# AD 57-05-01: Hydraulic Vent System

- Type: Airworthiness directive
- Status: Current
- Products: Airlift International C-46A, C-46D, C-46F, C-46R, C-46E, C-46A, C-46D, C-46E, C-46F, C-46A, C-46D, C-46F and 3 more
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 7 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D32BB57436CDE27B862569A700739463.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/57-05-01

## The airworthiness directive

57-05-01 CURTISS-WRIGHT: Applies to all C-46 Series aircraft.

Compliance required by August 1, 1957.

During emergency extension of the landing gear, hydraulic dump valves are actuated in the landing gear hydraulic system to vent fluid directly overboard in order to prevent trapped fluid from preventing the lowering of the landing gear.

On early model aircraft this fluid was vented overboard on the inboard side of the nacelles directly aft of the exhaust stack. This has resulted in fires in areas where no fire detection or protection is provided.

In order to prevent this occurrence, item (1), (2), or (3) should be accomplished.

  (1) The vent line should be rerouted to vent from nacelle tail cone in accordance with Curtiss-Wright Service Bulletin C-46 1226 or Curtiss-Wright Drawing No. 20-575-3206.

  (2) The vent line should be rerouted to return to the main system as outlined in change A of T.O. 01-25LA-209.

  (3) The vent line should be rerouted to anapproved equivalent of item (1) or (2).

Either item (1) or (2) may have been accomplished on later model aircraft at the factory or by the military; however, the aircraft may have been further modified and should be inspected for compliance.

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 2A5](https://openairdocs.org/tcds/2A5): Tempo Design Corporation; names 2 of 2 models: C-46/CW20-T, Super C-46/CW20-T
- [TCDS 3A2](https://openairdocs.org/tcds/3A2): Airlift International Inc.; names 1 of 4 models: C-46R

## 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: 7 (7 by airframe model, 0 by engine model)
- Makers: Curtiss Wright 7

Models with the most aircraft:

- [Curtiss Wright C-46F](https://openairdocs.org/model/curtiss-wright-c-46f): 4 aircraft (airframe model)
- [Curtiss Wright C-46A](https://openairdocs.org/model/curtiss-wright-c-46a): 1 aircraft (airframe model)
- [Curtiss Wright C-46D](https://openairdocs.org/model/curtiss-wright-c-46d): 1 aircraft (airframe model)
- [Curtiss Wright C-46R](https://openairdocs.org/model/curtiss-wright-c-46r): 1 aircraft (airframe model)

All 4 models: https://openairdocs.org/ad/57-05-01/models.md
Every aircraft: https://openairdocs.org/ad/57-05-01/aircraft.md

Its text cites no advisory circulars or STCs.

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