Chinook - Still Hitting Back 3 (Merged)
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Nothing based on RACAL can be considered factual reconstruction. RACAL tell you so. So most of what follows is theory.
The crew ditched their Waypoint because they had visually identified it at around 2 miles. (Holbrook) They were then expected to make a gentle left turn and follow the coast. They didn't. They took up a track of 035ish.
When the crew did the manual Waypoint Change the TANS was swiched on.
It must have been or they would have been looking at a blank screen when they pressed the ENT button to accept the new Waypoint.
It is unlikely that the crew were dealing with a major emergency at this point because pressing TANS buttons would then become a low priority.
Therefore any Major Emergency and Switch Off came after Waypoint change.
It must have come very soon afterwards.
No TANS computers produce Navigation Data. They process other equipment.
When the TANS computer is switched off these other equipments continue to work.
The GM compass still sends data to all the other instruments.
The Doppler is still working and can be accessed through an analogue display in the cockpit.
The Trimble GPS and the Air Data Computer are still working. You can't access the Data with the TANS swiched off, but if you could get test equipment to the appropriate avionics rack you could still extract Data.
It is therefore perfectly feasible to supply the battery powered storage unit with all Data after TANS switch off.
The only answer required from RACAL is, was that particular aircraft wired that way.
The RACAL analysis gives GPS time of final powerdown as 1659.38
It gives GMT at shutdown as 1659.10
GPS time is precise. GMT time starts from a time entered by the crew. It is as accurate as the crews inital entry.
The RACAL report states:
"The difference of (26?) seconds between GMT and UTC is not significant since initial setting is based on keyboard entry by the aircrew."
If the TANS power switch had remained in the On position that is the only explanation. But:
I, and all the crew members I knew, started the day with a timecheck.
When entering data on a precise Navaid such as TANS, I would use an IN chart or similar to input position. I was almost as careful with time.
A 26 second entry error is a bit gash but possible. It is a pity it was not entered 26 secs late, rather than early because then it would have to be Aircrew Error.
One way of stopping the GMT clock is to switch the TANS off.
So did the crew Switch Off the TANS at 26 secs to impact or:
Did they set the time wrong by 26secs and in spite of the design safeguards in the switch, it was knocked off at impact.
From personal experience I favour the former.
It is a pity that RACAL never even mentioned the Power On / Off switch in their report.
My last rant on this subject.
The crew ditched their Waypoint because they had visually identified it at around 2 miles. (Holbrook) They were then expected to make a gentle left turn and follow the coast. They didn't. They took up a track of 035ish.
When the crew did the manual Waypoint Change the TANS was swiched on.
It must have been or they would have been looking at a blank screen when they pressed the ENT button to accept the new Waypoint.
It is unlikely that the crew were dealing with a major emergency at this point because pressing TANS buttons would then become a low priority.
Therefore any Major Emergency and Switch Off came after Waypoint change.
It must have come very soon afterwards.
No TANS computers produce Navigation Data. They process other equipment.
When the TANS computer is switched off these other equipments continue to work.
The GM compass still sends data to all the other instruments.
The Doppler is still working and can be accessed through an analogue display in the cockpit.
The Trimble GPS and the Air Data Computer are still working. You can't access the Data with the TANS swiched off, but if you could get test equipment to the appropriate avionics rack you could still extract Data.
It is therefore perfectly feasible to supply the battery powered storage unit with all Data after TANS switch off.
The only answer required from RACAL is, was that particular aircraft wired that way.
The RACAL analysis gives GPS time of final powerdown as 1659.38
It gives GMT at shutdown as 1659.10
GPS time is precise. GMT time starts from a time entered by the crew. It is as accurate as the crews inital entry.
The RACAL report states:
"The difference of (26?) seconds between GMT and UTC is not significant since initial setting is based on keyboard entry by the aircrew."
If the TANS power switch had remained in the On position that is the only explanation. But:
I, and all the crew members I knew, started the day with a timecheck.
When entering data on a precise Navaid such as TANS, I would use an IN chart or similar to input position. I was almost as careful with time.
A 26 second entry error is a bit gash but possible. It is a pity it was not entered 26 secs late, rather than early because then it would have to be Aircrew Error.
One way of stopping the GMT clock is to switch the TANS off.
So did the crew Switch Off the TANS at 26 secs to impact or:
Did they set the time wrong by 26secs and in spite of the design safeguards in the switch, it was knocked off at impact.
