title-14-part-27-sec27-1091

541

Federal Aviation Administration, DOT

§ 27.1091

sea level conditions of at least 100 de-
grees F. must be established. The as-
sumed temperature lapse rate is 3.6 de-
grees F. per thousand feet of altitude
above sea level until a temperature of

69.7 degrees F. is reached, above

which altitude the temperature is con-
sidered constant at

69.7 degrees F.

However, for winterization installa-
tions, the applicant may select a max-
imum ambient atmospheric tempera-
ture corresponding to sea level condi-
tions of less than 100 degrees F.

(c)

Correction factor (except cylinder

barrels). Unless a more rational correc-
tion applies, temperatures of engine
fluids and power-plant components (ex-
cept cylinder barrels) for which tem-
perature limits are established, must
be corrected by adding to them the dif-
ference between the maximum ambient
atmospheric temperature and the tem-
perature of the ambient air at the time
of the first occurrence of the maximum
component or fluid temperature re-
corded during the cooling test.

(d)

Correction factor for cylinder barrel

temperatures. Cylinder barrel tempera-
tures must be corrected by adding to
them 0.7 times the difference between
the maximum ambient atmospheric
temperature and the temperature of
the ambient air at the time of the first
occurrence of the maximum cylinder
barrel temperature recorded during the
cooling test.

(Secs. 313(a), 601, 603, 604, and 605 of the Fed-
eral Aviation Act of 1958 (49 U.S.C. 1354(a),
1421, 1423, 1424, and 1425); and sec. 6(c) of the
Dept. of Transportation Act (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. 27–14, 43 FR 2325, Jan. 16, 1978]

§ 27.1045

Cooling test procedures.

(a)

General. For each stage of flight,

the cooling tests must be conducted
with the rotorcraft—

(1) In the configuration most critical

for cooling; and

(2) Under the conditions most critical

for cooling.

(b)

Temperature stabilization. For the

purpose of the cooling tests, a tempera-
ture is ‘‘stabilized’’ when its rate of
change is less than two degrees F. per
minute. The following component and

engine fluid temperature stabilization
rules apply:

(1) For each rotorcraft, and for each

stage of flight—

(i) The temperatures must be sta-

bilized under the conditions from
which entry is made into the stage of
flight being investigated; or

(ii) If the entry condition normally

does not allow temperatures to sta-
bilize, operation through the full entry
condition must be conducted before
entry into the stage of flight being in-
vestigated in order to allow the tem-
peratures to attain their natural levels
at the time of entry.

(2) For each helicopter during the

takeoff stage of flight, the climb at
takeoff power must be preceded by a
period of hover during which the tem-
peratures are stabilized.

(c)

Duration of test. For each stage of

flight the tests must be continued
until—

(1) The temperatures stabilize or 5

minutes after the occurrence of the
highest temperature recorded, as ap-
propriate to the test condition;

(2) That stage of flight is completed;

(3) An operating limitation is

reached.

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27–23, 53 FR 34214, Sept. 2,
1988]

NDUCTION

YSTEM

§ 27.1091

Air induction.

(a) The air induction system for each

engine must supply the air required by
that engine under the operating condi-
tions and maneuvers for which certifi-
cation is requested.

(b) Each cold air induction system

opening must be outside the cowling if
backfire flames can emerge.

induction system, that system must
have drains that discharge fuel—

(1) Clear of the rotorcraft; and
(2) Out of the path of exhaust flames.
(d) For turbine engine powered rotor-

craft—

(1) There must be means to prevent

hazardous quantities of fuel leakage or
overflow from drains, vents, or other
components of flammable fluid systems

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542

14 CFR Ch. I (1–1–24 Edition)

§ 27.1093

from entering the engine intake sys-
tem; and

(2) The air inlet ducts must be lo-

cated or protected so as to minimize
the ingestion of foreign matter during
takeoff, landing, and taxiing.

[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]

§ 27.1093

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 degrees F., and with the en-
gines at 75 percent of maximum contin-
uous power—

(1) Each rotorcraft with sea level en-

gines using conventional venturi car-
buretors has a preheater that can pro-
vide a heat rise of 90 degrees F.;

(2) Each rotorcraft with sea level en-

gines using carburetors tending to pre-
vent icing has a sheltered alternate
source of air, and that the preheat sup-
plied to the alternate air intake is not
less than that provided by the engine
cooling air downstream of the cyl-
inders;

(3) Each rotorcraft with altitude en-

gines using conventional venturi car-
buretors has a preheater capable of
providing a heat rise of 120 degrees F.;
and

(4) Each rotorcraft with altitude en-

gines using carburetors tending to pre-
vent 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 through-
out the flight power range of the en-
gine (including idling)—

(i) Without accumulating ice on en-

gine or inlet system components that
would adversely affect engine oper-
ation 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 estab-
lished for the rotorcraft.

(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

and

C) and has a liq-

uid 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 oper-
ating condition because of super-
charging.

(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]

XHAUST

YSTEM

§ 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;

clear of the engine air intake, fuel sys-
tem 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 sys-
tem carrying flammable fluids or va-
pors will not result in a fire caused by
impingement of the fluids or vapors on