AD 52-01-08

52-01-08 HILLER: Applies to All Models UH-12, -12A and -12B Helicopters, Serial Numbers 104 and Up. (Incorporating Chrome Plated Main Rotor Blade Incidence Arms P/N 31114-1.)

Compliance required not later than the next 25-hour inspection, or not later than February 1, 1952, whichever occurs first and also as noted below.

As a precautionary measure to preclude possible serious danger which could result from failure of the main rotor blade collective pitch incidence arms (P/N 31114-1), the following should be accomplished:

(a) Inspect all main blade incidence arms (P/N 31114-1) to determine if chrome plated arms are installed.

(b) If chrome plated arms are installed, remove and magnaflux or magnaglow inspect each arm for possible minute cracks in the circumferential area of the flange radii.

(c) If the arm has had 100 hours service and cracks are not found, the part may be reinstalled and further compliance with this Note is not required. If the arm has lessthan 100 hours service, it must again be inspected at 100 hours or not to exceed 125 hours of service. If cracks are found in any arm, it must be replaced immediately.

(d) This Note also applies to spare and replacement chrome plated arms which should be inspected at 25 and 100 hours service as indicated above.

(Hiller Helicopter's Mandatory Service Bulletin No. 20 covers this same subject.)