AD 55-20-03 ACTIVE

55-20-03 MARTIN: Applies to All Models 202, 202A, and 404 Aircraft.

Compliance required as indicated.

Several cases of nose gear steering shaft failures have occurred at the machined splines, due to torsional fatigue. Accordingly, the following inspections using dye penetrant, magnetic particle or vapor blast, are required to check for the presence of cracks.

1. New type shafts, Menasco P/N 526681, installed on all 202 and 202A aircraft, and on all 404 aircraft incorporating shimmy dampeners, must be inspected every 2,500 hours. On 404 aircraft not incorporating shimmy dampeners, the inspection must be conducted every 1,000 hours. Cracked shafts should be removed from service pending instructions from Martin.

2. Original type shafts, Menasco P/N 511681, which have never cracked, may be continued in service subject to the same conditions and inspections as the new type in item 1 providing the 1.628+0.005-inch relief cut is added. This is accomplished by grinding the serration run out circumferentially to a relief diameter of 1.628 inches starting 5/8 inch from upper shoulder, with 1/16- inch corner radii. Cracked shafts may be ground down to a minimum diameter of 1.530 inches to remove cracks. If cracks are removed, the shaft may be returned to service, but must be reinspected as required in the following paragraph 3.

3. All original type shafts which have been ground to remove cracks must be inspected at 325-hour intervals. Shafts may be ground down to a 1.530-inch minimum diameter to remove cracks. If cracks are removed, the shafts may be returned to service, continuing this inspection. If cracks are not removed at the 1.530 diameter, the shaft must be replaced.