709 

Federal Aviation Administration, DOT 

§ 33.49 

occur within the endurance limit stress 
of the material. 

(c) Each accessory drive and mount-

ing attachment must be loaded, with 
the loads imposed by each accessory 
used only for an aircraft service being 
the limit load specified by the appli-
cant for the drive or attachment point. 

(d) The vibration survey described in 

paragraph (a) of this section must be 
repeated with that cylinder not firing 
which has the most adverse vibration 
effect, in order to establish the condi-
tions under which the engine can be op-
erated safely in that abnormal state. 
However, for this vibration survey, the 
engine speed range need only extend 
from idle to the maximum desired 
takeoff speed, and compliance with 
paragraph (b) of this section need not 
be shown. 

[Amdt. 33–6, 39 FR 35465, Oct. 1, 1974, as 
amended by Amdt. 33–10, 49 FR 6851, Feb. 23, 
1984] 

§ 33.45

Calibration tests. 

(a) Each engine must be subjected to 

the calibration tests necessary to es-
tablish its power characteristics and 
the conditions for the endurance test 
specified in § 33.49. The results of the 
power characteristics calibration tests 
form the basis for establishing the 
characteristics of the engine over its 
entire operating range of crankshaft 
rotational speeds, manifold pressures, 
fuel/air mixture settings, and altitudes. 
Power ratings are based upon standard 
atmospheric conditions with only those 
accessories installed which are essen-
tial 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. Any change in power charac-
teristics which occurs during the en-
durance 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. 

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as 
amended by Amdt. 33–6, 39 FR 35465, Oct. 1, 
1974] 

§ 33.47

Detonation test. 

Each engine must be tested to estab-

lish that the engine can function with-

out detonation throughout its range of 
intended conditions of operation. 

§ 33.49

Endurance test. 

(a) 

General. Each engine must be sub-

jected to an endurance test that in-
cludes a total of 150 hours of operation 
(except as provided in paragraph 
(e)(1)(iii) of this section) and, depend-
ing upon the type and contemplated 
use of the engine, consists of one of the 
series of runs specified in paragraphs 
(b) through (e) of this section, as appli-
cable. The runs must be made in the 
order found appropriate by the Admin-
istrator for the particular engine being 
tested. During the endurance test the 
engine power and the crankshaft rota-
tional speed must be kept within 

±

3 

percent of the rated values. During the 
runs at rated takeoff power and for at 
least 35 hours at rated maximum con-
tinuous power, one cylinder must be 
operated at not less than the limiting 
temperature, the other cylinders must 
be operated at a temperature not lower 
than 50 degrees F. below the limiting 
temperature, and the oil inlet tempera-
ture must be maintained within 

±

10 de-

grees F. of the limiting temperature. 
An engine that is equipped with a pro-
peller shaft must be fitted for the en-
durance test with a propeller that 
thrust-loads the engine to the max-
imum thrust which the engine is de-
signed to resist at each applicable op-
erating condition specified in this sec-
tion. Each accessory drive and mount-
ing attachment must be loaded. During 
operation at rated takeoff power and 
rated maximum continuous power, the 
load imposed by each accessory used 
only for an aircraft service must be the 
limit load specified by the applicant 
for the engine drive or attachment 
point. 

(b) 

Unsupercharged engines and en-

gines incorporating a gear-driven single- 
speed supercharger. For engines not in-
corporating a supercharger and for en-
gines incorporating a gear-driven sin-
gle-speed supercharger the applicant 
must conduct the following runs: 

(1) A 30-hour run consisting of alter-

nate periods of 5 minutes at rated take-
off power with takeoff speed, and 5 
minutes at maximum best economy 
cruising power or maximum rec-
ommended cruising power. 

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14 CFR Ch. I (1–1–24 Edition) 

§ 33.49 

(2) A 20-hour run consisting of alter-

nate periods of 1

1

⁄

2

hours at rated max-

imum continuous power with max-
imum continuous speed, and 

1

⁄

2

hour at 

75 percent rated maximum continuous 
power and 91 percent maximum contin-
uous speed. 

