243 

Federal Aviation Administration, DOT 

§ 23.697 

(c) Fairleads must be installed so 

that they do not cause a change in 
cable direction of more than three de-
grees. 

(d) Clevis pins subject to load or mo-

tion and retained only by cotter pins 
may not be used in the control system. 

(e) Turnbuckles must be attached to 

parts having angular motion in a man-
ner that will positively prevent binding 
throughout the range of travel. 

(f) Tab control cables are not part of 

the primary control system and may be 
less than 

1

⁄

8

inch diameter in airplanes 

that are safely controllable with the 
tabs in the most adverse positions. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as 
amended by Amdt. 23–7, 34 FR 13091, Aug. 13, 
1969] 

§ 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 op-

eration, 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 air-
speed must be selected for the activa-
tion 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 clear-
ly distinguishable to the pilot under all 
expected flight conditions without re-
quiring 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 down-
ward pitching of the airplane by a 
quick release (emergency) control that 
meets the requirements of § 23.1329(b). 

(e) A preflight check of the complete 

system must be established and the 
procedure for this check made avail-
able in the Airplane Flight Manual 
(AFM). Preflight checks that are crit-
ical to the safety of the airplane must 

be included in the limitations section 
of the AFM. 

(f) For those airplanes whose design 

includes an autopilot system: 

(1) A quick release (emergency) con-

trol installed in accordance with 
§ 23.1329(b) may be used to meet the re-
quirements of paragraph (d), of this 
section, and 

(2) The pitch servo for that system 

may be used to provide the stall down-
ward pitching motion. 

(g) In showing compliance with 

§ 23.1309, the system must be evaluated 
to determine the effect that any an-
nounced 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 con-
ditions that may result from such fail-
ures. This evaluation must consider 
the hazards that would result from the 
airplane’s flight characteristics if the 
system was not provided, and the haz-
ard 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] 

§ 23.693

Joints. 

Control system joints (in push-pull 

systems) that are subject to angular 
motion, except those in ball and roller 
bearing systems, must have a special 
factor of safety of not less than 3.33 
with respect to the ultimate bearing 
strength of the softest material used as 
a bearing. This factor may be reduced 
to 2.0 for joints in cable control sys-
tems. For ball or roller bearings, the 
approved ratings may not be exceeded. 

§ 23.697

Wing flap controls. 

(a) Each wing flap control must be 

designed so that, when the flap has 
been placed in any position upon which 
compliance with the performance re-
quirements of this part is based, the 
flap will not move from that position 
unless the control is adjusted or is 
moved by the automatic operation of a 
flap load limiting device. 

(b) The rate of movement of the flaps 

in response to the operation of the pi-
lot’s control or automatic device must 
give satisfactory flight and perform-
ance characteristics under steady or 

VerDate Mar<15>2010 

10:12 Mar 18, 2014

Jkt 232046

PO 00000

Frm 00253

Fmt 8010

Sfmt 8010

Y:\SGML\232046.XXX

232046

pmangrum on DSK3VPTVN1PROD with CFR