664 

14 CFR Ch. I (1–1–14 Edition) 

§ 27.672 

(b) Each element of each flight con-

trol system must be designed, or dis-
tinctively and permanently marked, to 
minimize the probability of any incor-
rect assembly that could result in the 
malfunction of the system. 

§ 27.672

Stability augmentation, auto-

matic, and power-operated systems. 

If the functioning of stability aug-

mentation or other automatic or 
power-operated systems is necessary to 
show compliance with the flight char-
acteristics requirements of this part, 
such systems must comply with § 27.671 
of this part and the following: 

(a) A warning which is clearly distin-

guishable to the pilot under expected 
flight conditions without requiring the 
pilot’s attention must be provided for 
any failure in the stability augmenta-
tion system or in any other automatic 
or power-operated system which could 
result in an unsafe condition if the 
pilot is unaware of the failure. Warning 
systems must not activate the control 
systems. 

(b) The design of the stability aug-

mentation system or of any other auto-
matic or power-operated system must 
allow initial counteraction of failures 
without requiring exceptional pilot 
skill or strength by overriding the fail-
ure by movement of the flight controls 
in the normal sense and deactivating 
the failed system. 

(c) It must be shown that after any 

single failure of the stability aug-
mentation system or any other auto-
matic or power-operated system— 

(1) The rotorcraft is safely control-

lable when the failure or malfunction 
occurs at any speed or altitude within 
the approved operating limitations; 

(2) The controllability and maneuver-

ability requirements of this part are 
met within a practical operational 
flight envelope (for example, speed, al-
titude, normal acceleration, and rotor-
craft configurations) which is described 
in the Rotorcraft Flight Manual; and 

(3) The trim and stability character-

istics are not impaired below a level 
needed to permit continued safe flight 
and landing. 

[Amdt. 27–21, 49 FR 44433, Nov. 6, 1984; 49 FR 
47594, Dec. 6, 1984] 

§ 27.673

Primary flight control. 

Primary flight controls are those 

used by the pilot for immediate control 
of pitch, roll, yaw, and vertical motion 
of the rotorcraft. 

[Amdt. 27–21, 49 FR 44434, Nov. 6, 1984] 

§ 27.674

Interconnected controls. 

Each primary flight control system 

must provide for safe flight and landing 
and operate independently after a mal-
function, failure, or jam of any auxil-
iary interconnected control. 

[Amdt. 27–26, 55 FR 8001, Mar. 6, 1990] 

§ 27.675

Stops. 

(a) Each control system must have 

stops that positively limit the range of 
motion of the pilot’s controls. 

(b) Each stop must be located in the 

system so that the range of travel of 
its control is not appreciably affected 
by— 

(1) Wear; 
(2) Slackness; or 
(3) Takeup adjustments. 
(c) Each stop must be able to with-

stand the loads corresponding to the 
design conditions for the system. 

(d) For each main rotor blade— 
(1) Stops that are appropriate to the 

blade design must be provided to limit 
travel of the blade about its hinge 
points; and 

(2) There must be means to keep the 

blade from hitting the droop stops dur-
ing any operation other than starting 
and stopping the rotor. 

(Secs. 313(a), 601, 603, 604, Federal Aviation 
Act of 1958 (49 U.S.C. 1354(a), 1421, 1423, 1424), 
sec. 6(c), Dept. of Transportation Act (49 
U.S.C. 1655(c))) 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–16, 43 FR 50599, Oct. 30, 
1978] 

§ 27.679

Control system locks. 

If there is a device to lock the con-

trol system with the rotorcraft on the 
ground or water, there must be means 
to— 

(a) Give unmistakable warning to the 

pilot when the lock is engaged; and 

(b) Prevent the lock from engaging in 

flight. 

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