(3) A 20-hour run consisting of alter-

nate periods of 1

1

⁄

2

hours at rated max-

imum continuous power with max-
imum continuous speed, and 

1

⁄

2

hour at 

70 percent rated maximum continuous 
power and 89 percent maximum contin-
uous speed. 

(4) A 20-hour run consisting of alter-

nate periods of 1

1

⁄

2

hours at rated max-

imum continuous power with max-
imum continuous speed, and 

1

⁄

2

hour at 

65 percent rated maximum continuous 
power and 87 percent maximum contin-
uous speed. 

(5) A 20-hour run consisting of alter-

nate periods of 1

1

⁄

2

hours at rated max-

imum continuous power with max-
imum continuous speed, and 

1

⁄

2

hour at 

60 percent rated maximum continuous 
power and 84.5 percent maximum con-
tinuous speed. 

(6) A 20-hour run consisting of alter-

nate periods of 1

1

⁄

2

hours at rated max-

imum continuous power with max-
imum continuous speed, and 

1

⁄

2

hour at 

50 percent rated maximum continuous 
power and 79.5 percent maximum con-
tinuous speed. 

(7) A 20-hour run consisting of alter-

nate periods of 2

1

⁄

2

hours at rated max-

imum continuous power with max-
imum continuous speed, and 2

1

⁄

2

hours 

at maximum best economy cruising 
power or at maximum recommended 
cruising power. 

(c) 

Engines incorporating a gear-driven 

two-speed supercharger. For engines in-
corporating a gear-driven two-speed su-
percharger the applicant must conduct 
the following runs: 

(1) A 30-hour run consisting of alter-

nate periods in the lower gear ratio of 
5 minutes at rated takeoff power with 
takeoff speed, and 5 minutes at max-
imum best economy cruising power or 
at maximum recommended cruising 
power. If a takeoff power rating is de-
sired in the higher gear ratio, 15 hours 
of the 30-hour run must be made in the 
higher gear ratio in alternate periods 
of 5 minutes at the observed horse-
power obtainable with the takeoff crit-

ical altitude manifold pressure and 
takeoff speed, and 5 minutes at 70 per-
cent high ratio rated maximum contin-
uous power and 89 percent high ratio 
maximum continuous speed. 

(2) A 15-hour run consisting of alter-

nate periods in the lower gear ratio of 
1 hour at rated maximum continuous 
power with maximum continuous 
speed, and 

1

⁄

2

hour at 75 percent rated 

maximum continuous power and 91 per-
cent maximum continuous speed. 

(3) A 15-hour run consisting of alter-

nate periods in the lower gear ratio of 
1 hour at rated maximum continuous 
power with maximum continuous 
speed, and 

1

⁄

2

hour at 70 percent rated 

maximum continuous power and 89 per-
cent maximum continuous speed. 

(4) A 30-hour run in the higher gear 

ratio at rated maximum continuous 
power with maximum continuous 
speed. 

(5) A 5-hour run consisting of alter-

nate periods of 5 minutes in each of the 
supercharger gear ratios. The first 5 
minutes of the test must be made at 
maximum continuous speed in the 
higher gear ratio and the observed 
horsepower obtainable with 90 percent 
of maximum continuous manifold pres-
sure in the higher gear ratio under sea 
level conditions. The condition for op-
eration for the alternate 5 minutes in 
the lower gear ratio must be that ob-
tained by shifting to the lower gear 
ratio at constant speed. 

(6) A 10-hour run consisting of alter-

nate periods in the lower gear ratio of 
1 hour at rated maximum continuous 
power with maximum continuous 
speed, and 1 hour at 65 percent rated 
maximum continuous power and 87 per-
cent maximum continuous speed. 

(7) A 10-hour run consisting of alter-

nate periods in the lower gear ratio of 
1 hour at rated maximum continuous 
power with maximum continuous 
speed, and 1 hour at 60 percent rated 
maximum continuous power and 84.5 
percent maximum continuous speed. 

(8) A 10-hour run consisting of alter-

nate periods in the lower gear ratio of 
1 hour at rated maximum continuous 
power with maximum continuous 
speed, and 1 hour at 50 percent rated 
maximum continuous power and 79.5 
percent maximum continuous speed. 

