Hoist cable snap causes damage to Sikorsky S 61 N during training

Casualties unknown • IE

A training flight involving a search and rescue helicopter resulted in significant rotor blade and cockpit damage after a winch cable snagged and sheared.

What happened

On 17 January 2006, a Sikorsky S 61 N helicopter, registration EI-SAR, was conducting a routine training mission near the Conningbeg Lightship, located approximately 5 nautical miles south-southwest of the Saltee Islands. The crew, consisting of five members, was performing winching exercises when an incident occurred during a transfer to the vessel's bow.

As the winchman attempted to detach from the hoist hook, the ship's bow pitched downward due to a 2-meter swell. This movement caused the winch cable to loop around a small steel protrusion on a ladder. As the winch operator began to retract the cable, the tension caused the cable to shear just above the hook attachment point. The sudden release caused the cable to recoil violently upward, striking the main rotor blades and the cockpit canopy. The impact punctured the cockpit'1s upper observation window and displaced the outside air temperature probe into the cockpit. Despite the damage, the crew successfully returned the aircraft to Waterford Airport without further incident. One crew member sustained a minor hand laceration.

The investigation

The investigation focused on the mechanics of the cable failure and the physical configuration of the rescue hoist. Investigators examined the damage to the two main rotor blades, which sustained extensive tearing and scoring, and the cockpit structure. The analysis also looked at the winch hook assembly, specifically noting the presence of a hoist ring.

Findings

  • The primary cause of the incident was the cable snagging on a welded steel protrusion on the lightship's ladder.
  • The sudden downward pitch of the vessel's bow placed extreme load on the snagged cable, leading to its failure.
  • The presence of a hoist ring on the assembly was identified as a contributing factor, as it can obstruct the operator's ability to quickly manipulate the hook and increases the profile of the assembly, creating a larger snagging hazard.
  • The recoil of the cable was responsible for the extensive damage to the rotor blades and the cockpit canopy.

Probable cause

The cable sheared because it became snagged on a metal protrusion on the lightship's ladder during a period of heavy vessel motion, with the hoist ring potentially complicating the operator's ability to clear the hazard.

Frequently asked questions

What happened in the null aircraft accident near IE?

A training flight involving a search and rescue helicopter resulted in significant rotor blade and cockpit damage after a winch cable snagged and sheared.

What aircraft was involved and where did it happen?

The accident on null involved a aircraft, registration EI-SAR, at IE.

What was the probable cause of the accident?

The cable sheared because it became snagged on a metal protrusion on the lightship's ladder during a period of heavy vessel motion, with the hoist ring potentially complicating the operator's ability to clear the hazard.

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