What happened
On a morning in July 1999, a Bell 214B helicopter departed a staging area near the Glacier Creek forest service road, northwest of Cranbrook, British Columbia. The flight was being conducted under local visual flight rules for heli-logging operations. The aircraft was occupied by a pilot and three crew members.
Shortly after takeoff, the pilot performed a power check and communicated via radio that foggy conditions prevented logging operations. While flying approximately 400 feet above the ground, the engine noise suddenly ceased. Witnesses observed the helicopter trailing white vapor from the exhaust as the main rotor blades began to slow. The aircraft performed a 180-degree left turn and descended into a shallow, rapidly flowing river. The impact was severe, causing the helicopter to break into several pieces. Four fatalities occurred; while the pilot survived the initial impact, he succumbed to his injuries 45 minutes later.
The investigation
The investigation focused on the engine, fuel system, and the pilot's recent training history. Investigators examined the Lycoming T55-08D engine and found that while certain components were worn, the engine could not be run following the crash. Analysis of the cockpit instruments revealed that at the moment of impact, the engine RPM was at only 3 percent and the rotor RPM had dropped to 16 percent. Warning lights for low fuel and a low boost pump were illuminated.
Technical examinations of the fuel system revealed that the aircraft's fuel quantity gauge could provide misleading information. Specifically, if a boost pump fails, the gauge may indicate more fuel is available than is actually usable because the system does not directly measure the fuel in the left forward cell. Additionally, the investigation noted that the aircraft had been modified to allow the pilot to fly from the left seat, but a required supplemental type certificate had not been issued.
Findings
- Inaccurate fuel quantity indications caused by the design of the fuel system can lead pilots to believe more fuel is available than is actually present.
- A failure of a fuel boost pump can lead to fuel starvation because fuel transfer between cells becomes slower than the engine's fuel consumption.
- The pilot had not received recent recurrent training on this specific aircraft type, and previous proficiency checks had noted a need for improved emergency procedure handling.
- The flight manual for the Bell 214B did not sufficiently explain the serious consequences of a boost pump failure or the potential for incorrect fuel readings.