Chinook - Still Hitting Back 3 (Merged)

[Robin Clark]

New Look......

New Look ?

After plotting all the KNOWN FACTS on a large scale contour map of the area , I think it is highly likely that the A/C hit the ground even earlier than supposed.............if they were at around 400 feet asl they would definitely have touched , at 450 feet asl , probably still clipped the ground , and at 500 feet maybe .
It is entirely possible to me that the A/C made contact with the hillside shortly after commencing a left turn and over a half kilometer from the assumed first point of impact.....quite what the effect of this would be , I am unable to predict exactly , but depending if it was the fuselage or a rotor tip that touched , the A/C must have been diverted from its intended path and may have been almost uncontrollable .....
One can hardly imagine what the reaction of the crew may have been in such an event , struggling with a disabled A/C ..
..but they nearly made it..............................the subsquent point of impact some 10-15 seconds later shows they were climbing and turning.......

You will recall the only evidence for a slight turn to the right after selecting waypoint 'B'.......... is the location of the main point of impact............which is slightly to the right of the previous track , and that it represents a 'turn' into wind .... my own calculations make it 2 degrees.......
It is tempting to think they may have flown there directly.......but I would suggest that if you have just wacked the ground you are not too interested in headings.....and there may have been some desperate gyrations before hitting the ground again.........

But how is it they were so far off course......????????....
If we go back to the start of the flight............ the first waypoint recorded (when the system was powered up?) was in a
grass field TWO MILES FROM THE AIRFIELD and over halfway to the town of Antrim.......??????????????????????????.........

Yes really........
.....I find it hard to believe that any NAV aid could be that bad ......but the LAT and LONG are in the report.!!!!!!..................

I bought a handheld GPS myself that summer , a Garmin GPS55 , and I was getting 100 metres accuracy even with Selective Availability still turned on (Selective Availability for civilian use was turned off in the year 2000) but military units were supposed to be ten times better ......

If I were contemplating this journey , and were aware of this error during preflight , my first thought would be disgust , being expected to use such [email protected] then.........I might consider that at least the error was on the SAFE side!!!! .
Having a two mile North/East to South/West error on the box meant you could safely fly to waypoint 'A' and know you were about a mile and a half out to sea as you passed abeam the lighthouse , in case you could not see it in the poor visibility predicted there......
You could head north then to track up the coast and expect to be back in better VMC before reaching Machrihanish , then weave through the mass of small islands and turn right onto 035 to track in towards Corran ...... Waypoint 'B' ...and so on..

But at the crash site the GPS error was in the opposite sense , directing one to fly .........NOT TWO MILES SOUTH AND WEST of
the true location , but 200 METRES NORTH AND EAST of the true location ............

So my interpretation of the facts....... suggests that they flew toward waypoint 'A' without being able to confirm their location visually as they approached , although they could see where the mass of land was , it was cloaked in mist and cloud . The Aldergrove TACAN accuracy is becoming diminished by the distance . Dead Reckoning is unreliable in this case (almost direct tail wind , picking the drift in the wrong direction is NOT GOOD)(would the doppler display give an indication of drift ..????..somebody must know)...
So they are using the superTANS , but with no way to check the accuracy..........there is open sea visible out to port as they get close to the cloud bank....
The 30 second alert of the pending waypoint prompted them to change to waypoint 'B' and they commenced the slight turn left onto north.............they dial up a heading of 035.........then they clip the hillside and all hell breaks loose........

The high point of the cliff they are approaching is at" 58deg. 18.35N 5 deg. 48.00W " ( 58deg.18'21" N 5deg. 48'00"W ) and they
would reach it only 9 or 10 seconds after crossing the shoreline....

The change in the GPS error has brought them over the obscured land , instead of being safely offshore........


I realise that there may no longer be any obvious debris trail after all this time , but it is worth a look . There may be some evidence.......... such as paint streaks on a rock .......gouges etc.

If this scenario is true , then the flight crew....far from being accused of anything.........should be commended for valiant efforts to recover from an impossible situation after being badly let down by their equipment .......................and RACAL and TRIMBLE should be in the dock answering questions..........
..........
Below is a copy of the chart I used , in which the locations of Waypoint change and Waypoint 'A' have been corrected using the apparent GPS error from the last two recorded locations in the superTANS....