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 | 4. Repair of Metal Propellers | 8-76. Propeller Hub and Flange Repair
9/8/98
AC 43.13-1B
(c) Step 3. Determine percent reduc-
tion in width (∆w%) from figure 8-27.
(d) Step 4. Calculate the blade width
repair allowable (∆w)
∆w =(∆w%) x (w) x(0.01) = (2.5) x (1.88) x
(0.01) = 0.05 in.
(e) Step 5. Calculate the minimum
blade width limit (w1) at the repair location
w1 = w - ∆w = 1.88 - 0.05 = 1.83 in.
(2) Example 2. Determine the blade
thickness repair allowable (∆t) and minimum
blade thickness limit (t1) for a blade having a
diameter (d) of 10 ft. 6 in. The repair location
(r1) is 43 in. from the shank and the original,
as manufactured, blade thickness (t) at the re-
pair location is 0.07 in.
(a) Step 1. Calculate the blade radius
(r)
r = d/2 = (10 ft 6 in)/2 = 126/2 = 63 in.
(b) Step 2. Calculate percent of
blade radius to repair (r%)
r% = r/r x 100 = (43/63) x 100 = 68
(c) Step 3. Determine percent reduc-
tion in thickness (∆t%) from figure 8-28.
(d) Step 4. Calculate the blade
thickness repair allowable (∆t)
∆t = (∆t%) x (t) (0.01) = (4.0) x (0.07) x (0.01)
= 0.003 in.
(e) Step 5. Calculate the minimum
blade thickness limit (t1) at the repair location
t1 = t - ∆t = 0.07 - 0.003 = 0.067 in.
8-75. STEEL HUBS AND HUB PARTS.
Repairs to steel hubs and parts must be ac-
complished only in accordance with the manu-
facturer’s recommendations. Welding and
remachining is permissible only when covered
by manufacturer’s service bulletins (SB).
8-76. PROPELLER HUB AND FLANGE
REPAIR. When the fixed-pitch propeller bolt
holes in a hub or crankshaft become damaged
or oversized, it is permissible to make repairs
by using methods (A) or (B) in figure 8-29, or
by use of aircraft standard bolts 1/16-inch
larger than the original bolts. Make the repairs
in accordance with the recommendations of the
propeller metal hub manufacturer or the engine
manufacturer, as applicable. Obtain from the
engine or propeller hub manufacturer suitable
flange bushings with threaded or smooth
bores, as illustrated in methods (A) or (B) of
figure 8-29. Drill the flange and insert the
bushings as recommended by the propeller to
accommodate the bushings, and protect the
holes with 2 coats of aluminum paint or other
high moisture-resistant coating. Use bolts of
the same size as those originally used. Any of
the following combinations may be used:
(1) drilled head bolt and castellated nut,
(2) drilled head bolt and threaded bushing, or
(3) undrilled bolt and self-locking nut. Where
it is desirable to use oversized bolts, obtain
suitable aircraft-standard bolts 1/16-inch larger
than the original bolts. Enlarge the crankshaft
propeller flange holes and the propeller hub
holes sufficiently to accommodate the new
bolts without more than 0.005-inch clearance.
Such reboring will be permitted only once.
Further repairs of bolt holes may be in accor-
dance with the methods listed in (A) or (B) of
figure 8-29.
NOTE: Method (A) or (B) is pre-
ferred over the oversized bolt method,
because a propeller hub flange re-
drilled in accordance with this latter
Par 8-74
Page 8-33