spaschal on DSK3GDR082PROD with CFR

Pt. 27, App. B

14 CFR Ch. I (1-1-19 Edition)

longitudinal control force stability at critical combinations of weight and center of
gravity at the conditions specified in paragraph IV (b) or (c) of this appendix, as appropriate. The stick force must vary with speed
so that any substantial speed change results
in a stick force clearly perceptible to the
pilot. For single-pilot approval, the airspeed
must return to within 10 percent of the trim
speed when the control force is slowly released for each trim condition specified in
paragraph IV(b) of the this appendix.
(b) For single-pilot approval:
(1) Climb. Stability must be shown in climb
throughout the speed range 20 knots either
side of trim with - 
(i) The helicopter trimmed at VYI;
(ii) Landing gear retracted (if retractable);
and
(iii) Power required for limit climb rate (at
least 1,000 fpm) at VYI or maximum continuous power, whichever is less.
(2) Cruise. Stability must be shown
throughout the speed range from 0.7 to 1.1 VH
or VNEI, whichever is lower, not to exceed Section20
knots from trim with - 
(i) The helicopter trimmed and power adjusted for level flight at 0.9 VH or 0.9 VNEI,
whichever is lower; and
(ii) Landing gear retracted (if retractable).
(3) Slow cruise. Stability must be shown
throughout the speed range from 0.9 VMINI to
1.3 VMINI or 20 knots above trim speed, whichever is greater, with - 
(i) the helicopter trimmed and power adjusted for level flight at 1.1 VMINI; and
(ii) Landing gear retracted (if retractable).
(4) Descent. Stability must be shown
throughout the speed range 20 knots either
side of trim with - 
(i) The helicopter trimmed at 0.8 VH or 0.8
VNEI (or 0.8 VLE for the landing gear extended
case), whichever is lower;
(ii) Power required for 1,000 fpm descent at
trim speed; and
(iii) Landing gear extended and retracted,
if applicable.
(5) Approach. Stability must be shown
throughout the speed range from 0.7 times
the minimum recommended approach speed
to 20 knots above the maximum recommended approach speed with - 
(i) The helicopter trimmed at the recommended approach speed or speeds;
(ii) Landing gear extended and retracted, if
applicable; and
(iii) Power required to maintain a 3Section glide
path and power required to maintain the
steepest approach gradient for which approval is requested.
(c) Helicopters approved for a minimum
crew of two pilots must comply with the provisions of paragraphs IV(b)(2) and IV(b)(5) of
this appendix.
V. Static Lateral Directional Stability. (a)
Static directional stability must be positive
throughout the approved ranges of airspeed,

power, and vertical speed. In straight and
steady sideslips up to Section10Section from trim, directional control position must increase without discontinuity with the angle of sideslip,
except for a small range of sideslip angles
around trim. At greater angles up to the
maximum sideslip angle appropriate to the
type, increased directional control position
must produce an increased angle of sideslip.
It must be possible to maintain balanced
flight without exceptional pilot skill or
alertness.
(b) During sideslips up to Section10Section from trim
throughout the approved ranges of airspeed,
power, and vertical speed, there must be no
negative dihedral stability perceptible to the
pilot through lateral control motion or
force. Longitudinal cyclic movement with
sideslip must not be excessive.
VI. Dynamic stability. (a) For single-pilot
approval - 
(1) Any oscillation having a period of less
than 5 seconds must damp to 1-2 amplitude in
not more than one cycle.
(2) Any oscillation having a period of 5 seconds or more but less than 10 seconds must
damp to 1-2 amplitude in not more than two
cycles.
(3) Any oscillation having a period of 10
seconds or more but less than 20 seconds
must be damped.
(4) Any oscillation having a period of 20
seconds or more may not achieve double amplitude in less than 20 seconds.
(5) Any aperiodic response may not achieve
double amplitude in less than 6 seconds.
(b) For helicopters approved with a minimum crew of two pilots - 
(1) Any oscillation having a period of less
than 5 seconds must damp to 1-2 amplitude in
not more than two cycles.
(2) Any oscillation having a period of 5 seconds or more but less than 10 seconds must
be damped.
(3) Any oscillation having a period of 10
seconds or more may not achieve double amplitude in less than 10 seconds.
VII. Stability Augmentation System (SAS).
(a) If a SAS is used, the reliability of the
SAS must be related to the effects of its failure. Any SAS failure condition that would
prevent continued safe flight and landing
must be extremely improbable. It must be
shown that, for any failure condition of the
SAS that is not shown to be extremely improbable - 
(1) The helicopter is safely controllable
when the failure or malfunction occurs at
any speed or altitude within the approved
IFR operating limitations; and
(2) The overall flight characteristics of the
helicopter allow for prolonged instrument
flight without undue pilot effort. Additional
unrelated probable failures affecting the control system must be considered. In addition - 

568

VerDate Sep<11>2014

12:50 Apr 30, 2019

Jkt 247046

PO 00000

Frm 00578

Fmt 8010

Sfmt 8002

Y:\SGML\247046.XXX

247046