310
14 CFR Ch. I (1–1–24 Edition)
§ 25.901
as not to endanger the airplane, per-
sonnel, or operation of the installed
electrical/electronic systems.
[Amdt. 25–123, 72 FR 63405, Nov. 8, 2007]
Subpart E—Powerplant
G
ENERAL
§ 25.901
Installation.
(a) For the purpose of this part, the
airplane powerplant installation in-
cludes each component 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—
(1) The installation must comply
with—
(i) The installation instructions pro-
vided under §§ 33.5 and 35.3 of this chap-
ter; and
(ii) The applicable provisions of this
subpart;
(2) The components of the installa-
tion must be constructed, arranged,
and installed so as to ensure their con-
tinued safe operation between normal
inspections or overhauls;
(3) The installation must be acces-
sible for necessary inspections and
maintenance; and
(4) The major components of the in-
stallation must be electrically bonded
to the other parts of the airplane.
(c) For each powerplant and auxiliary
power unit installation, it must be es-
tablished that no single failure or mal-
function or probable combination of
failures will jeopardize the safe oper-
ation of the airplane except that the
failure of structural elements need not
be considered if the probability of such
failure is extremely remote.
(d) Each auxiliary power unit instal-
lation must meet the applicable provi-
sions of this subpart.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5676, Apr. 8,
1970; Amdt. 25–40, 42 FR 15042, Mar. 17, 1977;
Amdt. 25–46, 43 FR 50597, Oct. 30, 1978; Amdt.
25–126, 73 FR 63345, Oct. 24, 2008]
§ 25.903
Engines.
(a)
Engine type certificate. (1) Each en-
gine must have a type certificate and
must meet the applicable requirements
of part 34 of this chapter.
(2) Each turbine engine must comply
with one of the following:
(i) Sections 33.76, 33.77 and 33.78 of
this chapter in effect on December 13,
2000, or as subsequently amended; or
(ii) Sections 33.77 and 33.78 of this
chapter in effect on April 30, 1998, or as
subsequently amended before Decem-
ber 13, 2000; or
(iii) Comply with § 33.77 of this chap-
ter in effect on October 31, 1974, or as
subsequently amended prior to April
30, 1998, unless that engine’s foreign ob-
ject ingestion service history has re-
sulted in an unsafe condition; or
(iv) Be shown to have a foreign object
ingestion service history in similar in-
stallation locations which has not re-
sulted in any unsafe condition.
N
OTE
: § 33.77 of this chapter in effect on Oc-
tober 31, 1974, was published in 14 CFR parts
1 to 59, Revised as of January 1, 1975. See 39
FR 35467, October 1, 1974.
(3) Each turbine engine must comply
with one of the following paragraphs:
(i) Section 33.68 of this chapter in ef-
fect on January 5, 2015, or as subse-
quently amended; or
(ii) Section 33.68 of this chapter in ef-
fect on March 26, 1984, or as subse-
quently amended before January 5,
2015, unless that engine’s ice accumula-
tion service history has resulted in an
unsafe condition; or
(iii) Section 33.68 of this chapter in
effect on October 31, 1974, or as subse-
quently amended prior to February 23,
1984, unless that engine’s ice accumula-
tion service history has resulted in an
unsafe condition; or
(iv) Be shown to have an ice accumu-
lation service history in similar instal-
lation locations which has not resulted
in any unsafe conditions.
(b)
Engine isolation. The powerplants
must be arranged and isolated from
each other to allow operation, in at
least one configuration, so that the
failure or malfunction of any engine, or
of any system that can affect the en-
gine, will not—
(1) Prevent the continued safe oper-
ation of the remaining engines; or
(2) Require immediate action by any
crewmember for continued safe oper-
ation.
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Federal Aviation Administration, DOT
§ 25.907
(c)
Control of engine rotation. There
must be means for stopping the rota-
tion of any engine individually in
flight, except that, for turbine engine
installations, the means for stopping
the rotation of any engine need be pro-
vided only where continued rotation
could jeopardize the safety of the air-
plane. Each component of the stopping
system on the engine side of the fire-
wall that might be exposed to fire must
be at least fire-resistant. If hydraulic
propeller feathering systems are used
for this purpose, the feathering lines
must be at least fire resistant under
the operating conditions that may be
expected to exist during feathering.
(d)
Turbine engine installations. For
turbine engine installations—
(1) Design precautions must be taken
to minimize the hazards to the airplane
in the event of an engine rotor failure
or of a fire originating within the en-
gine which burns through the engine
case.
(2) The powerplant systems associ-
ated with engine control devices, sys-
tems, and instrumentation, must be de-
signed to give reasonable assurance
that those engine operating limitations
that adversely affect turbine rotor
structural integrity will not be exceed-
ed in service.
(e)
Restart capability. (1) Means to re-
start any engine in flight must be pro-
vided.
(2) An altitude and airspeed envelope
must be established for in-flight engine
restarting, and each engine must have
a restart capability within that enve-
lope.
(3) For turbine engine powered air-
planes, if the minimum windmilling
speed of the engines, following the
inflight shutdown of all engines, is in-
sufficient to provide the necessary
electrical power for engine ignition, a
power source independent of the en-
gine-driven electrical power generating
system must be provided to permit in-
flight engine ignition for restarting.
(f)
Auxiliary Power Unit. Each auxil-
iary power unit must be approved or
meet the requirements of the category
for its intended use.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–23, 35 FR 5676, Apr. 8,
1970; Amdt. 25–40, 42 FR 15042, Mar. 17, 1977;
Amdt. 25–57, 49 FR 6848, Feb. 23, 1984; Amdt.
25–72, 55 FR 29784, July 20, 1990; Amdt. 25–73,
55 FR 32861, Aug. 10, 1990; Amdt. 25–94, 63 FR
8848, Feb. 23, 1998; Amdt. 25–95, 63 FR 14798,
Mar. 26, 1998; Amdt. 25–100, 65 FR 55854, Sept.
14, 2000; Amdt. 25–140, 79 FR 65525, Nov. 4,
2014; Amdt. No. 25–148, 87 FR 75710, Dec. 9,
2022; 88 FR 2813, Jan. 18, 2023]
§ 25.904
Automatic takeoff thrust con-
trol system (ATTCS).
Each applicant seeking approval for
installation of an engine power control
system that automatically resets the
power or thrust on the operating en-
gine(s) when any engine fails during
the takeoff must comply with the re-
quirements of appendix I of this part.
[Amdt. 25–62, 52 FR 43156, Nov. 9, 1987]
§ 25.905
Propellers.
(a) Each propeller must have a type
certificate.
(b) Engine power and propeller shaft
rotational speed may not exceed the
limits for which the propeller is certifi-
cated.
(c) The propeller blade pitch control
system must meet the requirements of
§§ 35.21, 35.23, 35.42 and 35.43 of this
chapter.
(d) Design precautions must be taken
to minimize the hazards to the airplane
in the event a propeller blade fails or is
released by a hub failure. The hazards
which must be considered include dam-
age to structure and vital systems due
to impact of a failed or released blade
and the unbalance created by such fail-
ure or release.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–54, 45 FR 60173, Sept.
11, 1980; Amdt. 25–57, 49 FR 6848, Feb. 23, 1984;
Amdt. 25–72, 55 FR 29784, July 20, 1990; Amdt.
25–126, 73 FR 63345, Oct. 24, 2008]
§ 25.907
Propeller vibration and fa-
tigue.
This section does not apply to fixed-
pitch wood propellers of conventional
design.
(a) The applicant must determine the
magnitude of the propeller vibration
stresses or loads, including any stress
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