[Code of Federal Regulations]
[Title 14, Volume 1]
[Revised as of January 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 14CFR25.331]
[Page 364-365]
TITLE 14--AERONAUTICS AND SPACE
CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES--Table of Contents
Subpart C--Structure
Sec. 25.331 Symmetric maneuvering conditions.
(a) Procedure. For the analysis of the maneuvering flight conditions
specified in paragraphs (b) and (c) of this section, the following
provisions apply:
(1) Where sudden displacement of a control is specified, the assumed
rate of control surface displacement may not be less than the rate that
could be applied by the pilot through the control system.
(2) In determining elevator angles and chordwise load distribution
in the maneuvering conditions of paragraphs (b) and (c) of this section,
the effect of corresponding pitching velocities must be taken into
account. The in-trim and out-of-trim flight conditions specified in
Sec. 25.255 must be considered.
(b) Maneuvering balanced conditions. Assuming the airplane to be in
equilibrium with zero pitching acceleration, the maneuvering conditions
A through I on the maneuvering envelope in Sec. 25.333(b) must be
investigated.
(c) Pitch maneuver conditions. The conditions specified in
paragraphs (c)(1) and (2) of this section must be investigated. The
movement of the pitch control surfaces may be adjusted to take into
account limitations imposed by the maximum pilot effort specified by
Sec. 25.397(b), control system stops and
[[Page 365]]
any indirect effect imposed by limitations in the output side of the
control system (for example, stalling torque or maximum rate obtainable
by a power control system.)
(1) Maximum pitch control displacement at VA. The
airplane is assumed to be flying in steady level flight (point
A1, Sec. 25.333(b)) and the cockpit pitch control is suddenly
moved to obtain extreme nose up pitching acceleration. In defining the
tail load, the response of the airplane must be taken into account.
Airplane loads that occur subsequent to the time when normal
acceleration at the c.g. exceeds the positive limit maneuvering load
factor (at point A2 in Sec. 25.333(b)), or the resulting
tailplane normal load reaches its maximum, whichever occurs first, need
not be considered.
(2) Specified control displacement. A checked maneuver, based on a
rational pitching control motion vs. time profile, must be established
in which the design limit load factor specified in Sec. 25.337 will not
be exceeded. Unless lesser values cannot be exceeded, the airplane
response must result in pitching accelerations not less than the
following:
(i) A positive pitching acceleration (nose up) is assumed to be
reached concurrently with the airplane load factor of 1.0 (Points
A1 to D1, Sec. 25.333(b)). The positive
acceleration must be equal to at least
[GRAPHIC] [TIFF OMITTED] TC28SE91.033
where--
n is the positive load factor at the speed under consideration, and V is
the airplane equivalent speed in knots.
(ii) A negative pitching acceleration (nose down) is assumed to be
reached concurrently with the positive maneuvering load factor (points
A2 to D2, Sec. 25.333(b)). This negative pitching
acceleration must be equal to at least
[GRAPHIC] [TIFF OMITTED] TC28SE91.034
where--
n is the positive load factor at the speed under consideration; and V is
the airplane equivalent speed in knots.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23,
35 FR 5672, Apr. 8, 1970; Amdt. 25-46, 43 FR 50594, Oct. 30, 1978; 43 FR
52495, Nov. 13, 1978; 43 FR 54082, Nov. 20, 1978; Amdt. 25-72, 55 FR
29775, July 20, 1990; 55 FR 37607, Sept. 12, 1990; Amdt. 25-86, 61 FR
5220, Feb. 9, 1996; Amdt. 25-91, 62 FR 40704, July 29, 1997]