UH-1C, UH-1E, UH-1L, UH-1M, AH-1J, TH-1L, TH-1G, and AH-1G Main Rotor Hub Assembly (540 Series Hub) Balance Check

TM 55-4920-201-14

m. For balance tolerance and application of

Key to figure 4-19:

balance correction, refer to applicable helicopter

manual.

1. Fixture (2337, 7HEL054

kit)

4-38. UH-1C, UH-1E, UH-1L, UH-1M, AH-1J,

2. Sleeve (2467, 7HEL054

TH-1L, TH-1G, and AH-1G Main Rotor Hub

kit)

Assembly (540 Series Hub) Balance Check. (See

3. Adapter (2588, 7HEL061

figure 4-20).

kit)

a. Assemble the hoist support structure by

4 . Adapter setscrew

substituting the part no. 2769 tube assembly to

5. Yoke (2589, 7HEL061

provide additional vertical arm height in lieu of

kit)

part no. 2288 tube (7A050 kit). The part no. 2769

6. Balancing arbor (2259,

tube is 38 inches long and is a supplementary

7A050 kit)

miscellaneous detail that is not available in the

7. Arbor scale

7A050 kit.

8. Rotor hub assembly

9. Spacer (7A050 kit) (2201

b. Center fixture (1, figure 4-20) on stand

or 2202)

table assembly (16, figure 4-20).

10. Drag strut

c. Install adapter (2, figure 4-20), heavy end

11. Drag strut positioning

downward, over top of fixture (1) and seat on upper

gage (2486, 7HEL061

shoulder of fixture central projection. Lock adapter

kit)

in this position by tightening adapter setscrew (3),

12. Gage inner position

using 1/8-inch hex wrench (7A050, 7HEL054, and

13. Gage outer position

7HEL066 kits).

14. Handwheel (2215, 7A050

d. Insure that two grip positioning links (15),

kit)

(Bell tool no. T101466), together with suitable eye

15. Stand table (7A050)

bolts, are installed on the rotor to hold blade grips

in symmetrical pitch positions. Arrangement of

F, H & N, install part no. 2201 spacer. Install hand

bolts, nuts, and washers used for attachement of

wheel (14) in bottom end of arbor and tighten to

these links should be identical on both sides.

clamp both legs of yoke (5) firmly against top

e. Carefully lower rotor hub assembly (8) over

surface of rotor hub.

fixture (1), aligning inside diameter of splined

k. Using gage (11) as shown, swing rotor hub

trunnion with piloting diameter of adapter (2), and

drag struts to symmetrical angular positions. For

insuring that cone surface of splined trunnion seats

UH-1A, use gage inner position 112); for UH-1B,

firmly on cone surface of adapter (2).

D, F, H & N models, use gage outer position (13).

f. Install yoke (4), legs downward on

Remove gage from rotor assembly during sub-

balancing arbor (5) and position so that top surface

sequent balance check.

of its locking collar (sensitivity setting reference,

l. Install quick-disconnect assembly with

figure 4-20) aligns with 15-3/8-inch position on arbor

3/16-inch cable (7A050

kit) on arbor (6)

scale (6). Lock yoke firmly in this position on arbor

suspension rod and engage cable in lifting plate of

with its collar screws, using 3/16-inch hex wrench

hydraulic pump assembly (7A050 kit). Hoist entire

(7HEL066 kit).

assembly approximately inch off work stand.

g. Install arbor downward through rotor

Check to insure that suspended assembly is free

trunnion and fixture assembly. Seat legs of yoke in

from interference with work stand and other ob-

milled areas on top surfaces of hub yoke, central

jects, and note balance condition indicated by black

with scribed lines.

indicator disc at top end of arbor.

h. Position jacks (7) on the top surface of the

NOTE

rotor hub yoke so that their inboard ends bear

In order to insure that the part no. 2215

against the central boss of the hub yoke, centered

hand wheel suspends free of interference

below the scribe lines mentioned in step g and their

within the inside diameter of the stand

outboard ends hear centrally against the shoulders

table, it may be necessary to adjust the level

of the inboard bearing housings of the blade grip

of the stand assembly by installing suitable

assemblies. Adjust jacks to provide uniform out-

wood blocks or spacers under the two

ward pressure sufficient to insure blade grips are

tubular stand legs.

seated in their full outward positions.

4-31