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.