From personal experience I favour the former.
It is a pity that RACAL never even mentioned the Power On / Off switch in their report.
My last rant on this subject.
Last edited by dalek; 26th Jun 2011 at 11:48.
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dalek
When you quote Mr Holbrook's evidence in respect of the weather it would be useful if you quoted which particular evidence you are referring to. Mr Holbrook in his written signed statement to the BOI sworn on oath stated that he was "2 NM Southwest of the Mull" and the visibility was "1 NM limited by haze"
He gave significantly different weather evidence to the Fatal Accident Inquiry when he said "I recall the conditions of visibility at sea level as being fine, perhaps as much as five miles. I think at that point I could even see the Antrim coast so it might have been as much as six or seven miles". There were further variations in the evidence he gave to the HOL Committee.
On the other hand there were 10 eyewitnesses on the Mull of Kintyre who reported the weather to generally foggy and very bad. Nine of these eyewitnesses (2 of whom were qualified Meteorological Observers) gave sworn evidence to the BOI in respect of the weather conditions at the time of the crash.
When you quote Mr Holbrook's evidence in respect of the weather it would be useful if you quoted which particular evidence you are referring to. Mr Holbrook in his written signed statement to the BOI sworn on oath stated that he was "2 NM Southwest of the Mull" and the visibility was "1 NM limited by haze"
He gave significantly different weather evidence to the Fatal Accident Inquiry when he said "I recall the conditions of visibility at sea level as being fine, perhaps as much as five miles. I think at that point I could even see the Antrim coast so it might have been as much as six or seven miles". There were further variations in the evidence he gave to the HOL Committee.
On the other hand there were 10 eyewitnesses on the Mull of Kintyre who reported the weather to generally foggy and very bad. Nine of these eyewitnesses (2 of whom were qualified Meteorological Observers) gave sworn evidence to the BOI in respect of the weather conditions at the time of the crash.
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Hi Caz
Mr Holbrook reported that he could see the area around the lighthouse and lower walls from around 2nms. He couldnt see the top where the keepers were because it was in fog. He could also see the aircraft clear of cloud at more or less the same time.
Is it unreasonable to assume that the aircraft could also make out the turning point from around 2nms and therefore change Waypoint?
If they couldn't make out the turning point area, ditching the old Waypoint makes no sense at all.
Mr Holbrook reported that he could see the area around the lighthouse and lower walls from around 2nms. He couldnt see the top where the keepers were because it was in fog. He could also see the aircraft clear of cloud at more or less the same time.
Is it unreasonable to assume that the aircraft could also make out the turning point from around 2nms and therefore change Waypoint?
If they couldn't make out the turning point area, ditching the old Waypoint makes no sense at all.
So Mr Holbrook was not a perfect witness, caz, but he was the sole eye-witness of the aircraft prior to it crashing into the fog enshrouded Mull hillside called to give evidence. He saw the aircraft, ie it was clear of cloud, indeed he remembers the sun glinting off it. He could see the lighthouse's distinctive wall, but as dalek says, the hillside above was obscured by the fog in which the "ear-witnesses" were. It is what he says he saw and what he couldn't see that is the point, caz, not what numbers he put to the very few questions asked of him.
That raises a curious issue. He was the only eye-witness called before the BoI. There were others, because Mr Holbrook himself mentions a fleet of fishing boats around him. Yet no-one else was called. Mr Holbrook was only sparsely questioned. All eerily reminiscent of the witnesses called to give evidence of the airworthiness problems that plagued the HC2- ie none whatsoever! Another example of the self-serving self-regulating system at work? Oh, and while we have your all too brief attention again caz, could you please respond to my earlier post. It seems to have slipped your notice:
That raises a curious issue. He was the only eye-witness called before the BoI. There were others, because Mr Holbrook himself mentions a fleet of fishing boats around him. Yet no-one else was called. Mr Holbrook was only sparsely questioned. All eerily reminiscent of the witnesses called to give evidence of the airworthiness problems that plagued the HC2- ie none whatsoever! Another example of the self-serving self-regulating system at work? Oh, and while we have your all too brief attention again caz, could you please respond to my earlier post. It seems to have slipped your notice:
Could I please make that three of us perplexed and curious as to your motives caz? JP's have become clearer as the thread has progressed, but yours remain an enigma. Given that you were a Group Flight Safety Staff Officer, and a Senior one at that, in the period following the accident and publication of the AOC's and AOC-in-C's Finding, you would have been privy to the ensuing staffing and directives. As such you could shine much light onto this tragedy and its aftermath. I do not expect you to fall foul of the OSA, but the pre-occupation of many of us here is to prevent such a tragedy recurring, ie the very Raison d'Étre of your then job. Or was it? I only ask because all we get from you is speculation on pilot performance, whether it be due to supposed malnutrition or Duty Hours pressure. Now I see that CRM has been thrown into the ring, everything indeed other than the tangible Gross Unairworthiness of the aircraft itself. The BoI didn't want to go there. Wratten and Day didn't want to go there. The MOD don't want to go there. Neither it seems do you. Why is that caz? Are you more concerned with Reputation than with Safety and if so, whose? Any response would be welcome if only to set our minds at rest.
