title-14-part-25-sec25-1091

327

Federal Aviation Administration, DOT

§ 25.1091

§ 25.1045

Cooling test procedures.

(a) Compliance with § 25.1041 must be

shown for the takeoff, climb, en route,
and landing stages of flight that cor-
respond to the applicable performance
requirements. The cooling tests must
be conducted with the airplane in the
configuration, and operating under the
conditions, that are critical relative to
cooling during each stage of flight. For
the cooling tests, a temperature is
‘‘stabilized’’ when its rate of change is
less than two degrees F. per minute.

(b) Temperatures must be stabilized

under the conditions from which entry
is made into each stage of flight being
investigated, unless the entry condi-
tion normally is not one during which
component and the engine fluid tem-
peratures would stabilize (in which
case, operation through the full entry
condition must be conducted before
entry into the stage of flight being in-
vestigated in order to allow tempera-
tures to reach their natural levels at
the time of entry). The takeoff cooling
test must be preceded by a period dur-
ing which the powerplant component
and engine fluid temperatures are sta-
bilized with the engines at ground idle.

flight must be continued until—

(1) The component and engine fluid

temperatures stabilize;

(2) The stage of flight is completed;

(3) An operating limitation is

reached.

(d) For reciprocating engine powered

airplanes, it may be assumed, for cool-
ing test purposes, that the takeoff
stage of flight is complete when the
airplane reaches an altitude of 1,500
feet above the takeoff surface or
reaches a point in the takeoff where
the transition from the takeoff to the
en route configuration is completed
and a speed is reached at which compli-
ance with § 25.121(c) is shown, which-
ever point is at a higher altitude. The
airplane must be in the following con-
figuration:

(1) Landing gear retracted.
(2) Wing flaps in the most favorable

position.

(3) Cowl flaps (or other means of con-

trolling the engine cooling supply) in
the position that provides adequate
cooling in the hot-day condition.

(4) Critical engine inoperative and its

propeller stopped.

(5) Remaining engines at the max-

imum continuous power available for
the altitude.

(e) For hull seaplanes and amphib-

ians, cooling must be shown during
taxiing downwind for 10 minutes, at
five knots above step speed.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–57, 49 FR 6848, Feb. 23,
1984]

NDUCTION

YSTEM

§ 25.1091

Air induction.

(a) The air induction system for each

engine and auxiliary power unit must
supply—

(1) The air required by that engine

and auxiliary power unit under each
operating condition for which certifi-
cation is requested; and

(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

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14 CFR Ch. I (1–1–24 Edition)

§ 25.1093

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. Except as pro-

vided in paragraph (b)(3) of this sec-
tion, each engine, with all icing protec-
tion systems operating, must:

(1) Operate throughout its flight

power range, including the minimum
descent idling speeds, in the icing con-
ditions defined in Appendices C and O
of this part, and Appendix D of part 33
of this chapter, and in falling and blow-
ing snow within the limitations estab-
lished for the airplane for such oper-
ation, without the accumulation of ice
on the engine, inlet system compo-

nents, or airframe components that
would do any of the following:

(i) Adversely affect installed engine

operation or cause a sustained loss of
power or thrust; or an unacceptable in-
crease in gas path operating tempera-
ture; or an airframe/engine incompati-
bility; or

(ii) Result in unacceptable temporary

power loss or engine damage; or

(iii) Cause a stall, surge, or flameout

or loss of engine controllability (for ex-
ample, rollback).

(2) Operate at ground idle speed for a

minimum of 30 minutes on the ground
in the following icing conditions shown
in Table 1 of this section, unless re-
placed by similar test conditions that
are more critical. These conditions
must be demonstrated with the avail-
able air bleed for icing protection at its
critical condition, without adverse ef-
fect, followed by an acceleration to
takeoff power or thrust in accordance
with the procedures defined in the air-
plane flight manual. During the idle
operation, the engine may be run up
periodically to a moderate power or
thrust setting in a manner acceptable
to the Administrator. Analysis may be
used to show ambient temperatures
below the tested temperature are less
critical. The applicant must document
the engine run-up procedure (including
the maximum time interval between
run-ups from idle, run-up power set-
ting, and duration at power), the asso-
ciated minimum ambient temperature,
and the maximum time interval. These
conditions must be used in the analysis
that establishes the airplane operating
limitations in accordance with § 25.1521.

(3) For the purposes of this section,

the icing conditions defined in appen-
dix O of this part, including the condi-
tions specified in Condition 3 of Table 1
of this section, are not applicable to
airplanes with a maximum takeoff
weight equal to or greater than 60,000
pounds.

ABLE

1—I

CING

ONDITIONS FOR

ROUND

ESTS

Condition

Total air temperature

Water concentration

(minimum)

Mean effective par-

ticle diameter

Demonstration

1. Rime ice condition

0 to 15

F (18 to

C) Liquid—0.3

g/m

........

15–25 microns ...........

By test, analysis or com-

bination of the two.

2. Glaze ice condition

20 to 30

F (

7 to

C).

Liquid—0.3 g/m