Federal Aviation Administration, DOT

Section 25.677

electrical or hydraulic system failures,
or any single failure in combination
with any probable hydraulic or electrical failure).
(3) Any jam in a control position normally encountered during takeoff,
climb, cruise, normal turns, descent,
and landing unless the jam is shown to
be extremely improbable, or can be alleviated. A runaway of a flight control
to an adverse position and jam must be
accounted for if such runaway and subsequent jamming is not extremely improbable.
(d) The airplane must be designed so
that it is controllable if all engines
fail. Compliance with this requirement
may be shown by analysis where that
method has been shown to be reliable.

spaschal on DSK3GDR082PROD with CFR

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5674, Apr. 8,
1970]

Section 25.672 Stability augmentation and
automatic and power-operated systems.
If the functioning of stability augmentation or other automatic or
power-operated systems is necessary to
show compliance with the flight characteristics requirements of this part,
such systems must comply with Section 25.671
and the following:
(a) A warning which is clearly distinguishable to the pilot under expected
flight conditions without requiring his
attention must be provided for any
failure in the stability augmentation
system or in any other automatic or
power-operated system which could result in an unsafe condition if the pilot
were not aware of the failure. Warning
systems must not activate the control
systems.
(b) The design of the stability augmentation system or of any other automatic or power-operated system must
permit initial counteraction of failures
of the type specified in Section 25.671(c) without requiring exceptional pilot skill or
strength, by either the deactivation of
the system, or a failed portion thereof,
or by overriding the failure by movement of the flight controls in the normal sense.
(c) It must be shown that after any
single failure of the stability augmentation system or any other automatic or power-operated system - 

(1) The airplane is safely controllable
when the failure or malfunction occurs
at any speed or altitude within the approved operating limitations that is
critical for the type of failure being
considered;
(2) The controllability and maneuverability requirements of this part are
met within a practical operational
flight envelope (for example, speed, altitude, normal acceleration, and airplane configurations) which is described in the Airplane Flight Manual;
and
(3) The trim, stability, and stall characteristics are not impaired below a
level needed to permit continued safe
flight and landing.
[Amdt. 25-23, 35 FR 5675 Apr. 8, 1970]

Section 25.675

Stops.

(a) Each control system must have
stops that positively limit the range of
motion of each movable aerodynamic
surface controlled by the system.
(b) Each stop must be located so that
wear, slackness, or take-up adjustments will not adversely affect the
control characteristics of the airplane
because of a change in the range of surface travel.
(c) Each stop must be able to withstand any loads corresponding to the
design conditions for the control system.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55466, Dec. 20,
1976]

Section 25.677

Trim systems.

(a) Trim controls must be designed to
prevent inadvertent or abrupt operation and to operate in the plane, and
with the sense of motion, of the airplane.
(b) There must be means adjacent to
the trim control to indicate the direction of the control movement relative
to the airplane motion. In addition,
there must be clearly visible means to
indicate the position of the trim device
with respect to the range of adjustment. The indicator must be clearly
marked with the range within which it
has been demonstrated that takeoff is
safe for all center of gravity positions
approved for takeoff.

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