AD 69-25-08
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Lycoming Engines | GO-435-C2A | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-435-C2A2 | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-A1A | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-B | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-B1A6 | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-B1B | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-B1C | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-B1D | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-C1B6 | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
| engine | Lycoming Engines | GO-480-C1D6 | LYCOMING ENGINES Model GO-435-C2A, GO-480, GSO-480 and IGSO-480, and IGO-540 and IGSO-540 type Engines |
Unsafe Condition
Failure of the reduction gear assembly due to improper torque on the pinion cage attaching nut and insufficient oil slinger design.
AI-generated summary from the source AD text. Verify against the official source before acting.
Required Actions
Inspect torque on the reduction gearing pinion cage attaching nut. Depending on torque reading, either replace components and adjust torque to 400 ft.-lbs. or disassemble, inspect components, and replace oil slinger and housing. Replace spline nut with an approved hexagonal nut. Stamp suffix (-1) on reduction gear housing if oil slinger P/N 77454 is used.
AI-generated summary from the source AD text. Verify against the official source before acting.
Compliance Time
Prior to the accumulation of 600 hours in service or 100 hours after the effective date of this AD whichever comes later for GO-435, IGO-540, and IGSO-540 engines; and prior to the accumulation of 700 hours in service or 100 hours after the effective date of this AD whichever comes later for GO-480, GSO-480, and IGSO-480 engines.
AI-generated summary from the source AD text. Verify against the official source before acting.
Affected Aircraft
Lycoming Engines models GO-435-C2A, GO-480, GSO-480, IGSO-480, IGO-540, and IGSO-540 type engines using specific reduction gear assemblies (spline type 72875, 72879; flange type 69346, 70412, 71803; and 72782, 74900, 75679, 76494, 77731).
AI-generated summary from the source AD text. Verify against the official source before acting.
Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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