-6-
Examination of the two propeller assembles revealed extensive damage as a result of ground contact. The left propeller blade angle at time of impact was on the low pitch stop; the right propeller was feathered.
No evidence of pre-impact failure was found in the propeller, fuel or oil systems of the left engine.
Tear down of the right engine indicated the front master rod bearing had failed and had been flattened and squeezed out over the link pins that connect the link rods to the master rod cluster. Extensive metal particles clogged the lubrication hole in the front crankpin, and the front crankpin journal was scored and imbedded wth metal. The secondary counterbalance and the rear master rod bearing and cam bearings were all heavily scored.
Metal particles were present in the nose case, the scavenger screens and pumps, the oil cooler, the front crankpin journal, and the lubrication holes of the front counterweight bearing. Many of the oil system jets were clogged by metal particles.
The right engine oil pressure regulator valve was found stuck in the "full pressure" or minimum by-pass position and its appearance indicated it had been subjected to considerable heat. There was no evidence of any foreign material in the valve.
A review of maintenance records on the right engine indicated that it had last been overhauled and zero timed on November 13, 1962. It was installed in the right position on another C-46, N 67941, on June 26, 1963, with 814:17 TSO.[1] Although the aircraft was under lease at the time, this installation was accomplished under the supervision of an AXXICO maintenance representative. A review of all writeups on the engine subsequent to its last overhaul revealed no significant chronic malfunctions or items to suggest future failures.
During the investigation of this accident, AXXICO maintenance records disclosed that N 67941 had been transferred from AXXICO to Captiol Airways in 1960; then to Zantop Air Transport in 1962; and back to AXXICO in 1963. By the use of the proratlon formula authorized in FAA Advisory Circular No. 121-1 in ascertaining the percentage of aircraft overhaul time expended by one operator when establishing the time remaining to overhaul for another operator acquiring the aircraft, AXXICO gained 791 hours of airframe time on N 67941.
When questioned about exceeding the engine's oil temperature and pressure limitations, the captain stated: "In the past, I have had an oil temperature running at the red line or above it. I never had attached - I felt that it is not normal according to the figures that are put down in the book, but I still felt it was normal for the airplane.“
The captain had renewed his C-46 type rating in 1950. He had acquired a total of over 15,800 hours and had flown approximately 5,800 hours in the C-46 as pilot-in-command since that time. He joined AXXICO Airlines on July 1, 1961, and for two years, flew as a captain on Douglas (C-118 aircraft operated by AXXICO on bailment from the U.S. Air Force; In preparation for flying C-46 aircraft on LOGAIR contracts, he was given 40 hours of ground school, 1:30 hours of bank
- ↑ 6/ The engine had been installed on and removed from two previous aircraft prior to this time.
