AD 56-25-04
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Lockheed Aircraft Corporation | 1049-54 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 1049C-55 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 149-46 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 49-46 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 649-79 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 649A-79 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 749-79 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
| aircraft | Lockheed Aircraft Corporation | 749A-79 | LOCKHEED Models 49, 149, 649, 649A, 749, 749A, 1049, and 1049C Aircraft |
Unsafe Condition
Flap asymmetry during extension, leading to potential loss of control due to uncommanded flap extension on one side of the aircraft.
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Required Actions
Install a hydraulic power shut-off mechanism to automatically disable flap actuating motors when asymmetry occurs, as per Lockheed Service Bulletins 49/SB-794 (49/749 Series) and 1049/SB-2270 (1049 Series).
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Compliance Time
First block overhaul following receipt of parts or by March 1, 1958, whichever occurs first.
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Affected Aircraft
Lockheed Models 49, 149, 649, 649A, 749, 749A; Model 1049 Serial Numbers 4001-4024; Model 1049C Serial Numbers 4501-4520 and 4523-4538.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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