Chinook - Still Hitting Back 3 (Merged)
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Seems to be lots of conjecture on the squawk code leading to a theory which is IMHO a total red herring.
First off, at the time of the accident, Aldergrove was not SSR equipped and therefore would not have observed any code. They would only have assigned one if the next SSR equipped agency had passed the required code to them. Otherwise, the pilot of the Chinook would have selected an appropriate conspicuity code in accordance with SOPs. (The code 7000 would be appropriate for this flight). In this accident, the only possible unit which could have done so would have been Scottish Area Control Centre (either Civil or Military). For low level VFR flight, it is not normal practice to assign a specific code unless the pilot requests a radar service. Additionally, the nearest radar sources available to ScACC are at Tiree or Lowther Hill, both of which would be very hard pushed to pick up a low level target in the accident area due to terrain shielding and line of sight restrictions. Otherwise the radar recordings would have been used to provide a lot more evidence of ground track and altitude in the accident enquiries.
Coming to the SSR codes, the UK Code Allocation Plan is a document in the public domain. The 77** series of codes, with the exception of 7700, are all in use in normal every day operations. The main bulk of the series is allocated to ATC agencies for inter European traffic, including the disputed code of 7760. There are no 'secret squirrel' codes in the group. ATC radar systems therefore do not assume anyone is on an emergency if they squawk 77**. It would be chaos in Europe if they did !!
7776 and 7777 are used for SSR monitors. These are low power transponders fixed in a location on the ground at a known distance and bearing from the SSR radar aerial which it serves. The SSR processing equipment has a tolerance box within which it expects to see the ground transponder. If it moves outwith this area, then the radar is potentially out of tolerance and warnings will be given to ATC engineering, and in some locations to the ATC controller on his/her screen. A pilot selecting one of these codes will also cause the same thing to happen since the chance of him remaining in a box of extremely small dimensions in a position unknown to him/her is improbable. These codes are nothing to do with clandestine DME units.
I think you will find this refers to R/T callsigns and not SSR codes. Transponders use octal code and the highest digit which can be displayed is 7, therefore 7799 is impossible to set. It's good fun getting a pilot to try occasionally 
First off, at the time of the accident, Aldergrove was not SSR equipped and therefore would not have observed any code. They would only have assigned one if the next SSR equipped agency had passed the required code to them. Otherwise, the pilot of the Chinook would have selected an appropriate conspicuity code in accordance with SOPs. (The code 7000 would be appropriate for this flight). In this accident, the only possible unit which could have done so would have been Scottish Area Control Centre (either Civil or Military). For low level VFR flight, it is not normal practice to assign a specific code unless the pilot requests a radar service. Additionally, the nearest radar sources available to ScACC are at Tiree or Lowther Hill, both of which would be very hard pushed to pick up a low level target in the accident area due to terrain shielding and line of sight restrictions. Otherwise the radar recordings would have been used to provide a lot more evidence of ground track and altitude in the accident enquiries.
Coming to the SSR codes, the UK Code Allocation Plan is a document in the public domain. The 77** series of codes, with the exception of 7700, are all in use in normal every day operations. The main bulk of the series is allocated to ATC agencies for inter European traffic, including the disputed code of 7760. There are no 'secret squirrel' codes in the group. ATC radar systems therefore do not assume anyone is on an emergency if they squawk 77**. It would be chaos in Europe if they did !!
7776 and 7777 are used for SSR monitors. These are low power transponders fixed in a location on the ground at a known distance and bearing from the SSR radar aerial which it serves. The SSR processing equipment has a tolerance box within which it expects to see the ground transponder. If it moves outwith this area, then the radar is potentially out of tolerance and warnings will be given to ATC engineering, and in some locations to the ATC controller on his/her screen. A pilot selecting one of these codes will also cause the same thing to happen since the chance of him remaining in a box of extremely small dimensions in a position unknown to him/her is improbable. These codes are nothing to do with clandestine DME units.
Another that suggests that 7760 has an interesting meaning is:
<< RRR 7750-7799 ANDOVER RAF SPECIAL TASKS>>
<< RRR 7750-7799 ANDOVER RAF SPECIAL TASKS>>
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Walter Kennedy
Firstly, I'm not convinced that the picture you refer to shows localised misting - could just be the tide coming in. The mist/cloud at the Mull on the day of the accident must have been caused by an orographic effect (moist air lifting over terrain, air cools, water condenses), not a shallow bank of radiation fog as is (possibly) seen in the picture you refer to. With respect, I don't need your help to picture the weather conditions as I have flown in them; I am therefore qualified to say that visual judgement, whilst not as easy as on a gin-clear day, is unlikely to have presented a significant problem, given that there was sufficient cloudbase to fly VFR over the sea and that it was not the crew's intention to cross the coastline once it became apparent that the original 'turning point' was in cloud.
<<I believe that it was risky to have approached closer than, say, the waypoint change in these conditions unless they had something else to go on, never mind aiming to turn right on the coastline.>> From your comments later in your latest posts, it is not what you intend, but this is the argument used by their Airships to show that the pilots were negligent. However, at waypoint change, the Chinook, as far as we can tell, was 0.81nm short of the coastline - a distance at which it would be perfectly safe to execute a 7 deg turn to the left using purely visual references. There is no evidence to suggest that they intended to turn "right on the coastline".
I'm not qualified to get too deeply into the workings of the
IFF/SSR but note Pprune Radar's comment about digits 8 & 9. The 77xx scenario that I was referring to was certainly true of the Jet Provost (ie if one selected 7760 or any other 4-digit code beginning with 77) the kit would squawk 'emergency'. I would agree with Pprune radar on his suggestion about likely squawk.
<<I remember reading somewhere on SSR codes that it may not be desirable or prudent to change (or attempt to change) the code in an emergency in certain situations (I’ll leave it to you airmen to look this up yourselves) – I can’t see what would have been the point in the limited time that they would have had and it may have caused his confusion (possibly one of the conditions where it is not recommended to attempt change?)>>
In the event of an emergency, it is desirable to select 7700. It shouldn't be necessary to attempt to do this whilst, say, IMC at low level, but it's entirely possible that one of the crew might have attempted this. I chose the words "one of the crew" with care because we should not discount the 3rd crewmember having tried to help with this
Without getting into a lengthy sidetrack about SuperTANS, my understanding (which is, admittedly, limited) is that
degradation in accuracy occurs when only a reduced number of satelites (3 or less ?) is LOS. I gather that those who 'milked' the TANS after the accident were able to ascertain that this was not the case and that the reported positions are therefore accurate. Notwithstanding this, and largely for the potential inaccuracies described, the crew would not have relied on SuperTANS alone if flying below Safety Altitude.
<<How things have changed from when I was young – I thought the QFE (“atmospheric pressure at aerodrome elevation”) on the ground at the departure airfield was set by zeroing the altimeter (by way of adjusting the pressure setting dial) so giving good accuracy for local flight.>>
I detect a note of sarcasm in this statement (something of which you earlier disapproved!) but just to put you straight on this point, a QFE is only used in the immediate airfield area, normally within the MATZ (Militarty Air Traffic Zone). Beyond this, the RPS is used, with all its attendant inaccuracies. A flight from NI to the Mull (& beyond) would not be considered (in this context) to be a local flight.
<<The problem was closing the gap from an obviously safe distance to being safe parallel above the shoreline without slowing down appreciably. As I have tried to describe so often, now, this one turn would have been awkward for anyone to judge in those all too common conditions – spoiling a nice low level flight with an arbitrary, often arguably unnecessary, early, untidy turn if playing it safe.>>
There was no need for them to fly above the coastline, they would simply have stayed a short distance out over the sea and parallelled the coastline to the next point. Never mind about an 'untidy' turn, the crew would simply turn at a safe distance, allowing a margin for their own potential error.
