498 

14 CFR Ch. I (1–1–24 Edition) 

§ 27.231 

(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. 

§ 27.241

Ground resonance. 

The rotorcraft may have no dan-

gerous tendency to oscillate on the 
ground with the rotor turning. 

M

ISCELLANEOUS

F

LIGHT

R

EQUIREMENTS

 

§ 27.251

Vibration. 

Each part of the rotorcraft must be 

free from excessive vibration under 
each appropriate speed and power con-
dition. 

Subpart C—Strength Requirements 

G

ENERAL

 

§ 27.301

Loads. 

(a) Strength requirements are speci-

fied in terms of limit loads (the max-
imum loads to be expected in service) 
and ultimate loads (limit loads multi-
plied by prescribed factors of safety). 
Unless otherwise provided, prescribed 
loads are limit loads. 

(b) Unless otherwise provided, the 

specified air, ground, and water loads 
must be placed in equilibrium with in-
ertia forces, considering each item of 
mass in the rotorcraft. These loads 
must be distributed to closely approxi-
mate or conservatively represent ac-
tual conditions. 

(c) If deflections under load would 

significantly change the distribution of 
external or internal loads, this redis-
tribution must be taken into account. 

§ 27.303

Factor of safety. 

Unless otherwise provided, a factor of 

safety of 1.5 must be used. This factor 
applies to external and inertia loads 
unless its application to the resulting 
internal stresses is more conservative. 

§ 27.305

Strength and deformation. 

(a) The structure must be able to 

support limit loads without detri-
mental or permanent deformation. At 
any load up to limit loads, the defor-
mation may not interfere with safe op-
eration. 

(b) The structure must be able to 

support ultimate loads without failure. 
This must be shown by— 

(1) Applying ultimate loads to the 

structure in a static test for at least 
three seconds; or 

(2) Dynamic tests simulating actual 

load application. 

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