AD 49-41-01 ACTIVE

49-41-01 LOCKHEED: Applies to All Models 649, 749 and 749A Aircraft Equipped With Curtiss Model C632S-A Propellers and Wright Model 749C18BD-1 Engines.

Compliance required on items 1, 2 and 3 by October 11, 1949.

In order to reduce the possibility of subjecting propellers to excessive stresses and to detect hub cracks which may have been caused by such stresses, the following steps are to be taken:

1. Change present 2,100-2,375 r.p.m. restriction to 2,050-2,375. Placard airplane or mark tachometer with green radial line for single point operation at 2,025 r.p.m. Other restrictions listed in AD 48-26-01 still apply.

2. Limit gross weight to 102,000 pounds maximum.

3. On hubs having more than 1,500 hours total service time, visually inspect for cracks the rear outboard portions of the hub barrels. Inspection is to be continued at intervals as close to 10 hours as practical but not exceeding 20 hours maximum. It is strongly recommended that whenever the necessary equipment is available, magnetic inspections be made at the same intervals in accordance with Curtiss Instruction entitled "Field Magnetic Inspection of C6832S-A Hubs." Remove from service any hub showing a crack. To facilitate these inspections, the propeller power unit is covered or sealed to prevent the entrance of water in the unit. As an alternate to the removal of the spinner, these inspections may be conducted through three 5-inch diameter holes located in the side of the spinner in accordance with instructions issued by Curtiss.

4. All C632S-A hubs (P/N 116366) with over 2,000 hours total time shall be retired from service as soon as possible and not later than November 30, 1949.

5. Items 1 and 2 also apply when the C-632S-B hub (P/N 129914) is used to replace the C632S-A hub (P/N 116366).