AD 57-08-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Hartzell Propeller, Inc. | HC-83X20-1 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-83X20-2 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-83XF-1 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-83XF-2 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-83XF-3 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-83XK-1 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-83XK-2 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-93Z20-1 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-93Z20-2 | HARTZELL Models HC-83X and HC-93Z Propellers |
| aircraft | Hartzell Propeller, Inc. | HC-93Z30-2 | HARTZELL Models HC-83X and HC-93Z Propellers |
Unsafe Condition
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, due to rotation of link arm P/N A-861 during propeller operation causing torsional force on the mounting pin.
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Required Actions
Replace screw AN 501-A10-6 with screw AN 501-A10-18 extending through link pin A-872-1 a maximum of two threads, peen projecting end of screw to prevent backing out, and ensure safety link RG-50 is properly seated during reassembly.
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Compliance Time
as soon as possible but not later than May 15, 1957
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Affected Aircraft
Hartzell Propeller, Inc. HC-83X and HC-93Z three-bladed feathering propellers installed on Aero Commander Models 520, 560, 560A, 560E, 680; Beech Model 50; and Piaggio P.136 aircraft.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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