TM 1-1520-238-23
5-8
Change 6
5.1.
MAIN ROTOR INSPECTION continued
5.1.3. Inspection
NOTE
The main rotor includes the main rotor blades.
Cracks in any main rotor component are cause for rejection.
Corroded areas will be treated and restored in accordance with paragraph 1.49.
a. Check main rotor for loose or missing lockwire and cotter pins. Replace if loose or missing.
NOTE
If a preload indicating (PLI) washer is loose, the washer must be removed and replaced.
b. Check main rotor hub (1), lower shoe (2), and attaching bolts (3) for loose preload indicating (PLI)
washers (4). None allowed.
NOTE
Debonding near the surface of the elastomeric and metal shims without lateral inboard/outboard
displacement or visible separation (gaps), has no functional impact on serviceability of the bearing
and is not reason for rejection.
Bearings should be examined visually and not probed with a feeler gauge or tools.
c. Check feathering bearing housing (5) for serviceability.
(1) Check housing (5) and retaining nut (6) for looseness. None allowed.
(2) Check feathering bearing (7) for the following:
(a) Check feathering bearing (7) for separation between elastomeric and metal shims. Maximum separa-
tion not to exceed 0.01 inch.
(b) Check feathering bearing (7) for separation between elastomeric and metal shims. Maximum separa-
tion not to exceed 0.01 inch.
(c) Black powdery discharge is evidence of normal deterioration of elastomeric compound which is
acceptable.
(d) Elastomeric compound surface cracks are allowed over entire area.
(e) Debonding along circular metal shim is allowable provided the shim has not separated. Displacement
of any shim (outboard or inboard) is cause for removal.
(f) Large pieces (0.050 INCH or larger) of extruding elastomer from bearing (7) is cause for removal.
(g) Metal shims for cracks. None allowed.
(3) If there is any doubt regarding the serviceability of the feathering bearing, remove (para 5.37) for closer
inspection.
(a) Bearings with displaced shims, large amounts of elastomer extruded, or have separated into two or
more pieces are unserviceable and shall be replaced (para 5.37).
GO TO NEXT PAGE