Stockport air disaster

Investigation

Investigators with the Accidents Investigation Branch (AIB) determined that the double engine failure had been caused by fuel starvation, due to a previously unrecognised flaw in the model's fuel system. The Argonaut had eight fuel tanks, divided into pairs. Each pair fed one engine, but there was also a cross-feed system that allowed fuel from a pair of tanks to be fed to other engines, if necessary. It was found that the selectors controlling the cross-feed valves were poorly placed in the cockpit, and difficult to operate, also giving an unclear indication of what was selected. This could cause the inadvertent selection of cross-feed from some pairs of tanks, leading to the exhaustion of fuel in those tanks and the failure of the associated engine.

These problems had been noticed by pilots of other Argonauts before, but neither British Midland nor the other airlines using the Argonaut (Trans-Canada Airlines and Canadian Pacific Airlines) had reported it to the manufacturer. Without this information, the AIB believed that it would have been extremely difficult for the pilots of G-ALHG to determine the exact nature of the emergency.

A fuel problem had been noted on the aircraft five days earlier, but this did not come to light until four months after the crash. A third contributory factor was fatigue: the captain had been on duty for nearly 13 hours. This was within legal and operational limits, but the inquiry noted that he had made several errors in repeating ATC messages.

The AIB also examined passenger and crew survivability during the accident. Post-mortem examinations on the passengers showed that those in the very front of the fuselage had been killed by rapid deceleration injuries, but those further aft had suffered massive crushing injuries to their lower legs that stopped them from escaping the burning wreckage. Investigators found that the bracing bars meant to keep the rows of seats separate were too weak to stop the rows from collapsing together like a concertina, and determined that had the bars been adequately strong, most of the passengers would have been able to escape the aircraft.

Harry Marlow, the captain, survived but had amnesia and did not remember the accident, and the first officer died. The aircraft was over an open area at the time the starboard engines cut out, and AIB investigators believed that it became completely uncontrollable after the loss of power. There was testimony from witnesses that it made a pronounced turn to port and levelled out before descending into the crash site. This suggests that Marlow exerted a degree of control and successfully avoided hitting houses.