Missed approaches to a Canadian oil rig in bad weather have triggered a lawsuit from the passengers, charging the experience caused mental distress, including post-traumatic stress disorder. Operated by Canadian Helicopters, the Canadian Helicopters Offshore (CHO) Sikorsky S-92A departed Halifax Stanfield airport at 11:54 local time on July 24, 2019, with two pilots and 11 passengers in conditions described by Canada’s Transportation Safety Board (TSB) as VFR for the 155-nm flight.
Observer weather reports at the landing area in the Thebaud Central Facility (TCF) were overcast, five-eighths mile visibility, and 300-foot broken ceiling. A surface vessel in the area reported fog and visibility of less than one-half mile.
The flight crew aborted two initial approaches to the rig off Sable Island, part of the TCF, due to limited visibility and lack of visual references. On the third approach, the helicopter became unstabilized across parameters of speed, bank, and pitch and entered a vortex ring state and a resultant spin through 845 degrees of rotation. The pilot flying depressed and held the cyclic trim release, which in turn degraded the performance of the automatic flight control system, according to the TSB.
“Flying the visual approach in a DVE (degraded visual environment) while depressing and holding the cyclic trim release button increased pilot workload and contributed to control difficulties that resulted in an unstable approach,” the TSB concluded. “As the helicopter descended below 250 feet radar altitude, it was in a steep, 800-fpm descent, at very low airspeed, with power being applied. When the pilot flying instinctively increased the collective, the helicopter’s rate of descent rapidly increased to 1,800 fpm. The application of power while in a steep, low-airspeed, high-rate-of-descent condition caused the helicopter to enter vortex ring state.”
The flight crew recovered, but not before committing flight control inputs that resulted in multiple torques and engine exceedances up to 146 percent and descending to just 13 feet above the waterline, substantially below the helideck’s altitude of 174 feet. There were no physical injuries to anyone onboard. The helicopter flew back to Halifax and was subsequently removed from service. CHO ceased operations at the end of 2019.