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Military Interception Signalling
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Under the heading 'interception and ACAS', the article says without qualification that the intercepting aircraft will have it's transponder selected on and therefore 'spurious' alerts should be expected. I offer two comments:
(1) In my experience, it is not guaranteed that an intercepting military fast jet will have a transponder selected during the intentional approach to a civilian aircraft so the first you know of it may well be the visual close encounter. I actually think that is the best way and does not prejudice safety since the 'loss of separation' is a controlled one and civil pilots rightly do not have an SOP to ignore ACAS RAs in the circumstances which would apply to an interception approach from behind.
(2) ACAS alerts are either genuine or false (i.e. technically incorrect). Some genuine alerts might be assessed (as would apply in this case) as nuisance. I do not think there is a useful place for the word 'spurious' regardless of the fact that it enjoyed widespread currency in the past. --John.Milner 11:16, 17 October 2008 (CEST)