328
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.
T
ABLE
1—I
CING
C
ONDITIONS FOR
G
ROUND
T
ESTS
Condition
Total air temperature
Water concentration
(minimum)
Mean effective par-
ticle diameter
Demonstration
1. Rime ice condition
0 to 15
°
F (18 to
¥
9
°
C) Liquid—0.3
g/m
3
........
15–25 microns ...........
By test, analysis or com-
bination of the two.
2. Glaze ice condition
20 to 30
°
F (
¥
7 to
¥
1
°
C).
Liquid—0.3 g/m
3
........
15–25 microns ...........
By test, analysis or com-
bination of the two.
VerDate Sep<11>2014
09:06 Jun 28, 2024
Jkt 262046
PO 00000
Frm 00338
Fmt 8010
Sfmt 8010
Y:\SGML\262046.XXX
262046
jspears on DSK121TN23PROD with CFR
329
Federal Aviation Administration, DOT
§ 25.1105
T
ABLE
1—I
CING
C
ONDITIONS FOR
G
ROUND
T
ESTS
—Continued
Condition
Total air temperature
Water concentration
(minimum)
Mean effective par-
ticle diameter
Demonstration
3. Large drop condi-
tion.
15 to 30
°
F (
¥
9 to
¥
1
°
C).
Liquid—0.3 g/m
3
........
100 microns (min-
imum).
By test, analysis or com-
bination of the two.
(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,
for the applicable altitude and oper-
ating condition because of super-
charging.
[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.
25–72, 55 FR 29785, July 20, 1990; Amdt. 25–140,
79 FR 65526, Nov. 4, 2014]
§ 25.1101
Carburetor air preheater de-
sign.
Each carburetor air preheater must
be designed and constructed to—
(a) Ensure ventilation of the pre-
heater when the engine is operated in
cold air;
(b) Allow inspection of the exhaust
manifold parts that it surrounds; and
(c) Allow inspection of critical parts
of the preheater itself.
§ 25.1103
Induction system ducts and
air duct systems.
(a) Each induction system duct up-
stream of the first stage of the engine
supercharger and of the auxiliary
power unit compressor must have a
drain to prevent the hazardous accu-
mulation of fuel and moisture in the
ground attitude. No drain may dis-
charge where it might cause a fire haz-
ard.
(b) Each induction system duct must
be—
(1) Strong enough to prevent induc-
tion system failures resulting from
normal backfire conditions; and
(2) Fire-resistant if it is in any fire
zone for which a fire-extinguishing sys-
tem is required, except that ducts for
auxiliary power units must be fireproof
within the auxiliary power unit fire
zone.
(c) Each duct connected to compo-
nents between which relative motion
could exist must have means for flexi-
bility.
(d) For turbine engine and auxiliary
power unit bleed air duct systems, no
hazard may result if a duct failure oc-
curs at any point between the air duct
source and the airplane unit served by
the air.
(e) Each auxiliary power unit induc-
tion system duct must be fireproof for
a sufficient distance upstream of the
auxiliary power unit compartment to
prevent hot gas reverse flow from burn-
ing through auxiliary power unit ducts
and entering any other compartment
or area of the airplane in which a haz-
ard would be created resulting from the
entry of hot gases. The materials used
to form the remainder of the induction
system duct and plenum chamber of
the auxiliary power unit must be capa-
ble of resisting the maximum heat con-
ditions likely to occur.
(f) Each auxiliary power unit induc-
tion system duct must be constructed
of materials that will not absorb or
trap hazardous quantities of flammable
fluids that could be ignited in the
event of a surge or reverse flow condi-
tion.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–46, 43 FR 50597, Oct. 30,
1978]
§ 25.1105
Induction system screens.
If induction system screens are
used—
(a) Each screen must be upstream of
the carburetor;
(b) No screen may be in any part of
the induction system that is the only
passage through which air can reach
the engine, unless it can be deiced by
heated air;
(c) No screen may be deiced by alco-
hol alone; and
VerDate Sep<11>2014
09:06 Jun 28, 2024
Jkt 262046
PO 00000
Frm 00339
Fmt 8010
Sfmt 8010
Y:\SGML\262046.XXX
262046
jspears on DSK121TN23PROD with CFR