Below the Glidepath - not correcting
Cgb,
You could save people a lot of reading by getting this put up as a sticky.
Most rational people feel that the pilots may have got things wrong. However, the same people argue that the 'verdict' is unsound. Whether the actual cause was airworthiness, pilot error, state murder or little green men is not the key point. The POINT is that the MOD's findings did/do not have the necessary substance.
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Don't worry, Chug - many queries to him 'slip his notice' especially if they are difficult ones. That is why I inexplicably stopped seeing his posts
My advice is not to bother, just ignore. Makes for a far more peaceful existence since when I was 'seeing' he had nothing of interest to add. I believe 'breakfast' was one item in those days. Now from other posts it appears to be 'visibility' - hey ho!
My advice is not to bother, just ignore. Makes for a far more peaceful existence since when I was 'seeing' he had nothing of interest to add. I believe 'breakfast' was one item in those days. Now from other posts it appears to be 'visibility' - hey ho!
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On the other hand there were 10 eyewitnesses on the Mull of Kintyre who reported the weather to generally foggy and very bad. Nine of these eyewitnesses (2 of whom were qualified Meteorological Observers) gave sworn evidence to the BOI in respect of the weather conditions where they were stood however none of the 10 could state what the actual weather at the crash site was at the time of the crash.
This why I do not ignore Caz, discrediting his daft assertions is like shooting fish in a barrel. If he had further qualified his daft statement with
Whilst none of the 10 witness's could swear as to the actual weather at the crash site at the time of the crash it is reasonable to assume that the crash site was in fog
And whilst that is the only sensible and logical thing to say the use of assumption rather blows the without doubt verdict out of the water.
It's because his offerings in here, in the very brief interludes of course that the French Internet is working are so blinkered as to be laughable that I do enjoy reading them.
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the French Internet is working
I rather see things as you do SFFP. It is because I disagree with caz, Walter, and of course we must not forget the eminence grise JP, that I welcome their posts.
The reason that this long running thread is a sticky is that 29 people died in this tragedy, and that two of them were found to have been Grossly Negligent in causing it. Never mind that the rules required that such a finding be with absolutely no doubt whatsoever, it was in fact with absolutely no proof whatsoever! The Royal Air Force is shamed with a scandal as infamous as that of the Dreyfuss Case.
There are those who post here sincere in the belief of what they write, among those I would include Walter. There are others who have chosen to prop up a dishonourable and increasingly ragged cover-up, either in misplaced loyalty to a discredited higher command or for more personal motives of self-preservation. I do not care to question individuals' motives, that is for them and their consciences, but this is not a game or a running joke about little green men. This is about Gross Negligence at the highest levels of the RAF, of illegal orders to subvert Regulations, and of cowardly and malevolent efforts thereafter to prevent that being known about. Most of all it is about a fatal air accident, and its totally inadequate investigation. We shall now never know for sure why those 29 victims died that day. We do know that the aircraft they were in was Grossly Unairworthy and should not have been Released to Service into the RAF in that state. If for no other reason we owe it to their memory to ensure that never happens again. The UK military urgently needs a separate and independent MAA and MAAIB, and time is of the essence.
The reason that this long running thread is a sticky is that 29 people died in this tragedy, and that two of them were found to have been Grossly Negligent in causing it. Never mind that the rules required that such a finding be with absolutely no doubt whatsoever, it was in fact with absolutely no proof whatsoever! The Royal Air Force is shamed with a scandal as infamous as that of the Dreyfuss Case.
