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."