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Federal Aviation Administration, DOT

§ 25.951

§ 25.941

Inlet, engine, and exhaust

compatibility.

For airplanes using variable inlet or

exhaust system geometry, or both—

(a) The system comprised of the

inlet, engine (including thrust aug-
mentation systems, if incorporated),
and exhaust must be shown to function
properly under all operating conditions
for which approval is sought, including
all engine rotating speeds and power
settings, and engine inlet and exhaust
configurations;

(b) The dynamic effects of the oper-

ation of these (including consideration
of probable malfunctions) upon the aer-
odynamic control of the airplane may
not result in any condition that would
require exceptional skill, alertness, or
strength on the part of the pilot to
avoid exceeding an operational or
structural limitation of the airplane;
and

graph (b) of this section, the pilot
strength required may not exceed the
limits set forth in § 25.143(d), subject to
the conditions set forth in paragraphs
(e) and (f) of § 25.143.

[Amdt. 25–38, 41 FR 55467, Dec. 20, 1976, as
amended by Amdt. 25–121, 72 FR 44669, Aug. 8,
2007]

§ 25.943

Negative acceleration.

No hazardous malfunction of an en-

gine, an auxiliary power unit approved
for use in flight, or any component or
system associated with the powerplant
or auxiliary power unit may occur
when the airplane is operated at the
negative accelerations within the
flight envelopes prescribed in § 25.333.
This must be shown for the greatest
duration expected for the acceleration.

[Amdt. 25–40, 42 FR 15043, Mar. 17, 1977]

§ 25.945

Thrust or power augmentation

system.

(a)

General.

Each fluid injection sys-

tem must provide a flow of fluid at the
rate and pressure established for proper
engine functioning under each intended
operating condition. If the fluid can
freeze, fluid freezing may not damage
the airplane or adversely affect air-
plane performance.

(b)

Fluid tanks.

Each augmentation

system fluid tank must meet the fol-
lowing requirements:

(1) Each tank must be able to with-

stand without failure the vibration, in-
ertia, fluid, and structural loads that it
may be subject to in operation.

(2) The tanks as mounted in the air-

plane must be able to withstand with-
out failure or leakage an internal pres-
sure 1.5 times the maximum operating
pressure.

(3) If a vent is provided, the venting

must be effective under all normal
flight conditions.

(4) [Reserved]
(5) Each tank must have an expan-

sion space of not less than 2 percent of
the tank capacity. It must be impos-
sible to fill the expansion space inad-
vertently with the airplane in the nor-
mal ground attitude.

must be designed and located in ac-
cordance with § 25.1455 if—

(1) The augmentation system fluid is

subject to freezing; and

(2) The fluid may be drained in flight

or during ground operation.

(d) The augmentation liquid tank ca-

pacity available for the use of each en-
gine must be large enough to allow op-
eration of the airplane under the ap-
proved procedures for the use of liquid-
augmented power. The computation of
liquid consumption must be based on
the maximum approved rate appro-
priate for the desired engine output
and must include the effect of tempera-
ture on engine performance as well as
any other factors that might vary the
amount of liquid required.

(e) This section does not apply to fuel

injection systems.

[Amdt. 25–40, 42 FR 15043, Mar. 17, 1977, as
amended by Amdt. 25–72, 55 FR 29785, July 20,
1990; Amdt. 25–115, 69 FR 40527, July 2, 2004]

UEL

YSTEM

§ 25.951

General.

(a) Each fuel system must be con-

structed and arranged to ensure a flow
of fuel at a rate and pressure estab-
lished for proper engine and auxiliary
power unit functioning under each
likely operating condition, including
any maneuver for which certification is
requested and during which the engine

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