What happened
On a flight near La Grande-4 Airport, Quebec, a DHC-2 MKI Beaver, registration C-GUGQ, experienced an engine failure approximately 40 minutes after departing from Mirage Outfitter. The aircraft, operated by Propair Inc. for the purpose of locating caribou, was flying at an altitude of roughly 1,800 feet when the engine stopped. The pilot, who was monitoring caribou tracks, initially mistook a low fuel pressure warning light for a sun reflection. Shortly after, the engine sputtered and lost all power.
Unable to reach a nearby lake, the pilot performed a forced landing on rough, sparsely wooded terrain. During the impact, the aircraft's skis and main landing gear were torn off, and the right wing broke. The impact caused the seat anchors in the second row to detach, leading to two serious injuries: one passenger suffered a serious back injury, and another sustained a head injury that resulted in the loss of an eye.
The investigation
The investigation focused on the aircraft's modified fuel system, which had been altered following the installation of new wings by Advanced Wing Technologies Corporation. Investigators examined the fuel level estimation method used by the pilot, which involved a manual wooden gauge. They also analyzed the fuel level indication system and the reliability of the low fuel pressure warning light.
Technical examinations revealed that the fuel senders were unreliable, often providing incorrect readings due to ice or water. Furthermore, the investigation looked into the regulatory oversight regarding the Supplementary Type Certificate (STC) that authorized the fuel system modifications.
Findings
- The engine failure was caused by fuel starvation.
- The pilot's estimate of available fuel was inaccurate because the wing tanks contained less fuel than believed.
- The fuel level gauges provided erroneous readings, and the low fuel pressure warning light was prone to random illumination.
- The low altitude at the time of the engine failure left insufficient time to execute emergency restart procedures.
- The pilot's attention was diverted by the task of searching for caribou.
- The severity of the injuries was increased because the pilot and the front passenger were not wearing their shoulder harnesses, which were stored in an inaccessible location under the interior covering.
- The STC issued by Transport Canada contained several technical deficiencies, including non-compliant fuel senders and improper valve guards.