AD 80-25-06 R1
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Continental Motors | GTSIO-520-L | TELEDYNE CONTINENTAL MOTORS Model GTSIO-520-L, GTSIO-520-M, GTSIO-520-N Engines |
| engine | Continental Motors | GTSIO-520-M | TELEDYNE CONTINENTAL MOTORS Model GTSIO-520-L, GTSIO-520-M, GTSIO-520-N Engines |
| engine | Continental Motors | GTSIO-520-N | TELEDYNE CONTINENTAL MOTORS Model GTSIO-520-L, GTSIO-520-M, GTSIO-520-N Engines |
Unsafe Condition
Engine failure due to loss of engine oil pressure, damage due to contaminated oil, and propeller shaft damage resulting from a malfunctioning thrust washer.
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Required Actions
Perform a special oil pressure check before and after each flight until 100 hours total time in service. Remove oil filter, inspect element for metallic contaminants exceeding 1/4 inch coverage, and inspect propeller drive shaft end play exceeding 0.020 inch. Change oil and filter at 25, 50, and 100 hours total time in service, using specified oil types based on ambient temperature. Record all maintenance actions.
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Compliance Time
Before further flight or prior to the next flight as specified, with oil changes at 25, 50, and 100 hours total time in service.
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Affected Aircraft
TELEDYNE CONTINENTAL MOTORS Models GTSIO-520-L (serials 608324-608627), GTSIO-520-M (serials 606619-606890), GTSIO-520-N (serials 610001-610107) engines with 100 hours or less total time in service on March 23, 1981, installed on but not limited to certain Cessna Models 404 and 421C airplanes.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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