I have heard the term squawk many times on my scanner and fs. I am thoroughly confused what they mean so if anyone could clarify, I would appreciate it. Thanks.

Most aircraft have a radar transponder installed. A transponder is required for instrument flight. The transponder responds to ATC radar signals and it has four dials on the front that can be set to a number from 0 through 9. ATC will instruct a pilot to Squawk 0465, for instance, and the pilot will dial that number into the four dials on his transponder. The radar blip on the ATC's radar for that airplane will then show the number 0465 directly under the blip. There is also a button in the plane on the transponder labeled IDENT. When instructed, the pilot will squawk a code and push the IDENT button which makes the blip for his plane really bright on ATC's radar screen.

There are special codes for hijack, emergencies, loss of radios, etc. that a pilot can squawk. ATC sees these codes and acts accordingly.

Just some examples of what Glenn is referring to:

7700 Emergency
7600 Lost communications
7500 Hijack
1200 VFR (and not likely in contact with ATC)

But normally, local ATC (when contacted and VFR) will assign you a squawk code starting with a zero depending where you are. But when you get into "the system" for VFR flight following with center or a TRACON, you will get assigned something in their own designated block of codes.

I once received VFR flight following with Jacksonville Center on my way to Miami and was assigned a transponder code of something like 4657. Soon after, the controller announced that he had run out of transponder codes for new IFR flights and informed us VFR guys that he would have to terminate VFR flight following with all of us to free up the codes. I must confess that this was a first for me. I considered picking up an IFR, but figured the guy was seriously overloaded already, so I went on my merry way in beautiful weather until entering the Miami sector where I contacted the appropriate Miami Center controller.

First time for everything....

By 9, you do of course mean 7, right?

Yeah, that completely escaped me. It is 7.

LOL ! !

So, when a controller gives a code, he or she can then assign the callsign to the blob, or any other information?

hum... isn't declaring a hijack supposed to be stealth? you'd think the terrorists know what the code is by now... how discreetly can you type in 7500?

Well, you're just learning about it now and you frequently visit an aviation forum, so the chance of a common terrorist knowing is pretty slim. Even assuming they do know, it gets pretty busy in a cockpit and pilots can be pretty sneaky people ("Hey Mr. Terroist, isn't that Bob Barker on the wing?" punch in 7500 while he looks, "Oh, nevermind. I must be seeing things..."). The system isn't foolproof, but it's just another possible option in a bad situation.

I did ask a question similar to this way back in my PPL ground days and the assuring CFI said that line pilots are taught other ways to get the message across that are not publicly known (I'm not sure how accurate this statement is though).

Yes and No. On the modern Mode S transponders, you also put in your callsign. However, if that is not forthcoming I'm sure that ATC can put one in manually. Against the "Blob", the ATC software can then attach data tags such as destination, route and requested level (ie. complete flight plan data). But don't forget that we also transmit our flight level as well as our squawk code. I also believe that we have the ability to receive ATC clearances via Mode S and in return, transmit the values set on the FMP so that they can see their clearance has been correctly received. However, these bits are not enabled/implemented in any of our aircraft (yet!).

PM

Just because there are hijackers doesn't mean they've infiltrated the cockpit. They could be banging on the door or holding hostages giving the pilots a chance to squawk 7500.

Thank you everyone, I understand it now. Its interesting how the ATC system has been set up, making it pretty easy to understand and use.

Just to make things more difficult to us pilots, the Australian airspace is implementing an ADS-B system (Automatic Dependent Surveillance - Broadcast). The new system is an air to ground and air to air surveillance system. In some areas of Australia this new system is actually replacing the tradition radar environment. This new technology is a great leap for Australian airspace but no-doubt it will create a lot of confusion amongst both veteran and student pilots...

