What happened
On 24 August 1998, during the Tall Ships Event in Dublin Port, a Sikorsky S61N helicopter, registration EI-MES, performed a demonstration involving the deployment of nine swimmers from the Irish Naval Service Diving Section into the River Liffey. The plan, which was a last-minute alternative to a winch-based rescue display, involved dropping the personnel from the aircraft while it was in forward flight rather than a stationary hover.
As the aircraft moved along the river, the crew dispatched the swimmers at intervals. During the maneuver, the aircraft was flying at a low altitude, descending to between 30 and 35 feet. As the personnel exited the aircraft, the high forward speed of the helicopter caused them to strike the water with significant force. The second person to jump suffered a concussion, and another diver sustained broken ribs and a collapsed lung. All nine passengers, including the crew, sustained various levels of injury, with several members of the diving team suffering extensive bruising.
The investigation
The AAIU investigation revealed that the demonstration was largely unrehearsed and lacked formal oversight. The aircraft commander and co-pilot had no prior experience in dropping personnel from helicopters. Furthermore, the mission was conducted without permission from the Irish Aviation Authority, as the activity fell outside the operator's approved manual.
Investigators found a significant discrepancy in the planning of the flight path. While the intended drop zone was approximately 1,300 meters long, the planned 5-second intervals between jumpers would have required a ground speed of roughly 64 knots—far exceeding the safe limit of 10 knots typically used for such maneuvers. The investigation also noted that the participants were under considerable pressure to deliver a spectacular display for the large public audience, and no independent safety coordinator was appointed to oversee the risks of the maneuver.
Findings
- The primary cause of the injuries was the excessive forward speed of the aircraft during the deployment of the swimmers.
- The aircrew lacked specific training and experience for this type of operation.
- There was a critical lack of planning, rehearsal, and established procedures for the demonstration.
- The absence of management supervision and a dedicated safety coordinator contributed to the unsafe execution of the flight.
- The jumping techniques employed by the Naval Service personnel were inconsistent with established safety standards used by comparable organizations.
Safety action
Following the incident, the AAIU issued an interim safety recommendation to cease the dropping of persons from civil helicopters until formal procedures and training requirements were implemented. Subsequent permanent recommendations directed the IAA to establish criteria for such operations and urged contractors to ensure that all public displays are properly rehearsed and supervised by a safety coordinator.