Page:NTSB Aircraft Accident Report, United Airlines Flight 389.pdf/13

 A review of the aircraft records revealed a number of pilot writeups regarding the autopilot. In summation, the complaints were that the auto-pilot was trimming for pitch attitude, but the stabilizer did not trim to make a correction. The out-of-trim light on early B-727 aircraft had a delay relay which was set for two seconds, in the circuit. If the elevator held a pitch correction signal for more than two seconds, the out-of-trim light illuminated until the stabilizer corrected for trim. None of the writeups reflected any difficulty with control of the aircraft. A total of seven pitch channel assemblies were removed to answer these pilot complaints and five of them were bench checked and found to be satisfactory. The last writeup on the autopilot was cleared at Los Angeles on August 15, 1965 and no further entries regarding it were found in the aircraft records.

The aircraft was serviced with 2,443 gallons of aviation kerosene which gave it a total of approximately 4,950 gallons of fuel aboard before taxi-out. The total aircraft weight was 123,013 pounds and the c.g. was computed to be 26.2 percent MAC, within the limits specified for this operation.

The aircraft was equipped with three Pratt and Whitney JT8D-l engines. Two of these engines were installed by the manufacturer of the aircraft and had 610 hours of operation. The No. 2 engine was installed July 5, 1965, and had operated a total of 34 hours. None of these engines had been overhauled.

All the airworthiness directives applicable to this aircraft had been complied with.