better airplane handling characteristics, with one engine inoperative, than any propeller driven airplane (reciprocating or turbine engine powered). The JAA recognizes that part 23 is intended to provide a simplified airworthiness code appropriate to simple airplane designs. The JAA recognizes that the use of turbojet engines has the potential to convey a performance capability involving design complexities not envisioned in formulating FAR 23. The JAA states that it is not opposed to the use of turbojet engines on airplanes certificated to commuter category requirements, subject to a review of requirements related to a higher performance capability (speed and altitude).
Performance Limitations Based on Weight, Altitude and Temperature (WAT)
While not proposing any rule change in the NPRM, the FAA requested comment on the need for WAT criteria, as information or as a limitation on piston-powered twin-engine part 23 airplanes. It also requested comments about WAT criteria on turbine-powered twin-engine part 23 airplanes, specifically during takeoff and landing. The FAA received comments from the JAA, the GAMA, and the ALPA. The ALPA supports the requirement that WAT information be furnished during the certification process. The ALPA cites the variety of operational uses, including scheduled air carrier and regional airline service, and the need for "one level" of safety as justification. The GAMA "believes that WAT information is useful but certainly not the only way to present operating data for any airplane" and that making WAT criteria an airplane or operating limitation for part 23 airplanes is "an unnecessary and unjustified expansion or redirection of operating criteria." The JAA generally supports the use of WAT criteria for part 23 airplane certifications. The JAA believes that the chance of a single-engine failure on any airplane is high. Also, the JAA warns that safety considerations include airplane occupants and personnel on the ground. According to the JAA, transport category airplanes do this by limiting the operation of the airplane. Beyond the point where takeoff can be rejected, one-engine-inoperative climb must guarantee obstacle clearance. The JAA recognizes the need for generally similar requirements for commuter category airplanes.
The JAA believes that a continued flight capability would preclude the operation of single-engine airplanes. Also, the JAA believes that airplane size and stall speed provide characteristics that permit safe landings.
The JAA points out that between the two extremes within present part 23 (from single-engine airplanes to commuter category airplanes) lie the light twin-engine reciprocating and turbine engine airplanes, ranging from four to nine seats and 4,000 to 12,500 pounds. The JAA notes that, for these types of airplanes, it would be burdensome to require compliance with full net flight path obstacle clearance. In the JAA's opinion, a safe forced landing becomes less satisfactory with increased takeoff weight, involving longer stopping distances even for the same landing speed. The JAA notes that twin-engine airplanes have other significant adverse characteristics compared to single-engine airplanes. First, an engine failure is twice as probable; second, asymmetric power demands immediate pilot action.
The JAA also points out that the inability to continue flight with one engine inoperative creates the following situation: The chance of a second engine failure is increased; a suitable site for an emergency landing is reduced; and the pilot resists the inevitable forced landing and tries to maintain flight. Training, under more favorable conditions, may have taught the pilot to expect success in these situations. In unfavorable conditions, attempts to maintain flight lead to loss of airspeed at high asymmetric power and, commonly, loss of directional control that results in a stall/spin accident.
The JAA advocates certification and operations criteria for multiengine airplanes that blend the performance requirements for a single-engine airplane and a transport category airplane. The JAA believes that the requirements accept a limited period for risk just before and just after liftoff where engine failure may not be fully accounted for. The JAA believes that the application of WAT limits clearly accounts for actual conditions, although the climb gradient requirements are lower than those of FAR/JAR 25.
The JAA recommends using compensating operational criteria, like transport category airplanes use, for the lower performance commuter category airplanes. Cockpit visibility and a reasonable maximum speed provide adequate compensation for takeoff so the pilot can see and avoid obstacles as the airplane returns for landing. The JAA does not propose a distinction between reciprocating and turbine engines. Where applicable, the WAT criteria should be imposed, in the JAA's opinion, as limitations through the Airplane Flight Manual (AFM).
The JAA does not believe that such proposals would involve costs disproportionate to the benefits. The JAA suggests that the comment from the airworthiness conference, that such criteria would "eliminate the certification of an entire class of airplanes," is an exaggeration. The proposals are achievable, in the JAA's view, by typical modern light twin-engine airplanes with realistic payloads, particularly the more significant executive/air taxi airplanes. It is the JAA's opinion that adopting this concept would instill a greater awareness of performance consideration in pilots from an early stage of their training.
