OH-13 (Series H, Serial NO. 58-1497 and Subsequent and Series S) Tail Rotor Hub and Blade Assembly Balance Check

TM 55-4920-201-14

4-34. OH-13 (Series H, Serial NO. 58-1497 and

terference. and note the balance condition indicated

Subsequent and Series S) Tail Rotor Hub and

by the black indicator disc at top end of the arbor.

Blade Assembly Balance Check. (See figure 4-17.)

i. For balance tolerance and application of

balance corrections, refer to applicable helicopter

a. Set fixture assembly (2), recessed side

manual. (Refer to appendix .A.)

downward, on auxiliary support blocks (1) as

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

into two diametrically opposite tapped holes (B,

4-34A. OH-13 SERIES S AND TH-13T, TAIL RO-

view A) in top surface of fixture. Using fingers only,

TOR HUB AND BLADE ASSEMBLY BALANCE

insure that post assemblies are firmly seated on

CHECK. (See figure 4-17A).

fixture.

a. Set. fixture assembly (2), recessed side

b. Place spacer (13) central on top of fixture

downward on stand assembly or auxiliary support

assembly (2) hub.

block (1) as shown. Screw stud ends of two post

assemblies (8) into two diametrically opposite

c. Install pilot bushing (12), flange upward,

tapped holes (A) in top surface of fixture. Using

on balancing arbor (8) so that its top surface aligns

fingers only, insure that post assemblies are

with 7-inch position on arbor scale (9). Lock

firmly seated on fixture.

bushing in this position by moderate and uniform

b. Temporarily install balancing arbor (8) in

tightening of two pilot bushing setscrews (11),

fixture assembly (2) using set screw (12) to lock

using 3/32-inch hex wrench (2, figure 1-18).

arbor in place. A sensitivity setting is not neces-

d. Set tail rotor hub and blade assembly (4,

sary at this time.

C. Install adapter (11) on arbor (8) with re-

figure 4-17) on fixture assembly (2) so that bottom

cessed portion of adapter downward to set on

(flat) surface of rotor hub trunnion rests on spacer

fixture assembly (2).

(13), flat surface of rotor hub is upward, and rotor

d. Install tail rotor hub and blade assembly

blade shanks are clear of post assemblies (3).

on fixture assembly flat surface up. Adapter (11)

e. Insert lower end of arbor downward

is positioned against bottom side of trunnion with

through rotor hub trunnion, spacer (13), and hub

cambered sides between the trunnion sleeves.

of fixture assembly (2). Press cone of pilot bushing

e. Install plate (6) on flat surface of tail

(12) firmly into cone seat of rotor hub trunnion,

rotor hub and blade assembly.

and lock arbor in this position by moderate and

f, Install bushing (7) with flange downward.

g. Rotate swivel heads of post assemblies

uniform tightening of two lower fixture setscrews

(14).

(3) and rotorhub cuffs on arbor until small ends of

index pins enter rotor pitch arm bracket holes

f. Rotate swivel heads of post assemblies (3),

from outboard side.

and rotate hub on arbor until small ends of post

b. Push down On plate assembly (6) so flat

assembly index pins (5) enter rotor pitch arm

surface of rotor hub is flush with plate. Loosen

bracket holes. Seat index pins and swivel heads

set screw on fixture assembly (2) and move arbor

radially outward against rotor pitch arm brackets.

(8) up or down until a sensitivity setting of 7

g. Install part no. 2586 or 2531 plate (6) over

inch position is aligned on arbor scale (9) with

top end of arbor, followed by bushing (7). with

top surface of bushing (7). Tighten set screw

flange downward. The part no. 2586 is a

(10). Press bushing and plate firmly downward

against flat top surface of rotor hub and lock

miscellaneous component, and is not supplied in

entire hub in position by moderate and uniform

any kit included in this manual. Press bushing and

tightening of lower fixture set screws (12).

plate firmly downward against flat top surface of

i. Install quick-disconnect coupling on arbor

rotor hub, and lock plate and bushing in this

suspension coupler and suspend entire assembly

position by moderate and uniform tightening of two

free of interference, and note balance condition

bushing setscrews (10).

indicated by black indicator disc at top of arbor.

Install quick-disconnect coupling

j. For balance tolerance and application of

(7HEL053 or 7A050 kit) on arbor suspension

balance corrections, refer to applicable helicopter

coupler, and suspend entire assembly free of in-

manual. (Refer to appendix A.)

4-26 Change 1