# AD 55-08-04: Ignition Filter Replacement

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-22
- Published: December 4, 1956
- Issued: December 4, 1956
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Registered aircraft: 277 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/F9E1D820DEF5B44B8625698B007647B1.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/55-08-04

## The airworthiness directive

55-08-04 PIPER: Applies to Model PA-22 Serial Numbers 22-1621 Through 22-1625, 22-1627, 22-1630, 22-1633, 22-1634, 22-1637.

Compliance required as soon as possible but not later than July 1, 1955.

The Hypass No. 48P6 ignition filters should be removed from the magnetos and replaced with magneto filter, Piper No. 63149 (Lear) obtainable from the Piper Service Department. It has been found that the Hypass No. 48P6 filters short and ground out the magnetos when subjected to a temperature which has been reported to be equal to the engine accessory temperature after a series of takeoffs have been performed.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [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: 277 (277 by airframe model, 0 by engine model)
- Makers: Piper 277

Models with the most aircraft:

- [Piper PA-22](https://openairdocs.org/model/piper-pa-22): 277 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/55-08-04/models.md
Every aircraft: https://openairdocs.org/ad/55-08-04/aircraft.md

Its text cites no advisory circulars or STCs.

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