Brian
You wrote <<But what is in doubt is how far out from the Mull the cloud cover extended, and how far down the Mull the could cover went. Every time the MoD provide a visual representation (including Air Marshal Day in his slide show to the HoL Select Committee), the cloud is always presented as extending quite some way from the landmass. I fear that this is both misleading and unfair as there is no evidence that this was ever the case.
Those witnesses in the cloud/mist/fog were in no position to answer the above question. The only people who could accurately answer that point were lost in the accident.>>
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You are quite right to question the (misre) presentation of the cloud cover; while your last sentence is true (“The only people …”), we can assume from what we know that it was typical of that area at that time of day, at that time of year, with that prevailing wind – clear at sea, mist forming just after shoreline as air rises following ground, often clear at a small height above sloping ground so that a/c can be in clear air over ground hugging mist on the lower part of the slope at least. These conditions are very, very common in that part of the world under similar circumstances and there can be no excuse for, say, AVM Day to have misrepresented conditions on those slides - he had to have been selling the simplistic picture that they were flying VFR in IMC conditions – and why the hell have those on this thread who have flown this area at low level not spoken up loudly on this point?
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On another issue, Cazatou’s point about the second witness is important in regard to how the authorities managed the investigations: I do not believe that the second yottie would have contributed to the judgment of the speed as neither would have been able to give even an approximate guess (large unfamiliar object with nothing nearby to compare with, etc); however, that one of only two witnesses of the final part of the flight was not called is indeed extraordinary – just by way of examples, he could have seen something the other had missed, say a plume of smoke that the other had dismissed as exhaust, a jink, a bit falling off, someone mooning, anything odd – even the local bobbies looking into a bike theft would ask around more diligently – unless they too had a preconceived idea of who was going to get blamed.
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Now what is it that is so confusing about the nav systems and the sequence of events after all these years?
I’ll put my view as simply as I can (again):
They did not go straight on at waypoint change, they TURNED RIGHT – towards danger.
The SuperTANS of the time was intrinsically unreliable to any degree of accuracy after such a water crossing as the algorithm more heavily weights the Doppler input (in case of complete loss of GPS due to jamming) which is sporadic due to wave velocities and specular reflection and only the combined result was available (unlike in previous TANS as I believe); these pilots were aware of this and cautioned other members of their flight – they would not have trusted it better than ½ a mile – if relying upon it to turn in plenty of time clear of the misty headland and remain well in the clear air they would have turned much sooner rather than later – waypoint A was very close in, remember.
Nevertheless, the experts pronounced that it had been accurate in this case at the crucial time (from analysis of the stored data, etc).
This is very important – it means that at the time of waypoint change, the SuperTANS (in this instance) had been reasonably accurate – so that if they had had a clear visual reference by which they were judging their distance to go to their turn, it should have agreed with the SuperTANS at waypoint A AND THEY SHOULD HAVE STARTED THEIR TURN. This suggests to me that they did not have a clear visual reference at that point. They did have control though and made a steer to the right of a few degrees.
To carry on with their ferry job safely, they only had to turn left a few degrees at that point.
They were flying in clear air until the last few seconds and demonstrated control by starting an appropriate emergency manoeuvre in those circumstances for a large twin rotor to turn, climb, and slew (to lose speed) – the start of this manoeuvre coincided with when they would have seen the shoreline passing beneath them, entering mist, and the RADALT going off all in very quick succession - this suggests to me that they were taken by surprise when these events happened, that they had not realized just how close they had got – they could have seen the Mull for miles but its ground detail was obscured making it difficult to judge their distance visually at that speed.
If they had had a good visual reference, they would have turned AT waypoint A; if they did not have vis conditions and were relying upon the SuperTANS to keep them well clear of the dodgy area, they would have turned well before waypoint A (remember, they would not have trusted the accuracy of the SuperTANS).
The turn to the right is a vital clue – they had to be heading for something specific to make such a change.
There is only one system that helo pilots trust enough that it can overwhelm their visual judgment of range – DME. A system that gives accurate range (UHF DME function) and an azimuth bearing to a portable handset (PRC-112) had just been delivered to the RAF about that time, specially for fitting to the HC2 Chinooks. If they were doing a demo of the new system (some on board would have been very interested), say overflying a guy on the ground at the lighthouse heli pad, he could actually vector the pilot in (the handling pilot’s intercom was set appropriately); there were plenty of PRC-112s on the Mull that day as the American unit there had them issued to a man – how handy!
Provided the man on the ground was where he was supposed to be there wouldn’t have been a problem.
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If you disagree with the possibility of the use of the PRC-112 system, why not tell us all when exactly it was first used in RAF Chinooks? 12 years on hardly a super sensitive secret defence wise – yet the topic is avoided like a floater in the jacuzzi– smells like there is a connection.