• Boeing 234LR Chinook helicopter
On 6th November 1986, Boeing 234LR Chinook helicopter G-BWFC crashed near the Sumburgh Airport in Shetland Islands into the ocean and sank. It is also known as Sumburgh Disaster that had taken the lives of 43 people and two crew members.
On that day, the flight was delayed due to an oil leak from an engine gearbox, but was rectified and the helicopter left Sumburgh Airport at 08:58 a.m. When the helicopter was returning back to Sumburgh Airport, one of the crew members detected an increased sound level in flight deck. Regardless of applying full cyclic pitch control (to achieve controlled aerodynamic flight), the helicopter did not respond and dropped towards ocean from an altitude of 46 m (150 feet).
A Coastguard rescue and search helicopter that had just departed from the Sumburgh Airport reported lifeboats in the ocean. It saw a survivor sticking to a significant piece of debris and another survivor among the floating bodies. The Coastguard helicopter helped and took the survivors to Lewrick and from there they were taken to the hospital.
According to the Investigation report of Air Accidents Investigation Branch (AAIB), the accident was caused due to failure of bevel ring gear that allowed the two rotors to collide.
• Sikorsky S-61
Sikorsky S-61 G-Beon crashed in the southern Celtic sea, while returning in thick fog from Penzance to the St. Mary’s, Isles on 16th July 1983. This disaster had taken the lives of 20 people out of 26, including crew members.
G-Beon left the Penzance to St. Mary’s Airport at 12:40 p.m. as it was scheduled. It was flying at an elevation of 80 meters (250 feet) from the Celtic sea. At 12:58 pm, St. Mary’s ATC (Air Traffic Control) lost contact with the G-Beon. Later, it had crashed into the Celtic Sea and sunk instantly. The six survivors were able to float for 30 minutes before the rescue team helped them.
According to the investigation report of Air Accidents Investigation Branch, Hampshire, the accident was caused due to pilot error. The pilot had not observed and corrected an unintended descent before the helicopter crashed in the Celtic Sea. The official report also added that the following were contributory factors –
• Insufficient flight instrument.
• Lack of audio height warning tools.
