AD 58-11-01

58-11-01 DOUGLAS: Applies to All DC-6 and DC-7 Series Aircraft as Indicated.

Several instances have been reported wherein cracks have been found or failures have occurred in the nose wheel upper retract link assembly, P/N 5325437. In at least one case, failure resulted in folding of the nose gear when the aircraft stopped, following landing and taxi.

The failures occurred in the forged end fitting, P/N 5328993, caused by a crack starting in the vicinity of the 1/8-inch radius where the fitting is machined to the O.D. of the tube, P/N 2329712. Cracks in the unfailed parts were found in the same location. Failures occurred on two airplanes having a total of 24,000 and 13,800 hours respectively and a crack was reported on one airplane with 7,521 hours. The airplane time is not significant since the interchange of landing gear components at major overhaul may result in the gear components actually having more or less time than the airplanes themselves.

Subsequent to DC-6 Series fuselage No. 435 and DC-7 Series fuselage No. 434, Douglas increased the 1/8-inch radius to 3/4-inch radius. The following must be accomplished on all nose gear upper retract link assemblies, P/N 5325437, delivered by the manufacturer that do not incorporate the larger radius.

1. Inspect the right and left hand forged end fitting with the 1/8-inch radius at the earliest possible opportunity where facilities are available, and in any case, at the inspection period nearest 100 hours. Inspection should preferable be accomplished by magnaflux; however, dye penetrant inspection can be considered satisfactory if parts are uniformly warned to open tight cracks.

2. If cracks are found, parts must be replaced. No rework is considered feasible.

3. Parts which are not cracked should be reworked at the earliest practicable opportunity to increase the 1/8-inch radius to 3/4-inch and polish the area to a 32-micro-inch finish. The reworked area should be protected with zinc chromate primer and aluminized lacquer and the reworked parts properly identified to distinguish them from those manufactured with the 3/4-inch radius.

4. After the initial inspection, all parts must be inspected regularly at the inspection period nearest to 300 hours until rework is accomplished.

5. After rework, inspections at frequent intervals should continue to assure that the rework has removed damaged material and/or incipient cracks.

(Douglas Alert Service Bulletin A-677 for the DC-6 Series and A-139 for the DC-7 Series cover the above subject and describe how to increase the 1/8-inch radius to a 3/4-inch radius.)