<<The book “Chinook” by David McMullen suggests very active involvement in navigation by the non-pilot crew – I just suggested that one of them may have been watching the SAR readout >>
I'm prepared to stand corrected by a Chinook operator, but I think you'll find that the kind of assistance rendered is of the "line of pylons coming in from the left", "town at 1 o'clock, range 2" type.
<<At least most of you can now appreciate the local weather conditions.>>
I hope you don't mean that this is thanks to your expertise! There are a lot of Ppruners out there who have observed similar weather conditions from the air on many more occasions than you have.
<<the debate on this thread has made it clear to all that the intended flight path was low level with a slight turn up the coast>> I don't see that there can be any doubt either, but their Airships do and it is their apparent contention that the crew intended to overfly the Mull that we must negate.
<<Whether such a beacon was correct or not, its exclusion from consideration at the inquiries renders the verdicts on the pilots untenable>>
Sorry, Walter, but I disagree with this statement. You might just as well say that the fact that astazou's tongue-in-cheek "little green men shining lasers at the crew" has not been considered, also renders the verdicts untenable.
What must be done is to show that by being 0.81nm short of the coast, flying at 150 kts groundspeed, VFR at low level is NOT a negligent thing to be doing. I think that, if anything, your theory about portable IFFs or DMEs has the opposite effect, implying that the crew might have been relying on something which could not be relied upon - a situation that some might attempt to use as evidence that they were negligent. I must therefore echo astazou's request to "Please drop it and let's get back to putting pressure on the MOD to give the crew some justice."
Firstly, I'm not convinced that the picture you refer to shows localised misting - could just be the tide coming in. The mist/cloud at the Mull on the day of the accident must have been caused by an orographic effect (moist air lifting over terrain, air cools, water condenses), not a shallow bank of radiation fog as is (possibly) seen in the picture you refer to. With respect, I don't need your help to picture the weather conditions as I have flown in them; I am therefore qualified to say that visual judgement, whilst not as easy as on a gin-clear day, is unlikely to have presented a significant problem, given that there was sufficient cloudbase to fly VFR over the sea and that it was not the crew's intention to cross the coastline once it became apparent that the original 'turning point' was in cloud.
<<I believe that it was risky to have approached closer than, say, the waypoint change in these conditions unless they had something else to go on, never mind aiming to turn right on the coastline.>> From your comments later in your latest posts, it is not what you intend, but this is the argument used by their Airships to show that the pilots were negligent. However, at waypoint change, the Chinook, as far as we can tell, was 0.81nm short of the coastline - a distance at which it would be perfectly safe to execute a 7 deg turn to the left using purely visual references. There is no evidence to suggest that they intended to turn "right on the coastline".
I'm not qualified to get too deeply into the workings of the
IFF/SSR but note Pprune Radar's comment about digits 8 & 9. The 77xx scenario that I was referring to was certainly true of the Jet Provost (ie if one selected 7760 or any other 4-digit code beginning with 77) the kit would squawk 'emergency'. I would agree with Pprune radar on his suggestion about likely squawk.
<<I remember reading somewhere on SSR codes that it may not be desirable or prudent to change (or attempt to change) the code in an emergency in certain situations (I’ll leave it to you airmen to look this up yourselves) – I can’t see what would have been the point in the limited time that they would have had and it may have caused his confusion (possibly one of the conditions where it is not recommended to attempt change?)>>
In the event of an emergency, it is desirable to select 7700. It shouldn't be necessary to attempt to do this whilst, say, IMC at low level, but it's entirely possible that one of the crew might have attempted this. I chose the words "one of the crew" with care because we should not discount the 3rd crewmember having tried to help with this
Without getting into a lengthy sidetrack about SuperTANS, my understanding (which is, admittedly, limited) is that
degradation in accuracy occurs when only a reduced number of satelites (3 or less ?) is LOS. I gather that those who 'milked' the TANS after the accident were able to ascertain that this was not the case and that the reported positions are therefore accurate. Notwithstanding this, and largely for the potential inaccuracies described, the crew would not have relied on SuperTANS alone if flying below Safety Altitude.
<<How things have changed from when I was young – I thought the QFE (“atmospheric pressure at aerodrome elevation”) on the ground at the departure airfield was set by zeroing the altimeter (by way of adjusting the pressure setting dial) so giving good accuracy for local flight.>>
I detect a note of sarcasm in this statement (something of which you earlier disapproved!) but just to put you straight on this point, a QFE is only used in the immediate airfield area, normally within the MATZ (Militarty Air Traffic Zone). Beyond this, the RPS is used, with all its attendant inaccuracies. A flight from NI to the Mull (& beyond) would not be considered (in this context) to be a local flight.
<<The problem was closing the gap from an obviously safe distance to being safe parallel above the shoreline without slowing down appreciably. As I have tried to describe so often, now, this one turn would have been awkward for anyone to judge in those all too common conditions – spoiling a nice low level flight with an arbitrary, often arguably unnecessary, early, untidy turn if playing it safe.>>
There was no need for them to fly above the coastline, they would simply have stayed a short distance out over the sea and parallelled the coastline to the next point. Never mind about an 'untidy' turn, the crew would simply turn at a safe distance, allowing a margin for their own potential error.
<<The book “Chinook” by David McMullen suggests very active involvement in navigation by the non-pilot crew – I just suggested that one of them may have been watching the SAR readout >>
I'm prepared to stand corrected by a Chinook operator, but I think you'll find that the kind of assistance rendered is of the "line of pylons coming in from the left", "town at 1 o'clock, range 2" type.
<<At least most of you can now appreciate the local weather conditions.>>
I hope you don't mean that this is thanks to your expertise! There are a lot of Ppruners out there who have observed similar weather conditions from the air on many more occasions than you have.
<<the debate on this thread has made it clear to all that the intended flight path was low level with a slight turn up the coast>> I don't see that there can be any doubt either, but their Airships do and it is their apparent contention that the crew intended to overfly the Mull that we must negate.
<<Whether such a beacon was correct or not, its exclusion from consideration at the inquiries renders the verdicts on the pilots untenable>>
Sorry, Walter, but I disagree with this statement. You might just as well say that the fact that astazou's tongue-in-cheek "little green men shining lasers at the crew" has not been considered, also renders the verdicts untenable.
What must be done is to show that by being 0.81nm short of the coast, flying at 150 kts groundspeed, VFR at low level is NOT a negligent thing to be doing. I think that, if anything, your theory about portable IFFs or DMEs has the opposite effect, implying that the crew might have been relying on something which could not be relied upon - a situation that some might attempt to use as evidence that they were negligent. I must therefore echo astazou's request to "Please drop it and let's get back to putting pressure on the MOD to give the crew some justice."
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PPRuNe Radar
I appreciate your informed input – this is what has been needed all along; had such detail been freely discussed from the start, the nav issue could have been taken to closure a long time ago. However we are not quite there yet and so I would like to continue with a few aspects, if you will bear with me.
<<… a total red herring.>>
I would not regard consideration of a precision navigation aid (that the HC2 was equipped to use) as a red herring – although numerous inaccuracies at the inquiries (eg actual weather, intended flight route, etc) could be described as such and I am in wonder why so many have been so smart in denigrating a view when the inquiries had been wasted. From a navigation systems point of view (outside the constraints of particular flying regulations) with regard to the prevailing conditions on the Mull that confront helicopters making that regular crossing, it strikes one as an obvious option.
<< Aldergrove was not SSR equipped and therefore would not have observed any code.>>
How can we find out what code it started the flight with for certain? Could you approach the Scottish Area Control Centre?
<<… the pilot of the Chinook would have selected an appropriate conspicuity code in accordance with SOPs.>> In your view, within the range of codes that the Pilot could have chosen with regard to SOPs, was 7760 indeed “meaningless” as concluded by one of the inquiries? Was the pilot restricted to those codes or were there special circumstances (apart from usual emerg etc)?
<<Coming to the SSR codes … ATC …do not assume anyone is on an emergency if they squawk 77**…>>
I never thought this to be the case – I was addressing someone else’s post who said anything 77 something was always emergency (now corrected).
