The possibility of CFIT has been raised a few times, but there is also a weather phenomenon which hasn't been mentioned, probably because it is extremely unlikely to have played a part. It is the waterspout, which most of us have seen, but never at this time of year that I can recall.
Some 10 years ago a helicopter was returning to Shetland from the Basin and was flying inside cloud. Suddenly it swung violently, so much so that the pilots thought they had lost drive to the tail rotor. Immediately they entered autorotation and commenced the drills for a power-off ditching.
Shortly their descent brought them out of cloud and the handling pilot began to feel that he still had control of the tail rotor with his pedals. Very fortunately they had not yet shut down the engines, as required in a tail rotor drive failure and gingerly pulled out of the descent until they found themselves back in normal flight.
The aircraft landed safely back at base and was eventually given a complete overhaul and replacement of any components which might have been overstressed. The investigation concluded that a waterspout was to blame.
The weather last Fiday wasn't of the kind where I might expect waterspouts. The wind was quite strong from about 140 degrees, so at 2 miles on final approach to 09, they were 3 miles downwind of Sumburgh Head and probably descending a few hundred feet above the surface.
We have all experienced the effect of the Grampian mountains giving strong up and down air currents, even beyond 80 miles out to sea when the wind is strong westerly. What's the possibility of being caught in a strong downdraught when only 3 miles from Sumburgh Head?
Yes, it's all too far-fetched, but I want our passengers to appreciate that there are other possibilities than aircraft failure.
Last edited by Colibri49; 29th Aug 2013 at 10:35.