AD 53-20-01
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Martin-Marietta Corporation | 202 | MARTIN Models 202 and 202A Airplanes |
| aircraft | Martin-Marietta Corporation | 202A | MARTIN Models 202 and 202A Airplanes |
Unsafe Condition
With the reverse pitch stop ring relocated to act as a low pitch stop, inadvertent energization of the reverse solenoid valve can cause the stop ring to fail under extreme loads from high oil pressure surge and high blade twisting moments, leading to jamming of the pitch changing mechanism or propeller reversal.
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Required Actions
Modify the propeller dome's internal mechanism by removing the low pitch stop lever assembly and installing a dump valve to maintain 50-100 p.s.i. oil pressure. Modify the propeller control system by disconnecting specific wires, isolating solenoid circuits, revising solenoid circuits per Service Bulletin 236, adding throttle lever stops, and updating operating instructions. Compliance with AD 52-15-02 and Service Bulletin 264 is required.
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Compliance Time
Compliance required prior to November 1, 1954 for dome modifications and by April 1, 1954 for control system modifications. Operating instructions must be updated by November 1, 1953.
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Affected Aircraft
Martin-Marietta Corporation Models 202 and 202A airplanes with Hamilton Standard reversing propeller installations where the reverse feature is not used and the normal reverse pitch stop ring has been relocated as a low pitch stop.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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