TM 1-1500-204-23-1
between
pump
and
main
bearing
is
negligible.
However, centrifugal force increases oil pressure at
crankpins which increases flow through the bearings and
sprays more oil on cylinder walls. The rings do not
follow the cylinder as closely at higher speeds, and a
greater amount of oil Is passed to the combustion
chamber instead of being scraped back to the
crankcase.
(b)
Engine temperature. High engine
temperature and low oil viscosity tend to increase losses
of oil from crankcase seals and breathers. Oil loss
increases due to increased blowby, or gas flow, past
piston rings at higher engine speeds. Blowby raises
crankcase pressure and forces oil or oil vapor out of the
crankcase.
(c)
Engine wear. Engine wear in the
form of worn bearings increases clearance and allows
increased oil loss. Worn pistons and cylinders provide
space for thicker oil films and increase loss due to
failure of rings to seal.
(d)
Lubricant
characteristics.
An
increase in oil viscosity decreases oil consumption only
up to the point at which the slower draining of the more
viscous oil from the cylinder wall, and tendency of the
rings to ride over the oil film causes more oil to pass the
piston and flow into the combustion chamber
(2)
Aircraft
range
as
related
to
oil
consumption. Remove an engine if oil consumption is
high enough to limit range of aircraft. Variations In oil
system capacity of different aircraft causes maximum oil
consumption to vary according to type aircraft and type
of mission being performed (see figure 7-22).
7-6. Engine Conditioning. Engine conditioning
provides a standard method for detecting engine
malfunctioning prior to development of serious trouble
and establishes a systematic routine for keeping the
engine in condition to provide maximum trouble-free
performance. The types of engine conditioning are
complete
engine
conditioning
and
minor
engine
conditioning.
Figure 7-22. Oil Consumption Chart
7-29
