Recognition Lights and WWII IFF

Ken · **Posted:** Wed Aug 13, 2008 11:01 am

In a couple TOM photos it appears that P-51B Old Crow's underwing recognition lights are functional. Can anyone describe how often these were actually used in WWII? Night only? Daytime? What do the switches look like in the cockpit for selecting the light sequence?

On a related note, I'm quite familiar with today's IFF procedures, but I don't remember many wartime accounts speaking to different light codes and transponder squawks used in WWII. No doubt it was classified at the time and not discussed ... but have we now lost all the details to time?

Just curious ...

Ken

Bluedharma · **Posted:** Wed Aug 13, 2008 11:39 am

Interesting...
http://www.ww2aircraft.net/forum/aviation/recognitiion-lights-11908.html

n5151ts · **Posted:** Wed Aug 13, 2008 12:42 pm

the underwing lights on the wing tips were formation lighting. as I recall they were red white and green

Dave Smith · **Posted:** Wed Aug 13, 2008 2:28 pm

I have a notebook detailing all the RAF radio phraseology in use in mid-1942. A wartime Flying Controller gave me this many years ago. It was for the fighter OTU at Hawarden in North Wales (Don Gentile was one of one many Americans who did a course here). The only mention of IFF is the instruction to pilots to switch it on - "Make your cockerel crow." After landing, the pilot would switch off the IFF and report "Cockerel strangled." It would seem that the modern term Squawk originated from this. I guess that the USAAF, in the UK at least, would have adopted a lot of RAF terminology and radio procedure.

I am sure that transponder codes as used today were not allocated. The IFF of that era was a basic transponder that had only an on or off position.

Ken · **Posted:** Wed Aug 13, 2008 3:30 pm

Today it's still called the "parrot" because, I assume, it squawks back a reply to the proper interrogation. A check is said to be "sweet" or "sour" and turning it of is still "strangle". I like knowing that the fundamentals of some things don't need to change.

Taigh Ramey · **Posted:** Wed Aug 13, 2008 4:02 pm

The Recognition lights are made up of three lower lights; Red Green and Amber on the bottom of the aircraft and one upper white light which was typically teardrop shaped. The three lower lights were flush mounted and in line fore and aft. They are fairly high intensity and are easily seen in the day. I recall a placard on some installations limiting their use as the resin lens could be damaged by the heat from the bulb. Most of the recognition lights I have seen had glass lenses though so I am not sure if this limit was universal of for the resin lenses only.

They must have made a lot of them in WWII as they are not too hard to find today still new in the box.

There was a standard control box for the recognition lights used in WWII made out of both aluminum and plastic but the switches were also incorporated into the regular switch panels by some aircraft manufacturers.

The switches could be toggled on steady or momentarily and they would also have a push button for keying the code of the day. I haven't come across any documentation specifying their use or what codes they may have flashed. If you ever come across such information please let me know as I would like to see how they were used.

IFF, or Identification Friend or Foe, was a radio/radar based system which is the grandfather to our transponder system today. Often the recognition lights get confused with the IFF system.

Formation lights are also an entirely different system and were a series of variable intensity, typically blue, lights mounted on the wings and tail surfaces and were used for night formation flying. These were usually found on heavy and very heavy bombers.

The bombers also had a formation bomb release light mounted in the tail. Some Boeing and Consolidated aircraft used two separate lights one red and one white. Other installations used one bomb release light unit which was all in one. The white light was turned on when the bomb bay doors were opened. When the bombs were released the white light went off and the red was turned on. A relay, called an Agastat relay, would keep the red light on for 5 seconds after any bomb release impulse and then it would go back to white.

Does anyone know what the passing light was used for? The passing light was a red light in the leading edge of the left wing on most all WWII aircraft. How was this used?

Oscar Duck · **Posted:** Wed Aug 13, 2008 4:53 pm

Guys, can anyone find me a set of those recce lights to install on my A-26 Invader. I've not been able to locate any around here in Australia?

Thanks...

:roo:

Old SAR pilot · **Posted:** Wed Aug 13, 2008 5:29 pm

About the "passing light" - from what I've been able to dig out, it was used in the same manner as those in the nautical world. When seen on approach, you pass to the right of it, which will place you off the approaching aircraft's left wing.

Eric Friedebach · **Posted:** Wed Aug 13, 2008 6:50 pm

Oscar Duck wrote:

Guys, can anyone find me a set of those recce lights to install on my A-26 Invader. I've not been able to locate any around here in Australia?

Thanks...

:roo:

Check your PM inbox…

Taigh Ramey · **Posted:** Wed Aug 13, 2008 11:12 pm

Thats the best explanation for the passing light that I have heard yet.

Thanks Bob.

Randy Haskin · **Posted:** Wed Aug 13, 2008 11:24 pm

So, we still don't know functionally how the recognition light system worked.

WRT the "passing" light, the only military aircraft I know that has it in current use is the T-37. On that jet, it has nothing to do with the "red, right, return" mantra of the boating world.

On the Tweet, the passing light is on steady if the gear is not down and locked and flashing if the gear is down and locked. It's a ground recognition feature to help tower controllers keep students from landing gear up.

Ken wrote:

Today it's still called the "parrot" because, I assume, it squawks back a reply to the proper interrogation. A check is said to be "sweet" or "sour" and turning it of is still "strangle". I like knowing that the fundamentals of some things don't need to change.

Except that now it's not an on/off system...it consists of Mode 1, Mode 2, Mode 3, Mode C, Mode 4, Mode S, and other modes. Significantly more complicated, but same concept.

Oscar Duck · **Posted:** Thu Aug 14, 2008 8:13 am

Thanks Eric>

Ken · **Posted:** Thu Aug 14, 2008 9:34 am

Randy Haskin wrote:

Except that now it's not an on/off system...it consists of Mode 1, Mode 2, Mode 3, Mode C, Mode 4, Mode S, and other modes. Significantly more complicated, but same concept.

Exactly. I was trying to oversimplify. Our panel may be like yours, maybe not. There is a 3-way TEST-ON-OUT toggle for each mode (except 3 and S share the same switch).

Taigh Ramey · **Posted:** Thu Aug 14, 2008 9:57 am

Hello Randy,

Functionally the recognition lights were either turned on steady or switched so they could be keyed by a push button. One toggel switch for each of the four lights.

I would sure like to know how it was used operationally in service.

The passing light in WWII aircraft were also turned on with a single toggle switch and had no direct connection to the landing gear system, at least in the schematics that I have come across.

So the Tweet has a red passing light in the left wing?

Taigh

Ken · **Posted:** Thu Aug 14, 2008 10:38 am

There are two lights in the nose, either side of the pitot tube. The one to the viewer's right has a red lens - that's the passing light.

http://www.airliners.net/photo/Portugal ... id=1173456

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Recognition Lights and WWII IFF

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