<<7776 and 7777 are used for SSR monitors.>> Thank you for your description of the use of these monitors – we can eliminate these at least.
<<… These codes are nothing to do with clandestine DME units.>>
An odd word to use, “clandestine”, putting the navaid discussion into “conspiracy theory” for the casual reader, perhaps. My point here is that there is a group of codes existent that are used in SAR operations – I would have thought that some would have been applicable to a helicopter homing in on a SAR transponder; 7760 is very close to some of them. The questions remain: was 7760 set at the start of the flight (as opposed to being moved in the accident by the crew in attempting to set an emergency squawk or being accidentally displaced)? And, if set, what could its meaning have been?
<< RRR 7750-7799 ANDOVER RAF SPECIAL TASKS>>
<<I think you will find this refers to R/T callsigns and not SSR codes. Transponders use octal code and the highest digit which can be displayed is 7, therefore 7799 is impossible to set. It's good fun getting a pilot to try occasionally>>
Ah, missed that! But they must have had a set of codes; or rather, particular codes that was their habit to choose depending on what type of activity they were conducting – could you expand on your answer and enlighten us as to the range and meaning of their codes? If there is a “need to know” thing, how about a clear statement (just on the one of interest) as to whether they used 7760 and what was the meaning? I am sure that by now you must realize that I am trying to establish absolutely the significance (if any) of the code 7760 as was found set in the wreckage of ZD576 – a fair enough objective, I would have thought – please help.
I appreciate your informed input – this is what has been needed all along; had such detail been freely discussed from the start, the nav issue could have been taken to closure a long time ago. However we are not quite there yet and so I would like to continue with a few aspects, if you will bear with me.
<<… a total red herring.>>
I would not regard consideration of a precision navigation aid (that the HC2 was equipped to use) as a red herring – although numerous inaccuracies at the inquiries (eg actual weather, intended flight route, etc) could be described as such and I am in wonder why so many have been so smart in denigrating a view when the inquiries had been wasted. From a navigation systems point of view (outside the constraints of particular flying regulations) with regard to the prevailing conditions on the Mull that confront helicopters making that regular crossing, it strikes one as an obvious option.
<< Aldergrove was not SSR equipped and therefore would not have observed any code.>>
How can we find out what code it started the flight with for certain? Could you approach the Scottish Area Control Centre?
<<… the pilot of the Chinook would have selected an appropriate conspicuity code in accordance with SOPs.>> In your view, within the range of codes that the Pilot could have chosen with regard to SOPs, was 7760 indeed “meaningless” as concluded by one of the inquiries? Was the pilot restricted to those codes or were there special circumstances (apart from usual emerg etc)?
<<Coming to the SSR codes … ATC …do not assume anyone is on an emergency if they squawk 77**…>>
I never thought this to be the case – I was addressing someone else’s post who said anything 77 something was always emergency (now corrected).
<<7776 and 7777 are used for SSR monitors.>> Thank you for your description of the use of these monitors – we can eliminate these at least.
<<… These codes are nothing to do with clandestine DME units.>>
An odd word to use, “clandestine”, putting the navaid discussion into “conspiracy theory” for the casual reader, perhaps. My point here is that there is a group of codes existent that are used in SAR operations – I would have thought that some would have been applicable to a helicopter homing in on a SAR transponder; 7760 is very close to some of them. The questions remain: was 7760 set at the start of the flight (as opposed to being moved in the accident by the crew in attempting to set an emergency squawk or being accidentally displaced)? And, if set, what could its meaning have been?
<< RRR 7750-7799 ANDOVER RAF SPECIAL TASKS>>
<<I think you will find this refers to R/T callsigns and not SSR codes. Transponders use octal code and the highest digit which can be displayed is 7, therefore 7799 is impossible to set. It's good fun getting a pilot to try occasionally>>
Ah, missed that! But they must have had a set of codes; or rather, particular codes that was their habit to choose depending on what type of activity they were conducting – could you expand on your answer and enlighten us as to the range and meaning of their codes? If there is a “need to know” thing, how about a clear statement (just on the one of interest) as to whether they used 7760 and what was the meaning? I am sure that by now you must realize that I am trying to establish absolutely the significance (if any) of the code 7760 as was found set in the wreckage of ZD576 – a fair enough objective, I would have thought – please help.
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meadowbank
<<Firstly, I'm not convinced that the picture you refer to shows localised misting … I don't need your help to picture the weather conditions as I have flown in them; I am therefore qualified to say that visual judgement, whilst not as easy as on a gin-clear day, is unlikely to have presented a significant problem, given that there was sufficient cloudbase to fly VFR over the sea …>>
Like the altimeter analogy, you have missed the point – I was using the picture to describe to readers (who may not appreciate what it looks like from the sea side – not having had your experience) what such a coastline looks like with no familiar features to scale from – it is very hard indeed to judge distance without, say, a building/boat/known feature/ etc..
<<… and that it was not the crew's intention to cross the coastline once it became apparent that the original 'turning point' was in cloud.>>
And
<<… However, at waypoint change, the Chinook, as far as we can tell, was 0.81nm short of the coastline - a distance at which it would be perfectly safe to execute a 7 deg turn to the left using purely visual references. There is no evidence to suggest that they intended to turn "right on the coastline".>>
Waypoint A was not in cloud. A point right above the shoreline (the suggested turning point) would not have been in cloud, either. The mist formed (as you said yourself) as the air rose over the ground (very common conditions at the Mull).
The problem was judging the start of the turn, a few hundred metres before the mist, without entering it; had this been achieved they would have been parallel to and above the shoreline, in clear air around them and to their left (nice sea views), with the shoreline visible beneath them, but with a wall of grey to their immediate right. According to me and a witness who lived at the site (lighthouse keeper) this was the path helicopters took “all the time”.
With my experience of such coastal weather conditions, I fundamentally disagree that it would have been safe at any kind of speed relying on the eyeball alone to have turned in so close (they would not have trusted the TANS so how would they have known they were 0.8nm out – it was not that far to go). The evidence I use to say that they were going to turn right on the shoreline is my own observation (in identical weather conditions) and the lighthouse keepers comments regarding flights on that route – also, that the track of the aircraft took it very close in without (in my humble opinion) any evidence of control difficulties that would have prevented earlier evasive action (before the final desperate flare, in which control was evident).
<<I'm not qualified to get too deeply into the workings of the
IFF/SSR but note Pprune Radar's comment about digits 8 & 9. The 77xx scenario that I was referring to was certainly true of the Jet Provost (ie if one selected 7760 or any other 4-digit code beginning with 77) the kit would squawk 'emergency'. I would agree with Pprune radar on his suggestion about likely squawk.>>
So, let’s be clear on this – 77** did not have to mean emergency – I think you are in agreement with this now. The point is that 7760 could have been a valid code and could have had significance if it was selected earlier in the flight. Again, it would be nice to know if this was the case
<<I remember … on SSR codes that it may not be desirable or prudent to change (or attempt to change) the code in an emergency … point in the limited time that they would have …>>
<<In the event of an emergency, it is desirable to select 7700. It shouldn't be necessary to attempt to do this whilst, say, IMC at low level, but it's entirely possible that one of the crew might have attempted this. I chose the words "one of the crew" with care because we should not discount the 3rd crewmember having tried to help with this >>
Even with PPRuNe Radar’s input that no one could have picked it up in their locale? Let’s not forget that we are to believe that the radio transmissions were not complete (another angle all together – remember the unanswered call? Or at least the lack of recording of or statement regarding it.). At least it sounds like you agree that it is not a high priority to change code. Let me say again that I am questioning whether the code was altered – it would be nice to know what code was set before the crash (and not generalizations like what it could have set) because it could have had a significance.
