(Re)setting transponder codes
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squawking standby
Here we go again, making everything more complicated than it has to be becasue we're British
EA
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I echo CM's response, 7000/C. If you've got it, use it.
Beagle - being at a unit that interrogates every 4 seconds, it is entirely possible to watch a transponder change through all 4096 codes (OK a bit of poetic licence). This can get extremely confusing when the Code Callsign Conversion system is trying to play catch-up. Before you know it you have a C152 out of Elstree indicating that he is BAW1 routing via Dublin.
A military ORCAM ssytem, now that's a good idea. The major stumbling block is the lack of networked communications. Come the replacement of MSSR (allegedly due 2006) we may be able to do something about this; don't hold your breath. In the meantime, get those fingers on your knobs!
Beagle - being at a unit that interrogates every 4 seconds, it is entirely possible to watch a transponder change through all 4096 codes (OK a bit of poetic licence). This can get extremely confusing when the Code Callsign Conversion system is trying to play catch-up. Before you know it you have a C152 out of Elstree indicating that he is BAW1 routing via Dublin.
A military ORCAM ssytem, now that's a good idea. The major stumbling block is the lack of networked communications. Come the replacement of MSSR (allegedly due 2006) we may be able to do something about this; don't hold your breath. In the meantime, get those fingers on your knobs!
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What a stupid phrase ! Sqwarking indicates 'transmitting' and standby indicates 'not transmitting' so what they are really telling you is to "transmit not transmit". Whats wrong with 'turn off your transponder'???
Turn off your transponder - 6 syllables and a real gob full when given with the contact tower part of the message. The idea of R/T useage is brevity, not who can transmit the longest sentence possible.
You'll be saying we should adopt that bloody ridiculous Americanism "Taxy into position and hold next!" (How many runway incursions did that cause when the good ol' CAA termed Holding points as 'positions' for a short while - enough said!
)CM
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As regards the 10-second scan rate ... I just got back from a delightful day out at Bourn, and on the way there and back, and while we bimbled around Bourn and Grafham Water, I reckon my transponder was flashing something like two to three times a SECOND.
Could have been all sorts, including 2Donkeys TCAS interrogating me.
Could have been all sorts, including 2Donkeys TCAS interrogating me.
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What the controller sees depends to a large extent on what radar processing system is used.
What happens often depends on code callsign conversion.
Taking the 7700 case first. If one sets 7700 then an alarm goes off etc etc. However since many radar systems are programmed to know that 7700 is an aircraft in distress then when the 7700 disappears, the computer will freeze the target at a location so that SAR aircraft can be directed to that place. Thus the busy controller has to take time out to clear the false alarm.
On the normal codes, if the processing system has been given your callsign then it will display your callsign insted of the code. If the code changes or you select standby, then the computer will do a thing called coasting the target. This means that it will continue to paint the target a positions where it expects you to be. The symbol will change slightly to indicate this to the controller. After about 3 updates, the callsign will disappear. The reason for this is that not every transponder reply is correctly received and processed by the ATC system and thus it makes allowances for mised replies.
If someone else selects your code then the computer will remove your identification from the target because it knows that ther can not be two aircraft with the same callsign.....better to have no aircraft displayed than the wrong one.
I expect that in the USA, the continuity of the system ensures that every unit has your code and callsign programmed in advance so that the target with your name attached will simply coast whilr you fiddle with the codes......provided you don't select the 75,76,7700 codes which will stop the coast and set off the alarm.
regards,
DFC
What happens often depends on code callsign conversion.
Taking the 7700 case first. If one sets 7700 then an alarm goes off etc etc. However since many radar systems are programmed to know that 7700 is an aircraft in distress then when the 7700 disappears, the computer will freeze the target at a location so that SAR aircraft can be directed to that place. Thus the busy controller has to take time out to clear the false alarm.