There are those who post here sincere in the belief of what they write, among those I would include Walter. There are others who have chosen to prop up a dishonourable and increasingly ragged cover-up, either in misplaced loyalty to a discredited higher command or for more personal motives of self-preservation. I do not care to question individuals' motives, that is for them and their consciences, but this is not a game or a running joke about little green men. This is about Gross Negligence at the highest levels of the RAF, of illegal orders to subvert Regulations, and of cowardly and malevolent efforts thereafter to prevent that being known about. Most of all it is about a fatal air accident, and its totally inadequate investigation. We shall now never know for sure why those 29 victims died that day. We do know that the aircraft they were in was Grossly Unairworthy and should not have been Released to Service into the RAF in that state. If for no other reason we owe it to their memory to ensure that never happens again. The UK military urgently needs a separate and independent MAA and MAAIB, and time is of the essence.
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It is without doubt the TANS was functioning until impact.
It certainly is not. The internal battery was allowing storage of incoming data but at the 26 (or 32 sec point before impact, depending on which document you read), the power switch was moved to the off position and NAV display and all other functions were lost.
It certainly is not. The internal battery was allowing storage of incoming data but at the 26 (or 32 sec point before impact, depending on which document you read), the power switch was moved to the off position and NAV display and all other functions were lost.
Surely the most likely scenario is that they turned it off 26+ seconds before the crash.
But why?
Looking at the Analysis of Available Data report, this places the switchoff at shortly before they should have reached waypoint change. Have I read that right?
I don't think that they would have had trouble controlling the aircraft at that point - they would have had other more important things to worry about than the TANS in that case.
Most likely they didn't believe what it was telling them.
And why would that be? Surely because it was telling them they were nowhere near where they thought they were.
If my reasoning is correct, then this suggests things had gone badly wrong before waypoint change.
Still loads of ifs and maybes here. Apologies for the ramble.
TN
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Thor
If RACAL is to be believed at all, then the crew did a manual Waypoint change shortly before impact. They wouldn't bother if they had already lost confidence in the equipment.
Also if they were already dealing with a major catastophe like a FADEC runaway or a UFCM I doubt Waypoint Change would be high on the agenda.
Given the timescale, I think that the act of changing the Waypoint, caused, or at least drew the attention of the crew to another real or perceived emergency situation.
But, as you say, who knows?
If RACAL is to be believed at all, then the crew did a manual Waypoint change shortly before impact. They wouldn't bother if they had already lost confidence in the equipment.
Also if they were already dealing with a major catastophe like a FADEC runaway or a UFCM I doubt Waypoint Change would be high on the agenda.
Given the timescale, I think that the act of changing the Waypoint, caused, or at least drew the attention of the crew to another real or perceived emergency situation.
But, as you say, who knows?
Last edited by dalek; 27th Jun 2011 at 13:20.
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Can you think of any reason why they might switch off TANS if they hadn't lost confidence in it?
TN
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They may have thought it spot on, but causing problems with other equipment. (EMI) They may have spotted an electrical problem and were load shedding. You need to ask a Chinook operator who used exactly the same mark of TANS. The ones I used were on trials aircraft. The Emergency Drills would be different
Last edited by dalek; 27th Jun 2011 at 14:47.
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Dalek,
I understand now, thanks for being so patient.
But to clarify one thing, for them to switch off TANS before the last waypoint change would seem to indicate that something (forever unknowable) was amiss, would you agree that is a fair assumption?
TN
I understand now, thanks for being so patient.
But to clarify one thing, for them to switch off TANS before the last waypoint change would seem to indicate that something (forever unknowable) was amiss, would you agree that is a fair assumption?
TN
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Various.....
The Switches...Are we entirely sure that the switch shown in the photo is actually the power switch for the Tans alone.??????????......it is an appendage piggy-backed to the Tans and extends across the top and down over the rear of the Tans 'proper' ...........it could be anything from a master avionics switch to a control for the DTD from which the Tans waypoints can be loaded . It is not an attachment used in all installations...?????????.....
..plus the lower rotary switch does not seem to be in the EXT position as described.....?????........or is there a reflection caused by the camera flash which looks like an index mark on the knob...????...
The Turn...........
..Again I challenge the suggestion that there was any defined 'turn' on approach to the Mull , the average course for the whole journey and the GPS locations show :---
...................BEL VOR to true point of impact = 21.23 degrees true....
