AD 78-17-05
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Pratt & Whitney Canada Corp. | PT6T-3 | PRATT & WHITNEY AIRCRAFT OF CANADA, LIMITED Model PT6T-3 and PT6T-6 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6T-3A | PRATT & WHITNEY AIRCRAFT OF CANADA, LIMITED Model PT6T-3 and PT6T-6 Engines |
| engine | Pratt & Whitney Canada Corp. | PT6T-6 | PRATT & WHITNEY AIRCRAFT OF CANADA, LIMITED Model PT6T-3 and PT6T-6 Engines |
Unsafe Condition
Rupture of the bypass valve diaphragm in the automatic fuel control unit.
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Required Actions
Replace part number 2526477 diaphragm with part number 323451 diaphragm in accordance with Pratt & Whitney Aircraft of Canada, Limited Alert Service Bulletin No. 5153, or approved equivalent parts and procedure. Equivalent parts and procedures must be approved by the Chief, Engineering and Manufacturing Branch, Eastern Region FAA.
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Compliance Time
within the next 50 hours in service after the effective date of this AD
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Affected Aircraft
Pratt & Whitney Aircraft of Canada, Limited PT6T-3 and PT6T-6 turboshaft engines with automatic fuel control using Aviation Electric Ltd. Parts List 2524381-5, 3244712-1 and -2, 3244717-1 through -5, 3244721-1 through -5, 3244735-1 through -7, and 3244737-1 through -7.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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