<<Without getting into a lengthy sidetrack about SuperTANS … Notwithstanding this, and largely for the potential inaccuracies described, the crew would not have relied on SuperTANS alone if flying below Safety Altitude.>>
I described (I thought) adequately the use by SuperTANS of inputs from both GPS and Doppler – over sea the Doppler input can significantly degrade the net result. That the SuperTANS was found to have been very accurate at the crash position was chance. I think that we are in agreement in that the crew would not have relied on the SuperTANS for a critical turn – I would argue that they would not have come in as close as the waypoint. ZD576 did not have radar. They had their visual judgment or possibly could have been using a SAR transponder – and that’s it.
<<How things have … QFE … for local flight.>>
<<I detect a note of sarcasm in this statement (something of which you earlier disapproved!) but just to put you straight on this point, a QFE is only used in the immediate airfield area, normally within the MATZ (Militarty Air Traffic Zone). Beyond this, the RPS is used, with all its attendant inaccuracies. A flight from NI to the Mull (& beyond) would not be considered (in this context) to be a local flight. >>
What a distraction – the altimeter analogy was just that, as I thought I explained last post.
<<The problem was closing the … untidy turn if playing it safe.>>
<<There was no need for them to fly above the coastline, they would simply have stayed a short distance out over the sea and parallelled the coastline to the next point. Never mind about an 'untidy' turn, the crew would simply turn at a safe distance, allowing a margin for their own potential error.>>
But it WAS the practice (my own observation in identical weather conditions and talking to the lighthouse keeper who lived there).
<<The book “Chinook” … watching the SAR readout >>
<<… I think you'll find that the kind of assistance rendered is of the "line of pylons coming in from the left" … type.>>
Hey, it was just a suggested scenario in answer to one part of one of your pms << …Even at that speed, I would never have considered using DME as a turning cue. It is not realy viable to watch an instrument, waiting for the distance to run down (or up if flying away from the DME beacon) whilst flying at speed at low altitude>>
I was just making the point that they had a spare set of eyes.
<<At least most of you can now appreciate the local weather conditions.>>
<<I hope you don't mean that this is thanks to your expertise! There are a lot of Ppruners out there who have observed similar weather conditions from the air on many more occasions than you have.>>
I don’t understand this comment at all – the ACTUAL conditions have only been brought to light by debate – if you revisit the transcripts of the inquiries you will find that the perception was one of generally poor visibility, not clear with localized mist – I have pushed for clarification of the actual conditions for 10 years – yes with my “limited” personal experience – it is to the shame of others that you describe that they did not clear this perception up at the time of the inquiries (the point was even made by one of the law Lords that their demonstration flight was made in clear weather and not as on the crash day).
<<the debate on this thread has made it clear to all that the intended flight path was low level with a slight turn up the coast>> << I don't see that there can be any doubt either, but their Airships do and it is their apparent contention that the crew intended to overfly the Mull that we must negate.>> So we are in agreement - so why throw it back at me? I’m not in a match with you – take the ball forward, get your colleagues to petition a correction – inform the legal side – whatever. It was my impression that the actual intended flight plan was deliberately confused by the top brass’s obfuscation at the inquiries – for what possible reason?, you should ask yourselves. In my opinion, denying the inquiries the starting point of the actual intended flight path, and further presenting a wrong impression of the weather conditions, suggests that they did not want to get to the truth.
<<Whether such a beacon was correct or not, its exclusion from consideration at the inquiries renders the verdicts on the pilots untenable>>
<<Sorry, Walter, but I disagree with this statement. You might just as well say that the fact that astazou's tongue-in-cheek "little green men shining lasers at the crew" has not been considered, also renders the verdicts untenable.>>
While the “Campaign” has for years focused on possible malfunctions that showed no effect (other than the flight continuing on until the final evasive flare) or evidence for having happened, you put the omission of any reference to or consideration of a precision navigation aid (that the HC2 was equipped to use) on a par with "little green men shining lasers at the crew".
<<What must be done is to show that by being 0.81nm short of the coast, flying at 150 kts groundspeed, VFR at low level is NOT a negligent thing to be doing. I think that, if anything, your theory about portable IFFs or DMEs has the opposite effect, implying that the crew might have been relying on something which could not be relied upon - a situation that some might attempt to use as evidence that they were negligent. I must therefore echo astazou's request to "Please drop it and let's get back to putting pressure on the MOD to give the crew some justice.">>
I am about getting to the truth about what happened – not just clearing the crew. I am concerned with getting justice for the passengers whose loss was a profound blow to the people of the United Kingdom and Northern Ireland. This team was in the hands of the RAF – the objectives of this debate should not be limited to just clearing the crew (although I agree that this would be worthy in its own right). Every possibility of sabotage needed to be explored – to date there has been a severe case of “groupthink” in this respect. The interference with a navaid is just one possible method which I thought needed following up – I will happily shut up if and when this possibility has been exhausted, which it has not quite been yet. What has been very interesting is that, over the years, the arguments against this have been getting of better quality – the initial (including official) put downs were often demonstrably wrong (although the dismissive tone is often the same) and the inquiries were misled on basic conditions; this does rather imply that the powers-that-be just don’t want to go there.
<<Firstly, I'm not convinced that the picture you refer to shows localised misting … I don't need your help to picture the weather conditions as I have flown in them; I am therefore qualified to say that visual judgement, whilst not as easy as on a gin-clear day, is unlikely to have presented a significant problem, given that there was sufficient cloudbase to fly VFR over the sea …>>
Like the altimeter analogy, you have missed the point – I was using the picture to describe to readers (who may not appreciate what it looks like from the sea side – not having had your experience) what such a coastline looks like with no familiar features to scale from – it is very hard indeed to judge distance without, say, a building/boat/known feature/ etc..
<<… and that it was not the crew's intention to cross the coastline once it became apparent that the original 'turning point' was in cloud.>>
And
<<… However, at waypoint change, the Chinook, as far as we can tell, was 0.81nm short of the coastline - a distance at which it would be perfectly safe to execute a 7 deg turn to the left using purely visual references. There is no evidence to suggest that they intended to turn "right on the coastline".>>
Waypoint A was not in cloud. A point right above the shoreline (the suggested turning point) would not have been in cloud, either. The mist formed (as you said yourself) as the air rose over the ground (very common conditions at the Mull).
The problem was judging the start of the turn, a few hundred metres before the mist, without entering it; had this been achieved they would have been parallel to and above the shoreline, in clear air around them and to their left (nice sea views), with the shoreline visible beneath them, but with a wall of grey to their immediate right. According to me and a witness who lived at the site (lighthouse keeper) this was the path helicopters took “all the time”.
With my experience of such coastal weather conditions, I fundamentally disagree that it would have been safe at any kind of speed relying on the eyeball alone to have turned in so close (they would not have trusted the TANS so how would they have known they were 0.8nm out – it was not that far to go). The evidence I use to say that they were going to turn right on the shoreline is my own observation (in identical weather conditions) and the lighthouse keepers comments regarding flights on that route – also, that the track of the aircraft took it very close in without (in my humble opinion) any evidence of control difficulties that would have prevented earlier evasive action (before the final desperate flare, in which control was evident).
<<I'm not qualified to get too deeply into the workings of the
IFF/SSR but note Pprune Radar's comment about digits 8 & 9. The 77xx scenario that I was referring to was certainly true of the Jet Provost (ie if one selected 7760 or any other 4-digit code beginning with 77) the kit would squawk 'emergency'. I would agree with Pprune radar on his suggestion about likely squawk.>>
So, let’s be clear on this – 77** did not have to mean emergency – I think you are in agreement with this now. The point is that 7760 could have been a valid code and could have had significance if it was selected earlier in the flight. Again, it would be nice to know if this was the case
<<I remember … on SSR codes that it may not be desirable or prudent to change (or attempt to change) the code in an emergency … point in the limited time that they would have …>>
<<In the event of an emergency, it is desirable to select 7700. It shouldn't be necessary to attempt to do this whilst, say, IMC at low level, but it's entirely possible that one of the crew might have attempted this. I chose the words "one of the crew" with care because we should not discount the 3rd crewmember having tried to help with this >>
Even with PPRuNe Radar’s input that no one could have picked it up in their locale? Let’s not forget that we are to believe that the radio transmissions were not complete (another angle all together – remember the unanswered call? Or at least the lack of recording of or statement regarding it.). At least it sounds like you agree that it is not a high priority to change code. Let me say again that I am questioning whether the code was altered – it would be nice to know what code was set before the crash (and not generalizations like what it could have set) because it could have had a significance.
