# AD 68-21-03: Exhaust Tailpipe Assemblies

- Type: Airworthiness directive
- Status: Current
- Products: Piper PA-23-250 (Navy UO-1) and PA-E23-250 with STC SA909WE or SA978WE
- Effective: October 28, 1968
- Published: October 11, 1968
- Issued: October 3, 1968
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Small airplane
- Amendment: 39-667
- Registered aircraft: 899 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/5B52E4465CC513A286256997005820FC.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ad/68-21-03

## The airworthiness directive

68-21-03 PIPER: Amendment 39-667. Applies to Model PA-23-250 and PA-E23-250 Aircraft Serial Nos. 27-2505 through 27-3858 that Incorporate AiResearch Turbosupercharged Lycoming IO-540-J4A5 or IO-540-C4B5 Engines Installed in accordance with Supplemental Type Certificate No. SA909WE or SA978WE, or in accordance with Piper Aircraft Corporation Drawing No. 32016.

Compliance required within 10 hours of aircraft operations after the effective date of this Airworthiness Directive, unless previously accomplished.

To preclude failures of the exhaust tailpipe assemblies, AiResearch P/N 286-P23-060-5 and P/N 286-P23-060-9:

  (a) Visually inspect both the left and right hand engine tailpipes for cracks or deformation. If a crack or deformation is found in either tailpipe, retire the affected tailpipe assembly and replace with a new tailpipe assembly of the same part number.

  (b) Visually inspect both the left and right hand engine tailpipes for sufficient clearance betweenthe tailpipes and the firewalls and between the tailpipes and the cowl flaps in accordance with AiResearch Aviation Service Company Service Bulletin No. 14.1.8 dated April 25, 1968, or later FAA approved revisions. If sufficient clearance does not exist, install AiResearch Kit P/N 301-P23-063 and adjust for sufficient clearance in accordance with the above service bulletin.

This amendment becomes effective October 28, 1968.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 1A10](https://openairdocs.org/tcds/1A10): Piper Aircraft Inc.; names 2 of 6 models: PA-E23-250, PA-23-250 (Navy UO-1)

## 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: 899 (899 by airframe model, 0 by engine model)
- Makers: Piper 899

Models with the most aircraft:

- [Piper PA-23-250](https://openairdocs.org/model/piper-pa-23-250): 894 aircraft (airframe model)
- [Piper PA-23-250 (6PCLM)](https://openairdocs.org/model/piper-pa-23-250-6pclm): 5 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/68-21-03/models.md
Every aircraft: https://openairdocs.org/ad/68-21-03/aircraft.md

## Related documents

- [STC SA909WE](https://openairdocs.org/stc/SA909WE): Installation of turbosupercharged Lycoming IO-540-J4A5 engines. (PA-E23-250 SN 27-2505 and up). GE Engine Services-Corporate Aviation Inc.
DBA Garrett Aviation Services, Named in the applicability
- [STC SA978WE](https://openairdocs.org/stc/SA978WE): Installation of turbosupercharged Lycoming O-540-C4B5 engines.  Approved for serial numbers 27-2505 and subsequent.. GE Engine Services-Corporate Aviation Inc.
DBA Garrett Aviation Services, Named in the applicability

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