The Transportation Safety Board of Canada (TSB) recently released its final report (A03P0247) into the fatal crash of a Bell 204B helicopter that occurred shortly after take-off during a firefighting mission on Aug. 17, 2003.
The TSB investigation found that an imbalance of the engine compressor rotor assembly resulted in an engine failure. Due to extensive internal damage to the helicopter, no conclusion could be reached as to what caused the imbalance. The TSB also found that the helicopter pilot was unable to complete an emergency landing because of low altitude, and that the longline carrying an empty water bucket got tangled in trees.
The TSB is concerned with inconsistent placement of the external cargo release switch, which increases the risk of pilot confusion during an emergency when trying to release an external load hung underneath a helicopter. Furthermore, the report notes that the approved foot pedal backup release, used as an alternate means of releasing the line and external cargo during an emergency, is reduced in its effectiveness because the pilot must take one foot off of a primary flight control to operate it.
The Bell 204B helicopter operated by Gemini Helicopters Inc. was involved in forest fire suppression at Bonaparte Lake, British Columbia. At about 11:05 local time, the helicopter departed a staging site slinging an empty water bucket on a 100-foot longline for the first mission of the day.
Shortly after take-off, the helicopter emitted a high-pitched, oscillating sound. The flight path and behaviour of the helicopter were normal as it went out of view over some trees. Immediately thereafter, there was the pronounced sound of main-rotor blades flapping, followed by the sounds of impact with the trees. The helicopter struck the ground just short of reaching a small clearing adjacent to a fire road. A post-impact fire ensued. The water bucket was found in a tree, detached from the longline. The longline was wrapped around another tree, and 15 feet of the end of the line attached to the helicopter was burned away.
British Columbia Forest Service crews attended the site and extinguished the fire. The pilot was the sole occupant of the aircraft.
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