<<Without getting into a lengthy sidetrack about SuperTANS … Notwithstanding this, and largely for the potential inaccuracies described, the crew would not have relied on SuperTANS alone if flying below Safety Altitude.>>
I described (I thought) adequately the use by SuperTANS of inputs from both GPS and Doppler – over sea the Doppler input can significantly degrade the net result. That the SuperTANS was found to have been very accurate at the crash position was chance. I think that we are in agreement in that the crew would not have relied on the SuperTANS for a critical turn – I would argue that they would not have come in as close as the waypoint. ZD576 did not have radar. They had their visual judgment or possibly could have been using a SAR transponder – and that’s it.
<<How things have … QFE … for local flight.>>
<<I detect a note of sarcasm in this statement (something of which you earlier disapproved!) but just to put you straight on this point, a QFE is only used in the immediate airfield area, normally within the MATZ (Militarty Air Traffic Zone). Beyond this, the RPS is used, with all its attendant inaccuracies. A flight from NI to the Mull (& beyond) would not be considered (in this context) to be a local flight. >>
What a distraction – the altimeter analogy was just that, as I thought I explained last post.
<<The problem was closing the … untidy turn if playing it safe.>>
<<There was no need for them to fly above the coastline, they would simply have stayed a short distance out over the sea and parallelled the coastline to the next point. Never mind about an 'untidy' turn, the crew would simply turn at a safe distance, allowing a margin for their own potential error.>>
But it WAS the practice (my own observation in identical weather conditions and talking to the lighthouse keeper who lived there).
<<The book “Chinook” … watching the SAR readout >>
<<… I think you'll find that the kind of assistance rendered is of the "line of pylons coming in from the left" … type.>>
Hey, it was just a suggested scenario in answer to one part of one of your pms << …Even at that speed, I would never have considered using DME as a turning cue. It is not realy viable to watch an instrument, waiting for the distance to run down (or up if flying away from the DME beacon) whilst flying at speed at low altitude>>
I was just making the point that they had a spare set of eyes.
<<At least most of you can now appreciate the local weather conditions.>>
<<I hope you don't mean that this is thanks to your expertise! There are a lot of Ppruners out there who have observed similar weather conditions from the air on many more occasions than you have.>>
I don’t understand this comment at all – the ACTUAL conditions have only been brought to light by debate – if you revisit the transcripts of the inquiries you will find that the perception was one of generally poor visibility, not clear with localized mist – I have pushed for clarification of the actual conditions for 10 years – yes with my “limited” personal experience – it is to the shame of others that you describe that they did not clear this perception up at the time of the inquiries (the point was even made by one of the law Lords that their demonstration flight was made in clear weather and not as on the crash day).
<<the debate on this thread has made it clear to all that the intended flight path was low level with a slight turn up the coast>> << I don't see that there can be any doubt either, but their Airships do and it is their apparent contention that the crew intended to overfly the Mull that we must negate.>> So we are in agreement - so why throw it back at me? I’m not in a match with you – take the ball forward, get your colleagues to petition a correction – inform the legal side – whatever. It was my impression that the actual intended flight plan was deliberately confused by the top brass’s obfuscation at the inquiries – for what possible reason?, you should ask yourselves. In my opinion, denying the inquiries the starting point of the actual intended flight path, and further presenting a wrong impression of the weather conditions, suggests that they did not want to get to the truth.
<<Whether such a beacon was correct or not, its exclusion from consideration at the inquiries renders the verdicts on the pilots untenable>>
<<Sorry, Walter, but I disagree with this statement. You might just as well say that the fact that astazou's tongue-in-cheek "little green men shining lasers at the crew" has not been considered, also renders the verdicts untenable.>>
While the “Campaign” has for years focused on possible malfunctions that showed no effect (other than the flight continuing on until the final evasive flare) or evidence for having happened, you put the omission of any reference to or consideration of a precision navigation aid (that the HC2 was equipped to use) on a par with "little green men shining lasers at the crew".
<<What must be done is to show that by being 0.81nm short of the coast, flying at 150 kts groundspeed, VFR at low level is NOT a negligent thing to be doing. I think that, if anything, your theory about portable IFFs or DMEs has the opposite effect, implying that the crew might have been relying on something which could not be relied upon - a situation that some might attempt to use as evidence that they were negligent. I must therefore echo astazou's request to "Please drop it and let's get back to putting pressure on the MOD to give the crew some justice.">>
I am about getting to the truth about what happened – not just clearing the crew. I am concerned with getting justice for the passengers whose loss was a profound blow to the people of the United Kingdom and Northern Ireland. This team was in the hands of the RAF – the objectives of this debate should not be limited to just clearing the crew (although I agree that this would be worthy in its own right). Every possibility of sabotage needed to be explored – to date there has been a severe case of “groupthink” in this respect. The interference with a navaid is just one possible method which I thought needed following up – I will happily shut up if and when this possibility has been exhausted, which it has not quite been yet. What has been very interesting is that, over the years, the arguments against this have been getting of better quality – the initial (including official) put downs were often demonstrably wrong (although the dismissive tone is often the same) and the inquiries were misled on basic conditions; this does rather imply that the powers-that-be just don’t want to go there.
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Walter
I genuinely never wanted to have this conversation, however it is now becoming inevitable. It may be time you found a resolution to the (rather speculative) theory that you have. However, I don't think you will find it here, since very few of us believe there is any mileage in offering 'alternative' theories. Perhaps it is time you expended your energy along other avenues of inquiry.
For the record (and off the top of my head) let me state the following.
1) As a retired SF Chinook pilot, I am not aware of any equipment fitted to Chinook aircraft, that would allow a DME type, range read-out, from the IFF/SSR system. I am not even sure why one would be required, in view of the accuracy of alternative navigation aids.
2) The AAIB ascribed 'confidence' levels to all instrument readings, and switch positions retrieved from the wreckage of the cockpit of ZD576. I cannot recall precise details, however (because I too was interested in the transponder code at one time) I know that the level of confidence associated with the selected code was low. In other words, the selected code 7760, was likely to have been affected by the mechanics of the impacts of the aircraft with the hillside, and therefore could not be relied upon as being set prior to the accident by any conscious act.
3) I do not believe that this crew would have proceeded at low level, in the vicinity of the Mull, unless the weather was unambiguously suitable for flight in accordance with the Visual Flight Rules. To suggest that they were using ANY instrument to prolong 'marginal' VFR, makes the hairs on the back of my neck stand up. It is simply NOT a runner!
4) You mention the author Dave Mcmullon. Dave is a personal friend of mine, and a very talented navigator (and now training Captain!) Neither he, nor the two crew members on board, would have sat idly by watching the two pilots, fly towards the Mull, counting down DME from a beacon. Dave has suggested to me, he would be waving the fire axe around in the cockpit to prevent it! I know him, I believe him!!
5) You seem to imply some kind of official 'cover up' of the use of this equipment (at least in the circumstances of this accident!) I simply cannot accept this. As cynical as I am about the whole affair, I know people involved in the BOI, not least, the president, and cannot accept either their complicity, or ignorance, in such a situation.
I remain a little bemused by the amount of bandwidth you seek to air your theory (though I have to respect your perseverence, and have recently thanked you for it in a pm)
I feel a little uncomfortable asking you this, but I must. Please accept, that the track you are on, is at odds with the track that we here are pursuing.
