AD 58-17-03

58-17-03 CURTISS-WRIGHT AND MARTIN: Applies to C-46 Series (including C- 46/CW20-T) and 202, 202A, 404 aircraft having propeller hydraulic feathering lines routed over or attached to engine cylinder assemblies.

Compliance recommended at the next engine overhaul but required by June 1, 1959.

Several cases of engine cylinder failures have occurred in which it was subsequently impossible to feather the propeller. In these cases, the feathering line which was routed over a front row cylinder was severed by a dislodged cylinder, thus preventing feathering and causing an additional fire hazard from oil being pumped over 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 is required:

1. The propeller feathering line must be routed between cylinders. It must be supported in a manner avoiding attachment toa cylinder, and the line located at least three to four inches from the cylinder flanges.

2. The propeller feathering line must be routed between cylinders on the front row of cylinders in the manner described above. However, it will be acceptable for the line to be routed over a rear row cylinder provided it can be determined that sufficient flexibility is provided to prevent feathering line damage in the event of cylinder failure.