Woodreau From United States of America, joined Sep 2001, 933 posts, RR: 7 Reply 3, posted (10 years 11 months 1 day 13 hours ago) and read 1561 times:
Such a thing does exist, however the information you get is not whether it is friendly or enemy. Rather you will get that it is "positively friendly" or "not friendly."
A "not friendly" could be a civilian commercial airliner (because it won't respond to a Mode 4 interrogation because it doesn't have the equipment to do so) or a friendly fighter/bomber whose IFF transponder got a bad crypto load (it can't respond properly) or it may be a real-live enemy bad guy.
You have to take a look at what information you do get from a transponder, a civilian aircraft will give you the Mode 3/A and Mode C, and other information, where it is, it's flight profile / speed / altitude , it's origin, and look at what the expected threat is. Is the aircraft in question flying the appropriate return-to-force profile?
By taking a look at other factors it helps in determining what that "not friendly" is and to determine whether or not to commit CAP to do a visual ID on the contact of interest.
Woodreau / KMVL
Good judgement comes from experience. Experience comes from surviving bad judgement.