Federal Aviation Administration, DOT
Section 25.941 Inlet, engine,
compatibility.

and

Section 25.951

exhaust

For airplanes using variable inlet or
exhaust system geometry, or both - 
(a) The system comprised of the
inlet, engine (including thrust augmentation 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 operation of these (including consideration
of probable malfunctions) upon the aerodynamic 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
(c) In showing compliance with paragraph (b) of this section, the pilot
strength required may not exceed the
limits set forth in Section 25.143(d), subject to
the conditions set forth in paragraphs
(e) and (f) of Section 25.143.
[Amdt. 25-38, 41 FR 55467, Dec. 20, 1976, as
amended by Amdt. 25-121, 72 FR 44669, Aug. 8,
2007]

Section 25.943

Negative acceleration.

No hazardous malfunction of an engine, 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 Section 25.333.
This must be shown for the greatest
duration expected for the acceleration.
[Amdt. 25-40, 42 FR 15043, Mar. 17, 1977]

spaschal on DSK3GDR082PROD with CFR

Section 25.945 Thrust or power augmentation
system.
(a) General. Each fluid injection system 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 airplane performance.

(b) Fluid tanks. Each augmentation
system fluid tank must meet the following requirements:
(1) Each tank must be able to withstand without failure the vibration, inertia, fluid, and structural loads that it
may be subject to in operation.
(2) The tanks as mounted in the airplane must be able to withstand without failure or leakage an internal pressure 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 expansion space of not less than 2 percent of
the tank capacity. It must be impossible to fill the expansion space inadvertently with the airplane in the normal ground attitude.
(c) Augmentation system drains
must be designed and located in accordance with Section 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 capacity available for the use of each engine must be large enough to allow operation of the airplane under the approved procedures for the use of liquidaugmented power. The computation of
liquid consumption must be based on
the maximum approved rate appropriate for the desired engine output
and must include the effect of temperature 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]

FUEL SYSTEM
Section 25.951 General.
(a) Each fuel system must be constructed and arranged to ensure a flow
of fuel at a rate and pressure established 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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