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IFF squawk


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I copied the following from a discussion on Airliners.net. Don't know how true it is, though.

Don R.

"Why We Squawk

During WWII the British developed a top secret 10" x 10" x 10" radar transceiver. It would respond to a radar interrogating signal by responding with a coded transmission. A code would allow the land based radar station to distinguish British from German aircraft on their radar screen. The radio also contained an internal thermite bomb which, when triggered by an inertial switch (crash), would destroy the interior of the set. This was supposed to prevent German discovery of the codes. (A reverse ELT?) The British code named the system Parrot. The United States Army Air Forces version of the system was called IFF, for Identification Friend or Foe.

As with many WWII developments, the IFF system was designed to prevent a clever German ruse. The Germans were following the night bombers back to England. German aircraft would join in the stream of returning British bombers. They would wait until the bombers were most vulnerable, just prior to landing, and then shoot them down. Parrot allowed detection of these German aircraft since their (primary) return would not have a distinctive code.

To control the operation of the airborne coded set to the best advantage, the ground based radar station would radio instructions regarding the operation of "Parrot". The aircraft would be directed to "squawk your parrot", meaning to turn on the set for identification; or to "strangle (not kill) your parrot" as a directive for turning the set off. The power of the transponder signal would often hide other targets.

The only vestige of this that remains today, other than the entire ATC system itself, is the term "Squawk", as an ATC directive for operation or code for the transponder. Old time ATC controllers may still have you "strangle" your parrot (x-ponder)"

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Geez, that triggers a Pope memory. This was during the time right after the TS1843s were installed. We had a UHF and o-scope set up and when the aircraft were preflighting they would call us for a "parrot check". We would ask them to squaw mode 3, code 7600 and would check for the proper display on the scope. After the check we tell them to return the system to standby until required for flight. I even rmember the scope was one of the old Lavoie, round face, boat anchors. Never knew why we called it a "parrot check" until now.

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  • 5 months later...

In the Comm/Nav shop at Naha we always had trouble with the F-102's. They had a cannon plug that would get wet from humidity and when the pilot or C/C started the plane it would squawk mode III 7/7 which was the emergency code. They always called for a parrot check whenever power was applied on the ground. As soon as the canopy was closed and the a/c took over the cannon plug would dry out and the SIF would function properly.

No amount of potting compound ever fixed the problem. We used a UPX-7 hooked to an "o" scope in the shop. Naha 63-67 How's that for a memory! LOL Ralph

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