OH-23 Engine Fan Assemblies Track and Concentricity Check

TM 55-4920-201-14

4-45. OH-23 Engine Fan Assemblies Track and

setscrew (12), using 3 / 32-inch hex wrench (2,

Concentricity Check. (See figure 4-26).

a. Select applicable extension pilot plug as

e. Clamp fixture assembly (2, figure 4-26),

follows: use extension pilot plug (11) for fan

recessed side downward, on surface plate (1) or

assemblies prior to OH-23 series D (view A); use

other firm support surface.

extension pilot plug (15) for OH-23 series D, F,

f. Install plug (4) in hub of fixture assembly

and G fan assemblies (view B).

(2) so that approximately 1 inches of plug

projects above top of hub. Lock plug securely in

b. Assemble applicable extension pilot plug

this position with two upper fixture setscrews (3),

in coupling (6) against coupling stop pins (7) as

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

shown. Secure plug with two upper coupling set-

g. Install open end of coupling (6, figure 4-

screws (8) at extension pilot plug end of coupling,

26) (attached to fan assembly) over plug (4),

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

bottoming plug against coupling stop pins (7). Do

c. Insert extension pilot plug through hub of

not lock coupling lower setscrews.

engine fan assembly (9, figure 4-26) from flat side

h. Install inch mushroom point on dial

of fan assembly.

indicator (13), and adjust height gage assembly

d. Install collar (10) over projecting end of

(14) to read track or concentricity variations as

extension pilot plug as follows: for fan assemblies

required. Rotate fan assembly to determine range

prior to OH-23 series D, install collar with flat end

of variations.

toward fan assembly (view A); for OH-23 series D,

i. For track and concentricity tolerances and

F, and G fan assemblies, install collar with cone

application of corrections, refer to applicable

end toward fan assembly (view B). Seat collar and

extension pilot plug firmly against sides of fan

helicopter manual. (Refer to appendix A).

assembly hub, and lock in position with collar

4-43