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 Federal Register Information
 Header Information
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-323-AD; Amendment 39-11456; AD 99-25-13]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 777-200 and -300 Series Airplanes
PDF Copy (If Available):
Preamble Information
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
SUMMARY: This amendment adopts a new airworthiness directive (AD) that is applicable to all Boeing Model 777-200 and -300 series airplanes. This action requires revising the Limitations Section of the Airplane Flight Manual to prohibit the dispatch of certain airplanes under certain conditions. This amendment also requires repetitive inspections to ensure correct operation of the backup generators; and, for certain airplanes, a one-time inspection to detect damage of the engine external gearbox; and corrective actions, if necessary. This amendment is prompted by reports of inflight shutdowns due to sheared backup generator shafts. The actions specified in this AD are intended to prohibit the dispatch of an airplane with an engine-mounted backup generator having a sheared shaft; and to detect and correct damage to the engine, which could result in inflight shutdowns.
DATES: Effective December 23, 1999.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of December 23, 1999.
Comments for inclusion in the Rules Docket must be received on or before February 7, 2000.
ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-323-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
FOR FURTHER INFORMATION CONTACT: Ed Hormel, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2681; fax (425) 227-1181.
SUPPLEMENTARY INFORMATION: The FAA has received reports of two recent inflight engine shutdowns that were initiated by a failure of the engine-driven backup generator (including a sheared shaft), and consequent failure of the engine gearbox oil pump due to contamination from the damaged backup generator drive bearing in the engine gearbox. Most backup generator shaft shear events are the result of leaking driveshaft seals, or improper servicing of the backup generator during maintenance. The current Model 777 Master Minimum Equipment List allows airplane operation for up to 10 days with a failed backup generator shaft. Both inflight shutdowns occurred on Boeing Model 777 series airplanes equipped with Rolls-Royce Trent 800 series turbofan engines. However, the FAA has determined that the same unsafe condition may also occur on General Electric GE90 and Pratt & Whitney PW4000 series turbofan engines, since the same backup generators are installed on airplanes having these engines.
Investigation continues in determining the exact reason for the backup generator shaft shear events and consequent engine failures. However, the FAA considers that improper servicing of the backup generator oil system could be a contributing factor. Consequently, improper servicing or improper replacement of the backup generator by the same individual, on both engines on the same flight, could lead to the failure of both generators, and result in a common-cause failure and inflight shutdown of both engines.
Explanation of Relevant Service Information
The FAA has reviewed and approved the following Boeing 777 Service Letters that recommend temporary revisions to the backup generator servicing and dispatch (operational) procedures for Model 777 series airplanes equipped with Trent 800, GE90, and PW4000 series turbofan engines.
777-SL-24-023-B, dated August 16, 1999, "Back Up Generator Servicing and Dispatch Requirements-Temporary Revision-RR Installations."
777-SL-24-024, dated August 16, 1999, "Back Up Generator Servicing and Dispatch Requirements-Temporary Revision-GE Installations."
777-SL-24-025, dated August 18, 1999, "Back Up Generator Servicing and Dispatch Requirements-Temporary Revision-PW Installations."
The FAA also has reviewed and approved Rolls-Royce Service Bulletin RB.211-72-C813, Revision 1, dated July 16, 1999, which describes certain maintenance actions (i.e., an inspection of the engine external gearbox to detect damage, and corrective actions, if necessary) for Trent 800 series turbofan engines, which are recommended by Rolls-Royce in the event of a backup generator low oil pressure/shaft shear event.
Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to exist or develop on other Boeing Model 777 series airplanes of the same type design, this AD is being issued to require revising the Limitations Section of the Airplane Flight Manual (AFM) to prohibit the dispatch of Model 777 series airplanes having backup generators with sheared shafts; and to prohibit any extended twin-engine operations (ETOPS) flight until a non-ETOPS flight of at least one hour in duration is accomplished, following replacement of the backup generator on both the left and right engines with a new or serviceable backup generator. This amendment also requires repetitive inspections to ensure correct operation of the backup generators; and, for certain airplanes, a one-time inspection to detect damage of the engine external gearbox; and corrective actions, if necessary. The actions are required to be accomplished in accordance with the service information described previously except as discussed below.
