FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 8. Engines, Fuel, Exhaust, and Propellers | 1. Engines | 8-11. Plating
9/8/98
AC 43.13-1B
engines the cylinder baffles, rocker box covers,
drive covers and pads, and accessory and su-
percharger housings are fastened with fiber in-
sert lock nuts which are limited to a maximum
temperature of 250 °F. Above this tempera-
ture, the fiber insert will usually char and, con-
sequently, lose its locking characteristic. For
locations such as the exhaust pipe attachment
to the cylinder, a locknut which has good
locking features at elevated temperatures will
give invaluable service. In a few instances, fi-
ber insert lock nuts have been approved for use
on cylinder hold-down studs. This practice is
not generally recommended, since especially
tight stud fits to the crankcase must be pro-
vided, and extremely good cooling must pre-
vail so that low temperatures exist where the
nut is installed.
e. Information concerning approved
self-locking nuts and their use on specific en-
gines are usually found in engine manufac-
turer’s manuals or bulletins. If the desired in-
formation is not available, it is suggested that
the engine manufacturer be contacted.
f. Refer to Chapter 7, Aircraft Hardware,
Control Cables, and Turnbuckles, for addi-
tional information on self-locking nuts.
factory; however, engineering evaluation of the
details for the processes used should be ob-
tained.
a. Dense chromium plating of the crank-
pin and main journals of some small engine
crankshafts has been found satisfactory, except
where the crankshaft is already marginal in
strength. Plating to restore worn, low-stress
engine parts, such as accessory drive shafts
and splines, propeller shaft ends, and seating
surfaces of roller and ball-type bearing races is
acceptable but requires compliance with
FAA-approved data.
b. Porous chromium-plated walls of
cylinder barrels have been found to be satis-
factory for practically all types of engines.
Dense or smooth chromium plating, without
roughened surfaces on the other hand, has not
been found to be satisfactory.
(1) Cylinder barrel pre-grinding and
chromium plating techniques used by the
military are considered acceptable for all en-
gines, and military-approved facilities engaged
in doing this work in accordance with military
specifications are eligible for approval by the
FAA.
8-10. METALLIZING. Metallizing inter-
nal parts of aircraft engines is not acceptable
unless it is proven to the FAA that the metal-
lized part will not adversely affect the airwor-
thiness of the engine. Metallizing the finned
surfaces of steel cylinder barrels with alumi-
num is acceptable, since many engines are
originally manufactured in this manner.
8-11. PLATING. Before restoring the plat-
ing on any engine part in accordance with the
manufacturer’s instructions, the part should be
visually inspected and have an NDI performed
before any cylinder reconditioning. In general,
chromium plating would not be applied to
highly-stressed engine parts. Certain applica-
tions of this nature have been found to be satis-
(2) Chromium-plated cylinder barrels
have been required for some time to be identi-
fied in such a manner that the markings are
visible with the cylinder installed. Military-
processed cylinders are banded with orange
enamel above the mounting flange. It has been
the practice to etch on either the flange edge or
on the barrel skirt the processor’s initials and
the cylinder oversize. Most plating facilities
use the orange band as well as the permanent
identification marks.
(3) A list of engine and maximum per-
missible cylinder barrel oversize are referenced
in table 8-1.
Par 8-9
Page 8-5