Pilot Debrief

EUROCOPTER AS350 B3 near Beluga, AK — 2012-12-15

Final reportANC13FA017
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Date
2012-12-15
Location
Beluga, AK, USA
Aircraft
EUROCOPTER AS350 B3
Registration
C-GYPH
Category
Helicopter
Highest injury
Serious
Fatalities
0
Phase of flight
Cruise

Probable cause

The pilot's failure to stabilize the external load, which led to the synthetic long-line separating about midspan and the remaining line becoming entangled in the tail rotor gearbox output shaft and resulted in the separation of the tail rotor gearbox and subsequent loss of control. Contributing to the accident was the pilot's inadequate training.

Contributing factors

Contributing to the accident was the pilot's inadequate training.

NTSB narrative

The commercial helicopter pilot was transporting a 1,000-pound external sling load attached to a lightweight, synthetic 100-foot long-line when the load began to spin and swing underneath the helicopter. As the helicopter neared its destination, it suddenly yawed, and then started to spin uncontrollably, and the pilot immediately jettisoned the external load. As the helicopter continued to spin uncontrollably, it descended into an area of tall trees and then came to rest on its left side. A postaccident inspection of the helicopter revealed that portions of the severed lightweight synthetic long-line had become entangled in the tail rotor gearbox output shaft and that the tail rotor gearbox assembly was torn free of the tail boom. Examination of the long-line revealed that its entire length was tightly wrapped, knotted, and kinked. The pilot reported that he had not received training in procedures to adequately stabilize external sling loads. Given the postaccident condition of the lightweight synthetic long-line, the pilot's statements, and the lack of a rotating swivel, it is likely that, once the external load began to spin, the long-line continued to tangle and tightly knot and ultimately reached its breaking point. Once the synthetic long-line separated, the portion still attached to the belly of the helicopter recoiled upward and eventually became entangled with the tail rotor gearbox output shaft. In addition, it is likely the pilot did not adequately monitor the condition of the external sling load while en route, and he failed to recognize the need to stabilize the load.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have used a different long-line with a rotating swivel to prevent load issues.

NTSB coding

Evidence available

  • Photos
  • 15 docket documents
View NTSB final reportView NTSB docket

Docket documents15

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