If you feel like a read, the full document is available on the CASA website as a PDF. Seeing as I am a nice bloke I will even link it for you. Linky

auctually. your wrong. the squawk codes are 0-7. they dont use 8 or 9. and no. it does not make it "bright" on their SCOPE. its called a "MODE C TRANSPONDER" mainly, every aircraft has one, the older ones dont, which is why you use visual separation from the ones who do not. the MODE C TRANSPONDER lets an air traffic controller see your plane at your altitude, at your heading, at your speed, your airline, flight number. IT DOES NOT SHOW SQUAWK CODE. i dont know where you got your information from but it is almost completely wrong. i am an AT-CTI student so i'm pretty familiar with this. since i just took my mid term on it this morning. you need more information....come to me. this is all easy and fresh in my head...and yes, there are 3 codes for emergencies. 7500- hijack. 7600-radio failure, 7700- general emergency.

Someone already cleared up the 8 and 9 thing. And yes the IDENT button will make the blip brighter on ATC radar screens for a certain amount of time. I'm pretty sure a mode C transponder only has altitude encoding.. ATC can get your heading and speed from their radar even if you don't have mode C. Also, I'm about 99.9% sure it does show your squawk. Think about that for a second.. if it didn't show your squawk code then why the hell would you need to put one in? Maybe your confused with mode S? Mode S, as said before, will transmit callsigns and other flight data.

BTW, the people here are all really friendly and knowledgeable pilots. Most of them have way more experience than you (me as well), so you might not want to try to come in here and act like you know it all. Cause you don't. None of us know it all.. but we all can learn something from each other here. So I suggest you throttle back on the attitude.

Let's get this one cleared up. Us Civilians have three active modes available. Mode A is where we transmit a four digit code, Mode C transmits our code and our altitude (referenced to 1013.2 Hpa (29.92 ins)) and Mode S transmit codes, our levels, our callsign, settings from our Flight Mode Panel, contents of Captains wallet etc... In addition to all that, we can also temporarily transmit an extra On/Off status known as an "Ident" so that a controller can positively verify who they are speaking to. How the "ident" is displayed depends on the radar display systems. Some make the "blobs" brighter, some put a ring around the target, others overlay symbols.

7500hijack: I don't think you have been listening properly. Mode C does not show "your heading, at your speed, your airline, flight number" because this is not transmitted. This data is generated from the raw radar and other feeds by various sub-systems and added to the data stream before it gets to the controller's display. Also, your assumptions regarding separation are also a bit flaky. Most Control Centres have primary as well as secondary radar feeds and keep as many dots (primary and secondary) as they can from bumping into each other. Also not all aircraft have transponders because they don't have to. It all depends on local rules and the class of airspace they fly in. And if I need more information, you will have to forgive me, but I won't be coming to you.

As an aside, the squawk codes allocated depend on the area you are flying in. In Western Europe, we are given a code and rarely have to change it if we stay inside controlled airspace. These codes are generated by various flight panning systems around Europe and are often destination dependent. But as soon as we leave controlled airspace the agency who then handles us allocates a code from a block they have available. For example, London Military in the East give codes starting 615, Teesside's codes start 70. The reason for this is so that other controllers can see who is handling a particular blob just by the transponder code.

Personally, it don't think it really matters that the bad guys know what the emergency transponder codes are. We've all lost when it gets to that point.

PM

Please, do tell me more. I find these experienced pilots completely useless (what do they know) and would love for you to pass more of your extensive knowledge onto me, who is nothing more than a rookie PPL. And perhaps if you hadnt been so quick to see a mistake and try and show off by correting it, you'd have seen that it had already been corrected. Welcome, by the way.

And just to add something of relevance to this post, in the UK, the conspicuity code is 7000 as opposed to 1200 as it is in the states. I know some flights get their own squawks that remain with them for pretty much the whole flight, unless asked to change specifically by the controller.

A couple of us do. Well, most things. OK, maybe just a lot.

What does 7600 mean again?

Nope, ADS is a wonderful thing. And it's pretty simple to use. It's part of the Future Air Navigation System or FANS. There are a great many equipment requirements as well as training. But once the money is spent and the system is operational, it's a snap from the crew point of view. As far as it's impact on student pilots, unless the Aussie government has gone completely off the deep end, the impact should be zero. It's close to cost prohibitive for the individual aircraft owner.

Just wondering here ... is it a generational thing or have the English language gurus made a change that I'm not clued into yet?

