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FAR § 25.203 Stall characteristics.

Sun Jul 14, 2019 10:18 am

Does anyone know what jet prompted this law?
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25-84, 60 FR 30750, June 9, 1995]

It seems unlikely that it was the B737 since the first order for that jet was on Feb. 15, 1965.
Any other technical comments would be welcome. I am curious if the B737 MAX is the first design to require something like MCAS to keep in compliance with this regulation.

§ 25.203 Stall characteristics.
(a) It must be possible to produce and to correct roll and yaw by unreversed use of the aileron and rudder controls, up to the time the airplane is stalled. No abnormal nose-up pitching may occur. The longitudinal control force must be positive up to and throughout the stall. In addition, it must be possible to promptly prevent stalling and to recover from a stall by normal use of the controls.
(b) For level wing stalls, the roll occurring between the stall and the completion of the recovery may not exceed approximately 20 degrees.
(c) For turning flight stalls, the action of the airplane after the stall may not be so violent or extreme as to make it difficult, with normal piloting skill, to effect a prompt recovery and to regain control of the airplane. The maximum bank angle that occurs during the recovery may not exceed -
(1) Approximately 60 degrees in the original direction of the turn, or 30 degrees in the opposite direction, for deceleration rates up to 1 knot per second; and
(2) Approximately 90 degrees in the original direction of the turn, or 60 degrees in the opposite direction, for deceleration rates in excess of 1 knot per second.
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Re: FAR § 25.203 Stall characteristics.

Sun Jul 14, 2019 11:16 am

Part 25 and its predecessor CAR 4B go back a long ways. Stall characteristics for non-FBW planes are pretty settled matter. There needs to be a speed stable without stick force lightning in the approach to stall, basically once in trim slowing requires a constant increase in back force. That’s the basic with some exceptions.

Planes have had various “fixes” for any lack of natural buffet or roll off for decades-shakers, pushers, auto trim inputs and the FBW planes have it all in the software.

It’s not a law, it is a CFR and the AMC Advisory Circular goes into more detail. It’s a not a cut and dried process

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