AD 56-24-01

56-24-01 CONVAIR: Applies to All 240, 340 and 440 Series Aircraft.

Compliance recommended at the next engine overhaul but required on all aircraft by September 1, 1957.

Several cases of engine cylinder failures have occurred in which it was subsequently impossible to feather the propeller. The feathering line is presently routed over the top of the No. 8 cylinder and when this cylinder is dislodged, due to stud failures or flange failure, the feathering line is severed thus preventing feathering and causing an additional fire hazard from oil being pumped onto the engine. The record of cylinder failures from studs loosening or breaking indicates that the front row cylinders are mainly involved.

To prevent loss of feathering control from such failures, either of the following actions is required:

1. The propeller feathering line is to be rerouted between cylinders.

(Convair Service Bulletins Nos. 240-479, 340-205 and 440-23 cover an acceptable method of complying with this modification on Models 240, 340 and 440, respectively.)

2. The propeller feathering line is to be routed between cylinders on the front row of cylinders. It shall be acceptable for the line to pass over the top of a rear row cylinder provided there is adequate flexibility in the line assembly to allow for some displacement without breaking line or fittings in the event of a cylinder failure.