# AD 78-17-05: Automatic Fuel Control Unit

- Type: Airworthiness directive
- Status: Current
- Products: Pratt & Whitney Canada PT6T-3, PT6T-3A and PT6T-6
- Effective: August 31, 1978
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-3285
- Registered aircraft: 78 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/4D306CB3CCAF7C8C8625682C0058B4DB.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/78-17-05

## The airworthiness directive

78-17-05 PRATT & WHITNEY AIRCRAFT OF CANADA, LIMITED: Amendment 39-3285. Applies to all Pratt & Whitney Aircraft of Canada, Limited PT6T-3 and PT6T-6 turboshaft engines with automatic fuel control with Aviation Electric Ltd. Parts List 2524381-5, 3244712-1 and -2, 3244717-1 through -5, 3244721-1 through -5, 3244735-1 through -7 and 3244737-1 through -7.

Compliance required within the next 50 hours in service, after the effective date of this AD, unless already accomplished.

To preclude rupture of the bypass valve diaphragm in the automatic fuel control unit, replace the part number 2526477 diaphragm with part number 323451 diaphragm in accordance with Paragraph 2, Accomplishment Instructions in Pratt & Whitney Aircraft of Canada, Limited, Alert Service Bulletin No. 5153, 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 approvedby the Chief, Engineering and 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 E22EA](https://openairdocs.org/tcds/E22EA): Pratt & Whitney Canada Corp.; names 3 of 11 models: PT6T-3A, PT6T-6, PT6T-3

## 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: 78 (0 by airframe model, 78 by engine model)
- Makers: Bell 38, Sikorsky 25, Agusta 6, Pilatus 3, Aero Commander 1, Air Tractor 1, Beech 1, Cessna 1, Compagnie Daher 1, Textron 1

Models with the most aircraft:

- [Pratt & Whitney PT6 series](https://openairdocs.org/engine/pratt-whitney-pt6-series): 43 aircraft (engine model)
- [Pratt & Whitney Canada PT6T-3 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6t-3-series): 17 aircraft (engine model)
- [Pratt & Whitney Canada PT6T-3](https://openairdocs.org/engine/pratt-whitney-canada-pt6t-3): 8 aircraft (engine model)
- [Pratt & Whitney Canada PT6T-6](https://openairdocs.org/engine/pratt-whitney-canada-pt6t-6): 5 aircraft (engine model)
- [Pratt & Whitney Canada PT6 series](https://openairdocs.org/engine/pratt-whitney-canada-pt6-series): 3 aircraft (engine model)
- [Pratt & Whitney PT6T-3](https://openairdocs.org/engine/pratt-whitney-pt6t-3): 1 aircraft (engine model)
- [Pratt & Whitney PT6T-6](https://openairdocs.org/engine/pratt-whitney-pt6t-6): 1 aircraft (engine model)

All 7 models: https://openairdocs.org/ad/78-17-05/models.md
Every aircraft: https://openairdocs.org/ad/78-17-05/aircraft.md

Its text cites no advisory circulars or STCs.

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