Chinook - Still Hitting Back 3 (Merged)

[walter kennedy]

Cazatou
So, did you go through the Boeing calculations? Understand the wind,etc?
You’ll find para 3.2 gives the calculations well explained in detail. It gives 148.8kt mean true airspeed from ATC fix to waypoint change using an average surface wind speed of 15kt. Had the wind actually been stronger than this estimate, then it would have further reduced the speed to a more normal cruise speed (also considering the relatively low load weight).
From the last steering command calculations, it gives 135.5kt true air speed and concludes “…that the aircraft was probably flying at a relatively high airspeed until the Mull coastline was approached, at which point the aircraft slowed. Interestingly, this reduction in airspeed is countered by the increase in wind strength at the Mull, such that the net aircraft ground speed remains effectively unchanged.”
With the (just about following) wind on the Mull given as 30kt (the sources of the wind used in the Boeing doc are given therein) it is all the same (135.5 + 30 is close to 162.8) – what is important is that the Boeing doc shows that significant reduction in true air speed at that critical time – and this reduction is compatible with the power settings found (matched and intermediate) suggesting, surely, an intended gradual slowing.

By the way, the speed of 135.5kt above has significance to the recent debate on VFR minima – they had slowed to below 140kt true air speed by my reckoning before they had entered the murk (otherwise I think they may have manouevred sooner) – they may have misjudged how far away the murk was, but does that not mean that the lower speed minima should have applied?
I think that that debate was academic anyway as they were approaching a fixed object covered in mist that was right on it as opposed to being amongst bad vis when approaching it.
It would be very interesting to hear from the Sea King pilot, that did land that evening, what line of approach he took, what he could see from out at sea rather than the conditions whilst trying to land (the only bit that seems to have been quoted at the inquiries), and what speed profile he had when arriving at the scene (ie at what distance off did he start slowing down). He had the benefit of radar guidance and so would know for sure how far off the land mass he was - and knowing that nothing would be coming out of the mist, I'll bet he could have approached it quite rapidly.