Differences Between the AD and the Service Information
Boeing Service Letters 777-SL-24-023-B and 777-SL-24-024 recommend against the dispatch of Boeing Model 777 series airplanes equipped with Trent 800 or GE90 series turbofan engines having a sheared shaft on the backup generator. Service Letter 777-SL-24-025, applicable to Boeing Model 777 series airplanes equipped with PW4000 series turbofan engines, does not recommend against the operation of Model 777 series airplanes having a sheared shaft on the backup generator. However, this AD prohibits dispatch of any Model 777 series airplane having a sheared shaft on the backup generator. This AD also prohibits any extended twin-engine operations (ETOPS) flight until a non-ETOPS flight of at least one hour in duration is accomplished, following replacement of the backup generator on both the left and right engines with a new or serviceable backup generator.
In addition, this AD requires certain Rolls-Royce Trent 800 engine maintenance actions that are recommended in Rolls-Royce Service Bulletin RB.211-72-C813, Revision 1, but that are not included in the Boeing Service Letter 777-SL-24-023-B for Rolls-Royce engines. Such maintenance actions are required by this AD if a backup generator shaft has sheared within the last 250 flight hours, or if the gearbox inspections specified in Revision 1 of the Rolls-Royce service bulletin were not accomplished.
Interim Action
This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption ADDRESSES. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 99-NM-323-AD." The postcard will be date stamped and returned to the commenter.
Regulatory Impact
The regulations adopted 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39-AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive:
Regulatory Information
99-25-13 Boeing: Amendment 39-11456. Docket 99-NM-323-AD.
Applicability: Model 777-200 and -300 series airplanes equipped with Rolls-Royce Trent 800, General Electric GE90, or Pratt & Whitney PW4000 series turbofan engines; certificated in any category.
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
Compliance: Required as indicated, unless accomplished previously.
To prohibit dispatch of an airplane with an engine-mounted backup generator having a sheared shaft; and to detect and correct damage to the engine, which could result in inflight shutdowns; accomplish the following:
Revisions to the Airplane Flight Manual
(a) For all airplanes: Within 14 days after the effective date of this AD, revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) to include the following information. This may be accomplished by inserting a copy of this AD in the AFM.
"Dispatch of the airplane with an engine-mounted backup generator having a sheared shaft is prohibited.
Following replacement of the backup generator on both the left and right engines, extended twin-engine operations (ETOPS) flight is prohibited until a non-ETOPS flight of at least one hour in duration is accomplished."
Prohibited Servicing or Replacement
(b) For all airplanes: As of 14 days after the effective date of this AD, servicing of both the left and right backup generators or replacement of both backup generators with new or serviceable components by the same individual prior to the same flight is prohibited.
One-Time Actions for Rolls-Royce Engines
(c) For airplanes equipped with Rolls-Royce Trent 800 series turbofan engines: Within 14 days after the effective date of this AD, determine whether the status message "ELEC BACKUP GEN L(R)" and the maintenance message "Backup generator L(R) has a sheared shaft" have occurred within the last 250 flight hours prior to the effective date of this AD. If these messages have occurred during that time, accomplish follow-on corrective actions, as applicable, at the times specified in paragraphs C.1.(c) and D. of Rolls-Royce Service Bulletin RB.211-72-C813, Revision 1, dated July 16, 1999, in accordance with the procedures specified in the service bulletin.
Note 2: Boeing Service Letter 777-SL-24-023-B, dated August 16, 1999, references Rolls-Royce Service Bulletin RB.211-72-C813, Revision 1, dated July 16, 1999, as an additional source of service information to accomplish certain actions required by this AD.
Inspections and Corrective Actions
(d) Within 14 days after the effective date of this AD, and thereafter prior to each flight: Accomplish paragraph (d)(1), (d)(2), or (d)(3) of this AD, as applicable.
