OH-13 and TH-13 Tail Rotor Hub and Blade Assembly Balance Check

TM 55-4920-201-14

4-33. OH-13 (Series E, G; Series H Through

downward through two bushings (8) and hub of

Serial No. 57-6244) and TH-13 Tail Rotor Hub

fixture assembly (2) until 71/4 inch position on

and Blade Assembly Balance Check. (See figure

arbor scale (7) aligns with top surface of upper

bushing (8). Lock arbor in this position by

moderate and uniform tightening of two lower

a. Set fixture assembly (2), recessed side

fixture setscrews (9), using 3/32-inch hex wrench

downward, on auxiliary support blocks (1) as

shown. Screw stud ends of two post assemblies (3)

e. Rotate swivel heads of post assemblies (3,

into two diametrically opposite tapped holes (C,

figure 4-16), and rotate rotor hub on arbor until

view Al in top surface of fixture. Using fingers only,

small ends of index pins enter rotor pitch arm

insure that post assemblies are firmly seated on fix-

bracket holes. Seat index pins and swivel heads

ture.

readily outward against the rotor pitch arm

b. Place one bushing (8), flange downward,

brackets.

central on top to fixture hub. Install tail rotor hub

and blade assembly (4) over pilot diameter of

f. Install quick-disconnect coupling

bushing, insuring that hub seats firmly on flange of

(7HEL053 or 7A050 kit) on arbor suspension

bushing and that blade shanks are clear of in-

coupler, and suspend entire assembly free of in-

terference with post assemblies (3).

terference, and note the balance condition indicated

by black indicator disc at top end of the arbor.

c. Install second bushing (8), flange upward,

in top of rotor hub, seating bushing flange against

g. For balance tolerance and application of

top of rotor hub.

balance corrections, refer to applicable helicopter

manual. (Refer to appendix A.)

d. Insert lower end of balancing arbor (6)

4-24