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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
AD 57-08-04

HARTZELL Models HC-83X and HC-93Z Propellers


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57-08-04 HARTZELL: Applies to All HC-83X and HC-93Z Three-bladed Feathering Propellers Installed on Aero Commander Models 520, 560, 560A, 560E and 680, Beech Model 50, and Piaggio P.136 Aircraft.

Compliance required as soon as possible but not later than May 15, 1957.

There have been several cases reported that screw P/N AN 501-A10-6 securing the RG- 50 safety link bar unscrewed, without breaking the safety wire, from the link arm mounting pin P/N A-872-1 located at piston end of pitch change link arm P/N A-861 on Hartzell HC-83X and HC-93Z three-bladed feathering propellers installed on twin engine aircraft. This occurs because link arm P/N A-861 rotates during propeller operation and thus applies a torsional force to the link arm mounting pin P/N A-872-1, thereby causing it to rotate. To preclude possible loss of propeller blade pitch control from this cause, accomplish the following modification on these propellers:

1. Feather propeller and remove safety link RG-50 and link pin A-872-1 from propeller pitch change piston.

2. Replace screw AN 501-A10-6 with screw AN 501-A10-18 that will extend through safety link pin P/N A-872-1 a maximum of two threads.

3. Peen projecting end of screw to prevent screw from backing out of link pin.

4. Replace safety link and link pin assembly in the piston. Be sure safety link RG- 50 is not held away from piston lug surface due to peened screw threads bottoming in pin hole. (This AD covers the same subject as CAA telegraphic instructions dated April 12, 1957.)

(Hartzell Service Bulletin No. 46 covers this same subject.)


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