You say you are seeking the truth, and are not interested in the limited aim of clearing the pilots. You have a 'theory'.
We believe we already KNOW the truth, and that is crystal clear, and simply this:
Even on the 'official' version of the 'truth' natural justice does not allow these two pilots to be found guilty of ANYTHING!
Yours is a search for 'truth' ours is the search for 'justice.'
I respectfully suggest that you are becoming a very major distraction, from what is an honourable, justified, and tough search for justice for these two young men.
By all means keep us informed of any major developments, but I doubt you will find any further answers here.
Fare well.
I genuinely never wanted to have this conversation, however it is now becoming inevitable. It may be time you found a resolution to the (rather speculative) theory that you have. However, I don't think you will find it here, since very few of us believe there is any mileage in offering 'alternative' theories. Perhaps it is time you expended your energy along other avenues of inquiry.
For the record (and off the top of my head) let me state the following.
1) As a retired SF Chinook pilot, I am not aware of any equipment fitted to Chinook aircraft, that would allow a DME type, range read-out, from the IFF/SSR system. I am not even sure why one would be required, in view of the accuracy of alternative navigation aids.
2) The AAIB ascribed 'confidence' levels to all instrument readings, and switch positions retrieved from the wreckage of the cockpit of ZD576. I cannot recall precise details, however (because I too was interested in the transponder code at one time) I know that the level of confidence associated with the selected code was low. In other words, the selected code 7760, was likely to have been affected by the mechanics of the impacts of the aircraft with the hillside, and therefore could not be relied upon as being set prior to the accident by any conscious act.
3) I do not believe that this crew would have proceeded at low level, in the vicinity of the Mull, unless the weather was unambiguously suitable for flight in accordance with the Visual Flight Rules. To suggest that they were using ANY instrument to prolong 'marginal' VFR, makes the hairs on the back of my neck stand up. It is simply NOT a runner!
4) You mention the author Dave Mcmullon. Dave is a personal friend of mine, and a very talented navigator (and now training Captain!) Neither he, nor the two crew members on board, would have sat idly by watching the two pilots, fly towards the Mull, counting down DME from a beacon. Dave has suggested to me, he would be waving the fire axe around in the cockpit to prevent it! I know him, I believe him!!
5) You seem to imply some kind of official 'cover up' of the use of this equipment (at least in the circumstances of this accident!) I simply cannot accept this. As cynical as I am about the whole affair, I know people involved in the BOI, not least, the president, and cannot accept either their complicity, or ignorance, in such a situation.
I remain a little bemused by the amount of bandwidth you seek to air your theory (though I have to respect your perseverence, and have recently thanked you for it in a pm)
I feel a little uncomfortable asking you this, but I must. Please accept, that the track you are on, is at odds with the track that we here are pursuing.
You say you are seeking the truth, and are not interested in the limited aim of clearing the pilots. You have a 'theory'.
We believe we already KNOW the truth, and that is crystal clear, and simply this:
Even on the 'official' version of the 'truth' natural justice does not allow these two pilots to be found guilty of ANYTHING!
Yours is a search for 'truth' ours is the search for 'justice.'
I respectfully suggest that you are becoming a very major distraction, from what is an honourable, justified, and tough search for justice for these two young men.
By all means keep us informed of any major developments, but I doubt you will find any further answers here.
Fare well.
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I’ll keep it brief. The Boeing document I refer to below is NOT A SIMULATION, it is
Mull of Kintyre -Analysis of Available Data
8-7D20-DS S-03 06, Enclosure 4
Dated: June 18,2002 prepared by
James Mitchell
Technical Fellow
The Boeing Company
It is downloadable from the web – it reconstructs the flight from the available data in a way that the reader can check out for himself – recommended for anyone interested in this crash.
Of special interest is the waypoint change:
Up to that point, the a/c appeared to have been keeping to its track;
On changing to the next waypoint in the TANS (which gave a required steer to the LEFT of some 7 deg) the a/c turned RIGHT 3 deg and maintained this track until the final flare;
The strength of the Boeing analysis is that, on that final leg, there was insufficient time (as they were already pretty much on their top cruising speed) to have done much significant maneuvering prior to that final flare other than to have kept to track;
To have turned consciously to the right of the original track suggests that they were not merely plodding on but completing this leg using a different reference point;
As this track does not take them to the lighthouse but rather inland of it suggests that they were not aiming at the lighthouse visually (why would they take a course to the right – into danger – if they had seen it) – don’t forget, this track was initiated at waypoint change when everyone is in agreement that they must have been in control with no apparent problems or they would not have been bothering with changing the en route waypoint in the TANS;
The SAR system I have referred to gives a bearing to the transponder (albeit at +/- 4 deg not as good as a fixed VOR, but useful);
Their actions at waypoint change were entirely consistent with taking up on a transponder near the Mull lighthouse (giving range AND a bearing);
And I challenge anyone to come up with a reasonable alternative.
I believe that this argument is strong enough to have justified its consideration at the inquiries – ignorance of a system that has been used in SAR and special forces helicopters in NATO countries since the 1980s is inexcuseable.
Mull of Kintyre -Analysis of Available Data
8-7D20-DS S-03 06, Enclosure 4
Dated: June 18,2002 prepared by
James Mitchell
Technical Fellow
The Boeing Company
It is downloadable from the web – it reconstructs the flight from the available data in a way that the reader can check out for himself – recommended for anyone interested in this crash.
Of special interest is the waypoint change:
Up to that point, the a/c appeared to have been keeping to its track;
On changing to the next waypoint in the TANS (which gave a required steer to the LEFT of some 7 deg) the a/c turned RIGHT 3 deg and maintained this track until the final flare;
The strength of the Boeing analysis is that, on that final leg, there was insufficient time (as they were already pretty much on their top cruising speed) to have done much significant maneuvering prior to that final flare other than to have kept to track;
To have turned consciously to the right of the original track suggests that they were not merely plodding on but completing this leg using a different reference point;
As this track does not take them to the lighthouse but rather inland of it suggests that they were not aiming at the lighthouse visually (why would they take a course to the right – into danger – if they had seen it) – don’t forget, this track was initiated at waypoint change when everyone is in agreement that they must have been in control with no apparent problems or they would not have been bothering with changing the en route waypoint in the TANS;
The SAR system I have referred to gives a bearing to the transponder (albeit at +/- 4 deg not as good as a fixed VOR, but useful);
Their actions at waypoint change were entirely consistent with taking up on a transponder near the Mull lighthouse (giving range AND a bearing);
And I challenge anyone to come up with a reasonable alternative.
I believe that this argument is strong enough to have justified its consideration at the inquiries – ignorance of a system that has been used in SAR and special forces helicopters in NATO countries since the 1980s is inexcuseable.
Just a numbered other
Walter
What ;available data' was 'analysed' to divine the aircraft's cruising speed? The non existant FDR?
Why it turned right is never going to be known beyond doubt, and that is why the finding is wrong.
IF they were that close to the high ground, and barrreling towards it relying on a piece of kit (which would have been less accurate than the on board TANS), to give them a DME countdown to the WP, then it's game set and match to Wratten and Day. That would have broken all the rules of VFR flight.
I'm with Tandem. This fanciful pursuit of the most unlikely use of a device no british military helicopter pilot has ever heard of is an unhelpful distraction. Furthermore, its use would have been totally negligent at the level being flown at. Please drop it.
BTW, back to TANS, (and Walter, the GPS and Doppler sides are separate. Poor doppler sea returns woulld have no effect on its sattelite accuracy) are we certain that it was in 'tactical steer' mode. In 'Route steer' mode, the waypoint change would have been automatic.
The strength of the Boeing analysis is that, on that final leg, there was insufficient time (as they were already pretty much on their top cruising speed) to have done much significant maneuvering prior to that final flare other than to have kept to track;
Why it turned right is never going to be known beyond doubt, and that is why the finding is wrong.
