# AD 51-24-01: Exhaust Valve Seats

- Type: Airworthiness directive
- Status: Current
- Products: Lycoming Engines GO-435-C2 (O-435-17)
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Registered aircraft: 2 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D3C0F38D56A945E586256827006FF4D6.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/51-24-01

## The airworthiness directive

51-24-01 LYCOMING: Applies to All Lycoming GO-435-C2 Engines Serially Numbered 1815-11 and Below Not Having the Letter "P" Stamped on the Upper Right-hand Corner of Each Cylinder Rocker Box and Installed in Navion Model B Aircraft. To be accomplished by June 1, 1952 or next overhaul, whichever occurs first. To prevent loosening of the exhaust valve seats in Lycoming GO-435-C2 engines installed in Navion Model B airplanes, the exhaust valve seats are to be peened in the cylinder head. The cylinders must be removed from the engine for this operation. When peening is accomplished, stamp "P" 1/8 inch high on upper right-hand corner of cylinder rocker box flange face near exhaust push rod. (Lycoming Service Bulletin No. 145 also covers this subject.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E-228](https://openairdocs.org/tcds/E-228): Lycoming Engines; names 1 of 20 models: GO-435-C2 (O-435-17)

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 2 (0 by airframe model, 2 by engine model)
- Makers: Grumman 1, Staudacher Hydroplanes 1

Models with the most aircraft:

- [Lycoming GO-435-C2](https://openairdocs.org/engine/lycoming-go-435-c2): 2 aircraft (engine model)

All 1 models: https://openairdocs.org/ad/51-24-01/models.md
Every aircraft: https://openairdocs.org/ad/51-24-01/aircraft.md

Its text cites no advisory circulars or STCs.

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