Oil and Gas People reported yesterday on a CHC helicopter that spun on an offshore helideck during landing. The incident damaged the West Franklin’s helideck and the wheels of the aircraft. The flight had minutes earlier taken off from the Elgin Production Utilities Quarters (PUQ) for the short personnel transfer to the West Franklin which is an unmanned wellhead platform.

It had been reported by one eye witness on the PUQ that the aircraft was flying erratically moments after take off, however this is thought to be unlikely due to the Pilots subsequent decision to land on an active platform.

It has also been widely speculated on social media that the incident occurred due to a complete tail rotor failure, but after speaking to industry professionals Oil and Gas People are convinced that this is unlikely.

In aviation there is a point during flight called a Landing Decision Point (LDP) which dictates the point at which a pilot fully commits to a landing. Prior to this point there is set procedures to follow in the event of a technical malfunction or emergency situation, the most common being to acheive safe flight speed and divert to an onshore alternate. However on this occasion the landing was performed on an active installation, a strong indication that a fault occured in the final stages of landing and not before.

In the offshore aviation sector, the LDP is called during the final moments of helideck landing and is typically at a ground speed of less than 10 knots and at a 45 degree offset from the helideck. At this point, the pilot is confident that he can safely land the aircraft on the helideck, even in the event of single or dual engine failure. Prior to this point, any technical issues would require the pilot to perform a ‘go-around’, attain take off safety speed (Vtoss) and divert to an onshore alternate.

The decision to land on the West Franklin is a strong indication that any issue that occured, developed in the final stages of flight and after LDP.

Although no official explanation has been provided by CHC, industry experts feel it is unlikely that a complete tail rotor failure occured due to the minimal amount of damage sustained to both the helideck and the aircraft itself.

CHC’s official statement does not contain any reference to a technical malfunction or warning light, simply stating: “We can confirm that one of the S92s operating from Aberdeen experienced unexpected control responses during the final stages of a landing at an offshore platform.”

The unexpected response may have been caused by a technical malfunction, but could also be caused by a phenomenon called Loss of Tail-Rotor Effectiveness, a situation that can occur during low airspeed situations with specific weather and wind conditions.

With the helicopter now arriving back in Aberdeen after being shipped back to shore on the Ben Nevis Supply Ship and with a team of engineers being sent to assess the aircraft it is hopeful that the cause will be uncovered soon and an in-depth report into the incident issued in a timely manner.

The image of the CHC helicopter at the top of this article has had the tail rotor blades removed for transport purposes.