What happened
On 21 October 2004, a Eurocopter SA 365N, registration EI-MIP, was performing a scheduled platform support flight within the Kinsale Gas Field. After completing a passenger transfer at Platform Alpha, the aircraft proceeded to Platform Bravo. While the crew was in the process of disembarking passengers, a heavy squall approached the platform from the southwest.
As the weather closed in, the helicopter was subjected to intense turbulence and violent shaking. To prevent a potential rollover, the pilot flying applied a roll correction and subsequently increased collective to lift the aircraft off the deck. During this period of extreme weather, the aircraft encountered heavy rain and hail, which severely limited visibility. The crew managed to fly the aircraft out of the squende and return to Cork Airport. A technical inspection following the event revealed that the helicopter's gearbox had experienced a slight over-torque of 3.3%.
The investigation
The AAIU examined flight data from the Flight Data Recorder (FDR) and the Integrated Helicopter Usage Monitoring System (IHUMS). The data confirmed that the aircraft was subjected to significant turbulent conditions while on the deck, with the flight crew intentionally taking off to avoid the worst of the weather. The investigation also reviewed meteorological data from Met Éireann, including radar images and tephigrams, to understand the nature of the atmospheric event.
Investigators also looked into the structural aspects of the offshore platform. While the helideck was properly certified, the investigation considered how the presence of ancillary equipment, such as water tanks and shelters, located within the air gap beneath the deck might influence airflow and turbulence during extreme wind events.
Findings
- The primary cause of the event was a severe Cb downdraught associated with an active squall/shower.
- The pilot flying demonstrated exceptional skill in maintaining control of the aircraft during near-instrument meteorological conditions while in close proximity to the platform.
- The intense rain and hail significantly reduced visual references during the critical period of takeoff.
- While the aircraft's air gap was designed to allow disturbed air to pass under the deck, the presence of equipment in that space may have contributed to the turbulence experienced.