# AD 55-22-01: Oil Outlet Check Valve

- Type: Airworthiness directive
- Status: Current
- Products: Textron 35, 35-33, 35-A33, 35-B33, 35-C33, 35-C33A and 35R
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 1,077 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D8E7B7FD5ED1D07786256A0800731F57.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/55-22-01

## The airworthiness directive

55-22-01 BEECH: Applies to All Model 35 Airplanes, Serial Numbers D-1 Through D- 550, Equipped With Unmodified Oil Tank Check Valves.

Compliance required as soon as possible but not later than January 1, 1956.

To prevent complete loss of the engine oil supply resulting from failure of oil supply line hose connects caused by engine counter rotation, the check valve located at oil tank outlet requires valve modification or removal of the valve internal parts. Modified valves supplied by Beech Aircraft (Beech P/N 35-939082) include 1/16-inch holes drilled in the face of the valve poppet to prevent pressure buildup in the oil supply line in case of engine counter rotation. Modified valves are not available from Beech Aircraft. Unmodified valves should have the internal parts (poppet pivot pin, spring and poppet) removed.

(Beech Service Bulletin Model 35, No. 30, issued July 15, 1955; Service Letter Model 35, No. 44, issued March 28, 1950, and Service Letter Model 35, No. 18, issued July 18, 1947, cover this same subject.)

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 3A15](https://openairdocs.org/tcds/3A15): Textron Aviation Inc.; names 5 of 27 models: 35-C33A, 35-A33, 35-C33, 35-33, 35-B33
- [TCDS A-777](https://openairdocs.org/tcds/A-777): Textron Aviation Inc.; names 2 of 9 models: 35R, 35

## 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: 1,077 (1,077 by airframe model, 0 by engine model)
- Makers: Beech 1,077

Models with the most aircraft:

- [Beech 35-B33](https://openairdocs.org/model/beech-35-b33): 291 aircraft (airframe model)
- [Beech 35](https://openairdocs.org/model/beech-35): 266 aircraft (airframe model)
- [Beech 35-C33](https://openairdocs.org/model/beech-35-c33): 185 aircraft (airframe model)
- [Beech 35-33](https://openairdocs.org/model/beech-35-33): 130 aircraft (airframe model)
- [Beech 35-C33A](https://openairdocs.org/model/beech-35-c33a): 113 aircraft (airframe model)
- [Beech 35-A33](https://openairdocs.org/model/beech-35-a33): 85 aircraft (airframe model)
- [Beech 35R](https://openairdocs.org/model/beech-35r): 7 aircraft (airframe model)

All 7 models: https://openairdocs.org/ad/55-22-01/models.md
Every aircraft: https://openairdocs.org/ad/55-22-01/aircraft.md

Its text cites no advisory circulars or STCs.

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