SQUWARK CODE - LIES IN INQUIRY OR MISUNDERSTANDING?
In one list of squwark codes I have come across,
7760 means “Ground Transponders Tests/Trials”.
That is, in mode 3a ZD576 was using its IFF system to interrogate a ground transponder and was telling the world it was doing so. This would have given ZD576 a range to a portable transponder of a common type used by US & UK special forces (the PRC-112 family or equivalent). The US unit at the mull at the time would have had access to these items if equipment – they can easily be set to a DME transponder mode. Without going into conspiracy theories, I would have thought that this situation should have been discussed at the inquiries – especially as the question of the 7760 code was raised several times; I think it appropriate to paste some relevant sections here:
Questions 826-829
<<Witness A raised the matter of the transponder settings found in the wreckage of ZD576. These were "0000" and "7760" and Witness A pointed out that the emergency setting is "7700".
The normal responder codes for a Visual Flight Rules flight would be "0000" and "7000". "7760" is a meaningless code and it is most likely that the settings were disturbed by the impact with the Mull.>>
<<(iii) Is it likely that the crew would have had the mindset attributed to them by H to the effect that the Mull of Kintyre was to their right and not directly in front of them and hence have underestimated the imminence of their landfall?
…… It appears that the aircraft's TACAN, VOR and ADR were unlikely to have been relied upon by the crew at the time of the accident. The IFF/Transponder was found in mode 1 with the numbers 0000 selected and in mode 3A with the numbers 7760. So apart from the SuperTANS the only other methods of navigation available to the crew were maintaining visual references so far as possible and dead reckoning.>>
<< 712. Was there any significance in the finding that the emergency squawk code was at 7760?
A. I cannot give you an answer to that. There may well be but I just do not know. They had a very professional crewman. The late Mr Forbes was the best crewman I had ever flown with, incidentally. He was very quick in emergency procedures when he was reacting. If I was flight testing I would try and get him. If there was anything really serious he was there. >>
826. One entirely different matter, the IFF was found at 7,700 squawk.
A. No, my Lord, I think you will find it was 7,760.[8]
827. Am I right in thinking that is not the normal setting you would expect?
A. That is correct, my Lord.
828. What is the normal setting?
A. The normal setting for a helicopter flying at low level not in receipt of a radar service would be 7000.
829. Yes.
A. The emergency squawk is 7,700 and I believe in the aftermath of the accident the IFF in this particular aircraft was found at 7,760. The significance of this is that in the IFF system, there are no eights and nines, the rotating dial where you select numbers goes from zero to seven. The rotating dial where you select the numbers goes from zero to seven and back to zero again so the selection of 7760 is pretty close to the emergency squawk setting.
830. Would you draw a possible inference from that setting that somebody thought they were in trouble and made an alteration or not?
A. That could be nothing more than pure speculation, my Lord, but I guess if any inference were to be drawn on that then it would be that someone was trying to set a different squawk from 7000.
<< 831. Supposing they decided to fly IMC, what would be the normal setting for that?
A. The normal setting would still be 7000 until they were in receipt of a radar service from an aircraft control unit when they would be allocated a separate code to set into the equipment. The only variation to that would be if they were doing an emergency low level abort which took them into controlled airspace when they would be obliged to set 7700. From memory, there was no such airspace above the area they were flying at the time >>
<<993. What about the transponder settings? We have been told that one of them was not what would normally be expected to be found, 7760, instead of 7000; could that have been displaced by the impact?
(Mr Cable) Yes, my Lord Chairman. I cannot remember what confidence level I put on that, but certainly it was possible. I believe you asked me about this before.
994. I did, I think; then I am sorry.
(Mr Cable) But, certainly, in the impact, yes, the way in which the digits were changed was with a little sticking-out lever, if you like, next to each drum of digits; yes, it appeared quite possible that there could have been a mild impact in that area that would have changed the setting and not have left evidence of the impact.>>
AND especially this from Lord Bowness:
995. My Lord Chairman, I do not think it actually had a sort of, it was not categorised, was it, as I read it, it has not got a number? If I am reading the right thing, it says "IFF Functioned; Transponding 7760, BITE and Mode 1,2,3A Tx check passed." Paragraph 7.2.11 of your report. Please tell me if I am reading the wrong thing, but it does not appear to have a category assigned to it?
(Mr Cable) This was the functional test that was done on this piece of equipment after the examination.
996. Forgive me; does it tell me it worked?
(Mr Cable) With 7760 set, it transponded on the 7760 code. So, that said, yes, it was transponding the code that was set, in this case; it does not tell you whether that code was set before or after impact.
997. No, I appreciate that; but would it work in the way that you describe, if it had been damaged by the impact?
(Mr Cable) When I say damaged, I am talking about the face of the indicator which has the four drums of digits, which are set manually by means of a little lever next to each drum. So to change a code you move it round, as I recall, on this type. All I was saying was, it would seem possible to me that in the general turmoil of the impacts that it would be possible for those levers to get knocked and change the setting, and not necessarily for there to be marks on the panel which would show that they had been knocked. It is another case of a single indication, which I do not feel that I can place too much reliance on in isolation.
Now, I think that there was ample opportunity for someone to address this issue in the inquiries – I do not take the view that any other security concerns regarding, say code allocation, could possibly justify leaving the inquiries in ignorance.
I am half expecting the thrust of future posts from some contributors to be on the lines of “why was this leaked out” rather than progress to what the actual navigation practice was.
My personal feeling has been, for the last 10 years, that the crew were using DME of some form and that they were not negligent in doing this as special forces crews used extra navigation practices (including the use of a non pilot crewman checking nav) but rather that they were using an aid that could have been used to willfully mislead them and THIS POSSIBILTY SHOULD HAVE AT LEAST BEEN CONSIDERED BEARING IN MIND WHO WAS ABOARD. I think that most readers will agree that the tone of the responses to the reasonable questions at the inquiries appears intended to obfuscate and mislead.