Obsolete oil cooler belts caused S-61N ditching
FAILURE of two obsolete oil cooler fan belts caused the July 31 ditching of a British Airways Helicopters (BAH) Sikorsky S-61N, 24 n.m. ESE of Aberdeen, according to the Accident Investigation Branch of the UK Department of Trade. A cautionary note issued by Sikorsky on June 5 this year warned operators that the original belt was prone to low service time failure and that a newly designed belt was the only one recommended. At the time of the incident the aircraft (G-BEID) was the only BAH S-61N to have the obsolete belts.
G-BEID left the Atlantic II oil rig 150 n.m. ESE of Aberdeen and was cruising at FL45 when the crew noticed the transmission oil temperature rising and a slight fall in pressure.
When the temperature reached 110° clearance to descend on track was obtained from Aberdeen. Emergency services were alerted and a search and rescue equipped RAF Shackleton diverted to intercept the helicopter. The oil temperature continued to rise and the hot oil warning light came on at an indicated 140°C. Emergency gearbox lubrication was selected and the oil pressure rose from 30 to 50 p.s.i., later stabilising at 40 p.s.i. When the oil temperature reached 150°C the captain decided to ditch in accordance with the company's emergency procedures. A power-on landing was made in light wind and a sea swell of three to five feet. Sea fog and low stratus gave
about 1/2 m visibility. An attempt to taxi towards the coast caused an uncomfortable roll, and as the oil temperature continued to rise the rotor was stopped and the sea anchor deployed.
After abandoning the aircraft all 15 persons were rescued from a liferaft by helicopter and lifeboat.