AD 54-08-01

54-08-01 MARTIN: Applies to All Models 202, 202A and 404 Aircraft.

Compliance required as indicated.

Several cases of finding cracks in the nose landing gear piston and fork assembly (P/N 202SD84483) have been reported. These cracks were located in the change of cross section fillets which blend the barrel section of the terminal into the legs of the lower fork. To preclude further difficulties of this nature, all aircraft must be inspected and reworked as follows:

I. Compliance required not later than July 1, 1954.

Inspect the piston and fork assembly in the fillets which blend the barrel section of the terminal into the legs of the fork. This inspection must be accomplished with the aid of a 20-power enlarging lens, dye penetrant or magnaflux. Any assembly found to incorporate fillets of less than 11/32-inch radius must be further inspected or reworked as follows:

If a crack is found, rework the part in accordance with item II.

If no cracks exist, the part must be reinspected, as above, every No. 1 inspection but not to exceed 115 hours of service until reworked in accordance with item III. Should cracks be found in reinspection, the part must be reworked in accordance with item II.

II. Compliance required prior to return to service.

If a crack is found, the piston and fork assembly may be repaired by grinding out the crack within the following limits:

(The crack lengths, specified below, are based upon the total length of a crack or cracks in a single fork leg fillet. The depths of material removable pertain to the fork leg cross section and should be measured from the plane of the fork leg surface.)

(A) A crack measuring up to 2 inches may be ground out to a maximum depth of 0.065 inch.

(B) A crack measuring from 2 to 4 inches in length may be ground out to a maximum depth of 0.055 inch.

(C) A crack measuring over 4 inches in length may be ground out to a maximum depth of 0.040 inch. The reworked area is to be blended smoothly into the fork leg surface. The surface finish after grinding must be equivalent to RMS-32 with no tool marks present.

NOTE: Piston and fork assemblies not repairable within the above-stated limitations must be replaced.

III. Compliance required not later than March 1, 1955.

If no cracks exist, rework the fillets which blend the barrel section of the terminal into the legs of the fork to a radius of 3/8 + 1/32 inch. This new fillet should be ground tangent to the lowest point of material removed (Ref. item II) or the fork leg surface, as the case may be. Further, it is important that the fillet be blended into the surface of the terminal so that a smooth transition of cross sectional area is obtained, especially in the crotch of the fork. The surface finish after this rework must be equivalent to RMS-32 with no tool marks present.

(Martin Service Instruction Letters Nos. 30A and 404-64A, for the Models 202 and 404 aircraft respectively, cover this same subject.)