Changing squawk on transponder...
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Changing squawk on transponder...
I've got two questions:
1. Do you switch the transponder mode to SBY, when changing the squawk? Some say you should, some say it does not matter (as for me, I usually do not bother). So should we, or not?
2. One of the arguments for switching to SBY is that when you set 77XX (where XX may be whatever you want), you set off an alarm. Is that true, or only 7700 does make the radar screen red?
Greetings
Smola
1. Do you switch the transponder mode to SBY, when changing the squawk? Some say you should, some say it does not matter (as for me, I usually do not bother). So should we, or not?
2. One of the arguments for switching to SBY is that when you set 77XX (where XX may be whatever you want), you set off an alarm. Is that true, or only 7700 does make the radar screen red?
Greetings
Smola
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Light a/c concencus is yes turn it to sby incase you select 7700, or 7600 or 7500. It is only these that make the warnings flash up. E.g. have flown lgw departures with a 77xx squawk before.
Airliners (757 / 767 at least), leave it on, as turning it off, even momentarily turns the tcas off completely - this could be fatal. Just be careful what you are dialling up.
Airliners (757 / 767 at least), leave it on, as turning it off, even momentarily turns the tcas off completely - this could be fatal. Just be careful what you are dialling up.
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Don't go to STBY
An ATCO once told me never go to STBY as, if you do, they will lose you on their screen momentarily until the new squawk comes up but, given the idiosyncratic behaviou of computers, you may just not show up on his screen again, then he really has a problem! I believe this to be applicable to SSR, perhaps some ATCOs would comment?
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I concur with e_c.
77xx (where xx<>00) does not set off the alarms at ATC units for miles around. So don't worry too much about that. If you don't want to go to standby, set the least significant digits first, thus enduring you don't go through 7700 or whatever just as it's being interrogated.
On more advanced transponders (not the silly little things you get in a PA28 from your flying club) the transponder will put itself into standby for a few seconds the instant one of the digits is changed.
77xx (where xx<>00) does not set off the alarms at ATC units for miles around. So don't worry too much about that. If you don't want to go to standby, set the least significant digits first, thus enduring you don't go through 7700 or whatever just as it's being interrogated.
On more advanced transponders (not the silly little things you get in a PA28 from your flying club) the transponder will put itself into standby for a few seconds the instant one of the digits is changed.
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On RMU's we are told not to switch to standby as the machine does it automatically when the dials are turned.
77XX will not set the bells off. Codes are generated for routes, and if you fly to the Channel Islands from Southern Britain, you get a squak of something like 7772 - makes you careful when you set it.
77XX will not set the bells off. Codes are generated for routes, and if you fly to the Channel Islands from Southern Britain, you get a squak of something like 7772 - makes you careful when you set it.
*I have been told* 
that modern transponders fitted to airlines inhibit transponder replies for some short time after a code change, so that intermediate codes won't be sent while twirling the dials. Hence STBY isn't required in these cases.
that modern transponders fitted to airlines inhibit transponder replies for some short time after a code change, so that intermediate codes won't be sent while twirling the dials. Hence STBY isn't required in these cases.
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I was told this and used to do it, but the real world finally intervened and if they give me a code, I just dial it in.
Sometimes if I get a handoff, its supposed to be xxxx -> 1200 -> yyyy, but as I'm going to pick up a new code, I just leave it on the xxxx and maybe call in as "N12345 over such and such, level three thousand five xxxx"
One thing I was told (by a reliable source) which surprised me was to use STBY on the taxi out to let the vacuum tube warm up before selecting ALT. I laughed this off, but my source insisted that he'd read an article on that very model, and as it was his a/c, it felt listening to him was the least I could do.
The fancy new ones are all solid state, but if the old ones really do contain a tube, it'd explain why I continually hear "N12345 I've lost your transponder - again"
Sometimes if I get a handoff, its supposed to be xxxx -> 1200 -> yyyy, but as I'm going to pick up a new code, I just leave it on the xxxx and maybe call in as "N12345 over such and such, level three thousand five xxxx"
One thing I was told (by a reliable source) which surprised me was to use STBY on the taxi out to let the vacuum tube warm up before selecting ALT. I laughed this off, but my source insisted that he'd read an article on that very model, and as it was his a/c, it felt listening to him was the least I could do.
