Unexplained Rotor RPM Decay Leads to Forced Landing of Eurocopter AS-350D

Casualties unknown • Cranbrook VOR Site, British Columbia, CA

A helicopter pilot was forced to perform an emergency landing in deep snow near Cranbrook after an uncommanded loss of rotor RPM during a climb.

What happened

Following a brief shutdown at a helipad near the Cranbrook VOR site, the pilot of a ski-equipped Eurocopter AS-350D, registration C-GBRC, prepared for departure with two passengers. After a successful initial hover and transition into a climbing, forward flight at approximately 7,500 feet, the aircraft experienced a sudden, uncommanded decay in main rotor RPM.

As the rotor speed dropped, the pilot attempted to regain power by pushing forward on the cyclic and lowering the collective. However, the loss of RPM rendered continued flight impossible. Facing an inevitable forced landing on a downward-sllyping, snow-covered surface, the pilot flared the aircraft at 30 feet above the ground and landed straight ahead into deep snow. The impact caused the helicopter to slide and roll onto its right side. While the three occupants escaped the wreckage without injury, the aircraft sustained substantial damage.

Notably, the onboard emergency locator transmitter (ELT) failed to activate despite being armed for flight, and the pilot had previously noted that the engine appeared to be running hotter than normal during the flight.

Probable cause

The sudden decay in main rotor RPM occurred during a high-power demand phase of flight at an altitude and airspeed that left the pilot with no margin to recover. While the exact cause of the RPM loss could not be definitively determined, investigators could not rule out mechanical malfunctions in the engine control components or potential engine air intake contamination.

Frequently asked questions

What happened in the 1998-01-19 Eurocopter AS-350D (Helicopter) C-GBRC accident near Cranbrook VOR Site, British Columbia, CA?

A helicopter pilot was forced to perform an emergency landing in deep snow near Cranbrook after an uncommanded loss of rotor RPM during a climb.

What aircraft was involved and where did it happen?

The accident on 1998-01-19 involved a Eurocopter AS-350D (Helicopter) C-GBRC, operated by BigHorn Aviation Inc., at Cranbrook VOR Site, British Columbia, CA.

What was the probable cause of the accident?

The sudden decay in main rotor RPM occurred during a high-power demand phase of flight at an altitude and airspeed that left the pilot with no margin to recover. While the exact cause of the RPM loss could not be definitively determined, investigators could not rule out mechanical malfunctions in the engine control…

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