Sec. 23.729 - Landing gear extension and retraction
(a) General. For airplanes with
retractable landing gear, the following apply:
(1) Each landing gear retracting
mechanism and its supporting structure must be designed for maximum flight
load factors with the gear retracted and must be designed for the
combination of friction, inertia, brake torque, and air loads, occurring
during retraction at any airspeed up to 1.6 VS1
with flaps retracted, and for any load factor up to those specified in
§23.345 for the flaps-extended condition.
(2) The landing gear and retracting
mechanism, including the wheel well doors, must withstand flight loads,
including loads resulting from all yawing conditions specified in §23.351,
with the landing gear extended at any speed up to at least 1.6 VS1
with the flaps retracted.
(b) Landing gear lock. There must
be positive means (other than the use of hydraulic pressure) to keep the
landing gear extended.
(c) Emergency operation. For a
landplane having retractable landing gear that cannot be extended
manually, there must be means to extend the landing gear in the event of
(1) Any reasonably probable failure in
the normal landing gear operation system; or
(2) Any reasonably probable failure in a
power source that would prevent the operation of the normal landing gear
(d) Operation test. The proper
functioning of the retracting mechanism must be shown by operation tests.
(e) Position indicator. If a
retractable landing gear is used, there must be a landing gear position
indicator (as well as necessary switches to actuate the indicator) or
other means to inform the pilot that each gear is secured in the extended
(or retracted) position. If switches are used, they must be located and
coupled to the landing gear mechanical system in a manner that prevents an
erroneous indication of either "down and locked" if each gear is not in
the fully extended position, or "up and locked" if each landing gear is
not in the fully retracted position.
(f) Landing gear warning. For
landplanes, the following aural or equally effective landing gear warning
devices must be provided:
(1) A device that functions continuously
when one or more throttles are closed beyond the power settings normally
used for landing approach if the landing gear is not fully extended and
locked. A throttle stop may not be used in place of an aural device. If
there is a manual shutoff for the warning device prescribed in this
paragraph, the warning system must be designed so that when the warning
has been suspended after one or more throttles are closed, subsequent
retardation of any throttle to, or beyond, the position for normal landing
approach will activate the warning device.
(2) A device that functions continuously
when the wing flaps are extended beyond the maximum approach flap
position, using a normal landing procedure, if the landing gear is not
fully extended and locked. There may not be a manual shutoff for this
warning device. The flap position sensing unit may be installed at any
suitable location. The system for this device may use any part of the
system (including the aural warning device) for the device required in
paragraph (f)(1) of this section.
(g) Equipment located in the landing
gear bay. If the landing gear bay is used as the location for
equipment other than the landing gear, that equipment must be designed and
installed to minimize damage from items such as a tire burst, or rocks,
water, and slush that may enter the landing gear bay.
[Doc. No. 4080, 29 FR 17955, Dec. 18,
1964, as amended by Amdt. 23-7, 34 FR 13091, Aug. 13, 1969; Amdt. 23-21,
43 FR 2318, Jan. 1978; Amdt. 23-26, 45 FR 60171, Sept. 11, 1980; Amdt.
23-45, 58 FR 42164, Aug. 6, 1993; Amdt. 23-49, 61 FR 5166, Feb. 9, 1996]