72-80-01 GENERAL.
Engines in aircraft that are flown only occasionally tend to exhibit cylinder wall corrosion
more than engines in aircraft that are flown frequently.
Of
particular concern are new engines or engines with new or freshly honed cylinders after a
top or major overhaul. In areas of high humidity, there have been instances where corrosion
has been found in such cylinders after an inactive period of only a few days. When cylinders
have been operated for approximately 50 hours, the varnish deposited on the cylinder walls
offers some protection against corrosion. Hence a two step program for flyable storage
category is recommended.
Obviously, even then proper steps must be taken on engines used infrequently to lessen the
possibility of corrosion. This is especially true
if
the aircraft is based near the sea coast or in
areas of high humidity and flown less than once a week.
In all geographical areas the best method of preventing corrosion of the cylinders and other
internal parts of the engine, is to fly the aircraft at least once a week,
tong enough to reach
normal operating temperatures, which will vaporize moisture and other by-products of com-
bustion. In consideration of the circumstances mentioned, TCM has listed three reasonable
minimum preservation procedures, that
if
implemented, will minimize the detriments of rust
and corrosion. It is the owner's responsibility to choose a program that is viable to the
particular aircraft's mission.
Aircraft engine storage recommendations are broken down into the following categories:
A.
Flyable Storage (Program
I
or 11)
B.
Temporary Storage (up to
90
days)
C. Indefinite Storage
72-80-02 FLYABLE STORAGE
(Program
I
or
11).
Program
l
-
Engines or cylinders with less than
50
operating hours:
a. Propeller pull thru every
5
days as per paragraph
2;
and
b.
Fly every
15
days as per paragraph 3.
Program
I1
-
Engines or cylinders with more than 50 operating hours to
TBO
if
not
flown weekly:
a. Propeller pull thru every
7
days as per paragraph
2;
and
b. Fly every 30 days as per paragraph
3.
1.
Service aircraft per normal airframe manufacturer's instructions.
2.
The propeller should be rotated by hand without running the engine. For
4
and
6
cylinder straight driie engines, rotate the engine six revolutions. Stop the propeller
45O
to
90O
from the original position. For
6
cylinder geared engines, rotate the propeller
4
revolutions and stop the propeller 30° to
60°
from the original position.
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