Waypoint change GPS to Last steering update = 22.22 degrees true...
.....Last Steering update to Tans power down = 20.51 degrees true........
Tans power down to last GPS(not processed) = 20.69 degrees true....
which show the track only varies by about 1.72 degrees max. between recorded locations............this is more likely due to wind variations or hunting in the servo systems than any deliberate turn...
When you have a series of co-ordinates as I describe from the GPS source...........and you know that there are some errors on the GPS signal..but all the lat/longs. appear to be in a straight line on the map there are really only two possibilities.................
The wandering GPS signal error has magically followed and matched the turns of the aircraft in timing and rate and direction.............or
The GPS values are reliable and the aircraft was travelling in a straight line.................
..the other values from the Racal report such as heading are suspect......as the a/c may have already hit the ground when these were logged .......any gyro source would be suspect after a severe shock.........and the pitch and roll values( roll changes over 10 degrees in four seconds)suggest that the a/c was gyrating in pitch roll and yaw...........again probably after first impact......
.as the GPS antenna and the Doppler head are mounted forward of the cofg...any severe yaw would give inaccurate track indications as the signal 'source' is not moving on the same track as the fuselage as a whole , but on a slight diagonal....
The Times......
......any reference to 36 seconds should read 26......or more accurately 25.6 seconds.......as the difference between the 16:59:10.4 ..and 16:59:36.0 timestamps.....the GPS clock is as recorded inside the Tans........so when the Tans is powered off it saves the last value it had for the GPS clock.......but the two(Tans , GPS) may not have powered off at the same actual time , as the gps recorded a last location further on across the hillside.....The Tans had gone to a frozen state at this time and was not accepting any more data until the power came back.......depends where the power feed to the GPS was connected ..
The Waypoint Change
..I see nothing strange about changing to Waypoint B........they would have had a warning from the Tans one minute to run before passing (abeam) Waypoint A......depending apon what airspeed you like to believe that gives between 20 and 30 seconds to run when they made the change..........it would have required an extremely violent turn in order to avoid Waypoint A....as they were so close.
rgds all....
..plus the lower rotary switch does not seem to be in the EXT position as described.....?????........or is there a reflection caused by the camera flash which looks like an index mark on the knob...????...
The Turn...........
..Again I challenge the suggestion that there was any defined 'turn' on approach to the Mull , the average course for the whole journey and the GPS locations show :---
...................BEL VOR to true point of impact = 21.23 degrees true....
Waypoint change GPS to Last steering update = 22.22 degrees true...
.....Last Steering update to Tans power down = 20.51 degrees true........
Tans power down to last GPS(not processed) = 20.69 degrees true....
which show the track only varies by about 1.72 degrees max. between recorded locations............this is more likely due to wind variations or hunting in the servo systems than any deliberate turn...
When you have a series of co-ordinates as I describe from the GPS source...........and you know that there are some errors on the GPS signal..but all the lat/longs. appear to be in a straight line on the map there are really only two possibilities.................
The wandering GPS signal error has magically followed and matched the turns of the aircraft in timing and rate and direction.............or
The GPS values are reliable and the aircraft was travelling in a straight line.................
..the other values from the Racal report such as heading are suspect......as the a/c may have already hit the ground when these were logged .......any gyro source would be suspect after a severe shock.........and the pitch and roll values( roll changes over 10 degrees in four seconds)suggest that the a/c was gyrating in pitch roll and yaw...........again probably after first impact......
.as the GPS antenna and the Doppler head are mounted forward of the cofg...any severe yaw would give inaccurate track indications as the signal 'source' is not moving on the same track as the fuselage as a whole , but on a slight diagonal....
The Times......
......any reference to 36 seconds should read 26......or more accurately 25.6 seconds.......as the difference between the 16:59:10.4 ..and 16:59:36.0 timestamps.....the GPS clock is as recorded inside the Tans........so when the Tans is powered off it saves the last value it had for the GPS clock.......but the two(Tans , GPS) may not have powered off at the same actual time , as the gps recorded a last location further on across the hillside.....The Tans had gone to a frozen state at this time and was not accepting any more data until the power came back.......depends where the power feed to the GPS was connected ..
