Page:CAB Accident Report, New York Airways Flight 600.pdf/5

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This new assembly was operated in N 6675]) from January 23, 1963, until February 18, 1963, when it was removed by New York Airways, because of a machining curl on the sump plug. The assembly Was returned to Vertol for repair. The spec- imen was again taped in the transmissmn overhaul logbook. Accumulated times were T30 91;: 5 and TT 8:23:23. The final cement to Mechanical Reliability Report (MRR) 63-6E regarding this discrepancy stated in part, ". . . They were isolated as being foreign particles possibly originating from a previous machining operation. . . ." Followmg return to serVice February 23, 1963, it was operated for one week and again removed for metal on the sump plug and broken gear teeth in the sump. This discrepancy was MRR 63-9. The (3103ng report on this common stated, ". . . Disassembly of the mix box revealed failure of the Helical Gear P/N 107132059-2 installed on the input pinion shaft P/N 107D2058-2. Twenty—three (23) of the twenty-eight (28) teeth on this gear were sheared off. Three of the teeth eiridenced fatigue, the remainder were ultimate failures . . . Boeing-Vertol con- clude(s) that this failure is (attributable) to gear misaligmient caused by ex- cessnre bearing liner wear . . ." On April 23, 1963, the assembly was installed in N 667hD where it operated until August 6, 1963, when it was again removed. HER 63—32 described this discrepancy as steel particles found on the sump plug and strainer. TT was now 1170:16 and T80 hhl:h8. Vertol reported that spelling had occurred through approximately a 30-degree periphery of the roller path outer race on the aft collector gear bearing, P/N D2—h5365. FolloWing repair this assembly was installed in N 6673B September 5, 1963, where it remained until the accident when the TT was 1,338:35 and T80 610:06.

The metal shaVings found in aft transmissmn S/N TA 9-10 during the initial load run, and at TSO 9h25§ were removed from the transmssion overhaul log sheets where they were taped, and submitted for metallurgical tests. It was determined that they were both AISI [4130 steel. Additional tests were made on a metal mobili- ing curl taken from aft transmiSSion S/N TA 9-9 on November 3, 1963. This was identified as AISI h3h0 steel, a substitute grade for AISI 13130.

In an effort to duplicate the fatigue failure of the quill shaft, a test

run was performed at Vertol. An aft transmiSSion was mounted on the test stand which has an adapter to represent the mix box. A tapered shiws utilized to introduce one-half degree of misalignment on the quill shaft. Normal lubrica— tion was pronded for 35 hours at 100 percent of torque. This produced some fret— ting and slight wear of the Silver plate on the quill Shaft. The test conditions were then altered to provide only one-quarter degree of misalignment for the next 50 hours. Exanunation at the end of this time revealed the Silver plate was worn off in a Single Spot on each of three teeth. A magnaflux inepection failed to indicate any cracks. The normal lubrication was then stopped, and the one-half degree misalignment shim was reinstalled. Following 50 hours operation under these conditions With only 50 percent torque, the subgect quill shaft evidenced trans- verse cracks across three of the Spline teeth. The quill shaft had now accumula- ted 135 hours on the test stand. Sixteen more hours of operation produced addi- tional cracks and a previous crack had propagated through the wall of the shaft

13/ AIL MRR numbers are those of New York Airways and not those later asSigned by the—FAA.

111/ Warping of the castings of mix box S/N A 11-102 by post impact fire pre- vented—a determination of misalignment. The mammun misalignment found in checking other transmissions was 1/8 degree.