-10-
increase drag were used. It was found that with all engines developing approach power, the No. 3 propeller in reverse thrust, and the Nos. 1, 2, and 4 propellers in forward thrust, the descent rate would increase to about 1,845 feet per minute. Then, with approximately 50 inches of engine power applied to this combination it was indicated that the descent rate would eventually decrease to about 535 feet per minute.
Since it is difficult to predict or determine the exact blade angles and engine power that may have existed during each of these flight regimes, the calculations are intended only as a rough approximation of the relative magnitudes of the sudden increase in descent rate with which the pilot was suddenly confronted. Moreover, the value for drag used in the calculations is considered conservative in that no attempt was made to account for the increase in drag due to presumed large control surface deflections during the maneuver.
In addition, a series of L-1049G flight simulator runs were conducted in order to obtain more refined information concerning aircraft controllability under essentially the same conditions as used in the calculations. Data supplied to the simulator produced a 15 percent lift loss over the right wing due to propeller reversal and a less conservative drag value of approximately 9,000 pounds. The result of these tests, although qualitative, produced an initial descent rate of approximately 1,800 feet per minute and indicated that under these prescribed conditions of flight, Successful recovery could not be effected.
Examination of the four engines revealed no evidence of operating distress prior to impact; however, all of the engines did exhibit discrepancies[1] the nature of which did adversely affect the airworthiness qualification of the aircraft. Although these discrepancies did not in themselves directly relate to the cause of the accident, they are indicative of inadequate maintenance practices and inspection procedures on the part of the carrier.
Moreover, a comprehensive review of all maintenance records pertaining to aircraft N 189S revealed that these records both in terms of quantity and quality were not sufficient to present an accurate history of the aircraft and engine components. Many instances of inaccurate, erroneous, and incomplete data were found including evidence of time controlled components remaining on the aircraft beyond replacement times.
Similarly, maintenance records for the failed propeller power unit (S/N 165047), were conflicting, incomplete, and from them, accurate component time control information could not be obtained. However, on the basis of all investigative data, it can logically be concluded that the unit was installed in the No. 3 position of aircraft N 9742Z on July 10, 1962, following the overhaul on July 6, 1962. It remained in this position until February 4, 1963, at which time it was removed from N 9742Z and installed in the No. 3 position of aircraft N 189S. It remained in this position until the time of the accident. Consequently, the unit was in the No. 3 positlon of N 9742Z on January 6, 1963, when, according to the aircraft flight logs all propeller power units were adjusted. [2] This is the last record of any adjustment to this unit which would have involved removal and reinstallation of the brake cage.