IF they were that close to the high ground, and barrreling towards it relying on a piece of kit (which would have been less accurate than the on board TANS), to give them a DME countdown to the WP, then it's game set and match to Wratten and Day. That would have broken all the rules of VFR flight.
I'm with Tandem. This fanciful pursuit of the most unlikely use of a device no british military helicopter pilot has ever heard of is an unhelpful distraction. Furthermore, its use would have been totally negligent at the level being flown at. Please drop it.
BTW, back to TANS, (and Walter, the GPS and Doppler sides are separate. Poor doppler sea returns woulld have no effect on its sattelite accuracy) are we certain that it was in 'tactical steer' mode. In 'Route steer' mode, the waypoint change would have been automatic.
IF they were that close to the high ground, and barrreling towards it relying on a piece of kit (which would have been less accurate than the on board TANS), to give them a DME countdown to the WP.......,
I would have thought that such action would have had the other crew members reaching for the fire axe, as Tandemrotor suggests.
Avoid imitations
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Walter quoted:
"I believe that this argument is strong enough to have justified its consideration at the inquiries – ignorance of a system that has been used in SAR and special forces helicopters in NATO countries since the 1980s is inexcuseable".
That appears to be a very arrogant statement. Inexcusable in whom? If the aircraft were not so equipped, then it's totally irrelevant.
You have already made contact with some of us who were in theatre and trained to do the same job as this crew. Sorry to disappoint you, but we are saying that your line of inquiry is irrelevant because the type of equipment you are referring to was not in use in theatre.
"I believe that this argument is strong enough to have justified its consideration at the inquiries – ignorance of a system that has been used in SAR and special forces helicopters in NATO countries since the 1980s is inexcuseable".
That appears to be a very arrogant statement. Inexcusable in whom? If the aircraft were not so equipped, then it's totally irrelevant.
You have already made contact with some of us who were in theatre and trained to do the same job as this crew. Sorry to disappoint you, but we are saying that your line of inquiry is irrelevant because the type of equipment you are referring to was not in use in theatre.
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Ark, hi
The Racal 'Supertans Investigation Report, is very clear on the valid points you make:
"2.4.3.2
During the flight over the sea, the accuracy of maintaining a doppler position is reduced because of the movement of the water due to tide and wind. The system shows the Doppler position about 327 metres to the east of the GPS position. This is equivalent to less than 0.5% of distance flown, which is exceptionally good performance from Doppler over water."
As an aside, the correction for wind, or 'Surface Motion Compensation' as you will remember it, was operating in the automatic mode, since the operator had correctly selected SEA, on the SEA/LAND switch, but had not entered a surface wind through the keyboard.
It was this 'background' SMC calculation to estimate surface wind from system wind at low altitude, that has provided the estimated altitude of ZD576, at approximately 15 secs prior to powerdown.
The timing of this background activity is controlled by a simple counter 'LCOUNT' which increments by one, every half second between 0 to 31. This parameter LCOUNT was recorded at the value 30, which means that the last calculation of surface wind from system wind, and memory of the associated altitude used in the calculation, was performed at least 15 seconds before power down.
Interestingly, the same altimeter's (a Gilham encoding capsule within the RH pilot's altimeter) baro-compensated altitude at the time of power down is quoted as 665ft +/- 50ft.
Yet we know ZD576 struck the Mull at 810ft AMSL.
Perhaps this is why the RNS252 Supertans is "not designed to provide 'historic' data."
The Board had confidence in the calculated altitude of 468ft +/- 50ft, recorded at 15-18 secs prior to impact, but cast doubt on the accuracy of the same parameter at power down. The Board considered that the accuracy of this latter value was probably affected by the mechanics of the crash, and developing fireball, as the altitude is derived from a static pressure source, and suffers all the inherent inaccuracies associated with this method.
Any comments guys?
Supertans was selected to Tactical steer (ie, no automatic waypoint change) at powerdown, displaying:
Tac:B
<<025'M
Dis: 86.7Nm
vTTG: 32.0
If only they'd had a Flight Data Recorder!
The Racal 'Supertans Investigation Report, is very clear on the valid points you make:
"2.4.3.2
During the flight over the sea, the accuracy of maintaining a doppler position is reduced because of the movement of the water due to tide and wind. The system shows the Doppler position about 327 metres to the east of the GPS position. This is equivalent to less than 0.5% of distance flown, which is exceptionally good performance from Doppler over water."
As an aside, the correction for wind, or 'Surface Motion Compensation' as you will remember it, was operating in the automatic mode, since the operator had correctly selected SEA, on the SEA/LAND switch, but had not entered a surface wind through the keyboard.
It was this 'background' SMC calculation to estimate surface wind from system wind at low altitude, that has provided the estimated altitude of ZD576, at approximately 15 secs prior to powerdown.
The timing of this background activity is controlled by a simple counter 'LCOUNT' which increments by one, every half second between 0 to 31. This parameter LCOUNT was recorded at the value 30, which means that the last calculation of surface wind from system wind, and memory of the associated altitude used in the calculation, was performed at least 15 seconds before power down.
Interestingly, the same altimeter's (a Gilham encoding capsule within the RH pilot's altimeter) baro-compensated altitude at the time of power down is quoted as 665ft +/- 50ft.
Yet we know ZD576 struck the Mull at 810ft AMSL.
Perhaps this is why the RNS252 Supertans is "not designed to provide 'historic' data."
The Board had confidence in the calculated altitude of 468ft +/- 50ft, recorded at 15-18 secs prior to impact, but cast doubt on the accuracy of the same parameter at power down. The Board considered that the accuracy of this latter value was probably affected by the mechanics of the crash, and developing fireball, as the altitude is derived from a static pressure source, and suffers all the inherent inaccuracies associated with this method.
Any comments guys?
Supertans was selected to Tactical steer (ie, no automatic waypoint change) at powerdown, displaying:
Tac:B
<<025'M
Dis: 86.7Nm
vTTG: 32.0
If only they'd had a Flight Data Recorder!
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The bottom line is what the captain of the aircraft thought of the accuracy of the TANS.
He had expressed grave misgivings about it.
Further, there was some problem with the GPS reported by him prior to the final flight.
I put it to you that this crew, in particular, would not have trusted TANS for an accurate fix.
A DME system, on the other hand, is regarded as one giving pin point accuray.
He had expressed grave misgivings about it.
Further, there was some problem with the GPS reported by him prior to the final flight.
I put it to you that this crew, in particular, would not have trusted TANS for an accurate fix.
A DME system, on the other hand, is regarded as one giving pin point accuray.
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Chinook
Ark Royal,
Forgive me an innocent question, but on 10th Sept you say <why {the aircraft} turned right is never going to be known>.
But I was under the impression that you (and others) believed that the aircraft carried on from waypoint change straight into the hillside, ie the controls (all of them!!) had locked solid.
By the way, and in this regard, please see pages 196- 202 of Campbell's book, and then say what you think about his theory (yes, of course its a theory), but it does fit the known facts.
With all good wishes
John Purdey.
Forgive me an innocent question, but on 10th Sept you say <why {the aircraft} turned right is never going to be known>.
But I was under the impression that you (and others) believed that the aircraft carried on from waypoint change straight into the hillside, ie the controls (all of them!!) had locked solid.
By the way, and in this regard, please see pages 196- 202 of Campbell's book, and then say what you think about his theory (yes, of course its a theory), but it does fit the known facts.
With all good wishes
John Purdey.
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JP
Welcome back.
Ark will of course speak for himself. However, if I may:
You imply that there is one alternative theory to which many of us subscribe. If that is your position, you are of course completely wrong. The BOI itself was unable to positively exclude MANY possible alternative causes of this crash. One of which was indeed a serious flight control malfunction.
Of course they had very good reason to be suspicious of the flight control system in the new Mk2 Chinooks. ZD576 had itself suffered a very serious (potentially catastrophic!) failure of a vital component of the flight control system, only a week or so prior to the accident. RAF engineers instigated a Serious Fault procedure!