On the normal codes, if the processing system has been given your callsign then it will display your callsign insted of the code. If the code changes or you select standby, then the computer will do a thing called coasting the target. This means that it will continue to paint the target a positions where it expects you to be. The symbol will change slightly to indicate this to the controller. After about 3 updates, the callsign will disappear. The reason for this is that not every transponder reply is correctly received and processed by the ATC system and thus it makes allowances for mised replies.
If someone else selects your code then the computer will remove your identification from the target because it knows that ther can not be two aircraft with the same callsign.....better to have no aircraft displayed than the wrong one.
I expect that in the USA, the continuity of the system ensures that every unit has your code and callsign programmed in advance so that the target with your name attached will simply coast whilr you fiddle with the codes......provided you don't select the 75,76,7700 codes which will stop the coast and set off the alarm.
regards,
DFC
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Re: (Re)setting transponder codes
Bay,
PLEASE switch to standby before you rotate to another code, I've had numerous acft that were dialing in a new transponder code in flight cause a code for another acft that hasn't departed to activate and send a departure message through the NAS.
This forces more work on us because we then have to remove the flight plan that was in-advertantly activated and then enter a new proposed flight plan into the NAS so that the pilot has a flight plan on file when he calls for his IFR release.
Mike
PLEASE switch to standby before you rotate to another code, I've had numerous acft that were dialing in a new transponder code in flight cause a code for another acft that hasn't departed to activate and send a departure message through the NAS.
This forces more work on us because we then have to remove the flight plan that was in-advertantly activated and then enter a new proposed flight plan into the NAS so that the pilot has a flight plan on file when he calls for his IFR release.
Mike
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Thanks Chilli...
now that I think about it, I seem to recall being told squawk standy when I am approved to change to my destination frequency, ie from farnborough to White Waltham.
otherwise it's as you said, being told to squawk 7000.
Sky
otherwise it's as you said, being told to squawk 7000.
Sky
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I have to agree with W'Boy SATCO - if you have Mode C - select it.
I assume he speaks from an ATCO standpoint.
I fly in and out of Class D airspace controlled by NATS and there can be a multitude of 7000 squawks flying around the periphory some days. Whilst accepting that the Alt. readout will only be unverified against a 7000 squawk from an ATC standpoint, I would much prefer to have some idea of the altitude of potential conflicting traffic than not.
I was descending IMC out of 5,000 a few weeks ago (outside CA) with info on two radar contacts potentially conflicting but no Mode C.
It made me look for a hole in the clagg real fast
Is there any reason not to select Alt ?
I assume he speaks from an ATCO standpoint.
I fly in and out of Class D airspace controlled by NATS and there can be a multitude of 7000 squawks flying around the periphory some days. Whilst accepting that the Alt. readout will only be unverified against a 7000 squawk from an ATC standpoint, I would much prefer to have some idea of the altitude of potential conflicting traffic than not.
I was descending IMC out of 5,000 a few weeks ago (outside CA) with info on two radar contacts potentially conflicting but no Mode C.
It made me look for a hole in the clagg real fast
Is there any reason not to select Alt ?
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Is there any reason not to select Alt ?
But as someone who spends a lot of time pottering around outer London, under the TMA, I do always use ALT as the discipline, reminds me to stay well under 2500ft
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In basic PPL and IMC training (same instructor) I was taught to always switch to standby before changing squawk. However when doing IR training, a very well respected instructor (Eric at Stapleford), said very emphatically to keep mode A and C going while changing. He argued that, in CAS, the controller will not want to lose the SSR return even for one sweep. He also said that most radar processing kit (not the transponder) is set up to delay any emergency alarm caused by momentarily selecting 7x00. So I do not switch to standby when changing.
Keef:
I also saw lots of transponder interrogation flashes when we were flying around Bourn yesterday. There are Lakenheath, Cambridge (SSR operating, I believe, with controllers under training), Luton, Stansted and Cottesmore units all fairly close, but we all flew at 1200 feet altitude or less and I would have thought that we were under the radar horizon of all except Cambridge.
