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Old 3rd Jul 2009, 09:22
  #5074 (permalink)  
walter kennedy
 
Join Date: Sep 2003
Location: Perth, Western Australia
Posts: 786
BOAC
Once again I appreciate your attention to details – please excuse brief reply for now:
<<1) There is no way anyone here knows WHAT was actually SET on the altimeter, merely what was FOUND. The briefest acquaintance with aircraft accidents will show that is not a reliable deduction to draw.>> AAIB consider other indicators other than just what setting was found (eg indents from impact on dials which reflect the status on impact) – and, just from memory at the moment, I recall that the setting was “probable”.
<<2) It is, in any case, most likely that the difference between QFE lighthouse and QFE LDZ was nil in practical terms. One could equally surmise that the crew were being ultra-safe and had the most accurate setting available.>>
Quite right – elevations (in feet AMSL) of places of interest here are as follows:
Aldergrove runway 270;
Mull light house 270;
LZ 330;
Campbeltown aerodrome 44.
So <<4) Could they have set the latest Macrihanish QFE perchance?>> - no.
<<3) I do not know what the SOP for the heli-operation was regarding altimeter settings.>> Good point as perhaps a regional QNH may not be useful to or required for LL helo ops. - someone here should be able to answer that firmly.


By way of summarising this aspect for the benefit of readers here, I will paste part of my old notes below:
<<Altimeter Subscale Setting on QFE
The QNH at that time at Aldergrove aerodrome was 998,
The QNH at that time at Campbeltown aerodrome was 998,
The regional QNH forecast was given by Aldergrove ATC to ZD576 as follows:
The Belfast regional QNH from sixteen to seventeen hundred is niner niner one, changing on the hour niner niner zero and the Portree regional QNH sixteen to seventeen hundred niner niner one changing to niner niner zero”.
.
The AAIB gives “Barometric altimeter subscale settings were probably at 989 and 991.5 mb” – the “probably” indicating a high degree of confidence that the settings found in the wreckage had been set at these values before the crash.
Obviously the 991.5 makes sense as the regional QNH setting and thus increases confidence that both settings as found were as before the crash.
The 989 setting is a significant indication of their immediate intentions as explained below.
.
The elevation of the immediate area of the lighthouse complex is taken here as the elevation of the meteorological equipment located there at ground level according to the Met Office – this is 82m or 267ft. The landing pad is nearby - see fig ** – let us say its elevation is, roundly, 270ft ASL.(THIS IS THE HARD STANDING – TOO SMALL FOR CHINOOKS - AND NOT THE LZ OF INTEREST WHICH IS A BIT HIGHER.)
Waypoint A is 280m to the SE just before the LZ (described in preceding section *****) when on the 027M approach from NI and the threshold of this area of level ground is about at the 90m contour on the OS map (LZ long axis is gradual slope up through 100m contour).
[Using the approximation of 1 millibar for 30 ft altitude change.]
For a QFE to use for landing at the lighthouse pad at 270ft el, or for approaching the LZ from waypoint A, one could use the nearest suitable local QNH (from Met Office archives, RAF Macrihanish QNH at the time was 998) and compensate for the altitude of the site by reducing the figure by 270/30 = 9 millibar to give an altimeter subscale setting of 989.
This is what was found set on one of the altimeter subscales (handling pilot's).
(What is interesting is where they could have gotten the Mac QNH from - they did not appear to have got this from Aldergrove ATC nor Scot Mil as per recordings made available. PERHAPS AS THE ELEV OF THE LZ IS JUST ABOUT SAME AS ALDERGROVE THEREFORE THEY JUST ADJUSTED ON TARMAC AND EITHER LEFT SETTING OR NOTED IT AND USED IT AFTER CROSSING ANTRIM HILLS OVER WHICH THEY SHOULD HAVE BEEN USING QNH.)
.
The Rad alt warnings set support the idea that they were attempting to land – an experienced pilot has given this description:
”The Rad Alt warnings were not set in accordance with the SOP. One was set above cruising altitude and the other at minimum* where it would have given little, if any, warning of impact with the ground. Again there was no indication that these settings had been altered by the impact.”
*The lower Rad Alt warning was set at 69 ft – this would only make sense if they were intending to use the Rad Alt for touching down in bad local visibility.
.
The suggestion by the BOI that the subscale setting of 989 could have been the Aldergrove QFE without equal consideration of the lighthouse landing pad is misleading for the following reasons:
While the QFE for Aldergrove could have been 989 (at an elevation of 268 ft and with its local QNH of 998), they left with good visibility around the aerodrome and so would not have needed a QFE setting and indeed ATC informed them of the Aldergrove QNH which should imply a directive to use that setting;
It was 40 miles behind them;
They had crossed the Antrim hills with their track over a substantial area of ground in the region of 1000 ft ASL and with peaks nearby to 1500 ft;
There is a requirement that, if you are flying below Transition Altitude, regional QNH MUST be set unless approaching for a landing – that is to say, at the time of the flight, they should have had 991 set on BOTH subscales unless they were imminently landing at (or passing close to) a specific location.>>


