dalek , your 6738,6775,6796
The report shows the TANS to be working to a very high spec approaching the Mull. Seven satellites in solution and a doppler within 330 m of the GPS position. Overall accuracy would have been around 10 m, maybe even better
..... the overall accuracy of the Stans was nothing like as good as you surmise , the Racal report only tells half of the story........
Although the GPS and Doppler positions were 330m apart from each other , they were both wrong from the true location ....
The GPS position was 193 metres away from the real/true lat/long on a heading of 235 Degrees True......
The Doppler was 173 metres away from real/true on heading 102 Deg. T....
..(so when navigating on GPS , everything is moved up the hillside 193 metres in the direction 055 degrees.).
A Chinook contributor I have recently pm'd thinks Holbrooks initial estimate of speed was wrong but one of 120 - 130 IAS was more likely. This ties in with the RACAL estimate of 127.5 TAS 151 GS at impact. So just where was negligence at this point?
..not really an estimate I think , the Doppler and GPS groundspeeds were calculated directly...and were in close agreement , and although some values referred to in the Racal report are instantaneous ones , a sort of snapshot at the time.......the ground speed is a two minute rolling average , which covers the period of waypoint change and the earlier point of closest encounter with the yacht.....so the 151 knots groundspeed is probably correct .......and fits well with performing a high speed transit across open water , slowing as the coast was approached ...
So what I can easily understand is how RACAL could extract data at powerdown. What remains a mystery to me is how they could possibly interpret where the rotary switches were, and what buttons were pressed just leading up to the accident?
..in any modern equipment which computer based , various values are stored in memory locations , and may be used by different routines .( Only data which might be needed again is worth saving , so altitude for example is not saved regularly as it was only really intended to help the GPS receiver if it is struggling with too few satelites )
....the panel controls can be 'remote' ie... a separate circuit board with a cable to connect it to the main board....and again the control positions can be scanned and saved in memory locations........most car radios work this way today , thats why the volume control can go round and round ......it is no longer a logarithmic potentiometer , but a pair of sensors on a slotted disc which only has to tell the logic which way to step the volume ........
...there probably was a record of the last 50 or 100 keystrokes , but it was not felt pertinent to publish the information in the public domain....
rgds Robin...