Product Improvement Test of Mast, P/N 204-040-366-7, in the UH-1D Helicopter.
ARMY AVIATION TEST BOARD FORT RUCKER ALA
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The purpose of this report is to develop for and provide to the Iroquois Project Manager the results of operational experience on modified mast assembly, relative to its suitability. The established time between overhaul TBO of the standard mast assembly, PN 204-040-366, was 300 hours due to a history of excessive wear of the main mast bearing. Action was taken to modify main mast bearings to reduce bearing wear and increase the TBO of the mast assembly. The manufacturer modified the mast assembly by incorporating hardened steel M-50 ball bearings in the main mast bearing. The modified mast assembly PN 204-040-366-7 is the test item for this report. It is concluded that 1 The mast assembly incorporating the M-50 mast bearing is suitable for use on the UH-1 helicopter 2 The test mast bearing SN 10 is unserviceable for further flight testing 3 Further test data are required before an operating period beyond 1100 hours can be established. 4 The TBO of the mast assembly 1100 hours currently authorized by TM 55-1520-211-20, dated April 1965, is valid.
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