Helicopter Safety Steering Group report into incident on 20 March 2014

Helicopter safety

The Helicopter Safety Steering Group has published its own investigation into the events of Thursday 20 March when a Sikorsky S92 helicopter en route from Beryl Bravo to Aberdeen suffered an engine shutdown before landing safely at Aberdeen International Airport. The incident was reported widely by Aberdeen media, as follows:

The flight left Beryl Bravo at 0930 inbound to Aberdeen and began a normal descent into Aberdeen from an altitude of 2,500ft at 1108. Shortly after commencing its descent, a cockpit warning light came on and engine #2 shut down.

Power automatically and immediately transferred to engine #1 with no impact on power delivery to the gearbox and rotors. The helicopter continued its planned descent on one engine over the next two minutes under the full control of the pilots until levelling out at the planned approach level of 1500ft.

In accordance with standard procedure for engine failure, the crew put out a PAN call and identified Aberdeen International airport as the safest landing site.

The airport’s emergency response was activated. The helicopter then completed a planned descent on one engine, making a safe landing without incident at Aberdeen at 1142. The crew handled the incident in a calm and professional manner and followed standard operating procedures throughout.

Passengers were debriefed at the heliport immediately after the incident and appeared content. Examination of recorded data showed that after engine #2 shut down, engine #1 automatically increased power to compensate for the second engine and the helicopter continued its intended flight path, maintaining altitude, attitude, pitch and speed.

A loud whine heard during the flight came from engine #1 increasing power and revs, but the data shows that the helicopter did not drop quickly nor move violently and the levels of aircraft movement recorded were within normal air turbulence levels.

While twin engine aircraft are designed to fly safely on one engine, an unintended engine shutdown is serious, though not dangerous. It warrants an exhaustive investigation and technical follow-up is ongoing to determine the cause, which has thus far been attributed to a fuel supply problem to engine #2. The fuel pump was checked and a series of ground runs on engine #2 were successfully carried out.

Fuel samples were taken and all proved clear. The entire fuel system was vacuum tested. This revealed small bubbles in the engine #2 fuel supply, thought to be due to air ingress from isolating valves in the fuel pipes. The fuel system had not undergone recent maintenance so this has been eliminated as a possible cause.

Further investigations involving Sikorsky are progressing to determine the cause of the air ingress. Measures to prevent reoccurrence will then be implemented. This is the first engine shutdown on an S92 due to a fault of this type. Sikorsky will ensure that other S92s are checked out if required.

Further investigations involving Sikorsky are progressing to determine the cause of the air ingress. Measures to prevent reoccurrence will then be implemented. This is the first engine shutdown on an S92 due to a fault of this type. Sikorsky will ensure that other S92s are checked out if required.

 All UK offshore helicopters are designed and certified to cope with a single engine shutdown in flight, and crews are thoroughly trained and regularly checked (at least every six months) to handle this situation as part of a CAA regulated simulator training package. There has not been a dual engine failure in offshore UK in for over 25 years – however were one to happen, all helicopters are designed, and pilots are trained, to handle a worst case situation where all power is lost. The pilots immediately descend and “feather” the rotors so that they auto-rotate, using  the energy in the rotors to make a controlled landing.

Following the publication of the CAA Safety Report, the industry is faced with the challenge of how we work together to address the improvement actions and recommendations.

Consequently, the April 24 helicopter safety event  offers the opportunity to hear more about the critical work of HSSG, including presentations from CAA Airspace policy Director, Mark Swan and update on EBS, Passenger Size, Effective Communications, and EC225 gearshaft progress.

For more information:

http://www.stepchangeinsafety.net/newsevents/events/event.cfm/eventid/136

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