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Old 04-08-2020, 06:21 AM   #1
bephanten
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Default Iff system in warbirds

Both allied and german planes have their iff systems. Are they functional is a mystery.
How would ww2 pilots use them actually, without an onboard radar?
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Old 04-08-2020, 06:51 AM   #2
MAD-MM
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It will work in conjunction of Ground Based Radars.
Will send a impulse Back (IFF) to the Ground Radar, so they dont accidentally open up Anti Aircraft Fire on friendly Planes who return from a Mission.
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Old 04-08-2020, 06:53 AM   #3
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Great question, I am interested to know as well. The Fug-25 IFF system for the 190 is listed and explained in the manual so it would be great if we could use it.
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Old 04-08-2020, 07:14 AM   #4
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How IFF could work if ww2 planes don't have BVR mode ?
BTW P-51 has inboard radar if someone dont know that.
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Old 04-08-2020, 07:57 AM   #5
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My understanding is that the original concept came about during the introduction of Chain Home radar. Pilots were reminded to activate their IFF system so that plotters could discern friendly aircraft from foe. It then enabled GCI to talk fighters on to enemy bomber formations.

The term "squawk your parrot" was used as the reminder, which lead to today's aviation term "Squawk" for transponder settings.

https://journals.sagepub.com/doi/pdf...29400303600804

https://www.boldmethod.com/blog/list...e-transponder/

https://ethw.org/Radar_and_the_Fighter_Directors
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Old 04-08-2020, 08:10 AM   #6
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I read that the Tempest (but I think that was common) can send a bigger spot on the radar by pressing a control. So radar could know if the plane was the friendly or not.
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Old 04-08-2020, 08:12 AM   #7
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Quote:
Originally Posted by MAD-MM View Post
It will work in conjunction of Ground Based Radars.
Will send a impulse Back (IFF) to the Ground Radar, so they dont accidentally open up Anti Aircraft Fire on friendly Planes who return from a Mission.
It's unacceptable and ridiculous that they had ground radar in 1940 and we still don't have NOW!!!
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Old 04-08-2020, 10:01 AM   #8
vanir
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I'm by no means a technician but I have some corrections based upon what I've managed to figure out over the years from an armchair.

40s vintage IFF is a radio transponder set installation, nothing to do with radar but was an extension of the essential radio navigation network, which started off as simple beacons in the 20s and was becoming more complex through the 30s and during the war. In the early war for example, when tallied 50% of all combat losses for the RAF were due to navigational error and mechanical failures and no other reason. In one case an entire bomber stream was lost when it accidentally headed towards Norway instead of returning to base. This may seem shocking or unreal to modern thought but was completely commonplace during the period and punctuates how important the (international) radionavigation network was for aeronautics worldwide.
So radio beacons and increasingly a more complex radio navigation network existed throughout Europe in the 30s-40s, even in the Soviet Union although they lagged behind updating equipment and had simple beacons until about 44, meaning lend lease aircraft had more radio equipment installed than Russians could actually use and it was one of the things they loved about them in preference to their own aircraft, so many radios installed they didn't even know how to use some of them.
Anyway vintage IFF is a simple radio transceiver which automatically responds to a signal challenge typically transmitted by a ground station in the radio navigation network, ie. it is a radio transponder.

More modern transponder/ground station systems are commercially referred to as "passive radar" but are exactly as before, just a radio signals network primarily for navigation, but they add more information and are no longer just a simple "squawk" but actually transmit some instrument data (IAS, Altitude and Heading), as well as ID (type or flight number and operator), whilst the radionav network intrinsically provides its current position. Thus it gives all the necessary information an active radar would give, but it is not observational, it is a radio call making some claims and a ground station operator believing them, all his instruments actively tell him is current position of a squawker, the aircraft's transponder is telling him everything else. Passive radar is more like virtual radar, it was conceived essentially as the poor man's radar for smaller airfields that couldn't afford active radar to still perform tracking and traffic management independently of local radar stations which often have other tasking. Another idea that came as an extension of the radio transponder is the collision avoidance system, as computerization of flight management developed the manners in which a radio transponder can be used for the benefit of the aircraft increased.

Modern military IFF is not used the same way being integrated into the computerization of modern warfare, using a variety of tools at its disposal for something a little more involved, including radar and mission Intelligence systems such as datalinked local air traffic information on painted targets, piped though the base operator and/or AWACS to the pilots.

In WW2 some late war fighters had a radio set update capable of transmitting an IFF transponder challenge directly but again, nothing to do with radar, just a radio signals exchange, a squawk amounting to a radio fingerprint identifying the operator with some basic electronics: 15ohms lights orange bulb, 25ohms lights blue bulb, different squawks impede circuit differently to determine result, something like that.
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Old 04-08-2020, 12:58 PM   #9
xvii-Dietrich
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Quote:
Originally Posted by vanir View Post
I'm by no means a technician but I have some corrections based upon what I've managed to figure out over the years from an armchair.
Most of what follows doesn't make sense.

Do you have any references for any of it?
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Old 04-09-2020, 05:38 AM   #10
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Sure, look up the equipment specifications of a WW2 fighter fitted with IFF, you'll note the piece of equipment is called a radio transponder or may simply be referred to as a radio set "xxx series", which if looked up with the manufacturer will clarify it as a radio transponder.

Second, look up radio navigation beacons in the 1940s. Should be easily able to find a good explanation of the basic early war beacons and later war developments involving increased radio navigation equipment installed into military aircraft. You'll note the network, whilst the responsibility of individual nations did indeed stretch right across Europe and the United States from the very beginning, a sort of international air safety agreement.

Thirdly, look up technical descriptions of modern commercial airport "passive radar" or just watch a few episodes of Air Crash Investigations (Mayday: Air Disaster in the US), they describe its technical functions quite frequently throughout the series as it is an important factor when aircraft are lost, since it is not first hand information. As I described the aircraft transponder sends instrument data and identification to the ground, which can only read the position of the transponder signal because "passive radar" is just the more modern radio navigation beacons and aircraft transponder interacting and isn't actually any kind of radar, but is a colloquial term for a radar simulation using data that should, but isn't necessarily accurate.
When an airport loses a contact on "passive radar" they contact the nearest actual radar station, usually a military base and they locate the lost aircraft for them if it is still in the air.
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