60-04-04 LOCKHEED: Amdt. 101 Part 507 Federal Register February 13, 1960. Applies to All Models 049, 149, 649 and 749 Series Aircraft Which Have the Cleveland Pneumatic Model 8298 Series Main Landing Gear Struts Installed With the Removable Side Brace Attachment Collar.
Compliance required as indicated.
Due to fatigue failures found in the above main landing gear outer cylinder, the following inspections and rework must be accomplished on all main landing gears which have accumulated 25,000 or more hours' time in service.
(a) Unless already accomplished in the last 1,000 hours' time in service, within 400 hours' time in service inspect for cracks in the main landing gear outer cylinder surface, at the 0.125-inch radius of the shoulder against which the drag strut-side brace collar retaining nut bears, by means of one of the three methods in (b). Reinspect every 1,000 hours' time in service thereafter, until the rework in (c)(2) is accomplished. Outer cylinders with cracks must be replaced prior to further flight. Cracked cylinders may be returned to service after repair and rework is accomplished in accordance with (c). Rework on all uncracked outer cylinders must be accomplished in accordance with (c)(2) not later than the total accumulated hours' time in service indicated in (b).
(b) Inspection and rework:
(1) ULTRASONIC SHEAR WAVE DETECTION METHOD. This procedure may be used on cylinders with piston and oil in the cylinder or the cylinder only. Rework in accordance with (c)(2) must be accomplished within 4,000 hours' time in service if the ultrasonic method is used.
(2) MAGNETIC PARTICLE DETECTION METHOD. This method requires removing and dismantling of the strut assembly. Rework in accordance with (c)(2) must be accomplished within 4,000 hours' time in service if the magnetic particle method is used.
(3) RADIOGRAPHIC METHOD. This method requires the removal of the piston from the cylinder and complete 360 degree coverage. Reworkin accordance with (c)(2) must be accomplished within 3,000 hours' time in service if the radiographic method is employed.
(c) Repair and rework instructions:
(1) Outer cylinders with cracks in the radius described in (a) and for a distance of 0.5 inch below the radius tangency point circumferentially around the cylinder may be repaired by grinding out to a maximum depth of 0.017 inch. Complete removal of cracks must be verified by magnetic particle inspection or equivalent. If cracks are completely removed as verified by such inspection, remove an additional 0.008 inch of material from the repaired area. Rework may be acceptable on outer cylinders with cracks that cannot be removed by grinding to a depth of 0.017 inch. Such cases may be submitted to the FAA for evaluation of the extent of cracking and to determine if rework is possible. Rework accomplished subsequent to such an evaluation must be in accordance with FAA approved repair instructions.
(2) On all cylinders,whether cracks are found or not, rework the area described in (c)(1) as follows:
(i) Clean and polish the above cylinder area to remove all tool marks and corrosion.
(ii) Shotpeen the above area using steel shot 0.019-0.033-inch diameter to an intensity of 0.012-0.016 A(subscript 2) ALEMENT (Reference LAC Process Bulletin 217M, Revision 1).
(d) Upon completion of the rework described in (c)(2), all Model 8298 cylinders shall be reinspected for cracks at periods not to exceed 9,000 hours' time in service using one of the inspection methods noted in (b). Cracked cylinders must be replaced prior to further flight. Cracked cylinders may be returned to service after repair and rework is accomplished in accordance with (c).
(Lockheed Service Letter FS/239304 covers this same subject.)
Revised April 9, 1960.
Revised September 15, 1960.