Chinook - Still Hitting Back 3 (Merged)

[walter kennedy]

Brian
You wrote:
<<What we don't know, with absolutely no doubt whatsoever, are the following:
- What time was the waypoint change made?
- How far from landmass was the waypoint change made?
- Why a waypoint change was made, yet an apparent change of direction was not made.
- What the intention of the pilots was (ah for the luxury of a cockpit voice recorder!).
- Whether something untoward happened with an aircraft (and fleet), notorious for problems (ah for the luxury of an accident data recorder!).>>
But we can make make reasonable judgments on these points:
<<- What time was the waypoint change made?
- How far from landmass was the waypoint change made?>>
I recommend to all interested parties that they download a copy of the Boeing report by Mitchel – “Analysis of Available Data” – this is not the simulation but a reconstruction that you can all follow and is a good framework for you to start from; then plot the relevant positions and headings on an OS map of the Mull – you will then probably be surprised at the oblique angle of approach (not at all straight in) and just how close in waypoint A was – that’s just for starters.

<<- Why a waypoint change was made, yet an apparent change of direction was not made.>>
There was a change in direction – a small correction TO THE RIGHT – this should be of concern to all, happening so close to waypoint change when one could assume that they had no control problems or they would surely not have been bothering with the next route waypoint – not forgotten about – I believe it was indicative of them carrying on intentionally towards a specific point (waypoint A defined by another system perhaps) – don’t forget that they would not have regarded waypoint A defined by the SuperTANS to be more accurate than ½ a mile or so after a sea crossing).

<<- What the intention of the pilots was (ah for the luxury of a cockpit voice recorder!).>>
Well apart from constraints like icing, the conditions for continuing up the coast VFR would have suggested that that was the obvious intended route which, as should have been made very clear in all proceedings, was the usual route for mil helos doing that passage from NI. While I was observing a helo do a close in turn (at speed) in identical weather conditions as the day of the crash, a witness (who was in a position to know) pointed out the feature where it crossed the shoreline to begin the turn and said “ … they do that all the time …”.

<<- Whether something untoward happened with an aircraft (and fleet), notorious for problems (ah for the luxury of an accident data recorder!).>>
A very small window of opportunity, I suggest.

Thank you for posting Mr Holbrook’s description - I recognize the conditions described to be typical in that locale at that time of day at that time of year with the prevailing wind blowing – I have spent quite some time just off the coast of NW Scotland doing sea trials and know those conditions well – you could predict them the day before from a forecast - these conditions should have been recognized by enough people such that no inquiry should have been in any way confused about the local weather conditions – the strong wind would not have allowed sporadic patches of fog offshore (so clear at sea) but would generate mist as it rose on the land (but not before). Mr Holbrook described it well in that some features could be seen but their features were indistinct – that the Mull could be seen from a long way off effectively but with no clear detail easy to give a wide berth but very difficult to visually judge distance accurately if wanting to turn close in for whatever reason. The problem of judging range visually in these conditions is a pivotal point and I would like to give an actual personal experience to better describe the problem:
I was approaching a familiar wreck dive site on the SW of the Isle of Wight (IoW); it was close in under the cliffs; I could see the shoreline from a long way off but the landmass was shrouded in low cloud (same principal as on the Mull) and was approaching the position using Decca as a reference, the idea being to stop at the Decca position and loiter until a break in the cloud/mist allowed the transits to be visible (necessary for marking this wreck accurately); bearing in mind that I could see the landmass for miles and I could see the shoreline for the entire approach, one would not expect to make a significant error in visual judgment in getting to within a few hundred metres of that shoreline; in that immediate locale, the Decca was not so good as in open sea (hence the need for transits to accurately mark that wreck) and in any case lagged by its update rate; at 21kts I nearly came to grief on the rocky shoreline – at 50kts I would have been stuffed, let alone 175kts (the probable ground speed of ZD576 as it crossed the shoreline on the Mull). The point is that I was relying upon an aid to get me close enough in to then rely on other means of conducting myself – at any time on that approach my visual judgment could have cut in, but on that occasion it was almost too late. You know the conditions for judgment are difficult but you use an aid to get you most of the way to a point which you believe would still be safely clear of the danger – this method you would use to take a safe course well clear of such a danger in route navigation. The problem that day on the IoW was that I wanted to get to a specific point close in to the hazard – the performance of the Decca that day would have been on a par with that which could be expected from SuperTANS after a sea crossing – using either to define a safe turning point should have called for a conservative/prudent approach – I relied upon visual judgment for the last bit at 21kts and nearly came unstuck – ZD576 should have been more conservative at their speed and if they had nothing else to go on other than SuperTANS should have started their turn BEFORE waypoint A (look at your chart/map for how close in waypoint A was) - at the time of waypoint change - AND THEREFORE BEFORE TECH PROBLEMS WITH CONTROLS OR INDICATORS COULD HAVE BEEN AN ISSUE.
They HAD to be using another reference to shave their safety margin – and in those conditions, something they trusted more than the SuperTANS - BUT what?
Assuming they had thought that they we ½ - 1 mile further out, their cruise climb would have had them high enough to get Mac TACAN/DME (appropriate ch 107 was found set on their TACAN CU) - do a transaction on your OS map – you could also notice that the aerodrome lay approximately in line ahead, a point Mr Mitchel of Boeing makes in that report that I have suggested you read.
But this would have been of no use to them on their approach to that point as previously they would have been below the altitude to get LOS to that navaid.
So what could they have been referring to? – something that overrode their senses such that they thought they were ½ - 1 mile further out?
If you look at your chart/OS map with the course plotted, the oblique angle of approach to the coast makes it a nonsense that confusion with the fog signal station (a little along the coast) could have made a significant difference to their path – ie an insignificant azimuth error to a visual reference displaced laterally only slightly from the lighthouse at their approach angle would not account for this error in range judgment – indeed, rather than saying that the fog station was ¼ of a mile to the right (if they were approaching the shoreline directly) it should be said that the fog station was ¼ of a mile closer than the lighthouse at their (oblique) approach heading and so if mistakenly taken for the lighthouse would have been an error on the side of safety.
(Mr Purdey pls take note.)

While an error in range judgment appears the significant parameter here, the small steer to the right at waypoint change should not be forgotten – there is only one candidate for giving a range and bearing in that area that helo crews would trust and that is a UHF Personnel Locator System; suitable ground equipment was in abundance on the Mull that day (thanks to US SEAL section who had the PRC112 handsets issued down to a man); there was the opportunity to plug in the on board equipment (ARS6) in the nav racks when techs did an informal job on them before t/o at Aldergrove – and this came to light because of anomalies in those racks (stowage of unused connectors, etc?) found in the wreckage (I suggest evidence of the inexpert or hurried removal of the ARS6 module); the cherry on top is the admission by one of the SEALS, when challenged as to what they were doing all over the crash site, that they were looking for their equipment (so nice of them to lend it, eh? – the special relationship that requires copious amounts of preparation H).

You don’t have to accept the whole scenario – but following it in detail gives a framework to hang the known parameters on – at least some of the basic issues should be able to be agreed so that other scenarios have something to be based upon – there should be no doubt at this stage what the local weather conditions were, whether they were in breach of flying regs, what accuracy the SuperTANS had, whether they were going to turn or go over, etc, etc,.