Broken helicopter blade ‘narrowly missed’ worker on oil rig, report finds
The incident occurred on the Elgin Oil Platform in the North Sea in February 2023 during Storm Otto.
A helicopter blade “narrowly missed” an oil rig worker after it broke while they were trying to secure the aircraft to a helipad during high winds, an investigation has found.
According to an Air Accidents Investigation Branch (AAIB) report, the Airbus H175 helicopter had just ferried six passengers to the Elgin Oil Platform – about 135 nautical miles east of Aberdeen – and had landed shortly after 8am on February 17, 2023 in winds of up to 60 knots.
While the crew were preparing the vehicle for its return flight, a warning alert appeared in the cockpit, and after speaking with engineers the crew were advised to shut the vehicle down.
They applied the brake to stop the rotor from spinning but it “did not fully stop”, resulting in the vehicle’s commander and two members of the helideck team having to tie the vehicle down in high winds with the blades still “turning slowly”.
The report explained that by about 9.30am, three “tie-down straps” had been applied and the fourth was about to be attached when one of the turning blades suddenly “lifted near vertical”.
It said: “With the blades still turning above, one of the blades suddenly lifted near vertical, partially breaking off near the root with the broken portion hanging down and continuing to turn.
“As it did so, it narrowly missed the single deck crew member positioned at the rear of the helicopter, who was trying to attach the final strap to the helicopter.
“The blade then separated and fell into the sea.”
At this point the crew decided it was too dangerous and retreated back into the rig’s accommodation block, and over the next one hour 40 minutes three of the remaining four blades also broke and were later found on the helideck.
The helicopter showed “multiple impact marks” from where blades had struck it, including cracks and holes in the left pilot seat’s window and the loss of the external emergency door handle.
The report sets out a number of causes for the incident, as well as making six safety recommendations.
It notes that at about 6.45am while the helicopter was being towed out of the hangar in Aberdeen, ground staff had noticed the rotor was turning despite the brake being applied.
However the engineering staff said they had not been made aware of this so no checks were carried out prior to the aircraft taking off.
It was subsequently found that a “build-up of organic material” in the braking system had caused one of the pads to seize, resulting in the brake being unable to stop the rotor when it was being driven by the wind.
The report also comments on the effect of the high winds from Storm Otto, which was passing through the area at the time.
It states while measured wind speeds on the helipad were below the 60 knot limit for landing a helicopter, the windward edge of the helipad was “subject to vertical wind speeds considerably in excess of the limit in force at the time”.
This was due, it said, to the “cliff edge” effect caused by the accommodation block on which the pad had been built, which pushed winds up vertically when they hit the block and made them stronger as they passed over the pad.
Coupled with the fact it had not been possible to tie the turning blades down, this resulted in “blade sailing”, with the helicopter’s blades being bent upwards by the wind in an “ever-increasing arc” until they reached breaking point.
The report’s recommendations include changes to wind measurement on rig helipads and the inclusion of improved rotor brake maintenance processes in the Airbus EC175 manual.