So does the TCAS transmission also trigger a flash on mode A&C transponders? I seem to remember that the transponder return pulse (ie aircraft transmission) is at a separate frequency (+ or - 64MHz ??) to avoid triggering responses from other transponders in the area. If I am roughly correct, wouldn't this mean that TCAS will not trigger a 'flash?'
Keef:
I also saw lots of transponder interrogation flashes when we were flying around Bourn yesterday. There are Lakenheath, Cambridge (SSR operating, I believe, with controllers under training), Luton, Stansted and Cottesmore units all fairly close, but we all flew at 1200 feet altitude or less and I would have thought that we were under the radar horizon of all except Cambridge.
So does the TCAS transmission also trigger a flash on mode A&C transponders? I seem to remember that the transponder return pulse (ie aircraft transmission) is at a separate frequency (+ or - 64MHz ??) to avoid triggering responses from other transponders in the area. If I am roughly correct, wouldn't this mean that TCAS will not trigger a 'flash?'
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The transponders in a Agusta A109 Power have an automatic standby function whereby as soon as you change the sqawkcode it automatically goes to standby mode for a few seconds whilst you finish twiddling... even if its in the transmit position. Sorry can't tell you what make it is...
I've always been told to set to standby manually whilst you twiddle. And when in Standby, you appear as a dot on the radar screen as opposed to a proper 'blip'.
As for mode C - dont a lot of the new TCAS gizmo's rely on that to work out how far above/below someone else you are...?
I've always been told to set to standby manually whilst you twiddle. And when in Standby, you appear as a dot on the radar screen as opposed to a proper 'blip'.
As for mode C - dont a lot of the new TCAS gizmo's rely on that to work out how far above/below someone else you are...?
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Isn't it funny how all the old wives tales about not using standby when changing come from instructors who never actually see a radar screen and that they can all be disproved by the people who actually see the response . alphaalpha's and rotorhorns latest (the dot instead of the blip - not true I'm afraid) re-inforce that quite nicely
Gotta laugh haven't you
CM
. alphaalpha's and rotorhorns latest (the dot instead of the blip - not true I'm afraid) re-inforce that quite nicelyGotta laugh haven't you
CM
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May I suggest you select standby first.
Then there is no chance of transmitting an unwanted code as you cycle through the box to the one you wanted to send.
Just like everything else related to flying safely - Unless you KNOW BETTER FOR A FACT, why rely on old-wives tales, mythology, bull****, tradition or the belief that the kit will not let you down when you don't have to?
Be careful, be safe and do the sensible things.
Its just a thought I've been using for 30 ys of flying.
P.S. If you turn C off cos you might get noticed in CAS - you should be. The accompanying transponder code may just help to ensure the correct license gets pulled.
Then there is no chance of transmitting an unwanted code as you cycle through the box to the one you wanted to send.
Just like everything else related to flying safely - Unless you KNOW BETTER FOR A FACT, why rely on old-wives tales, mythology, bull****, tradition or the belief that the kit will not let you down when you don't have to?
Be careful, be safe and do the sensible things.
Its just a thought I've been using for 30 ys of flying.
P.S. If you turn C off cos you might get noticed in CAS - you should be. The accompanying transponder code may just help to ensure the correct license gets pulled.
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Stillin1 and Chilli:
Sorry, guys, I think you are a bit out of order suggesting that when a PPL follows instructors' advice, he is following an old wives tale. If you don't trust your instructor, who do you trust?
Of course there is bad advice and there is good advice and we should be prepared to learn from our experience and the experience and knowledge of others. I'm trying to do this from this thread.
I'm still confused as to the correct procedure so I looked up changing tx codes in MATS Pt 1 and the Air Pilot.
I could not find anything relevant in MATS.
The Air Pilot is not specific. ENR 1.6.2 covers SSR operating procedures but does not state that standby should or should not be used when changing code. It does say that the transponder should not be switched off or the code changed unless instructed by ATC. It also says that 'pilots are warned of the need for caution when selecting code 7000 cecause of the proximity of special codes...' These two points suggest that we should change code without switching to standby. [sorry, I couldn't pull the exact quotes out of the pdf file]
I did not do a very exhaustive search of the above publications.