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Federal Aviation Administration, DOT 

§ 33.49 

(9) A 20-hour run consisting of alter-

nate periods in the lower gear ratio of 
2 hours at rated maximum continuous 
power with maximum continuous 
speed, and 2 hours at maximum best 
economy cruising power and speed or 
at maximum recommended cruising 
power. 

(10) A 5-hour run in the lower gear 

ratio at maximum best economy cruis-
ing power and speed or at maximum 
recommended cruising power and 
speed. 

Where simulated altitude test equip-
ment is not available when operating 
in the higher gear ratio, the runs may 
be made at the observed horsepower ob-
tained with the critical altitude mani-
fold pressure or specified percentages 
thereof, and the fuel-air mixtures may 
be adjusted to be rich enough to sup-
press detonation. 

(d) 

Helicopter engines. To be eligible 

for use on a helicopter each engine 
must either comply with paragraphs 
(a) through (j) of § 29.923 of this chap-
ter, or must undergo the following se-
ries of runs: 

(1) A 35-hour run consisting of alter-

nate periods of 30 minutes each at 
rated takeoff power with takeoff speed, 
and at rated maximum continuous 
power with maximum continuous 
speed. 

(2) A 25-hour run consisting of alter-

nate periods of 2

1

⁄

2

hours each at rated 

maximum continuous power with max-
imum continuous speed, and at 70 per-
cent rated maximum continuous power 
with maximum continuous speed. 

(3) A 25-hour run consisting of alter-

nate periods of 2

1

⁄

2

hours each at rated 

maximum continuous power with max-
imum continuous speed, and at 70 per-
cent rated maximum continuous power 
with 80 to 90 percent maximum contin-
uous speed. 

(4) A 25-hour run consisting of alter-

nate periods of 2

1

⁄

2

hours each at 30 per-

cent rated maximum continuous power 
with takeoff speed, and at 30 percent 
rated maximum continuous power with 
80 to 90 percent maximum continuous 
speed. 

(5) A 25-hour run consisting of alter-

nate periods of 2

1

⁄

2

hours each at 80 per-

cent rated maximum continuous power 
with takeoff speed, and at either rated 
maximum continuous power with 110 

percent maximum continuous speed or 
at rated takeoff power with 103 percent 
takeoff speed, whichever results in the 
greater speed. 

(6) A 15-hour run at 105 percent rated 

maximum continuous power with 105 
percent maximum continuous speed or 
at full throttle and corresponding 
speed at standard sea level carburetor 
entrance pressure, if 105 percent of the 
rated maximum continuous power is 
not exceeded. 

(e) 

Turbosupercharged engines. For en-

gines incorporating a turbo-
supercharger the following apply ex-
cept that altitude testing may be simu-
lated provided the applicant shows that 
the engine and supercharger are being 
subjected to mechanical loads and op-
erating temperatures no less severe 
than if run at actual altitude condi-
tions: 

(1) For engines used in airplanes the 

applicant must conduct the runs speci-
fied in paragraph (b) of this section, ex-
cept— 

(i) The entire run specified in para-

graph (b)(1) of this section must be 
made at sea level altitude pressure; 

(ii) The portions of the runs specified 

in paragraphs (b)(2) through (7) of this 
section at rated maximum continuous 
power must be made at critical alti-
tude pressure, and the portions of the 
runs at other power must be made at 
8,000 feet altitude pressure; and 

(iii) The turbosupercharger used dur-

ing the 150-hour endurance test must 
be run on the bench for an additional 50 
hours at the limiting turbine wheel 
inlet gas temperature and rotational 
speed for rated maximum continuous 
power operation unless the limiting 
temperature and speed are maintained 
during 50 hours of the rated maximum 
continuous power operation. 