I always thought that the word, “YOUR” was an adjective that meant “belonging to you,” and the contraction, “YOU'RE,” meant “YOU ARE,” followed by what it was that you were accused of being (or were suspected or questioned of doing or becoming), as in “YOU’RE WRONG.” The use of this colloquial contraction seems to have been replaced with the use of the adjective ... or it would seem so ... as in the use of the newer colloquialism, "my bad," or "your bad," meaning either I have erred or you have. Is it now legitimate to use the adjective, "YOUR," in conjunction with the word, "WRONG" (as used in this thread "YOUR WRONG"), to indicate an opinion that a statement or position is (or was) an error committed by the accused person - much as one would have used the newer colloquialism, "YOUR BAD?"

I certainly don’t want the masses to be bereft of understanding whether or not the Rant Master still “HAS GAME!”

The reason that the code only uses 0-7 is the very low power of the ATC computers back in the late 50s (?) when the transponder was introduced.

As with many things in aviation it hasn't changed simply because it dosen't really need to.

Your right as usual. I'd be lieing if I said anything else. And there are to many other examples to list hear.

(Too subtle?)

To answer your question ... for some here ... way to subtle!

For some reason Octal was considered to be a more efficient way of transmitting numberical data in the eraly days of transponders. I'm sure an "old fashioned" radio technician could tell us why. Initially these devices were installed in military aircraft (WW2) and were part of a system called "Identification Friend or Foe" and were introduced into civilian aviation shortly after.

PM

Simple efficiency compromise...
You usually don't want to do unnecessary calculations or transmit more data than needed, especially back then where devices like a transponder had to be made of basic hard-wired logic circuits and a simple function would take heaps of hardware.

An octal digit is encoded into 3 bits, using all combinations. A decimal digit needs a 4th one, but then you only use 10 of the 16 available combinations, which is a waste of space (physical one to wire the extra circuitry needed, and time to transmit it). As the 4096 possible combinations allowed by 4 octal digits are already more than enough, it would make no sense wasting resources for nothing. And making 10-position rotary knobs isn't a fun idea either.

OK - why are squawks "octal"? Because the "system is set up as "binary" and the place to "stop" is 8 - otherwise, in order to complete the "cycle" it would need to go to 'F' (like in computer hexadecimal - 16 bit based - 10 wouldn't be efficient use as was said)

In the beginning (WWII), it was a TWO digit IFF (64 codes) that soon became 4 (4096 - 64 squared) as the system expanded to bring in the airlines. I would tell you also that MILITARY XPDR codes include "more" info than just the 4 digits (and it is "really still" IFF for the military. "IDENT" paints a double line on the screen for easy recognition

One code that isn't used IIRC at all is 0000 (don't remember exactly why, though)

And when changing codes, NEVER dial thru the first digit "7" - it might send off an emergency code by mistake (and the 7XXX codes light up the controller's screen - plus they are persistent - and one gets "urgent" radio calls )

Hang on one sec...in my area the codes assigned are "74XX", and sometimes we get an enroute change from "74" to "14". So, what's the thing about the 7XXX codes???

Ed

Airbuser, I agree. Dodgy old SSR processors were panicked by a 7nnn code. I'm not sure how many sweeps of the code there had to be to set it off, but apparently this did happen. Nowadays, as squawks of 7nnn are regularly allocated, this can no longer be the case.

PM

I once was assigned the 0001 code, needless to say I felt special.

Yes, yes, indeed... Alas( or should it be but), I have always wondered how is it that I can speak three (or should it be 3) languages, and orthograph ( or should it be spell) them correctly; whilst (or should it be while) others butcher away their (or should it be there) one native language in the name of simplicity (or should it be imbecility)? Blame it on internet "chatrooms", and mobile telephone text messages (or should it be SMS).
Dig this? You gots game R-master, don't you let nobody desrespect. There wrong!

N.B: Last sentence is evidently edited for the fun factor. Have no fear, I won't turn to the dark side. Thread hijacking over, you can stop bleeping your 7500s and resume your normal squawk codes.

Message received and understood. As my very favorite radio communication from ATC once said, "(Call sign), traffic twelve o'clock, your level, two miles and closing. Change transponder to one two zero zero. Squawk 'Ident.' Frequency change approved. Have a nice day."