The JAA also believes that the climb and handling qualities requirements of present Sections 23.65 and 23.67 are illogical and unreasonable. The JAA recommends using WAT criteria, so it applies equally to all airplane operations, because it offers improved airplane capability.
The JAA points out that the manufacturers of "WAT type" airplanes routinely determine performance under a wide range of conditions. The JAA also notes that flight manuals produced to the widely accepted General Aviation Manufacturers Association (GAMA) specification already contain performance data beyond the minimum requirements of part 23. Additional testing or scheduled data create no additional costs in the JAA's opinion. The JAA notes that present draft JAR 23 applies WAT limits only to piston-engine airplanes above 6,000 pounds and turbine-engine airplanes and that it has been proposed to the JAR Operations Group that WAT limits be applied to all JAR 23 airplanes in commercial operation.
Regulatory Evaluation Summary
This section summarizes the full regulatory evaluation prepared by the FAA that provides detailed estimates of the economic consequences of this regulatory action. This summary and the full evaluation quantify, to the extent practicable, estimates of the costs and benefits to the private sector, consumers, and Federal, State, and local governments.
Executive Order 12291, dated February 17, 1981, directs Federal agencies to promulgate new regulations or to modify existing regulations only if potential benefits to society outweigh potential costs for each regulatory change. The order also requires the preparation of a Regulatory Impact Analysis of all "major" rules except those responding to emergency situations or other narrowly-defined exigencies. A "major" rule is one that is likely to have an annual impact on the economy of $100 million or more, to have a major increase in consumer costs, or to have a significant adverse effect on competition.
The FAA has determined that this rule is not major as defined in the Executive Order. This section contains a summary of the regulatory evaluation, a regulatory flexibility determination as required by the 1980 Regulatory Flexibility Act, and an international trade impact assessment. The complete regulatory evaluation, which contains more detailed economic information than this summary provides, is available in the docket.
Cost-Benefit Analysis
Costs
Of the rule's 79 amendments, only six will result in more than negligible costs of compliance for airplane manufacturers. Each of these six amendments requires additional testing or analysis, costing about $5,800 per airplane certification. One of the amendments, Section 23.851, also requires a fire extinguisher in all part 23 airplanes that are produced under future certifications. Other regulations already require fire extinguishers in airplanes with greater than six passengers and in commuter airplanes. For purposes of estimating the cost of this requirement, the FAA assumes a worst case scenario under which all future part 23 certifications will involve airplanes with six or fewer passengers. The FAA estimates that a fire extinguisher and a suitable bracket cost $40.
The FAA assumes that an average of five airplanes will be certified under part 23 each year during the period of analysis from 1993-2012. Based on discussions with industry, the FAA also assumes that, during the first year following certification, 60 airplanes will be produced per certification. In the second, third, and fourth years following certification, 120 airplanes per year are assumed to be produced. In the fifth and subsequent years, 100 airplanes per year are assumed to be produced. Based on this assumption, the costs of the rule over the 20-year period of analysis total $3.7 million ($1.5 million discounted) or about $48 per airplane produced.
Benefits
The benefits of the rule are two-fold. First, the rule is expected to enhance safety. An examination of accidents that might have been prevented by this rule include those involving control locks that were not removed prior to flight (seven accidents over a five-year period with five fatalities, three airplanes destroyed, and four substantially damaged) and multiengine stall/spin accidents (four accidents over eight years, resulting in nine fatalities and all airplanes destroyed). Had those accidents been avoided by the rule, the benefits would be $5.4 million per year.
Other safety benefits will be realized from the rule. The requirement to demonstrate 1.5g pitch maneuver capability will ensure that a pilot can make 30-degree banked turns and slow down from potential overspeed conditions without encountering low-speed buffeting. Determination of spin-up and spring-back loads will ensure that landing gear fore and aft drag loads, which affect both landing gear and wing strength, will be considered in the design of new part 23 airplanes. The requirement that airplanes be free from flutter will ensure that this dangerous phenomenon does not occur, even after fatigue failure. The rule also requires that additional information about procedures, speeds, and configurations for a glide following an engine failure for single-engine airplanes and procedures for restarting engines in flight for multiengine airplanes be included in the airplane flight manual. This information can lessen the consequences of emergency landings after engine failures. Although the FAA has not quantified the benefits of these requirements, the benefits exceed the generally minor costs.
