Gavin Grimmer
With this in mind, you may now be starting to see the difficulties in working this out... and the accuracy you can achieve when it does calculate correctly. It may appear that I am making the evidence to fit the scenario, but this is not the case. Try doing the sums yourself and see if you can get anywhere as close... and then you will understand!
Because the calculated position is not in a place you would get a downdraught, it becomes obvious that he did have more of a tailwind component that we are calculating with, so looking at the winds shown in the image from the wind direction study, I would take an educated guess as it being at 291°T, so we will try the calculations at that...
After quite some time using various wind directions and likely wind speeds, I was still not able to get the calculated distance to get as far as the required ridge, so it was back to the drawing board.
Mike would have been wondering why he was continuing to get a downdraught after Craven as there were no ridges capable of producing this in the area he thought he was in. There was a ridge initially just after Craven, but after that, if anything it should have been reasonably smooth air.... That is - if he was on the correct track to Singleton.
When you think about it, the point he would have started to become suspicious would
have been soon after he said the ADF was all over the place. He was relying on the
ADF to get to Singleton (remember no AHI nor DI either) and when that also became
unreliable, he would have instinctively gone to the only instrument left that could
be trusted – the magnetic compass to verify they were on a reasonably steady course.
As soon as he was told his actual position that confirmed his suspicions, he would
have been ready to make a turn towards the south, in fact he may have already made
this turn, or at least started it...who knows? (May have wasted my time getting the
angle of intersection at Ident?) Recalculating using an initial immediate turn, we
get a position of the “downdraught call” right on top of the ridge.
When I say “downdraught,” I actually mean the end of the updraught as in a reduced amount of lift. To explain, we know freezing level was somewhere around 6500 ft, and as MDX was at 8000 ft they were in sub zero temperatures. As soon as they entered cloud (moisture) just after 'Craven', the airframe would have started to collect ice. The longer they remained in the cloud above freezing level, the more the ice build-up. The difficulty achieving a climb (be it just a cruise climb) of another 500 feet indicates the build-up had increased the aircraft's weight – not to mention altering the wing air-foil shape causing it not to produce as much lift. It was just after the Radar Ident that Mike radioed his difficulty of getting to 8500 even though he was trying for 10000, and in this area he would have been in an updraught. It is my belief at this stage that the only reason they were even able to reach 8500 feet was due to the extra lift produced by the updraught. Consequently, when the updraught ran out, was when they descended due to being heavily laden with ice – giving the illusion they were in a downdraught! The problem with the C210 was that due to it not having wing struts, it was not that obvious if you were picking up ice. The pilot had to lean forward to enable a view of the wing leading edges before confirming he had ice, although in more severe cases (as I think happened later with MDX) the ice builds over the windscreen. I've been in a C172 with probably up to an inch of ice over the windscreen... and there was not a lot of elevator travel left!
The reason why I am so interested in where MDX was when this updraught ran out is
because when you read the Radio Transmission Timeline, you'll see that according
to the radar operator (Sector One), MDX made a left hand turn at about the same time.
This left hand turn would also place the aircraft in a position where the updraught
disappeared. But there is still a further reason....
When I first read this transcript, the part where Mike said, “I can just make out a few light towns on the coast”, the thought went through my mind, they were above the cloud, and so if they could see
MDX pg 16
