646
14 CFR Ch. I (1–1–14 Edition)
§ 27.177
0.8 V
NE
+ 10 kt or, if V
H
is less than 0.8
V
NE
, from V
H
¥10 kt to V
H
+ 10 kt,
with—
(1) Critical weight;
(2) Critical center of gravity;
(3) Power for level flight at 0.8 V
NE
or
V
H
, whichever is less;
(4) The landing gear retracted; and
(5) The rotorcraft trimmed at 0.8 V
NE
or V
H
, whichever is less.
(c)
V
NE
. Static longitudinal stability
must be shown at speeds from V
NE
¥ 20
kt to V
NE
with—
(1) Critical weight;
(2) Critical center of gravity;
(3) Power required for level flight at
V
NE
¥10 kt or maximum continuous
power, whichever is less;
(4) The landing gear retracted; and
(5) The rotorcraft trimmed at V
NE
¥
10 kt.
(d)
Autorotation. Static longitudinal
stability must be shown in autorota-
tion at—
(1) Airspeeds from the minimum rate
of descent airspeed¥10 kt to the min-
imum rate of descent airspeed + 10 kt,
with—
(i) Critical weight;
(ii) Critical center of gravity;
(iii) The landing gear extended; and
(iv) The rotorcraft trimmed at the
minimum rate of descent airspeed.
(2) Airspeeds from best angle-of-glide
airspeed¥10 kt to the best angle-of-
glide airspeed + 10 kt, with—
(i) Critical weight;
(ii) Critical center of gravity;
(iii) The landing gear retracted; and
(iv) The rotorcraft trimmed at the
best angle-of-glide airspeed.
(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. 27–11, 41 FR 55468, Dec. 20, 1976;
Amdt. 27–14, 43 FR 2325, Jan. 16, 1978; Amdt.
27–21, 49 FR 44433, Nov. 6, 1984; Amdt. 27–34, 62
FR 46173, Aug. 29, 1997; Amdt. 27–44, 73 FR
10999, Feb. 29, 2008]
§ 27.177
Static directional stability.
(a) The directional controls must op-
erate in such a manner that the sense
and direction of motion of the rotor-
craft following control displacement
are in the direction of the pedal motion
with the throttle and collective con-
trols held constant at the trim condi-
tions specified in § 27.175(a), (b), and (c).
Sideslip angles must increase with
steadily increasing directional control
deflection for sideslip angles up to the
lesser of—
(1)
±
25 degrees from trim at a speed of
15 knots less than the speed for min-
imum rate of descent varying linearly
to
±
10 degrees from trim at V
NE
;
(2) The steady state sideslip angles
established by § 27.351;
(3) A sideslip angle selected by the
applicant, which corresponds to a
sideforce of at least 0.1g; or
(4) The sideslip angle attained by
maximum directional control input.
(b) Sufficient cues must accompany
the sideslip to alert the pilot when the
aircraft is approaching the sideslip
limits.
(c) During the maneuver specified in
paragraph (a) of this section, the side-
slip angle versus directional control
position curve may have a negative
slope within a small range of angles
around trim, provided the desired head-
ing can be maintained without excep-
tional piloting skill or alertness.
[Amdt. 27–44, 73 FR 11000, Feb. 29, 2008]
G
ROUND AND
W
ATER
H
ANDLING
C
HARACTERISTICS
§ 27.231
General.
The rotorcraft must have satisfac-
tory ground and water handling char-
acteristics, including freedom from un-
controllable tendencies in any condi-
tion expected in operation.
§ 27.235
Taxiing condition.
The rotorcraft must be designed to
withstand the loads that would occur
when the rotorcraft is taxied over the
roughest ground that may reasonably
be expected in normal operation.
§ 27.239
Spray characteristics.
If certification for water operation is
requested, no spray characteristics
during taxiing, takeoff, or landing may
obscure the vision of the pilot or dam-
age the rotors, propellers, or other
parts of the rotorcraft.
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