External Load Swing Causes Incident During Helicopter Delivery in Frankfurt

Casualties unknown • Frankfurt am Main, DE

A 350 kg external load swung over a skyscraper parapet during a delivery operation in Frankfurt, resulting in minor injuries to ground personnel and property damage.

What happened

On June 11, 2011, an Aérospatiale SA 365C3 helicopter was performing an external load delivery operation in downtown Frankfurt am Main. The mission involved placing a 350 kg load into a specific opening on the roof of a high-rise building. An instructor/observer was on board to assist the pilot, while ground crew waited on the rooftop to receive the load.

At approximately 12:45 local time, after the load had been positioned into the rooftop opening but while it was still attached to the aircraft, the helicopter began to drift backward during a hover. Upon being alerted, the pilot attempted to correct the position by maneuvering the aircraft forward. This movement caused the sling to tighten, which lifted the load and caused it to become wedged. In an attempt to resolve the unstable situation, the pilot released the load. The sudden tension caused the load to swing over the building's parapet, falling approximately 50 meters into an interior courtyard.

The investigation

The BFU investigation reviewed video footage of the flight, which confirmed that the helicopter initially hovered above the building before descending, moving forward, and being pulled downward by the load. The investigation also examined the pilot's credentials, noting 4,700 total flight hours, with 1,000 hours on the SA 365C3, though only 15 hours of experience specifically involving external load operations. The aircraft, a 1971 model, was found to have no mechanical damage following the incident, and the investigation confirmed the pilot was properly licensed for the aircraft type.

Findings

  • The primary cause of the incident was the uncontrolled movement of the external load after the pilot attempted to correct a backward drift.
  • The pilot's forward maneuver caused the sling to tighten, leading to the load wedging and subsequently swinging over the edge.
  • Limited visual references from the cockpit made it difficult for the pilot to maintain precise positioning during the hover over the high-rise.
  • The falling load struck several bicycles and a canopy in the courtyard, causing minor third-party property damage.
  • One ground crew member on the rooftop sustained one minor injury while attempting to move away from the shifting load.

Probable cause

The incident was caused by the sudden tensioning and subsequent swinging of the external load, triggered by the pilot's corrective maneuver to counteract the helicopter's backward drift during a hover.

Frequently asked questions

What happened in the 2011-06-11 Aérospatiale SA 365C3 accident near Frankfurt am Main, DE?

A 350 kg external load swung over a skyscraper parapet during a delivery operation in Frankfurt, resulting in minor injuries to ground personnel and property damage.

What aircraft was involved and where did it happen?

The accident on 2011-06-11 involved a Aérospatiale SA 365C3, at Frankfurt am Main, DE.

What was the probable cause of the accident?

The incident was caused by the sudden tensioning and subsequent swinging of the external load, triggered by the pilot's corrective maneuver to counteract the helicopter's backward drift during a hover.

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