AD 76-20-03
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Pratt & Whitney Division | JT9D-20 | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
| engine | Pratt & Whitney Division | JT9D-3A | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
| engine | Pratt & Whitney Division | JT9D-7 | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
| engine | Pratt & Whitney Division | JT9D-7A | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
| engine | Pratt & Whitney Division | JT9D-7AH | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
| engine | Pratt & Whitney Division | JT9D-7F | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
| engine | Pratt & Whitney Division | JT9D-7H | PRATT & WHITNEY AIRCRAFT Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 Engines |
Unsafe Condition
Excessive No. 3 bearing compartment labyrinth seal clearances could lead to possible engine fires.
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Required Actions
Measure breather air temperature per Pratt & Whitney Alert Service Bulletin No. 4391 or Service Bulletin No. 4703 after specific engine section removal/replacement. Compare temperature with defined limits; remove engine from service if above limit. If below limit, perform repetitive checks per specified intervals (200, 500, or 1000 hours based on temperature margin). Replace main bearing breather tube steel elbow P/N 708237 with magnesium P/N 613265 by March 31, 1977.
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Compliance Time
no later than March 31, 1977 for the replacement action. Repetitive inspections must occur within 200, 500, or 1000 hours based on temperature margin, or 200 hours after the effective date of this revision, whichever is later.
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Affected Aircraft
Pratt & Whitney Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 engines with labyrinth solid land seals P/N 589733, 589741, 647189, or 729774.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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