The Waypoint Change
..I see nothing strange about changing to Waypoint B........they would have had a warning from the Tans one minute to run before passing (abeam) Waypoint A......depending apon what airspeed you like to believe that gives between 20 and 30 seconds to run when they made the change..........it would have required an extremely violent turn in order to avoid Waypoint A....as they were so close.
rgds all....
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Thor
The GPS position when the waypoint was changed was derived from data to the next GPS waypoint (B) and so, within the GPS world of the GPS system, can be regarded as accurate.
The time of waypoint change was not recorded but calculated using groundspeed back from subsequent gps position data – while not absolute, I feel it would be accurate enough for meaningful analysis.
The GPS position when the waypoint was changed was derived from data to the next GPS waypoint (B) and so, within the GPS world of the GPS system, can be regarded as accurate.
The time of waypoint change was not recorded but calculated using groundspeed back from subsequent gps position data – while not absolute, I feel it would be accurate enough for meaningful analysis.
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Thor
Switching off the TANS makes the screen go blank. It is pointless then doing a Waypoint change. When you switch off your TV you don,t try to change channels or adjust volume. Same principle.
Robin
Just what does the TANS Power Switch control?
It certainly has no effect on the GM Compass. You can continue to use that.
It certainly has no effect on the raw doppler. Separate power switch, control panel and display.
I am pretty certain the ADC just works once power is supplied. It is on throughout the flight.
Trimble GPS?
If the TANS power switch was Switched Off by the crew some 26 secs before impact, and this did also switch off the Trimble GPS:
Then the final position recorded in the TANS should be 170 G/S x26 secs down track from the actual impact position. That is 1.4nms or 8500ft.
No such error is recorded.
Switching off the TANS makes the screen go blank. It is pointless then doing a Waypoint change. When you switch off your TV you don,t try to change channels or adjust volume. Same principle.
Robin
Just what does the TANS Power Switch control?
It certainly has no effect on the GM Compass. You can continue to use that.
It certainly has no effect on the raw doppler. Separate power switch, control panel and display.
I am pretty certain the ADC just works once power is supplied. It is on throughout the flight.
Trimble GPS?
If the TANS power switch was Switched Off by the crew some 26 secs before impact, and this did also switch off the Trimble GPS:
Then the final position recorded in the TANS should be 170 G/S x26 secs down track from the actual impact position. That is 1.4nms or 8500ft.
No such error is recorded.
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Robin Clark
Still you make the error of looking for a turn from the origin to the end points – rather basic, but I will explain again:
for a start, convert all your bearings/headings/etc to magnetic (using var of the time) so that you will be able to recognise any correlations between instruments, etc. and avoid confusion with true bearings;
I will try to explain why the flight as far as waypoint change can be regarded as a straight line followed by a significant turn:
a useful position from the reports was “first fix”, not at the take-off pad but a couple of miles into the flight, from where the bearing to waypoint A was exactly 027 – let us refer to the path between “first fix” and waypoint A as the “027 track” - remembering where the radar site was and that the ATC fix was relative to that, you will find that even the approximate ATC fix had them on this 027 track a few miles after take-off ;
the sighting at Carlough 20 miles into the flight was consistent with their being on this track at that point;
the position of waypoint change was exactly on this 027 track from “first fix”;
“A” was the waypoint the STANS was using until waypoint change and it is surely obvious that they would have been flying along this track reasonably closely for reasons of efficiency over the sea with no features in the way to need a deviation;
thus it is surely reasonable to assume that we can draw a straight line up until waypoint change;
if we take the last steering calculation position (some seconds before impact, a routine data storage, when the a/c was still in a steady state, as I have previously argued it to be right up until impact) the bearing from exactly waypoint change was 30 – thus a minimum value for the turn of 3 degrees if started instantly at waypoint change;
to have kept to track over such a distance, it is reasonable to assume that the HP's course selector would have been on 027 up at least until waypoint change;
the HP's course selector was found on 035 - allowing a couple of seconds to twiddle the course selector and turn would have extended their track along 027 by a couple of hundred yards at their speed which in turn (that close in) gets the bearing to that position of last altitude update to 035 – either this is an amazing coincidence or the turn onto 035 was intentional.
Further, you wrote <<..it would have required an extremely violent turn in order to avoid Waypoint A....as they were so close. >>
Recently I posted a graphic representation of the turning radii at their speed on a map of the area – at their altitude it was perfectly safe for them to start a moderate (30-60 bank) turn as they passed over the position of waypoint A – it was the optimum point to aim for if you wanted to swing around the lighthouse – the wave-off if you didn't want to actually touch down at the “green triangle” LZ.
