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Examination of the flight controls, wings, tail surfaces, and control surfaces failed to show any ev1dence of inflight malfunction or failure.
Human Factors
In an effort to determine whether or not any physiological factors may have caused or contributed to this accident, complete autops1es were performed on the captain and the copilot.
The captain was found to have had no preexisting disease, condition, or defect which could be related to the accident. Laboratory test failed to show the presence of either alcohol or drugs. The captain was found to have suffered multiple severe injuries caused by forces of abrupt deceleration.
The autopsy of the first officer was negative for evidence of preexisting disease, condition, or defect which could be related to this accident; however, it was determined that this first officer, who was 32 years old, had marked atherosclerosis of the coronary arteries. Examination of the heart including microscopic studies of the heart tissues, failed to adduce any evidence of either old or recent scars or of dead tissue. The autopsy showed the existence of multiple severe injuries which included a fracture of the skull, epidural hematoma (150 cc.), and traumatic amputation of the low extremities.
The distribution of cockpit wreckage and the position of the three crew members' bodies showed that the captain was occupying the left seat, the first officer was occupying the right seat, and the additional crew member was occupying the jump seat.
Analysis
Powerplants, Propellers, and Structures
The factual information developed in the investigation shows that no malfunction of the aircraft engines, propellers, or structure caused or contributed to this acc1dent.
Operational Aspects
The possibility of an inadvertent caging of the fluxgate compass while the aircraft was in the right landing pattern necessitated a detailed exploration of this possibility. The flight tests conducted showed that the caging switch could be actuated inadvertently by the foot of a person occupying the jump seat and that a serious error could thereby be induced into this system.
The policy Allegheny Airlines followed on an instrument landing approach such as the one at Williamsport is that the approach will be flown by the captain while occupying the left seat. During such an approach therefore the captain in the left seat and while flying in a right pattern would have the airport to his right and he would have had some difficulty in keeping it in sight. In addition, the aircraft on the base leg segment of the circling approach was intermittently in snow showers or clouds.
It is believed that during the base leg the captain relied on the MDI of the flux-gate compass owing to the weather and cockpit visibility restrictions that existed
