# AD 59-10-08: Gas Tank Cap Vent

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-18, PA-18A, PA-20 and PA-22
- Effective: July 15, 1959
- Published: June 25, 1959
- Issued: June 24, 1959
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 1,184 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/2ADFDA05A2D359F48625698B007655EE.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/59-10-08

## The airworthiness directive

59-10-08 PIPER: Applies to Models PA-18, PA-18A, PA-20 and PA-22, Aircraft.

Compliance required not later than July 15, 1959, for Models PA-18, PA-18A, and PA- 22, and not later than November 30, 1959, for the Model PA-20.

Recent occurrences have revealed improper compliance with AD 56-26-02 (Canceled March 24, 1958). Therefore, the tank vents drilled into the gas tank cap must be checked as follows: Insert a 0.030-inch diameter wire into the holes at the bottom of the cap. If the holes are properly drilled the wire can be inserted over 3/4 inch until it hits the inside top of the cap. If the holes are not properly drilled the wire will hit the baffle and only enter approximately 1/4 inch. Also, if the cap has one hole drilled and is marked with an "X" adjacent to the hole, and the cap rattles when shaken, a loose internal rivet is indicated. If either of the latter conditions exist, the following must be accomplished:

Rework the fuel tank caps by drilling two additional 0.067 holes 1/4 inch from the existing center hole. Drill through bottom part of cap and baffle only. Check these newly drilled holes with the 0.030-inch diameter wire as outlined above.

(This airworthiness directive supplements Piper Service Bulletin No. 148A dated May 29, 1957. The drawings included in this bulletin may be referred to as a guide in reworking the fuel tank caps.)

## Affected data sheets (3) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1A2](https://openairdocs.org/tcds/1A2): Piper Aircraft Inc.; names 1 of 18 models: PA-18
- [TCDS 1A4](https://openairdocs.org/tcds/1A4): Piper Aircraft Inc.; names 1 of 6 models: PA-20
- [TCDS 1A6](https://openairdocs.org/tcds/1A6): Piper Aircraft Inc.; names 1 of 8 models: PA-22

## 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: 1,184 (1,184 by airframe model, 0 by engine model)
- Makers: Piper 1,182, David B Piper 1, Piper-Root 1

Models with the most aircraft:

- [Piper PA-18](https://openairdocs.org/model/piper-pa-18): 477 aircraft (airframe model)
- [Piper PA-22](https://openairdocs.org/model/piper-pa-22): 277 aircraft (airframe model)
- [Piper PA-20](https://openairdocs.org/model/piper-pa-20): 276 aircraft (airframe model)
- [Piper PA-18A](https://openairdocs.org/model/piper-pa-18a): 152 aircraft (airframe model)
- [David B Piper PA18 REPLICA](https://openairdocs.org/model/david-b-piper-pa18-replica): 1 aircraft (airframe model)
- [Piper-Root PA-18 SUPER CUB](https://openairdocs.org/model/piper-root-pa-18-super-cub): 1 aircraft (airframe model)

All 6 models: https://openairdocs.org/ad/59-10-08/models.md
Every aircraft: https://openairdocs.org/ad/59-10-08/aircraft.md

Its text cites no advisory circulars or STCs.

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