Code of Federal Regulations

Title 14 - Aeronautics and Space
Volume: 1Date: 2021-01-01Original Date: 2021-01-01Title: Section § 25.253 - High-speed characteristics.Context: Title 14 - Aeronautics and Space. CHAPTER I - FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION. SUBCHAPTER C - AIRCRAFT. PART 25 - AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES. Subpart B - Flight. - Miscellaneous Flight Requirements.
§ 25.253 High-speed characteristics. (a) Speed increase and recovery characteristics. The following speed increase and recovery characteristics must be met: (1) Operating conditions and characteristics likely to cause inadvertent speed increases (including upsets in pitch and roll) must be simulated with the airplane trimmed at any likely cruise speed up to V MO / M MO . These conditions and characteristics include gust upsets, inadvertent control movements, low stick force gradient in relation to control friction, passenger movement, leveling off from climb, and descent from Mach to airspeed limit altitudes. (2) Allowing for pilot reaction time after effective inherent or artificial speed warning occurs, it must be shown that the airplane can be recovered to a normal attitude and its speed reduced to V MO / M MO, without— (i) Exceptional piloting strength or skill; (ii) Exceeding V D / M D, V DF / M DF, or the structural limitations; and (iii) Buffeting that would impair the pilot's ability to read the instruments or control the airplane for recovery. (3) With the airplane trimmed at any speed up to V MO /M MO , there must be no reversal of the response to control input about any axis at any speed up to V DF /M DF . Any tendency to pitch, roll, or yaw must be mild and readily controllable, using normal piloting techniques. When the airplane is trimmed at V MO /M MO , the slope of the elevator control force versus speed curve need not be stable at speeds greater than V FC /M FC , but there must be a push force at all speeds up to V DF /M DF and there must be no sudden or excessive reduction of elevator control force as V DF /M DF is reached. (4) Adequate roll capability to assure a prompt recovery from a lateral upset condition must be available at any speed up to V DF /M DF .
Code of Federal Regulations / Title 14 - Aeronautics and Space / Vol. 1 / 2021-01-01232
(5) With the airplane trimmed at V MO /M MO , extension of the speedbrakes over the available range of movements of the pilot's control, at all speeds above V MO /M MO , but not so high that V DF /M DF would be exceeded during the maneuver, must not result in: (i) An excessive positive load factor when the pilot does not take action to counteract the effects of extension; (ii) Buffeting that would impair the pilot's ability to read the instruments or control the airplane for recovery; or (iii) A nose down pitching moment, unless it is small. (b) Maximum speed for stability characteristics, V FC /M FC . V FC /M FC is the maximum speed at which the requirements of §§ 25.143(g), 25.147(f), 25.175(b)(1), 25.177(a) through (c), and 25.181 must be met with flaps and landing gear retracted. Except as noted in § 25.253(c), V FC /M FC may not be less than a speed midway between V MO /M MO and V DF /M DF , except that, for altitudes where Mach number is the limiting factor, M FC need not exceed the Mach number at which effective speed warning occurs. (c) Maximum speed for stability characteristics in icing conditions. The maximum speed for stability characteristics with the most critical of the ice accretions defined in Appendices C and O of this part, as applicable, in accordance with § 25.21(g), at which the requirements of §§ 25.143(g), 25.147(f), 25.175(b)(1), 25.177(a) through (c), and 25.181 must be met, is the lower of: (1) 300 knots CAS; (2) V FC ; or (3) A speed at which it is demonstrated that the airframe will be free of ice accretion due to the effects of increased dynamic pressure. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-23, 35 FR 5671, Apr. 8, 1970; Amdt. 25-54, 45 FR 60172, Sept. 11, 1980; Amdt. 25-72, 55 FR 29775, July 20, 1990; Amdt. 25-84, 60 FR 30750, June 9, 1995; Amdt. 25-121, 72 FR 44668, Aug. 8, 2007; Amdt. 25-135, 76 FR 74654, Dec. 1, 2011; Amdt. 25-140,79 FR 65525, Nov. 4, 2014]