questions on IFF and associated radar installations

[JackG]

Was this a system employed only for those aircraft based in the UK, or everywhere, such as even North Africa?

Were there portable radar stations? If there was, when were they introduced?

regards,

Jack

[e8n2]

IFF was quite widely used by the Allies during the war. I don't know about the Germans, but I would imagine they had something similar. There were (and basically still are) two parts involved, the interogator and responder. As part of the radar sweep, a coded interogator signal is sent out. The responder on the aircraft sends out coded return. Both ends have to have the same code so they are updated on a frequent basis. The wrong response means the aircraft being interogated is either a bad guy or has a previous code. In either event, the friendly forces will go to check him out and take him out if necessary. The radar screen comes up with a certain display to show if the proper IFF code was received. I am not sure if I remember reading what the proper return signal was, but something like a large arc being displayed a couple of miles or so behind the target sounds familiar. I've been out of radar ops for over a quarter century now so I don't know how the system display would look now if it has changed.

Later,

Dave

[JackG]

Thanks Dave.

So does that mean all RAF aircraft had the ability to respond - if yes, this system must have been factory installed to all front line aircraft?

regards,

Jack

[MikeC]

Google is your friend

http://en.wikipedia.org/wiki/Identification_friend_or_foe

http://www.dean-boys.com/extras/iff/iffqa.html

[JackG]

Mike - yup, I've seen those web links... but they don't answer the specific questions I've posted here. Note, I'm not inquiring how the system worked, but how widespread it was employed, particularly before the Mk III system came into being in early 1943.

Even more specific, I'm wondering about the Spitfire before the above date - was it standard for all of them to be outfitted with the wires leading out from the fuselage roundel to tail plane, regardless of their base of operations?

regards,

Jack

[Edgar]

This will probably indicate that there was no real hard-and-fast rule, at least in the Med; there are papers which talk of removing IFF equipment, before despatch to that theatre. Malta had radar, possibly fairly portable, since it was set up on a fairly remote (for a small island) headland.

The IFF wires weren't a permanent fixture (they were held taut, inside the fuselage, by bungee cords,) so, again, it's impossible to say which had them, and which didn't. It seems extremely likely that the Spitfire did not have them before December 1940, because the electrical fittings weren't put in before that date. Apart from bombers, I've only found references, in 1940, to Gladiators and Hurricanes having the wires, and, even then, their fittings were not like those of the Spitfire, travelling mostly inside the fuselage.

Edgar

[Selwyn]

This will probably indicate that there was no real hard-and-fast rule, at least in the Med; there are papers which talk of removing IFF equipment, before despatch to that theatre. Malta had radar, possibly fairly portable, since it was set up on a fairly remote (for a small island) headland.

The IFF wires weren't a permanent fixture (they were held taut, inside the fuselage, by bungee cords,) so, again, it's impossible to say which had them, and which didn't. It seems extremely likely that the Spitfire did not have them before December 1940, because the electrical fittings weren't put in before that date. Apart from bombers, I've only found references, in 1940, to Gladiators and Hurricanes having the wires, and, even then, their fittings were not like those of the Spitfire, travelling mostly inside the fuselage.

Edgar

Edgar just been re reading the Book "Blenheim Boy" by Richard passmore and in it he refers to the squadron Blenheim 1 ( I believe it was actually 90 sqn at Bicester) being fitted with IFF pre war (c1938). He describes it in good detail including its location in the aircraft and the routing of the antenna wires.

Selwyn

[Edgar]

Depending on the aircraft, there were different set numbers.

On the Mk.I set, R.3000 was 12 volt, R.3001 was 24; on the Mk.II, they were R.3002 and R.3003 respectively. I haven't found anything on the Mk.III yet.

Edgar

[Mikey W]

Am I getting this right when I gather that the wires running from the fuselage roundel to the horizontal stabilizer tip on a spitfire would only be correct from Oct./Nov. 1940 ? About the time they introduced the Spitfire Mk II then. Any other aircraft from the same period fitted likewise ? Could someone expand on what " Pip-Squeak " was. The reading I have done on the Battle of Britain refers to this quite often. I understand that it showed up on the Radar screen as a marker so that would make it an I.F.F. of some type wouldn't it ? As always, thanks for the education and enlightenment. Mikey W.

[Edgar]

As I understand it, "Pip-Squeak" was the remote contactor, which, when activated, sent out a 15-second signal in every minute, using the radio aerial, so that, when it was operating, the radio could not be used for normal purposes. Unlike IFF, it could be used within the U.K., since radio stations could triangulate on it, and fix the aircraft's position.

I.F.F. was separately switched, and worked on the radar frequency, producing a brighter return on the operator's screen, but could only (at first) operate beyond the Chain Home stations. Early radar could not differentiate between "front" & "back," so the signal had to be quenched inland to avoid getting reciprocal readings. Once inside the CH screen, we were dependant on the Observer Corps.

Apparently the first I.F.F. was clockwork, so was dependant on an erk remembering to wind it up before the scramble; Peter Vacher took some time finding one to put into Hurricane R4118.

Edgar