There were 108 recorded accidents that occurred from January 1989 through April 1991 in which there was fire after impact. Although the number of fatalities and injuries in these accidents that could have been avoided cannot be determined, it is likely that the presence of a fire extinguisher could have mitigated the consequences in at least some of these fires.
Less than $194,000 in average annual accident losses needs to be averted annually to render this rule cost-beneficial. For those control system lock and multiengine stall/spin accidents that could have been prevented or mitigated by the provisions of this rule, the annual losses averaged $5.4 million. This exceeds the $194,000 threshold value, thus, the rule is cost-beneficial. In addition, the avoidance of fatalities because of the presence of fire extinguishers in affected airplanes will further increase the benefits. Finally, other requirements, such as those discussed above, will provide additional safety benefits.
Another valuable additional benefit of this rule is that it comports to a large extent with international requirements, particularly the Joint Aviation Requirements (JAR) of the Joint Aviation Authorities (JAA). The creation of common international standards, or harmonization, will benefit manufacturers in the U.S. and those in the countries of the JAA.
The rule modifies certain testing requirements and allows optional evaluations and analysis. This may result in cost savings. However, the FAA does not have sufficient information to quantify such savings.
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (RFA) requires Federal agencies to review rules that may have a "significant economic impact on a substantial number of small entities." FAA Order 2100.14A, Regulatory Flexibility Criteria and Guidance, contains criteria for determining whether a proposed or existing rule has a significant economic impact on a substantial number of small entities.
The entities that will be affected by this rule are the manufacturers of airplanes certificated under part 23. Based on the Regulatory Flexibility Criteria and Guidance, the size threshold for manufacturers is 75 or fewer employees and the cost threshold is $18,200 in 1992 dollars.
Approximately 14 affected manufacturers are considered to be small entities. The annual cost of the rule per certification during peak production is estimated to be $5,700, which is substantially less than the cost threshold limit cited above. Therefore, the FAA has determined that the rule will not have a significant economic impact on a substantial number of small entities.
International Trade Impact Assessment
The rule will have little or no impact on international trade. Both foreign and domestic manufacturers seeking type certification in the United States will be required to comply with the rule. The Joint Aviation Authorities (JAA) is including many of the sections in this rule to harmonize with U.S. aviation regulations. It is expected that other countries will also adopt these requirements.
Federalism Implications
The regulations herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this regulation will not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
Conclusion
The FAA is revising the airworthiness standards for normal, utility, acrobatic, and commuter category airplanes as a result of comments received in reply to the Small Airplane Airworthiness Review Program Notice No. 4 dated June 28, 1990. The notice, which addresses airframe and flight items, was published as a result of recommendations discussed at the Small Airplane Airworthiness Review Conference held on October 22-26, 1984 in St. Louis, Missouri. Originally, the proposals reflected updated safety standards and advancements in technology while reducing the regulatory burden for some requirements and maintaining an acceptable level of safety. Harmonization with the European Joint Aviation Authorities Joint Airworthiness Requirements became a dominant factor at the close of the extended Notice of Proposed Rulemaking comment period, December 14, 1990. Considerable effort was invested to harmonize these airworthiness standards because aircraft industry estimates indicate reduced overall certification costs. These airworthiness standards will continue to provide adequate levels of safety for small airplanes used in both private and commercial operations.
For the reasons discussed in the preamble, and based on the findings in the Regulatory Flexibility Determination and the International Trade Impact Analysis, the FAA has determined that this regulation is not major under Executive Order 12291. In addition, the FAA certifies that this regulation will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. This regulation is considered significant under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979). A regulatory evaluation of the regulation, including a Regulatory Flexibility Determination and International Trade Impact Analysis, has been placed in the docket. A copy may be obtained by contacting the person identified under "FOR FURTHER INFORMATION CONTACT."
List of Subjects in 14 CFR Part 23
Aircraft, Air transportation, Aviation safety, Safety.
 Regulatory Information
Footer Information
Issued in Washington, DC, on July 28, 1993.
Joseph N Del Balzo,
Acting Administrator.
[FR Doc. 93-18569 Filed 9-5-93; 8:45 am]
BILLING CODE 4910-13-M
Comments
Document History
Notice of Proposed Rulemaking Actions:
Notice of Proposed Rulemaking. Notice No. 90-18; Issued on 06/15/90.
Other Final Rule Actions:
Not Applicable.
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