645
Federal Aviation Administration, DOT
§ 27.175
or (2) complete engine failure in the
case of other rotorcraft, must be con-
trollable over the range of speeds and
altitudes for which certification is re-
quested when such power failure occurs
with maximum continuous power and
critical weight. No corrective action
time delay for any condition following
power failure may be less than—
(i) For the cruise condition, one sec-
ond, or normal pilot reaction time
(whichever is greater); and
(ii) For any other condition, normal
pilot reaction time.
(f) For helicopters for which a V
NE
(power-off) is established under
§ 27.1505(c), compliance must be dem-
onstrated with the following require-
ments with critical weight, critical
center of gravity, and critical rotor
r.p.m.:
(1) The helicopter must be safely
slowed to V
NE
(power-off), without ex-
ceptional pilot skill, after the last op-
erating engine is made inoperative at
power-on V
NE
.
(2) At a speed of 1.1 V
NE
(power-off),
the margin of cyclic control must
allow satisfactory roll and pitch con-
trol with power off.
(Secs. 313(a), 601, 603, 604, and 605 of the Fed-
eral Aviation Act of 1958 (49 U.S.C. 1354(a),
1421, 1423, 1424, and 1425); and sec. 6(c) of the
Dept. of Transportation Act (49 U.S.C.
1655(c)))
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–2, 33 FR 963, Jan. 26,
1968; Amdt. 27–14, 43 FR 2325, Jan. 16, 1978;
Amdt. 27–21, 49 FR 44433, Nov. 6, 1984; Amdt.
27–44, 73 FR 10999, Feb. 29, 2008]
§ 27.151
Flight controls.
(a) Longitudinal, lateral, directional,
and collective controls may not exhibit
excessive breakout force, friction, or
preload.
(b) Control system forces and free
play may not inhibit a smooth, direct
rotorcraft response to control system
input.
[Amdt. 27–21, 49 FR 44433, Nov. 6, 1984]
§ 27.161
Trim control.
The trim control—
(a) Must trim any steady longitu-
dinal, lateral, and collective control
forces to zero in level flight at any ap-
propriate speed; and
(b) May not introduce any undesir-
able discontinuities in control force
gradients.
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–21, 49 FR 44433, Nov. 6,
1984]
§ 27.171
Stability: general.
The rotorcraft must be able to be
flown, without undue pilot fatigue or
strain, in any normal maneuver for a
period of time as long as that expected
in normal operation. At least three
landings and takeoffs must be made
during this demonstration.
§ 27.173
Static longitudinal stability.
(a) The longitudinal control must be
designed so that a rearward movement
of the control is necessary to obtain an
airspeed less than the trim speed, and a
forward movement of the control is
necessary to obtain an airspeed more
than the trim speed.
(b) Throughout the full range of alti-
tude for which certification is re-
quested, with the throttle and collec-
tive pitch held constant during the ma-
neuvers specified in § 27.175(a) through
(d), the slope of the control position
versus airspeed curve must be positive.
However, in limited flight conditions
or modes of operation determined by
the Administrator to be acceptable, the
slope of the control position versus air-
speed curve may be neutral or negative
if the rotorcraft possesses flight char-
acteristics that allow the pilot to
maintain airspeed within
±
5 knots of
the desired trim airspeed without ex-
ceptional piloting skill or alertness.
[Amdt. 27–21, 49 FR 44433, Nov. 6, 1984, as
amended by Amdt. 27–44, 73 FR 10999, Feb. 29,
2008]
§ 27.175
Demonstration of static longi-
tudinal stability.
(a)
Climb. Static longitudinal sta-
bility must be shown in the climb con-
dition at speeds from Vy ¥ 10 kt to Vy
+ 10 kt with—
(1) Critical weight;
(2) Critical center of gravity;
(3) Maximum continuous power;
(4) The landing gear retracted; and
(5) The rotorcraft trimmed at
V
Y.
(b)
Cruise. Static longitudinal sta-
bility must be shown in the cruise con-
dition at speeds from 0.8 V
NE
¥ 10 kt to
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