Code of Federal Regulations - Title 14

485

Federal Aviation Administration, DOT

§ 25.1093

(2) The air for proper fuel metering

and mixture distribution with the in-
duction system valves in any position.

(b) Each reciprocating engine must

have an alternate air source that pre-
vents the entry of rain, ice, or any
other foreign matter.

the cowling, unless—

(1) That part of the cowling is iso-

lated from the engine accessory section
by means of a fireproof diaphragm; or

(2) For reciprocating engines, there

are means to prevent the emergence of
backfire flames.

(d) For turbine engine powered air-

planes and airplanes incorporating aux-
iliary power units—

(1) There must be means to prevent

hazardous quantities of fuel leakage or
overflow from drains, vents, or other
components of flammable fluid systems
from entering the engine or auxiliary
power unit intake system; and

(2) The airplane must be designed to

prevent water or slush on the runway,
taxiway, or other airport operating
surfaces from being directed into the
engine or auxiliary power unit air inlet
ducts in hazardous quantities, and the
air inlet ducts must be located or pro-
tected so as to minimize the ingestion
of foreign matter during takeoff, land-
ing, and taxiing.

(e) If the engine induction system

contains parts or components that
could be damaged by foreign objects
entering the air inlet, it must be shown
by tests or, if appropriate, by analysis
that the induction system design can
withstand the foreign object ingestion
test conditions of §§ 33.76, 33.77 and
33.78(a)(1) of this chapter without fail-
ure of parts or components that could
create a hazard.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–38, 41 FR 55467, Dec. 20,
1976; Amdt. 25–40, 42 FR 15043, Mar. 17, 1977;
Amdt. 25–57, 49 FR 6849, Feb. 23, 1984; Amdt.
25–100, 65 FR 55854, Sept. 14, 2000]

§ 25.1093

Induction system icing pro-

tection.

(a)

Reciprocating engines. Each recip-

rocating engine air induction system
must have means to prevent and elimi-
nate icing. Unless this is done by other
means, it must be shown that, in air
free of visible moisture at a tempera-

ture of 30 F., each airplane with alti-
tude engines using—

(1) Conventional venturi carburetors

have a preheater that can provide a
heat rise of 120 F. with the engine at 60
percent of maximum continuous power;
or

(2) Carburetors tending to reduce the

probability of ice formation has a pre-
heater that can provide a heat rise of
100

F. with the engine at 60 percent of

maximum continuous power.

(b)

Turbine engines. (1) Each turbine

engine must operate throughout the
flight power range of the engine (in-
cluding idling), without the accumula-
tion of ice on the engine, inlet system
components, or airframe components
that would adversely affect engine op-
eration or cause a serious loss of power
or thrust—

(i) Under the icing conditions speci-

fied in appendix C, and

(ii) In falling and blowing snow with-

in the limitations established for the
airplane for such operation.

(2) Each turbine engine must idle for

30 minutes on the ground, with the air
bleed available for engine icing protec-
tion at its critical condition, without
adverse effect, in an atmosphere that is
at a temperature between 15

and 30

(between ¥9

and ¥1

C) and has a liq-

uid water content not less than 0.3
grams per cubic meter in the form of
drops having a mean effective diameter
not less than 20 microns, followed by
momentary operation at takeoff power
or thrust. During the 30 minutes of idle
operation, the engine may be run up
periodically to a moderate power or
thrust setting in a manner acceptable
to the Administrator.

(c)

Supercharged reciprocating engines.

For each engine having a supercharger
to pressurize the air before it enters
the carburetor, the heat rise in the air
caused by that supercharging at any
altitude may be utilized in determining
compliance with paragraph (a) of this
section if the heat rise utilized is that
which will be available, automatically,

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