I hope the above note saves readers some time in getting an understanding of the altimeter aspects.


BOAC <<Lastly - it doesn't actually make a scrap of difference, does it? I suppose it is a new toy to trifle with if we have given up breakfast and maps, IMC at waypoint change and the like. >> Not really, the altimeters are a significant part of a big picture as I am sure you will now realise.


Some other points:
the captains HoSI had a course setting of 028 on it; as I have explained before, just turning towards waypoint B (Corran) at the position of waypoint change or to 028 (all magnetic here) would not have given them a safe track; now if they had been going into that LZ on 035 (set on HP's HoSI, the track of the final leg, and optimum for approaching that LZ) and done their close pass, landing, or wave off they would have needed to head out to sea – I suggest a simple turn to roughly northwest away from the murk and granite into clear air would have been the immediate thing on their minds, but how far out to sea would have been desireable? Good pilots would surely have been thinking ahead, they would already have their next turning point and subsequent course worked out, one would expect. Now if you have waypoint B (Corran) selected on the STANS (as was found to be the case) and you have your course selector on 028 (as per Flt Lt Tapper's, the navigator if you like, HoSI) you have a track to head for on your HoSI which gets you well clear of the approach to Macrihanish aerodrome and, once on it and turning along it, puts you on a nice scenic long straight parallel to Jura along the sound (a bee line from waypoint H (54:47':42”N, 6:36'00”W) to waypoint B (56:43'00”N, 5:14'00”W) – put them in Google earth and draw a track between them and it will hit you). So after their excursion to the Mull they may have been returning to a clearer pleasant path for the remainder of their ferry flight – a path that someone not privy to their Mull business may have planned for their overall ferry flight using waypoint H as a reference which may explain its presence in the system.


Interference
With reference to the interference noted on their radio which was put down to either the TANS or both the TANS and the IFF (depending on whose statements you take) there is another piece of equipment known to cause radio interference – the American equivalent to the HC2 Chinook comes with a warning that operation of the ARS-6 (the onboard component of a CPLS) causes interference with some radios. While it is not in the public domain that such equipment was fitted to ZD576, just about all the other equipment that was fitted is, leaving just one item that was classified at the time that could have been the CPLS – if you play with the text of the section of the BOI transcript mentioning this classified equipment, it just so happens that you can fit in exactly the words “Covert Personnel Locator System” in the blacked out space – coincidence? … just a thought. Surely after all this time that blacked out classified equipment can be named? - unless for other reasons it is still sensitive ...


While so many of you criticise the relevence of many parameters in isolation, it seems like everything that is known about this flight is explained by the scenario I have described – not one out of so many rules it out and indeed when you have so many pointing to it you have a correlation of data that makes the probability of its being correct astronomically high.
At least high enough, I suggest, to be worthy of the Mull group considering it as a better option than, say, airworthiness to persue – if the concensus of the interested parties, after consultation with experienced aircrew and other aviation experts, is that it looks like they were involved in an extra task that has not thusfar been declared they can surely press this line as, if it was the case, then the verdicts must be thrown out at the very least – perhaps a new inquiry could point out who exactly was responsible and get real justice.

Last edited by walter kennedy; 3rd Jul 2009 at 09:31. Reason: correction
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