TM 1-1520-238-23
Change 3
5-11
5.1.
MAIN ROTOR INSPECTION – continued
j. Inspect droop stop ring (17) for serviceability.
(1) Check droop stop ring (17) for cracks and distortion. None allowed.
(2) Check droop stop ring (17) for surface wear, galling, or scoring. Not to exceed 0.025 INCH.
(3) Check droop stop ring (17) for ring wall thickness. Minimum ring wall thickness is 0.340 INCH.
k. After completion of steps g.(1) thru j.(3), check droop angle (para 5.10).
l. Check droop stop liner (18) for rotational shifting.
(1) Visually inspect for bending or misalignment of four equally spaced paint stripes around hub (19) and liner
(18).
(a) If rotational shifting has occurred, inspect liner (18) for vertical slippage. Go to step n.
(b) If no vertical slippage has occurred or vertical slippage is within tolerance, then measure, record, and
monitor rotational shifting prior to each flight for the next ten flight hours.
1 If rotational shifting does not increase within the next ten flight hours, then inspect every 10
hours/14 days (TM 1-1520-238-PMS).
(2) If paint stripes are not present or are faded, go to step m. to paint hub and liner, if necessary.
m. Apply four equally spaced paint stripes around hub (19) and liner (18) (TM 55-1500-345-23).
(1) Paint stripes shall be 0.125 to 0.1875 INCH wide and 1.0 to 1.5 INCHES long.
(2) Paint stripes shall be painted vertically, equally spaced, and centered between pitch housings. Use
polyurethane coating (item 141A, App F) (TM 55-1500-345-23).
n. Check droop stop liner (18) for vertical slippage.
(1) Visually inspect sealant bead at droop stop liner (18) to hub (19) interface (20). If sealant is cracked
completely around circumference and there is a color change (primer or loctite visible), droop stop liner
(18) has vertically slipped.
(a) If droop stop liner (18) has vertically slipped, inspect for gap between lower surface of electrical brush
holder (21) and lower flange of bearing liner (18.1).
1 If gap is less than 0.030 INCH, reseat lower oil seal retainer (22) in droop stop liner (18) (para
5.46A) and recheck gap. If unable to reseat lower oil seal retainer (22) to achieve gap of 0.030
INCH or greater, hub (1) is unserviceable.
2 If gap is greater than 0.030 INCH, hub (1) is serviceable.
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