AT'MCHMENT II
CIVIL AERONAUTICS BOARD WASHINGTON 25, D. C. c o
P Y December 2? , 1963
Mr. George 80 Moore Dlrector
Flight Standards Serv1ce Federal Aviatlon Agency Washington, D‘ ‘C. 20553
Dear Mr .. Moore 2
The Board‘s recent investigation of two acc1dents 1nvolv1ng Aaxlco Air] ines C—hé, EJ679141 and N67935 at Great Falls, Montana, on August 1h, 1963 and Las Vegas, Nevada, September 25, 1963, respec- tively, revealed malntenance practices which, in our opinion, warrant your attention.
Our revuew of the maintenance records of N 6791;]. showed that opera- tlon of the aircraft had been transferred three times With the first and last operator during these transfers being Aaxlco Airlines. At each transfer, the aircraft time Since overhaul (T80) was adjusted in accordance With the proratlon formula outlined on FAA Advisory Circular 121-1. These adgustments resulted in the aircraft being operated beyond their approved overhaul time perlod. In the f 1nal transfer back: to Aaxico Airlines, this carrier gained appromately 790 hours of flying time on the subject aircraft solely by applications of the proration formula9
The Bureau recognizes the need for an equitable plan to establish overhaul time lmts for operations with V'an experlence levals. However, we do not belleve that the proration time on the percent of time to overhaul and the actual tnne Since overhaul should exceed the
approved T800
As a result of our investigation of this problem 1t is recommended that the proration formula in FAA Adnsory Circular 121-1 be reviewed to assure that TSO cannot be adJusted, as a result of transfer of air— craft, beyond the approved actual tme since overhaul. Furthermore, it is suggested that the aircraft records of Aaxmo Airlines be checked to assure that no other aircraft are being operated beyond their approved time 1mit by virtue of application of the proratlon formula-