(2) For engines used in helicopters 

the applicant must conduct the runs 
specified in paragraph (d) of this sec-
tion, except— 

(i) The entire run specified in para-

graph (d)(1) of this section must be 
made at critical altitude pressure; 

(ii) The portions of the runs specified 

in paragraphs (d)(2) and (3) of this sec-
tion at rated maximum continuous 
power must be made at critical alti-
tude pressure and the portions of the 

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14 CFR Ch. I (1–1–24 Edition) 

§ 33.51 

runs at other power must be made at 
8,000 feet altitude pressure; 

(iii) The entire run specified in para-

graph (d)(4) of this section must be 
made at 8,000 feet altitude pressure; 

(iv) The portion of the runs specified 

in paragraph (d)(5) of this section at 80 
percent of rated maximum continuous 
power must be made at 8,000 feet alti-
tude pressure and the portions of the 
runs at other power must be made at 
critical altitude pressure; 

(v) The entire run specified in para-

graph (d)(6) of this section must be 
made at critical altitude pressure; and 

(vi) The turbosupercharger used dur-

ing the endurance test must be run on 
the bench for 50 hours at the limiting 
turbine wheel inlet gas temperature 
and rotational speed for rated max-
imum continuous power operation un-
less the limiting temperature and 
speed are maintained during 50 hours of 
the rated maximum continuous power 
operation. 

[Amdt. 33–3, 32 FR 3736, Mar. 4, 1967, as 
amended by Amdt. 33–6, 39 FR 35465, Oct. 1, 
1974; Amdt. 33–10, 49 FR 6851, Feb. 23, 1984] 

§ 33.51

Operation test. 

The operation test must include the 

testing found necessary by the Admin-
istrator to demonstrate backfire char-
acteristics, starting, idling, accelera-
tion, overspeeding, functioning of pro-
peller and ignition, and any other oper-
ational characteristic of the engine. If 
the engine incorporates a multispeed 
supercharger drive, the design and con-
struction must allow the supercharger 
to be shifted from operation at the 
lower speed ratio to the higher and the 
power appropriate to the manifold 
pressure and speed settings for rated 
maximum continuous power at the 
higher supercharger speed ratio must 
be obtainable within five seconds. 

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as 
amended by Amdt. 33–3, 32 FR 3737, Mar. 4, 
1967] 

§ 33.53

Engine system and component 

tests. 

(a) For those systems and compo-

nents that cannot be adequately sub-
stantiated in accordance with endur-
ance testing of § 33.49, the applicant 
must conduct additional tests to dem-
onstrate that systems or components 

are able to perform the intended func-
tions in all declared environmental and 
operating conditions. 

(b) Temperature limits must be es-

tablished for each component that re-
quires temperature controlling provi-
sions in the aircraft installation to as-
sure satisfactory functioning, reli-
ability, and durability. 

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as 
amended by Amdt. 33–26, 73 FR 48285, Aug. 19, 
2008] 

§ 33.55

Teardown inspection. 

After completing the endurance 

test— 

(a) Each engine must be completely 

disassembled; 

(b) Each component having an ad-

justment setting and a functioning 
characteristic that can be established 
independent of installation on the en-
gine must retain each setting and func-
tioning characteristic within the limits 
that were established and recorded at 
the beginning of the test; and 

(c) Each engine component must con-

form to the type design and be eligible 
for incorporation into an engine for 
continued operation, in accordance 
with information submitted in compli-
ance with § 33.4. 

[Amdt. 33–6, 39 FR 35466, Oct. 1, 1974, as 
amended by Amdt. 33–9, 45 FR 60181, Sept. 11, 
1980] 

§ 33.57

General conduct of block tests. 

(a) The applicant may, in conducting 

the block tests, use separate engines of 
identical design and construction in 
the vibration, calibration, detonation, 
endurance, and operation tests, except 
that, if a separate engine is used for 
the endurance test it must be subjected 
to a calibration check before starting 
the endurance test. 

(b) The applicant may service and 

make minor repairs to the engine dur-
ing the block tests in accordance with 
the service and maintenance instruc-
tions submitted in compliance with 
§ 33.4. If the frequency of the service is 
excessive, or the number of stops due 
to engine malfunction is excessive, or a 
major repair, or replacement of a part 
is found necessary during the block 
tests or as the result of findings from 
the teardown inspection, the engine or 

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