Tandemrotor,
The forecast surface wind for the North Channel was 150 degrees 12-18 kts, the 2000 ft wind forecast was 190 degrees 25 kts. The wind at take-off from Aldergrove was given as 170 degrees 10 kts. The forecast winds give a tail component of 9.2 kts at the surface and 24.5 kts at 2000 ft. The average groundspeed from the ATC fix on leaving the CTZ to impact was 158.0 kts. All sightings of the aircraft, and there were a large number of eyewitness reports of the aircraft over Antrim, reported the aircraft at very low level, typically at 100 ft AGL.
PS
The "positive fix" at 16:46:24 was from Aldergrove ATC giving the aircrafts position as 027 Degrees magnetic and 7 NM from the Aldergrove beacon. That fix was, of course, on tape.
Given that the Yachtsman estimated the height of the aircraft as 200-400 ft, a "significant tailwind" at the estimated height would have been reflected at the surface and given rise to possible gale conditions. Moreover, they had only approximately 2.1 NM to impact which occurred at a calculated groundspeed of 162.8 kts: which compares with the AAIB conclusion from their wreckage and crash site inspection that the groundspeed at intial impact was "of the order of 150 kts".
PPS
The difference between the "calculated" groundspeed and that recorded by AAIB is explained by a last minute manoeuvre to avoid impact by rapid application of aft cyclic stick. If applied to the difference in the groundspeeds a derived instantaneous flight path angle of +23 degrees climb is obtained.
Last edited by cazatou; 7th Aug 2006 at 14:32.