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.