Accident Overview
On a flight from Rivers Air Force Base in Manitoba to North Battleford, a technical failure occurred involving the front cargo door. The door detached in flight, prompting the crew to reduce altitude and attempt an emergency landing. The aircraft executed a belly landing in a field near North Battleford, slid several yards, and came to rest. No injuries were reported among the crew, but the aircraft was considered damaged beyond repair. After the accident, engine number one could not be stopped, likely due to debris impact.
Incident Sequence
During the flight, the front cargo door unexpectedly opened and separated from the aircraft. The crew responded by lowering altitude and initiating an emergency landing procedure. The belly landing was carried out in a field, where the aircraft slid before stopping. Post-accident, engine number one continued running uncontrollably, suspected to have been struck by debris from the door detachment.
Investigation Findings
Investigators determined that the door opened in flight, detached, and was later found 15 miles from the accident site. The cause was attributed to both material failure and maintenance error. The latching mechanism consisted of four eyebolts; failure occurred when the number 1 eyebolt ruptured due to over-stressing, subsequently causing the number 2 eyebolt to fail as the load was transferred. The number 1 eyebolt had been cracked for some time, with only two-thirds of its cross-sectional area carrying the load at the time of failure. Analysis indicated that both the initial crack and the ultimate failure resulted from overloading, with rough machining during manufacture contributing to crack formation. Misalignment during door rigging was strongly suspected as the source of the overload.