Code of Federal Regulations - Title 14

856

14 CFR Ch. I (1–1–14 Edition)

§ 33.37

applicant must show that foreign par-
ticles passing through the prescribed
filtering means will not critically im-
pair engine fuel system functioning.

(d) Each passage in the induction sys-

tem that conducts a mixture of fuel
and air must be self-draining, to pre-
vent a liquid lock in the cylinders, in
all attitudes that the applicant estab-
lishes as those the engine can have
when the aircraft in which it is in-
stalled is in the static ground attitude.

(e) If provided as part of the engine,

the applicant must show for each fluid
injection (other than fuel) system and
its controls that the flow of the in-
jected fluid is adequately controlled.

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as
amended by Amdt. 33–10, 49 FR 6851, Feb. 23,
1984]

§ 33.37

Ignition system.

Each spark ignition engine must

have a dual ignition system with at
least two spark plugs for each cylinder
and two separate electric circuits with
separate sources of electrical energy,
or have an ignition system of equiva-
lent in-flight reliability.

§ 33.39

Lubrication system.

(a) The lubrication system of the en-

gine must be designed and constructed
so that it will function properly in all
flight attitudes and atmospheric condi-
tions in which the airplane is expected
to operate. In wet sump engines, this
requirement must be met when only
one-half of the maximum lubricant
supply is in the engine.

(b) The lubrication system of the en-

gine must be designed and constructed
to allow installing a means of cooling
the lubricant.

the atmosphere to preclude leakage of
oil from excessive pressure in the
crankcase.

Subpart D—Block Tests;

Reciprocating Aircraft Engines

§ 33.41

Applicability.

This subpart prescribes the block

tests and inspections for reciprocating
aircraft engines.

§ 33.42

General.

Before each endurance test required

by this subpart, the adjustment setting
and functioning characteristic of each
component having an adjustment set-
ting and a functioning characteristic
that can be established independent of
installation on the engine must be es-
tablished and recorded.

[Amdt. 33–6, 39 FR 35465, Oct. 1, 1974]

§ 33.43

Vibration test.

(a) Each engine must undergo a vi-

bration survey to establish the tor-
sional and bending vibration character-
istics of the crankshaft and the pro-
peller shaft or other output shaft, over
the range of crankshaft speed and en-
gine power, under steady state and
transient conditions, from idling speed
to either 110 percent of the desired
maximum continuous speed rating or
103 percent of the maximum desired
takeoff speed rating, whichever is high-
er. The survey must be conducted
using, for airplane engines, the same
configuration of the propeller type
which is used for the endurance test,
and using, for other engines, the same
configuration of the loading device
type which is used for the endurance
test.

(b) The torsional and bending vibra-

tion stresses of the crankshaft and the
propeller shaft or other output shaft
may not exceed the endurance limit
stress of the material from which the
shaft is made. If the maximum stress
in the shaft cannot be shown to be
below the endurance limit by measure-
ment, the vibration frequency and am-
plitude must be measured. The peak
amplitude must be shown to produce a
stress below the endurance limit; if
not, the engine must be run at the con-
dition producing the peak amplitude
until, for steel shafts, 10 million stress
reversals have been sustained without
fatigue failure and, for other shafts,
until it is shown that fatigue will not
occur within the endurance limit stress
of the material.

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.

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