Port side door detachment leads to serious incident in Dauphin helicopter

Casualties unknown • 35 NM from Kamorta Helipad, IN

A Pawan Hans Ltd. Dauphin SA 365 N helicopter experienced the mid-flight detachment of its rear sliding and flap doors near Chowra Island.

What happened

On November 20, 2013, a Dauphin SA 365 N helicopter, registration VT-ELR, was performing scheduled inter-island services in the Andaman and Nicobar Islands. The flight was part of a multi-leg route involving Port Blair, Car Nicobar, Teressa, Katchal, and Kamorta. After completing several uneventful sectors, the aircraft departed Kamorta Helipad for Car Nicobar with five passengers and two crew members on board.

While cruising at 136 knots approximately 35 nautical miles from Kamorta, the flight crew experienced sudden vibrations. Shortly after, a loud bang echoed through the cabin, and the crew discovered that the port side rear sliding door and the flap door had completely detached from the aircraft. The pilot immediately reduced power and airspeed, then diverted to the nearest available landing site at Chowra Helipad. The aircraft landed safely at approximately 06:00 UTC with no injuries to the crew or passengers.

The investigation

An AAIB India inquiry examined the structural integrity of the aircraft and the maintenance history of the door components. Investigators analyzed the wreckage, including a portion of the flap door that had been recovered from the sea coast. The investigation also reviewed maintenance logs, noting that the aircraft had undergone both after-last-flight and before-first-flight inspections on the day of the incident, with no defects reported regarding the door mechanisms.

Findings

  • The investigation established that a progressive crack had developed in the upper rail of the left-hand sliding door, originating from a bolt hole.
  • This crack eventually led to a final overload fracture of a V-shaped portion of the upper rail.
  • The failure caused the front upper roller of the sliding door to detach from its track.
  • This detachment allowed excessive air pressure to enter the cabin through the partially opened door, which subsequently forced both the sliding door and the flap door to break free from their attachments.
  • The weather at the time of the incident was clear with good visibility, and the aircraft's weight and center of gravity were within limits.

Safety action

  • The operator was advised to review in-house inspection frequencies regarding door operations and the security of their attachments.
  • The inquiry recommended that the operator improve procedures for the traceability and record-keeping of non-serialized parts during replacement or cannibalization processes.

Probable cause

The incident was caused by the progressive failure of the left-hand sliding door's upper rail, which resulted in an overload fracture and subsequent detachment of the door and flap due to excessive air pressure.

Frequently asked questions

What happened in the 2013-11-20 M/s. PAWAN HANS LTD. DAUPHIN SA 365 N accident near 35 NM from Kamorta Helipad, IN?

A Pawan Hans Ltd. Dauphin SA 365 N helicopter experienced the mid-flight detachment of its rear sliding and flap doors near Chowra Island.

What aircraft was involved and where did it happen?

The accident on 2013-11-20 involved a M/s. PAWAN HANS LTD. DAUPHIN SA 365 N, registration VT-ELR, at 35 NM from Kamorta Helipad, IN.

What was the probable cause of the accident?

The incident was caused by the progressive failure of the left-hand sliding door's upper rail, which resulted in an overload fracture and subsequent detachment of the door and flap due to excessive air pressure.

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