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; 

or 

(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] 

I

NDUCTION

S

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. 

(c) If fuel can accumulate in any air 

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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