AD 60-10-06

60-10-06 LOCKHEED: Amdt. 150 Part 507 Federal Register May 13, 1960. Applies to All Model 1049 Series Aircraft Equipped With Drag Strut Assemblies With Ground Acme Threads, P/N 469080-5 and -6, Serial Numbers 6001 Through 6363 and 10001 Through 10036, Manufactured By Sargent Engineering Corporation.

Compliance required as indicated.

As a result of two failures of the main landing gear drag strut cylinder, P/N 471035-3, the following inspections and rework are required, unless already accomplished.

(a) Within the next 425 hours' time in service inspect the root of the 6 5/16-inch diameter thread and thread relief area in the cylinder, P/N 471035-3, for cracks using one of the following inspection methods:

(1) Dye penetrant method.

(2) Magnetic particle method (liquid suspension only).

(3) Eddy current method.

(b) If no cracks are found, reinspection is required as follows, except that such reinspection is not required if the parts are reworked in accordance with (c) or if inspection, in accordance with inspection method (a)(3), shows no indication of a heat-affected zone.

(1) If inspection method (a)(1) or (a)(2) is employed, reinspection is required every 1,000 hours' time in service.

(2) If inspection method (a)(3) is employed, reinspection is required every 5,000 hours' time in service.

(c) Rework instructions:

(1) Remove 0.020-inch material by remachining new Acme threads and new thread relief in the cylinder, taking care to prevent heating of the cylinder material which may affect its strength. Grinding or rolling processes must not be used for making the threads.

(2) Cadmium plate the machine surfaces in accordance with aircraft practices for heat-treated steel.

(3) A new nut, Lockheed P/N 557466-1, or equivalent, must be used to replace the existing nut.

(4) Reassemble the strut assembly and proof test to 12,300 p.s.i. (Lockheed 1049 Service Bulletin 3112 covers these rework instructions.)(d) Parts found cracked must be replaced prior to further flight. Parts in which a heat affected zone is indicated by inspection method (a)(3) must be reworked in accordance with (c) within 1,000 hours' time in service.

(e) Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, FAA Western Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for such operator.

(Lockheed Service Letter FS/240867L covers this same subject.)

Revised August 2, 1963.

Revised May 26, 1964.