Federal Aviation Administration, DOT

Section 27.1121

from entering the engine intake system; and
(2) The air inlet ducts must be located or protected so as to minimize
the ingestion of foreign matter during
takeoff, landing, and taxiing.

spaschal on DSK3GDR082PROD with CFR

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-2, 33 FR 964, Jan. 26,
1968; Amdt. 27-23, 53 FR 34214, Sept. 2, 1988]

Section 27.1093 Induction system icing protection.
(a) Reciprocating engines. Each reciprocating engine air induction system
must have means to prevent and eliminate icing. Unless this is done by other
means, it must be shown that, in air
free of visible moisture at a temperature of 30 degrees F., and with the engines at 75 percent of maximum continuous power - 
(1) Each rotorcraft with sea level engines using conventional venturi carburetors has a preheater that can provide a heat rise of 90 degrees F.;
(2) Each rotorcraft with sea level engines using carburetors tending to prevent icing has a sheltered alternate
source of air, and that the preheat supplied to the alternate air intake is not
less than that provided by the engine
cooling air downstream of the cylinders;
(3) Each rotorcraft with altitude engines using conventional venturi carburetors has a preheater capable of
providing a heat rise of 120 degrees F.;
and
(4) Each rotorcraft with altitude engines using carburetors tending to prevent icing has a preheater that can
provide a heat rise of - 
(i) 100 degrees F.; or
(ii) If a fluid deicing system is used,
at least 40 degrees F.
(b) Turbine engine. (1) It must be
shown that each turbine engine and its
air inlet system can operate throughout the flight power range of the engine (including idling) - 
(i) Without accumulating ice on engine or inlet system components that
would adversely affect engine operation or cause a serious loss of power
under the icing conditions specified in
appendix C of Part 29 of this chapter;
and
(ii) In snow, both falling and blowing,
without adverse effect on engine oper-

ation, within the limitations established for the rotorcraft.
(2) Each turbine engine must idle for
30 minutes on the ground, with the air
bleed available for engine icing protection at its critical condition, without
adverse effect, in an atmosphere that is
at a temperature between 15Section and 30 SectionF
(between Section9Section and Section1 SectionC) and has a liquid water content not less than 0.3
gram 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 superchargers
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 operating condition because of supercharging.
(Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49
U.S.C. 1354(a), 1421, and 1423; sec. 6(c), 49
U.S.C. 1655(c))
[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-11, 41 FR 55470, Dec. 20,
1976; Amdt. 27-12, 42 FR 15045, Mar. 17, 1977;
Amdt. 27-20, 49 FR 6849, Feb. 23, 1984; Amdt.
27-23, 53 FR 34214, Sept. 2, 1988]

EXHAUST SYSTEM
Section 27.1121

General.

For each exhaust system - 
(a) There must be means for thermal
expansion of manifolds and pipes;
(b) There must be means to prevent
local hot spots;
(c) Exhaust gases must discharge
clear of the engine air intake, fuel system components, and drains;
(d) Each exhaust system part with a
surface hot enough to ignite flammable
fluids or vapors must be located or
shielded so that leakage from any system carrying flammable fluids or vapors will not result in a fire caused by
impingement of the fluids or vapors on

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