Below 800ish ft they were not in oro cloud - the mist was on the slopes but turning in time would have kept them in the clear, probably able to see the lighthouse or its masts intermittently below and to the left - to the right the sloping ground intermittently showing through the surface mist, impossible to judge one's distance off.
At the risk of getting the size wrong, I'll try and post it here again:
Tuc
Is this relevant to the switch business?
From the “AAIB INVESTIGATION OF THE TRIMBLE TNL 8000 GPS NAVIGATION UNIT”:
<<2.6.2 The facility for switching the main DC power supply for the unit by utilising a lowcurrent/voltage line from the aircraft to an FET within the unit did not function in that it was not possible to switch off the power supply using this facility. Examination of the components showed that the FET had been damaged at some time, it was not possible to say when, by having a high voltage applied to it from the main DC power supply input to the unit The damaged FET was replaced and a bench test performed and this remote switching of the power supply was found to function correctly.>>
Still you make the error of looking for a turn from the origin to the end points – rather basic, but I will explain again:
for a start, convert all your bearings/headings/etc to magnetic (using var of the time) so that you will be able to recognise any correlations between instruments, etc. and avoid confusion with true bearings;
I will try to explain why the flight as far as waypoint change can be regarded as a straight line followed by a significant turn:
a useful position from the reports was “first fix”, not at the take-off pad but a couple of miles into the flight, from where the bearing to waypoint A was exactly 027 – let us refer to the path between “first fix” and waypoint A as the “027 track” - remembering where the radar site was and that the ATC fix was relative to that, you will find that even the approximate ATC fix had them on this 027 track a few miles after take-off ;
the sighting at Carlough 20 miles into the flight was consistent with their being on this track at that point;
the position of waypoint change was exactly on this 027 track from “first fix”;
“A” was the waypoint the STANS was using until waypoint change and it is surely obvious that they would have been flying along this track reasonably closely for reasons of efficiency over the sea with no features in the way to need a deviation;
thus it is surely reasonable to assume that we can draw a straight line up until waypoint change;
if we take the last steering calculation position (some seconds before impact, a routine data storage, when the a/c was still in a steady state, as I have previously argued it to be right up until impact) the bearing from exactly waypoint change was 30 – thus a minimum value for the turn of 3 degrees if started instantly at waypoint change;
to have kept to track over such a distance, it is reasonable to assume that the HP's course selector would have been on 027 up at least until waypoint change;
the HP's course selector was found on 035 - allowing a couple of seconds to twiddle the course selector and turn would have extended their track along 027 by a couple of hundred yards at their speed which in turn (that close in) gets the bearing to that position of last altitude update to 035 – either this is an amazing coincidence or the turn onto 035 was intentional.
Further, you wrote <<..it would have required an extremely violent turn in order to avoid Waypoint A....as they were so close. >>
Recently I posted a graphic representation of the turning radii at their speed on a map of the area – at their altitude it was perfectly safe for them to start a moderate (30-60 bank) turn as they passed over the position of waypoint A – it was the optimum point to aim for if you wanted to swing around the lighthouse – the wave-off if you didn't want to actually touch down at the “green triangle” LZ.
Below 800ish ft they were not in oro cloud - the mist was on the slopes but turning in time would have kept them in the clear, probably able to see the lighthouse or its masts intermittently below and to the left - to the right the sloping ground intermittently showing through the surface mist, impossible to judge one's distance off.
At the risk of getting the size wrong, I'll try and post it here again:
Tuc
Is this relevant to the switch business?
From the “AAIB INVESTIGATION OF THE TRIMBLE TNL 8000 GPS NAVIGATION UNIT”:
<<2.6.2 The facility for switching the main DC power supply for the unit by utilising a lowcurrent/voltage line from the aircraft to an FET within the unit did not function in that it was not possible to switch off the power supply using this facility. Examination of the components showed that the FET had been damaged at some time, it was not possible to say when, by having a high voltage applied to it from the main DC power supply input to the unit The damaged FET was replaced and a bench test performed and this remote switching of the power supply was found to function correctly.>>
Last edited by walter kennedy; 28th Jun 2011 at 06:51. Reason: pelling