So, I'm afraid I'm still not sure whether or not to switch to standby.
Sorry, guys, I think you are a bit out of order suggesting that when a PPL follows instructors' advice, he is following an old wives tale. If you don't trust your instructor, who do you trust?
Of course there is bad advice and there is good advice and we should be prepared to learn from our experience and the experience and knowledge of others. I'm trying to do this from this thread.
I'm still confused as to the correct procedure so I looked up changing tx codes in MATS Pt 1 and the Air Pilot.
I could not find anything relevant in MATS.
The Air Pilot is not specific. ENR 1.6.2 covers SSR operating procedures but does not state that standby should or should not be used when changing code. It does say that the transponder should not be switched off or the code changed unless instructed by ATC. It also says that 'pilots are warned of the need for caution when selecting code 7000 cecause of the proximity of special codes...' These two points suggest that we should change code without switching to standby. [sorry, I couldn't pull the exact quotes out of the pdf file]
I did not do a very exhaustive search of the above publications.
So, I'm afraid I'm still not sure whether or not to switch to standby.
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So, I'm afraid I'm still not sure whether or not to switch to standby
The words about "showing caution" you suggest as meaning you don't need to select standby. As a counter argument I could equally say that selecting standby IS showing caution. It just goes to show that if you read something sometimes you can read into it what you wish. Or am I just banging my head against a brick wall here
CM
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Chilli:
Thanks. Message received and I do bow to your professional knowledge. I was thinking this morning about what had been said on this thread. Although I was still uncertain, before flying today, I decided to change my SOP and switch to standby before changing code. The change was no big deal. This thread and your comments have now convinced me as to what may be better practice.
So, I'm sorted out, and thank to you and the other experts. As you say, many instructors are not giving clear advice on how to change squawk. Perhaps the Air Pilot should be more specific? Or would this be over the top?
I'm only a PPL, but it behoves me to fly to the highest standards possible, especially when IFR in CAS. What do the professionals do? I'm genuinely interested.
It seems this topic is a good example of PPrune's value.
Regards
Thanks. Message received and I do bow to your professional knowledge. I was thinking this morning about what had been said on this thread. Although I was still uncertain, before flying today, I decided to change my SOP and switch to standby before changing code. The change was no big deal. This thread and your comments have now convinced me as to what may be better practice.
So, I'm sorted out, and thank to you and the other experts. As you say, many instructors are not giving clear advice on how to change squawk. Perhaps the Air Pilot should be more specific? Or would this be over the top?
I'm only a PPL, but it behoves me to fly to the highest standards possible, especially when IFR in CAS. What do the professionals do? I'm genuinely interested.
It seems this topic is a good example of PPrune's value.
Regards
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As folks have said, it depends on the instructor. Those I've met in the UK "who know" seem consistently to say "standby before changing". So do the ATCOs.
I'd like to hear the view of some US ATCOs, because over there I got my knuckles rapped for selecting standby first!
I don't know whether TCAS causes the transponder light to flash - does anyone? From the rate mine was flashing at Bourn this week, there were a lot of interrogators in the vicinity. Can't have been ground-based SSR, so I concluded it must have been stuff up above.
But I have been known to be wrong
Where is 2Donkeys when you need him?
I'd like to hear the view of some US ATCOs, because over there I got my knuckles rapped for selecting standby first!
I don't know whether TCAS causes the transponder light to flash - does anyone? From the rate mine was flashing at Bourn this week, there were a lot of interrogators in the vicinity. Can't have been ground-based SSR, so I concluded it must have been stuff up above.
But I have been known to be wrong
Where is 2Donkeys when you need him?
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So does the TCAS transmission also trigger a flash on mode A&C transponders?
Standby is normal for the US as far as I'm aware.
Cheers
EA