- 7 -
The aircraft had been serviced with the proper type of fuel, and it is believed that the ADI and autofeathering systems were capable of normal operation.
Examination of the powerplants revealed that all four engines were capable of producing adequate power. Judging from the examination of the propeller assemblies, the power being developed by the engines was that customarily used to execute successfully a GCA approach to a normal landing under the existing weather conditions. The minima applicable to the captain for a GCA approach at Shemya were: ceiling 400 feet and visibility 3/4 mile. The weather transmitted to the flight by the GCA controller, according to his testimony, was ceiling 200 feet and visibility 1/2 mile.
Our examination of fuel management logs, the fuel quantities indicated on the main tank gauges, coupled with the fuel report given approximately 26 minutes prior to the accident, and the lack of any foreign matter in fuel lines, strainers, and sumps, leads us to conclude that fuel flow to all engines was normal prior to impact and was commensurate with the throttle settings.
Control surfaces and control mechanisms seem to have been in normal operation. There is no evidence that any of the aircraft systems malfunctioned.
Examination of the structures of the aircraft showed that they were integrally sound before impact. The landing gear was down and locked, and the wing flaps were properly and fully extended for completion of the final approach and landing. The landing lights were extended and believed to have been on inasmuch as they were observed by and eyewitness to have been on. Since the landing lights were on, it is believed that the aircraft was below the clouds during some portion of the approach. Use of these lights in the clouds would have caused adverse reflection to have been experienced by the crew. Consequently, this would have hampered their ability to make visual contact with the runway.
The No. 1 VHF radio equipment aboard the aircraft was operating normally, at least until the time the GCA operator actuated his transmitter on 134.1 mcs. to give instructions to the flight upon beginning the GCA final approach. If, during the final approach, the flight were to have transmitted a distress message on that frequency it would not have been heard by the GCA controller; however, it would probably have been heard by persons standing in the Northwest Airlines operations building who were monitoring 134.1 mcs. and 121.5 mcs. The lack of any transmissions on either frequency by the flight supports the view that no emergency existed. Since the No. 2 VHF receiver was tuned to 125.4 mcs. and the associated transmitter to 124.5 mcs, it is assumed that they were either mistuned or not used.
The weather conditions existing at Shemya Airport at the time of the accident averaged a 200-foot ceiling and one-half mile visibility. The ceiling was reported to have been varying from 100 to 300 feet and the reporting of a ceiling of 200 feet is permissible practice by the U. S. Weather Bureau under these conditions. The forward visibility of the crew when it was over the approach lights could have been as low as one-half statute mile if the aircraft had been clear of clouds in that area. Conditions of temperature and moisture in the approach zone were not conducive to structural icing, and it is therefore not considered to have been a problem. Also, according to the sun and moon data, the accident occurred during the hours of complete darkness.
