Tail boom distortion leads to Bell 214B1 crash in British Columbia

Casualties unknown • Ramsay Arm, British Columbia, CA

A heavy-lift helicopter crash in Ramsay Arm, British Columbia, was caused by a fractured tail rotor driveshaft following structural weakening of the tail boom.

What happened

During a heli-logging operation in Ramsay Arm, British Columbia, a Bell 214B1 helicopter, registration C-FWQU, experienced a mechanical failure while attempting to pick up a load. The crew, consisting of an experienced pilot and a new co-pilot, first noticed a loud growling noise while hovering at 200 feet. The flying pilot immediately released the longline load and attempted to return to a nearby service area.

As the aircraft entered a high hover over the landing site, the growle ceased, followed by low oil pressure warnings for both tail rotor gearboxes. The helicopter then underwent a rapid rightward rotation. Unable to maintain directional control with the pedals, the pilot attempted an emergency landing in adjacent trees. The aircraft struck the trees and landed hard on uneven ground, resulting in one serious injury and one minor injury. The helicopter sustained substantial damage, though no fire occurred.

The investigation

Investigators examined the wreckage and identified that the No. 3 shaft in the tail rotor driveshaft assembly (TRDS) had fractured. This failure caused the loss of drive to the tail rotor and the subsequent loss of control. The investigation focused on the structural integrity of the tail boom and the service history of the driveshaft.

Analysis revealed that the tail boom had been subjected to extreme temperatures from engine exhaust throughout its service life. This prolonged heat exposure likely degraded the metallurgical properties of the metal skins, significantly reducing their strength and stiffness. Furthermore, the heavy-lift nature of the logging operations subjected the airframe to high-cycle loads, causing the tail boom to twist and buckle.

Findings

  • The tail boom's structural strength was compromised by long-term exposure to high exhaust temperatures.
  • This weakened structure allowed the tail boom to distort excessively during high-power operations.
  • The tail rotor driveshaft fractured due to severe scoring caused by heavy contact with the tail boom, which was triggered by the aforementioned structural distortion.
  • The driveshaft was also subject to in-flight bending that worsened the contact between the shaft and the tail boom.
  • The pilot's injuries would likely have been less severe had the shoulder harness been in use.

Safety action

Following the investigation, Black Tusk Helicopters voluntarily implemented a program to replace its Bell 214B1 tail boom skins every 5,000 flight hours.

Probable cause

The primary cause of the accident was the fracture of the tail rotor driveshaft, which resulted from the driveshaft making heavy contact with the tail boom. This contact was made possible because the tail boom's structural integrity had been weakened by heat from engine exhaust and subsequently distorted under the stresses of heavy-lift operations.

Frequently asked questions

What happened in the 2007-07-02 Bell 214B1 (Helicopter) C-FWQU accident near Ramsay Arm, British Columbia, CA?

A heavy-lift helicopter crash in Ramsay Arm, British Columbia, was caused by a fractured tail rotor driveshaft following structural weakening of the tail boom.

What aircraft was involved and where did it happen?

The accident on 2007-07-02 involved a Bell 214B1 (Helicopter) C-FWQU, operated by Black Tusk Helicopters, at Ramsay Arm, British Columbia, CA.

What was the probable cause of the accident?

The primary cause of the accident was the fracture of the tail rotor driveshaft, which resulted from the driveshaft making heavy contact with the tail boom. This contact was made possible because the tail boom's structural integrity had been weakened by heat from engine exhaust and subsequently distorted under the…

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