The fancy new ones are all solid state, but if the old ones really do contain a tube, it'd explain why I continually hear "N12345 I've lost your transponder - again"
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On a slight sidetrack.
If a controller in Germany tells you to squawk Alpha xxxx. Don't do it!
Well do it of course, the numbers bit, but he didn't mean Alpha.
Well he did mean Alpha but only in as much as if you don't have Charlie, which of course, you do, so its only to confuse you.
Are you with me?
So to recap, if you didn't have a choice it wouldn't make a difference but if you do, and do as requested, you've done it wrong!
I'll get me coat!
If a controller in Germany tells you to squawk Alpha xxxx. Don't do it!
Well do it of course, the numbers bit, but he didn't mean Alpha.
Well he did mean Alpha but only in as much as if you don't have Charlie, which of course, you do, so its only to confuse you.
Are you with me?
So to recap, if you didn't have a choice it wouldn't make a difference but if you do, and do as requested, you've done it wrong!
I'll get me coat!
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If you are anywhere in the world and are told to squalk A****, then the controller is using the correct phraseology for a Squalk change. If you have a Mode C to suppliment, then leave it on too, a controller cannot tell you to deselect this unless it is discovered to be corrupt. Remember that the 4 number bit is the Mode A bit.
It is true that by switching to standby in some areas, the radar information associated with the return can be lost and not fully regained without re-identification. You are not 'foreground' therefore not bright green, and just a dull grey blending into the black behind. On a side note too, when selecting your numbers, don't hit the ident button. If you haven't got all four of yours correctly selected, and waited a few seconds for radar to receive the new selection, you may inadvertently process the flight details of an a/c using a similar squalk. Confused? Should see the controller who gets the 'ghost' flight details.
It is true that by switching to standby in some areas, the radar information associated with the return can be lost and not fully regained without re-identification. You are not 'foreground' therefore not bright green, and just a dull grey blending into the black behind. On a side note too, when selecting your numbers, don't hit the ident button. If you haven't got all four of yours correctly selected, and waited a few seconds for radar to receive the new selection, you may inadvertently process the flight details of an a/c using a similar squalk. Confused? Should see the controller who gets the 'ghost' flight details.
short flights long nights
So what is Mode S?
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So what if he doesn't want to see your Alt. readout? Can they remove that themselves?
Genuinely curious. I know there are some clutter reduction widgits but I've never actually been to a civil radar centre. Shame on me.
I suspect that this is a case of technology outgrowing the legislation. I'm sure there are a few in these forums who have never seen a transponder without mode C.
Genuinely curious. I know there are some clutter reduction widgits but I've never actually been to a civil radar centre. Shame on me.
I suspect that this is a case of technology outgrowing the legislation. I'm sure there are a few in these forums who have never seen a transponder without mode C.
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Mode S is a totally new system not used yet by anybody (properly). It involves full interactions between pilots and ATC without the use of comms RTF.
At Swanwick we are able to remove anything we want including the callsign (why???????), however, understandably most removals aren't permitted. This applies for both foreground and background tracks. The former being the traffic working/worked/to work a sector, the latter being traffic a sector is uninterested in.
At Swanwick we are able to remove anything we want including the callsign (why???????), however, understandably most removals aren't permitted. This applies for both foreground and background tracks. The former being the traffic working/worked/to work a sector, the latter being traffic a sector is uninterested in.
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I had always understood mode S to be used in TCAS equipped aircraft which allows two systems to 'talk' to each other so that if resolution advisories are given they do not conflict - i.e one to climb, the other to descend, but never to give advisories in the same sense such as for both to climb.
When first learning to fly I, I was advised by different instructors to either switch to standby whilst changing, or to dial it straight in as there is a delay built into the system. However, as all this was in light aircraft I'm still none the wiser. Best advice I did get I suppose was to avoid dialling through '7' altogether unless it is in the squawk.
When first learning to fly I, I was advised by different instructors to either switch to standby whilst changing, or to dial it straight in as there is a delay built into the system. However, as all this was in light aircraft I'm still none the wiser. Best advice I did get I suppose was to avoid dialling through '7' altogether unless it is in the squawk.
Since I don't have a clue whether or not the TXDR in the a/c I fly are fully transistored or have a valve somewhere then I switch to STBY after start.
