Page:CAB Accident Report, New York Airways Flight 600.pdf/6

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and was Visible around 90 degrees of the inner Circumference. The test continued another 10 hours to a total of 161 hours. At this time the largest crack had turned 90 degrees and traversed the unsplined center portion of the shaft, run- ning into the Splines on the forward end. A lO—percent loss in develOped torque was experienced during this 10 hours and the test of this quill shaft was discon— tinned. A Vertol staff engineer testified at the public hearing that the test equipment had no prOViSion for reverSing or altering the loads on the shaft splines while the equipment was operating, thus precluding the Simulation of a typical flight spectrum. Consequently, a direct relationship between the test hours and actual flight hours does not exist.

The initial operating time limitations governing the overhaul intervals on new aircraft and components is a determination of the FAA. A Maintenance Renew Board performs this function. It is composed of the Air Carrier Mainten- ance Branch Chief or his deSignated representative, who acts as chairman, and other specialists as deemed necessary. Representatives of the manufacturer and air carriers proposing to use the product may be invited to attend in an adirisory capaCity. The Component Sampling Program of the Maintenance Review Board Report for the Boemg-Vertol lOT-II states, ". . . Overhaul periods will be increased or substantiated on the heels of satisfactory semce experience and satisfactory disassembly inspections as speoified in each of the follomng notes. . . o " The aft transmission schedule requires two samples each at 150 and 200 hours, and three samples each at 1400, 600, 800, and 1,000 hours of operation.

The chairman of the Maintenance ReView Board for the Vertol lOT-II testified that the sampled quantity of aft transmissmns was approxnnately 75 percent of the New York Airways fleet, whereas normally the percentage sampled varies from 10—25. Also, there is an allowaole deviation in accumulated time on the exhibits to be sampled, not to eXceed an average of 50 hours below the dean-ed plateau for each.

The actual inspection of disassembled transmiSSions at Vertol is accomplished by representatives from New York Airways, Vertol, and inspectors from ACDO #3’4. The first aft transmiSSion assemblies to accumulate the deSired number of hours of Operation are removed from serVice and sent to the Vertol plant. Each is then disassembled and examined. If the exhibits sampled are found satisfactory, the overhaul limitation on all aft transmiSSion assemblies is then increased to the next plateau. It is the responSibility of the FAA Maintenance Inspector who attends this inspection to reco and approval or disapproval of the reViSion to the Operations SpeCifications}... - Maintenance. Authority for the actual apprOVal for New York Amys' requests is vested in the SuperViSing Inspector of A0330 #BE; however, it has been the practice of the FAA inepector present at the final sam— pling of each plateau, to grant verbal approval for an immediate increase in the overhaul period. He then recommends that the SuperViSing Inspector Sign the revi- sion request submitted by the carrier.

The PrinCipal Air Carrier Maintenance Inspector for New York Airways. and the SuperviSing InSpector of A0130 #3h testified at the public hearing that the in-serVice experience of all parts in use, and not Just those which are used as exhibits in the sampling process, are evaluated before deCiding whether an increase in overhaul time should be granted. They both indicated that there did not appear to be any history of time-related failures or malfunctions in aft transmiSSion assemblies.

IS/—Operations SpeCifications are rules of particular applicability issued to an air-carrier by the FAA Administrator.