Rolls-Royce Engines
(1) For airplanes equipped with Rolls-Royce Trent 800 series turbofan engines, accomplish paragraphs (d)(1)(i) and (d)(1)(ii) of this AD.
(i) Inspect the Electrical Maintenance Page of the engine indicating and crew alerting system (EICAS), and perform follow-on corrective actions, as applicable, at the times specified in and in accordance with the procedures specified in Boeing Service Letter 777-SL-24-023-B, dated August 16, 1999.
(ii) If the status message "ELEC BACKUP GEN L(R)" is active: Prior to further flight, inspect the Maintenance Access Terminal (MAT) for certain maintenance messages indicating a sheared shaft or low oil pressure, as specified in Step 2.a. of Boeing Service Letter 777-SL-24-023-B, dated August 16, 1999; and accomplish the corrective actions specified in Steps 2.a.(1) or 2.a.(2), as applicable, in accordance with that service letter.
General Electric Engines
(2) For airplanes equipped with General Electric GE90 series turbofan engines: If the status message "ELEC BACKUP GEN L(R)" is active, prior to further flight, inspect the MAT for certain maintenance messages indicating a sheared shaft or low oil pressure, as specified in Step 1.a. of Boeing Service Letter 777-SL-24-024, dated August 16, 1999; and accomplish the corrective actions specified in Steps 1.a.(1) or 1.a.(2), as applicable, in accordance with the service letter.
Pratt & Whitney Engines
(3) For Model 777 series airplanes equipped with Pratt & Whitney PW4000 series turbofan engines: If the status message "ELEC BACKUP GEN L(R)" is active, prior to further flight, inspect the MAT for certain maintenance messages indicating a sheared shaft or low oil pressure, as specified in Step 1.a. of Boeing Service Letter 777-SL-24-025, dated August 18, 1999, in accordance with that service letter.
(i) If any of the specified maintenance messages is active, prior to further flight, remove and replace the backup generator in accordance with Airplane Maintenance Manual (AMM) 24-25-01-000-801 or 24-25-01-400-801, as applicable.
(ii) If the backup generator shaft is found to be sheared, or either of the low oil pressure messages are active, prior to further flight, accomplish the corrective actions specified in Step 1.a.(1) of Boeing Service Letter 777-SL-24-025, dated August 18, 1999, in accordance with that service letter.
Flight Test After Replacement of Backup Generators
(e) For all airplanes: As of 14 days after the effective date of this AD, following any replacement of the backup generator on both the left and right engines, accomplish paragraphs (c)(1) and (c)(2) of this AD at the times specified in those paragraphs.
(1) Prior to any ETOPS flight, conduct a non-revenue test flight of at least one hour in duration, or a non-ETOPS flight that is either a non-revenue or revenue flight of at least one hour in duration.
(2) Prior to further flight after accomplishment of the action required by paragraph (e)(1) of this AD: Verify accomplishment of the maintenance actions required by paragraph (d)(1), (d)(2), or (d)(3) of this AD, as applicable.
Alternative Methods of Compliance
(f) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.
Note 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.
Special Flight Permits
(g) Special flight permits may be issued in accordance with Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.
Incorporation by Reference
(h) Except as provided by paragraphs (a) and (d)(3)(i) of this AD, the actions shall be done in accordance with Rolls-Royce Service Bulletin RB.211-72-C813, Revision 1, dated July 16, 1999; Boeing Service Letter 777-SL-24-023-B, dated August 16, 1999; Boeing Service Letter 777-SL-24-024, dated August 16, 1999; or Boeing Service Letter 777-SL-24-025, dated August 18, 1999; as applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(i) This amendment becomes effective on December 23, 1999.
Footer Information
Issued in Renton, Washington, on November 30, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate,
Aircraft Certification Service.
[FR Doc. 99-31472 Filed 12-7-99; 8:45 am]
BILLING CODE 4910-13-U
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