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 | 5. Inspection of Propellers | 8-94. Propeller Hub
9/8/98
AC 43.13-1B
dents and scars should be examined with a
magnifying glass to decide whether defects are
scratches or cracks.
b. Aluminum Propellers and Blades.
Carefully inspect aluminum propellers and
blades for cracks and other flaws. A trans-
verse crack or flaw of any size is cause for re-
jection. Multiple deep nicks and gouges on the
leading edge and face of the blade is cause for
rejection. Use dye penetrant or fluorescent dye
penetrant to confirm suspected cracks found in
the propeller. Refer any unusual condition or
appearance revealed by these inspections to the
manufacturer.
c. Limitations.
(1) Corrosion may be present on pro-
peller blades in varying amounts. Before per-
forming any inspection process, maintenance
personnel must examine the specific type and
extent of the corrosion. (See chapter 6, and/or
refer to AC 43-4A, Corrosion Control For Air-
craft.)
(2) Corrosion, other than small areas
(6 square inches or less) of light surface type
corrosion, may require propeller removal and
reconditioning by a qualified propeller repair
facility. When intergranular corrosion is pres-
ent, the repair can be properly accomplished
only by an appropriately certificated propeller
repair facility. Corrosion pitting under pro-
peller blade decals should be removed as de-
scribed in the propeller manufacturer’s SB’s
and applicable airworthiness directives (AD).
(3) Unauthorized straightening of blade,
following a ground strike or other damage, can
create conditions that lead to immediate blade
failure. These unapproved major repairs may
sometimes be detected by careful inspection of
the leading edges and the flat face portion of
the blade. Any deviation of the flat portion,
such as bows or kinks, may indicate
unauthorized straightening of the blade.
Sighting along the leading edge of a propeller
blade for any signs of bending can provide
evidence of unapproved blade straightening.
Blades should be examined for any discolora-
tion that would indicate unauthorized heating.
Blades that have been heated for any repair
must be rejected, since only cold straightening
is authorized. All blades showing evidence of
unapproved repairs should be rejected. When
bent propellers are shipped to an approved re-
pair facility for inspection and repair, the pro-
peller should never be straightened by field
service personnel to facilitate shipping, be-
cause this procedure can conceal damage.
Propeller tip damage will sometimes lead
maintenance personnel to consider removing
damaged material from the blade tips. How-
ever, propellers are often manufactured with a
particular diameter to minimize vibration.
Unless the TCDS and both the engine and pro-
peller manufacturers specifically permit short-
ening of the blades on a particular propeller,
any shortening of the blades would probably
create an unairworthy condition. When condi-
tions warrant, inspect the blade tips for evi-
dence of shortening and, if necessary, measure
the propeller diameter to determine if it has
been changed by an unauthorized repair.
8-94. PROPELLER HUB.
a. Fixed Pitch.
(1) Inspection procedures require re-
moval of the propeller spinner for examination
of the prop hub area. Cracks may be present in
the hub area between or adjacent to bolt holes
and along the hub pilot bore. Cracks in these
areas cannot be repaired and require immediate
scrapping of the propeller.
(2) Propeller attach bolts should be ex-
amined for looseness or an unsafetied or
cracked condition. Cracked or broken bolts
are usually the result of overtorquing. Correct
Par 8-93
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