AD 57-05-01

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.