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14 CFR Ch. I (1–1–24 Edition) 

§ 27.901 

Subpart E—Powerplant 

G

ENERAL

 

§ 27.901

Installation. 

(a) For the purpose of this part, the 

powerplant installation includes each 
part of the rotorcraft (other than the 
main and auxiliary rotor structures) 
that— 

(1) Is necessary for propulsion; 
(2) Affects the control of the major 

propulsive units; or 

(3) Affects the safety of the major 

propulsive units between normal in-
spections or overhauls. 

(b) For each powerplant installa-

tion— 

(1) Each component of the installa-

tion must be constructed, arranged, 
and installed to ensure its continued 
safe operation between normal inspec-
tions or overhauls for the range of tem-
perature and altitude for which ap-
proval is requested; 

(2) Accessibility must be provided to 

allow any inspection and maintenance 
necessary for continued airworthiness; 

(3) Electrical interconnections must 

be provided to prevent differences of 
potential between major components of 
the installation and the rest of the 
rotorcraft; 

(4) Axial and radial expansion of tur-

bine engines may not affect the safety 
of the installation; and 

(5) Design precautions must be taken 

to minimize the possibility of incorrect 
assembly of components and equipment 
essential to safe operation of the rotor-
craft, except where operation with the 
incorrect assembly can be shown to be 
extremely improbable. 

(c) The installation must comply 

with— 

(1) The installation instructions pro-

vided under § 33.5 of this chapter; and 

(2) The applicable provisions of this 

subpart. 

(Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49 
U.S.C. 1354(a), 1421, and 1423; sec. 6(c), 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. 27–12, 42 FR 15044, Mar. 17, 1977; 
Amdt. 27–23, 53 FR 34211, Sept. 2, 1988] 

§ 27.903

Engines. 

(a) 

Engine type certification. Each en-

gine must have an approved type cer-
tificate. Reciprocating engines for use 
in helicopters must be qualified in ac-
cordance with § 33.49(d) of this chapter 
or be otherwise approved for the in-
tended usage. 

(b) 

Engine or drive system cooling fan 

blade protection. (1) If an engine or rotor 
drive system cooling fan is installed, 
there must be a means to protect the 
rotorcraft and allow a safe landing if a 
fan blade fails. This must be shown by 
showing that— 

(i) The fan blades are contained in 

case of failure; 

(ii) Each fan is located so that a fail-

ure will not jeopardize safety; or 

(iii) Each fan blade can withstand an 

ultimate load of 1.5 times the cen-
trifugal force resulting from operation 
limited by the following: 

(A) For fans driven directly by the 

engine— 

(

1) The terminal engine r.p.m. under 

uncontrolled conditions; or 

(

2) An overspeed limiting device. 

(B) For fans driven by the rotor drive 

system, the maximum rotor drive sys-
tem rotational speed to be expected in 
service, including transients. 

(2) Unless a fatigue evaluation under 

§ 27.571 is conducted, it must be shown 
that cooling fan blades are not oper-
ating at resonant conditions within the 
operating limits of the rotorcraft. 

(c) 

Turbine engine installation. For 

turbine engine installations, the pow-
erplant systems associated with engine 
control devices, systems, and instru-
mentation must be designed to give 
reasonable assurance that those engine 
operating limitations that adversely 
affect turbine rotor structural integ-
rity will not be exceeded in service. 

(d) 

Restart capability. (1) A means to 

restart any engine in flight must be 
provided. 

(2) Except for the in-flight shutdown 

of all engines, engine restart capability 
must be demonstrated throughout a 
flight envelope for the rotorcraft. 

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