Accident Overview
On a fire-management mission, Tanker 86, a Lockheed Electra, departed from Runway 16 at Cranbrook Airport in British Columbia. The aircraft was tasked with delivering fire retardant on a small ground fire designated N10156, located two nautical miles southwest of the township of Cranbrook.
Flight Details
A partner aircraft, a Turbo Commander serving as a "bird dog," had departed Cranbrook seven minutes earlier to assess flight path profiles and establish a suitable retardant delivery program. After the bird dog's demonstrations, Tanker 86 proceeded to execute the retardant drop. Following the delivery, the Electra was observed turning right initially, then entering a left turn.
Impact and Aftermath
At 1221 Mountain Standard Time, the Electra struck the terrain on the side of a steep ridge at approximately 3,900 feet above sea level. The aircraft exploded on impact, and both pilots were fatally injured. An intense post-crash fire consumed much of the wreckage and ignited a forest fire at the crash site and surrounding area. The onboard emergency locator transmitter (ELT) was damaged by impact forces and did not activate.
Probable Cause
The official investigation identified the following causes and contributing factors: 1. For undetermined reasons, the Electra did not climb sufficiently to avoid striking the rising terrain. 2. Given the flight path and the rate of climb chosen, a collision with the terrain was unavoidable. 3. The characteristics of the terrain were deceptive, making it difficult for the pilots to perceive their proximity and rate of closure to the rising ground in sufficient time to avoid it.
Other Findings
Additional findings from the investigation include:
- Performance calculations indicated that, in the absence of a limiting mechanical malfunction, the Electra could have climbed at a rate sufficient to avoid the terrain.
- Although a functional cockpit voice recorder was installed, it was not required by regulation and was not used; consequently, vital clues that could have shed light on the accident circumstances were unavailable.
- The ELT failed to transmit due to severe impact forces that exceeded its design criteria.