I also don't know if it auto-STBY during code changes so I manually select STBY during code changes. That guards against inadvertant 7x00 alarm bells. It's also easier/faster to get the code set if it's entered in the order given, instead of of out-of-sequence as one person has suggested.
The argument about not using STBY when entering the code due to ATC issues falls apart if there are TXDRs that use STBY automatically.
I also don't know if it auto-STBY during code changes so I manually select STBY during code changes. That guards against inadvertant 7x00 alarm bells. It's also easier/faster to get the code set if it's entered in the order given, instead of of out-of-sequence as one person has suggested.
The argument about not using STBY when entering the code due to ATC issues falls apart if there are TXDRs that use STBY automatically.
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ICAO
ICAO doc 4444 PANS-RAC and doc 8668 PANS-OPS do not specify selection of "stby" mode while changing sqawk codes.
As far as I am concerned all operators should have adopted the above when designing their respective SOP's.
As far as I am concerned all operators should have adopted the above when designing their respective SOP's.
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Nope
I have never bothered to switch to STBY before changing the code, and I have never received any complaints. Never had a u/s transponder either.
Mr. Jeppesen says that in some corners of the world, any code starting with 75, 76, 77, may trigger an alarm.
Mr. Jeppesen says that in some corners of the world, any code starting with 75, 76, 77, may trigger an alarm.
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It may well be true that changing a squawk resets the transponder to sby, but how do you know? Certainly less complex ones (ie GA sets) do not, so how is it safe to just assume that yours will? Surely good airmanship dictates that you go to sby before changing squawk, unless you have read the spec on the unit - and who has ever seen one of those?
The argument that says just dial it up because you would disappear off the screens if you go to sby manually is spurious - because youll disappear anyway if the thing goes to sby on its own, wont you? Surely better safe than sorry?
The argument that says just dial it up because you would disappear off the screens if you go to sby manually is spurious - because youll disappear anyway if the thing goes to sby on its own, wont you? Surely better safe than sorry?
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I think it might help if we had a bit more ATC and Engineer input here.
I have never heard before of any transponder that automatically went into stby when the numbers are changed, equally I have been told that by going to stby one can disappear from the screen and computers being computers, one may not always reappear as required. As it was during a visit to LATCC that we, as a group of pilots, were specifically asked NOT to select stby I have never done it since, (over twenty years now).
Any ATCOs and Radio Engineers care to comment please?
I have never heard before of any transponder that automatically went into stby when the numbers are changed, equally I have been told that by going to stby one can disappear from the screen and computers being computers, one may not always reappear as required. As it was during a visit to LATCC that we, as a group of pilots, were specifically asked NOT to select stby I have never done it since, (over twenty years now).
Any ATCOs and Radio Engineers care to comment please?
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So you disappear from the screen for 3 seconds. So what? They knew who and where you were, they told you to change squawk so if you drop off the screen (if the primary is that poor) for an instant before popping back up in another guise it is hardly a surprise to ATC, is it?
That argument sounds perilously like cobblers to me. I'd be far more concerned by accidentally passing 7*00 and setting off all the alarms, so I'll continue to select SBY before changing squawk as good airmanship seems to require.
Whats the problem with that?
That argument sounds perilously like cobblers to me. I'd be far more concerned by accidentally passing 7*00 and setting off all the alarms, so I'll continue to select SBY before changing squawk as good airmanship seems to require.
Whats the problem with that?
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The problem is that in more advanced systems, by selecting Standby you disable TCAS. If you simply twirl the numbers, the system puts itself into Standby without disabling TCAS - it still operates.
If, for some reason, you get distracted by another (more urgent) job, there is a danger that you may forget to put the Txpdr back to ALT/RA and not only are you then bereft of TCAS advisories, but so is anyone else into whose path you may blunder.
On the more simple systems - the type of King Silver Crown gear you find in little piston-engine puddlejumpers for example - the level of sophistication requires more care to operate. But applying that level of care to systems with more sophistication holds additional dangers.
If, for some reason, you get distracted by another (more urgent) job, there is a danger that you may forget to put the Txpdr back to ALT/RA and not only are you then bereft of TCAS advisories, but so is anyone else into whose path you may blunder.
On the more simple systems - the type of King Silver Crown gear you find in little piston-engine puddlejumpers for example - the level of sophistication requires more care to operate. But applying that level of care to systems with more sophistication holds additional dangers.