Sec. 23.691 - Artificial stall barrier system.
If the function of an artificial stall
barrier, for example, stick pusher, is used to show compliance with
§23.201(c), the system must comply with the following:
(a) With the system adjusted for
operation, the plus and minus airspeeds at which downward pitching control
will be provided must be established.
(b) Considering the plus and minus
airspeed tolerances established by paragraph (a) of this section, an
airspeed must be selected for the activation of the downward pitching
control that provides a safe margin above any airspeed at which any
unsatisfactory stall characteristics occur.
(c) In addition to the stall warning
required §23.07, a warning that is clearly distinguishable to the pilot
under all expected flight conditions without requiring the pilot's
attention, must be provided for faults that would prevent the system from
providing the required pitching motion.
(d) Each system must be designed so that
the artificial stall barrier can be quickly and positively disengaged by
the pilots to prevent unwanted downward pitching of the airplane by a
quick release (emergency) control that meets the requirements of
(e) A preflight check of the complete
system must be established and the procedure for this check made available
in the Airplane Flight Manual (AFM). Preflight checks that are critical to
the safety of the airplane must be included in the limitations section of
(f) For those airplanes whose design
includes an autopilot system:
(1) A quick release (emergency) control
installed in accordance with §23.1329(b) may be used to meet the
requirements of paragraph (d), of this section, and
(2) The pitch servo for that system may
be used to provide the stall downward pitching motion.
(g) In showing compliance with §23.1309,
the system must be evaluated to determine the effect that any announced or
unannounced failure may have on the continued safe flight and landing of
the airplane or the ability of the crew to cope with any adverse
conditions that may result from such failures. This evaluation must
consider the hazards that would result from the airplane's flight
characteristics if the system was not provided, and the hazard that may
result from unwanted downward pitching motion, which could result from a
failure at airspeeds above the selected stall speed.
[Doc. No. 27806, 61 FR 5165, Feb. 9, 1996]