# AD 78-17-07: Fuel Control Unit

- Type: Airworthiness directive
- Status: Current
- Products: Pratt & Whitney Canada PT6A-38, PT6A-41 and PT6A-45A
- Effective: August 31, 1978
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-3287
- Registered aircraft: 2,347 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/490AD72D1C77769E8625682C0058D7E9.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/78-17-07

## The airworthiness directive

78-17-07 PRATT & WHITNEY AIRCRAFT OF CANADA, LIMITED: Amendment 39-3287. Applies to all Pratt & Whitney Aircraft of Canada, Limited PT6A-38, PT6A-41 and PT6A-45A engines and Pratt & Whitney Aircraft PT6A-38 engines with fuel control unit Aviation Electric Part Numbers 3244723-3 through -10, 3244738-5, 3244738-6, 3244752-6 through -10, and 3244755-7 through -11.

Compliance required within the next 100 hours in service, after the effective date of this AD, unless already accomplished.

To preclude rupture of the bypass valve diaphragm in the fuel control unit, replace the part number 2526477 diaphragm with part number 343451 diaphragm in accordance with Paragraph 2, Accomplishment Instructions, in Pratt & Whitney Aircraft of Canada, Limited Service Bulletin No. 3103 or approved equivalent parts and procedure.

Aircraft may be flown to a base for performance of maintenance required by this AD per FAR 21.197.

Any equivalent parts and procedure must be approved by the Chief, Engineering & Manufacturing Branch of the Eastern Region of the Federal Aviation Administration (FAA).

This amendment is effective August 31, 1978.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E4EA](https://openairdocs.org/tcds/E4EA): Pratt & Whitney Canada Corp.; names 3 of 54 models: PT6A-38, PT6A-41, PT6A-45A

## 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: 2,347 (0 by airframe model, 2,347 by engine model)
- Makers: Beech 578, Cessna 435, Air Tractor 393, Raytheon 240, Piper 228, Pilatus 110, Socata 92, Dehavilland 57, Ayres 45, Epic 20

Models with the most aircraft:

- [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series): 2,217 aircraft (engine model)
- [Pratt & Whitney PT6 series](https://openairdocs.org/engine/pratt-whitney-pt6-series): 43 aircraft (engine model)
- [Pratt & Whitney Canada PT6A-41](https://openairdocs.org/engine/pratt-whitney-canada-pt6a-41): 42 aircraft (engine model)
- [U/A Canada PT6A-41](https://openairdocs.org/engine/u-a-canada-pt6a-41): 42 aircraft (engine model)
- [Pratt & Whitney Canada PT6 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6-series): 3 aircraft (engine model)

All 6 models: https://openairdocs.org/ad/78-17-07/models.md
Every aircraft: https://openairdocs.org/ad/78-17-07/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.