In the wreckage, all similar flight control components had suffered the same failure, but of course no one is able to say whether this failure occured immediately prior to, or during the accident!
Because they didn't have a flight data, or cockpit voice recorder!
Of course the BOI where unaware of a US Chinook that completed un undemanded barrell role, whilst leaving no physical evidence of any fault! Though contaminated hydraulic fluid (similar to that in ZD576!) may have been a implicated.
Since the AAIB were unable to rule out a flight control malfunction, I assume you don't rule it out either?
With all good wishes to you too
Welcome back.
Ark will of course speak for himself. However, if I may:
You imply that there is one alternative theory to which many of us subscribe. If that is your position, you are of course completely wrong. The BOI itself was unable to positively exclude MANY possible alternative causes of this crash. One of which was indeed a serious flight control malfunction.
Of course they had very good reason to be suspicious of the flight control system in the new Mk2 Chinooks. ZD576 had itself suffered a very serious (potentially catastrophic!) failure of a vital component of the flight control system, only a week or so prior to the accident. RAF engineers instigated a Serious Fault procedure!
In the wreckage, all similar flight control components had suffered the same failure, but of course no one is able to say whether this failure occured immediately prior to, or during the accident!
Because they didn't have a flight data, or cockpit voice recorder!
Of course the BOI where unaware of a US Chinook that completed un undemanded barrell role, whilst leaving no physical evidence of any fault! Though contaminated hydraulic fluid (similar to that in ZD576!) may have been a implicated.
Since the AAIB were unable to rule out a flight control malfunction, I assume you don't rule it out either?
With all good wishes to you too
Just a numbered other
Jp, hello again.
You wrote:
Your impression is wrong.
I have not postulated that the aircraft did any of the things you state. It is not for any of us to SPECULATE, but to rely on FACTS to support whichever argument.
Tandemrotor's post illustrates my views well.
My only thrust is that there is no EVIDENCE with which to find the pilots guilty of gross negligence, therefore they should be exonerated. Show me such EVIDENCE and I will agree with you.
But, remember that absence of evidence is NOT evidence of absence, ar anything else.
You wrote:
But I was under the impression that you (and others) believed that the aircraft carried on from waypoint change straight into the hillside, ie the controls (all of them!!) had locked solid.
I have not postulated that the aircraft did any of the things you state. It is not for any of us to SPECULATE, but to rely on FACTS to support whichever argument.
Tandemrotor's post illustrates my views well.
My only thrust is that there is no EVIDENCE with which to find the pilots guilty of gross negligence, therefore they should be exonerated. Show me such EVIDENCE and I will agree with you.
But, remember that absence of evidence is NOT evidence of absence, ar anything else.
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Chinook
Ark Royal
I'm afraid I find it quite impossible to accept the idea of complete and catastrophic control failure, but that is just my professional (and non-Helo) opinion. But please see what 'Chinook Crash' has to say about failure of that kind, and about what the various Inquiries said. . Your views on that will be very interesting.
With all good wishes JP
I'm afraid I find it quite impossible to accept the idea of complete and catastrophic control failure, but that is just my professional (and non-Helo) opinion. But please see what 'Chinook Crash' has to say about failure of that kind, and about what the various Inquiries said. . Your views on that will be very interesting.
With all good wishes JP
JP,
I can't speak for anyone else but, before we get distracted onto old ground, I would be really grateful if you would answer my last question to you, some weeks ago.
That was, "What do you KNOW that tells you beyond any doubt that the pilots of ZD576 were being negligent at the point of way point change. What could they see and what could they not see at that point, 0.81 miles from the Mull?" What is your evidence?
I am really trying to understand how you can be so certain. I am trying to follow your reasoning and it gets a bit frustrating when you just disappear and then shoot off on another argument.
I look forward to your reply.
Regards, p1
I can't speak for anyone else but, before we get distracted onto old ground, I would be really grateful if you would answer my last question to you, some weeks ago.
That was, "What do you KNOW that tells you beyond any doubt that the pilots of ZD576 were being negligent at the point of way point change. What could they see and what could they not see at that point, 0.81 miles from the Mull?" What is your evidence?
I am really trying to understand how you can be so certain. I am trying to follow your reasoning and it gets a bit frustrating when you just disappear and then shoot off on another argument.
I look forward to your reply.
Regards, p1
Just a numbered other
quite, pulse1
JP, I have never postulated that the aircraft suffered a
but it was not discounted (albeit in less tabloid terms) by Mr Cable of the AAIB, who I would prefer to trust above your good self.
I, pulse 1, and all of us simply require proof beyond any doubt what DID happen to cause this tragedy.
If you cannot do this, then the finding is plain wrong.
The book to which you direct me. Full title, and author please. I'll try to get hold of a copy.
JP, I have never postulated that the aircraft suffered a
complete and catastrophic control failure
I, pulse 1, and all of us simply require proof beyond any doubt what DID happen to cause this tragedy.
If you cannot do this, then the finding is plain wrong.
The book to which you direct me. Full title, and author please. I'll try to get hold of a copy.
A really irritating PPRuNer
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Hi Mr Purdey,
welcome back to the thread. I trust this finds you well.
The waypoint change seems pretty cruicial to the negligence claim, so I wonder if I may put a few questions to you.
1. What time was the waypoint change made?
2. What height was the Chinook when the change was made?
3. What was the speed of the Chinook?
4. What was the heading at the time of the change?
5. Onto what heading did the Chinook turn (if at all) immediately after the waypoint change?
6. What was the rate of climb (if at all any) immediately after the waypoint change?
All answers need to have factual evidence to support them, as opposed to theory, speculation, best guess, best fit etc. If you cannot answer these questions with absolutely no doubt whatsoever, then I don't see how the verdict can remain.
To answer your point on Campbell's book, he bases his theory on the point that the Chinook entering cloud was a breach of regulations. That is, of course, assuming that both pilots were in agreement and made a conscious decision to do so. In other words, entering cloud was a deliberate action. I would have to say that without the benefit of a cockpit voice recorder, one will never know if this was, indeed, a deliberate action. Surely the pilots deserve the benefit of the doubt?
Ark - Chinook Crash by Stueart Campbell. Save your cash and get it from the library, if you have to (IMHO)
I look forward to the answers to my questions, Mr Purdey.
My best, as always.
Brian
"Justice has no expiry date" - John Cook
welcome back to the thread. I trust this finds you well.
The waypoint change seems pretty cruicial to the negligence claim, so I wonder if I may put a few questions to you.
1. What time was the waypoint change made?
2. What height was the Chinook when the change was made?
3. What was the speed of the Chinook?
4. What was the heading at the time of the change?
5. Onto what heading did the Chinook turn (if at all) immediately after the waypoint change?
6. What was the rate of climb (if at all any) immediately after the waypoint change?
All answers need to have factual evidence to support them, as opposed to theory, speculation, best guess, best fit etc. If you cannot answer these questions with absolutely no doubt whatsoever, then I don't see how the verdict can remain.
To answer your point on Campbell's book, he bases his theory on the point that the Chinook entering cloud was a breach of regulations. That is, of course, assuming that both pilots were in agreement and made a conscious decision to do so. In other words, entering cloud was a deliberate action. I would have to say that without the benefit of a cockpit voice recorder, one will never know if this was, indeed, a deliberate action. Surely the pilots deserve the benefit of the doubt?
Ark - Chinook Crash by Stueart Campbell. Save your cash and get it from the library, if you have to (IMHO)
I look forward to the answers to my questions, Mr Purdey.
My best, as always.
Brian
"Justice has no expiry date" - John Cook
Just a numbered other
Hi Brian
That was my cunning plan
Don't hold yer breath 
Ark - Chinook Crash by Stueart Campbell. Save your cash and get it from the library, if you have to (IMHO)
I look forward to the answers to my questions, Mr Purdey.