727 

Federal Aviation Administration, DOT 

§ 33.87 

compliance can be shown shall be sub-
stantiated and defined in the installa-
tion instructions required by § 33.5. 

[Doc. No. 28107, 61 FR 28433, June 4, 1996, as 
amended by Amdt. 33–33, 77 FR 39624, July 5, 
2012; 77 FR 58301, Sept. 20, 2012] 

§ 33.84

Engine overtorque test. 

(a) If approval of a maximum engine 

overtorque is sought for an engine in-
corporating a free power turbine, com-
pliance with this section must be dem-
onstrated by testing. 

(1) The test may be run as part of the 

endurance test requirement of § 33.87. 
Alternatively, tests may be performed 
on a complete engine or equivalent 
testing on individual groups of compo-
nents. 

(2) Upon conclusion of tests con-

ducted to show compliance with this 
section, each engine part or individual 
groups of components must meet the 
requirements of § 33.93(a)(1) and (a)(2). 

(b) The test conditions must be as 

follows: 

(1) A total of 15 minutes run at the 

maximum engine overtorque to be ap-
proved. This may be done in separate 
runs, each being of at least 2

1

⁄

2

minutes 

duration. 

(2) A power turbine rotational speed 

equal to the highest speed at which the 
maximum overtorque can occur in 
service. The test speed may not be 
more than the limit speed of take-off 
or OEI ratings longer than 2 minutes. 

(3) For engines incorporating a reduc-

tion gearbox, a gearbox oil tempera-
ture equal to the maximum tempera-
ture when the maximum engine over-
torque could occur in service; and for 
all other engines, an oil temperature 
within the normal operating range. 

(4) A turbine entry gas temperature 

equal to the maximum steady state 
temperature approved for use during 
periods longer than 20 seconds when op-
erating at conditions not associated 
with 30-second or 2 minutes OEI rat-
ings. The requirement to run the test 
at the maximum approved steady state 
temperature may be waived by the 
FAA if the applicant can demonstrate 
that other testing provides substan-
tiation of the temperature effects when 
considered in combination with the 
other parameters identified in para-

graphs (b)(1), (b)(2) and (b)(3) of this 
section. 

[Doc. No. 2007–28502, 74 FR 45310, Sept. 2, 2009] 

§ 33.85

Calibration tests. 

(a) Each engine must be subjected to 

those calibration tests necessary to es-
tablish its power characteristics and 
the conditions for the endurance test 
specified § 33.87. The results of the 
power characteristics calibration tests 
form the basis for establishing the 
characteristics of the engine over its 
entire operating range of speeds, pres-
sures, temperatures, and altitudes. 
Power ratings are based upon standard 
atmospheric conditions with no 
airbleed for aircraft services and with 
only those accessories installed which 
are essential for engine functioning. 

(b) A power check at sea level condi-

tions must be accomplished on the en-
durance test engine after the endur-
ance test and any change in power 
characteristics which occurs during the 
endurance test must be determined. 
Measurements taken during the final 
portion of the endurance test may be 
used in showing compliance with the 
requirements of this paragraph. 

(c) In showing compliance with this 

section, each condition must stabilize 
before measurements are taken, except 
as permitted by paragraph (d) of this 
section. 

(d) In the case of engines having 30- 

second OEI, and 2-minute OEI ratings, 
measurements taken during the appli-
cable endurance test prescribed in 
§ 33.87(f) (1) through (8) may be used in 
showing compliance with the require-
ments of this section for these OEI rat-
ings. 

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as 
amended by Amdt. 33–6, 39 FR 35468, Oct. 1, 
1974; Amdt. 33–18, 61 FR 31328, June 19, 1996] 

§ 33.87

Endurance test. 

(a) 

General. 

Each engine must be sub-

jected to an endurance test that in-
cludes a total of at least 150 hours of 
operation and, depending upon the type 
and contemplated use of the engine, 
consists of one of the series of runs 
specified in paragraphs (b) through (g) 
of this section, as applicable. For en-
gines tested under paragraphs (b), (c), 

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