title-14-part-27-sec27-903

528

14 CFR Ch. I (1–1–24 Edition)

§ 27.901

Subpart E—Powerplant

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.

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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Federal Aviation Administration, DOT

§ 27.923

(3) Following the in-flight shutdown

of all engines, in-flight engine restart
capability must be provided.

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–11, 41 FR 55469, Dec. 20,
1976; Amdt. 27–23, 53 FR 34211, Sept. 2, 1988;
Amdt. 27–44, 73 FR 11000, Feb. 29, 2008; Amdt.
27–51, 88 FR 8737, Feb. 10, 2023]

§ 27.907

Engine vibration.

(a) Each engine must be installed to

prevent the harmful vibration of any
part of the engine or rotorcraft.

(b) The addition of the rotor and the

rotor drive system to the engine may
not subject the principal rotating parts
of the engine to excessive vibration
stresses. This must be shown by a vi-
bration investigation.

may be subjected to excessive vibra-
tion stresses.

OTOR

RIVE

YSTEM

§ 27.917

Design.

(a) Each rotor drive system must in-

corporate a unit for each engine to
automatically disengage that engine
from the main and auxiliary rotors if
that engine fails.

(b) Each rotor drive system must be

arranged so that each rotor necessary
for control in autorotation will con-
tinue to be driven by the main rotors
after disengagement of the engine from
the main and auxiliary rotors.

in the rotor drive system, it must be
located so as to allow continued con-
trol of the rotorcraft when the device
is operating.

(d) The rotor drive system includes

any part necessary to transmit power
from the engines to the rotor hubs.
This includes gear boxes, shafting, uni-
versal joints, couplings, rotor brake as-
semblies, clutches, supporting bearings
for shafting, any attendant accessory
pads or drives, and any cooling fans
that are a part of, attached to, or
mounted on the rotor drive system.

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–11, 41 FR 55469, Dec. 20,
1976]

§ 27.921

Rotor brake.

If there is a means to control the ro-

tation of the rotor drive system inde-

pendently of the engine, any limita-
tions on the use of that means must be
specified, and the control for that
means must be guarded to prevent in-
advertent operation.

§ 27.923

Rotor drive system and con-

trol mechanism tests.

(a) Each part tested as prescribed in

this section must be in a serviceable
condition at the end of the tests. No in-
tervening disassembly which might af-
fect test results may be conducted.

(b) Each rotor drive system and con-

trol mechanism must be tested for not
less than 100 hours. The test must be
conducted on the rotorcraft, and the
torque must be absorbed by the rotors
to be installed, except that other
ground or flight test facilities with
other appropriate methods of torque
absorption may be used if the condi-
tions of support and vibration closely
simulate the conditions that would
exist during a test on the rotorcraft.

scribed in paragraph (b) of this section
must be run at not less than maximum
continuous torque and the maximum
speed for use with maximum contin-
uous torque. In this test, the main
rotor controls must be set in the posi-
tion that will give maximum longitu-
dinal cyclic pitch change to simulate
forward flight. The auxiliary rotor con-
trols must be in the position for nor-
mal operation under the conditions of
the test.

(d) A 30-hour or, for rotorcraft for

which the use of either 30-minute OEI
power or continuous OEI power is re-
quested, a 25-hour part of the test pre-
scribed in paragraph (b) of this section
must be run at not less than 75 percent
of maximum continuous torque and the
minimum speed for use with 75 percent
of maximum continuous torque. The
main and auxiliary rotor controls must
be in the position for normal operation
under the conditions of the test.

(e) A 10-hour part of the test pre-

scribed in paragraph (b) of this section
must be run at not less than takeoff
torque and the maximum speed for use
with takeoff torque. The main and aux-
iliary rotor controls must be in the
normal position for vertical ascent.

(1) For multiengine rotorcraft for

which the use of 2

⁄

minute OEI power