Changing squawk on transponder...
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I don't know about transmissions on 121.5 or 343 but 77xx squawks are regularly assigned to routine traffic.
I suspect your ATC sources are mistaken, and that the information several ATCO's have given me is correct - that it is only 7700, 7600 or 7500 that set off alarms.
I suspect your ATC sources are mistaken, and that the information several ATCO's have given me is correct - that it is only 7700, 7600 or 7500 that set off alarms.
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Agaricus bisporus
Think you may have missed the point there. Not everywhere has Primary all the time, TMAs and dense European areas maybe but once you get out on airways in the more remote parts it is SSR only and if you drop off the screen and DON'T come back due some computer glitch, then you are going to cause problems.
The reason I stopped going to stby was because the controllers at LATCC asked us not to, to have continued after that would have been bad airmanship, don't you agree?
The reason I stopped going to stby was because the controllers at LATCC asked us not to, to have continued after that would have been bad airmanship, don't you agree?
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Switching to standby is a matter of personal preferance and nothing more. If you're afraid of the 7's then don't dial them in.
Follow the instructions in the book that came with the thing or are written in your company's operations manual. Theoretically someone who knows something about your transponder wrote the instructions.
Whether or not the transponder goes momentarily to standby when you change a digit is fully a function of manufacturer's design and shouldn't be a concern of the operator. I've tested and certified myriad types and it seems that no two operate the same. Some go to standby when you change one digit, some transmit the new code as soon as a digit is changed, and a couple transmit the new code two or more seconds after the code has been changed. The transponders all have to meet FAA/JAA TSO-C74b [Mode A] or any class of TSO-C74c [Mode A with altitude reporting capability] as appropriate, or the appropriate class of TSO-C112 [Mode S] standards and are built to do so.
Mode S is the name given to a type of transponder (a unit that responds automatically to an interrogation) that may also act as an interrogator (a unit that automatically initiates an interrogation). It incorporates the features of Mode A, Mode C, and may interrogate other aircraft when needed. It identifies the aircraft being interrogated as well as the interrogating aircraft by an assigned code (in the US it's the N number). The S stands for "selective interrogation".
It's used in conjunction with TCAS to determine the relative altitude to your aircraft and, with the TCAS processor, the potential threat and Closest Point of Approach (CPA). If the target is determined to be a threat by TCAS the Mode S increases the frequency of target interrogation as the CPA is neared.
If anyone wants more information I'll be glad to cut and paste some stuff for you.
Follow the instructions in the book that came with the thing or are written in your company's operations manual. Theoretically someone who knows something about your transponder wrote the instructions.
Whether or not the transponder goes momentarily to standby when you change a digit is fully a function of manufacturer's design and shouldn't be a concern of the operator. I've tested and certified myriad types and it seems that no two operate the same. Some go to standby when you change one digit, some transmit the new code as soon as a digit is changed, and a couple transmit the new code two or more seconds after the code has been changed. The transponders all have to meet FAA/JAA TSO-C74b [Mode A] or any class of TSO-C74c [Mode A with altitude reporting capability] as appropriate, or the appropriate class of TSO-C112 [Mode S] standards and are built to do so.
Mode S is the name given to a type of transponder (a unit that responds automatically to an interrogation) that may also act as an interrogator (a unit that automatically initiates an interrogation). It incorporates the features of Mode A, Mode C, and may interrogate other aircraft when needed. It identifies the aircraft being interrogated as well as the interrogating aircraft by an assigned code (in the US it's the N number). The S stands for "selective interrogation".
It's used in conjunction with TCAS to determine the relative altitude to your aircraft and, with the TCAS processor, the potential threat and Closest Point of Approach (CPA). If the target is determined to be a threat by TCAS the Mode S increases the frequency of target interrogation as the CPA is neared.
If anyone wants more information I'll be glad to cut and paste some stuff for you.
seems that no two operate the same. Some go to standby when you change one digit, some transmit the new code as soon as a digit is changed, and a couple transmit the new code two or more seconds after the code has been changed.
Hence my position about selecting STBY before changing. I wouldn't have a clue about the TXDR's behaviour while changing code. There's certainly no information supplied in any documentation I've seen for any of the a/c I've flown. Maybe in the engineering documentation...
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Most simply put: when operating a piece of equipment it's always best to do exactly what the manual says and usually ONLY what the manual says. Don't add steps.
With regard to going to standby, if I were conducting an evaluation or giving a test, I would reduce the evaluee's score for performing extra procedures not in the manual or handbook.
Selecting standby, any time other than when when the unit is malfunctioning or the operator is directed by ATC, would be one such time.
With regard to going to standby, if I were conducting an evaluation or giving a test, I would reduce the evaluee's score for performing extra procedures not in the manual or handbook.
Selecting standby, any time other than when when the unit is malfunctioning or the operator is directed by ATC, would be one such time.
Early generation transponders had no inbuilt transmit inhibitor when changing channels therefore all pilots were instructed to switch to standby when changing.
Most modern transponders will inhibit transmission until a number of seconds after a digit has been changed. This delay is increased if the new selection is one of the emergency codes. If the a/c flight manual doesn't give any info (which most don't) check with your maintenance org or the equipment manufacturer. KNOW YOUR EQUIPMENT but if in doubt, switch to standby.
What a boring subject - suprised this generated so much discussion.
Most modern transponders will inhibit transmission until a number of seconds after a digit has been changed. This delay is increased if the new selection is one of the emergency codes. If the a/c flight manual doesn't give any info (which most don't) check with your maintenance org or the equipment manufacturer. KNOW YOUR EQUIPMENT but if in doubt, switch to standby.
What a boring subject - suprised this generated so much discussion.
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Sadly, I don't think this is boring... Guess I've got to get a life...
Quick observation having to do with the US regs and the AIM: 91.215 says that when you're in airspace requiring a transponder, the transponder has to be "operated." Ok. Cryptic.
So, looking at the AIM (4-19(e)(1)) we find:
*********
When making routine code changes, pilots should avoid inadvertent selection of Codes 7500, 7600 or 7700 thereby causing momentary false alarms at automated ground facilities. For example, when switching from Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to 7700 and then 7200. This procedure applies to nondiscrete Code 7500 and all discrete codes in the 7600 and 7700 series (i.e. 7600-7677, 7700-7777) which will trigger special indicators in automated facilities. Only nondiscrete Code 7500 will be decoded as the hijack code.
**********
Of course, the AIM is NOT regulatory. Still, I get the impression that the FAA's position on this is that you shouldn't go to standby when changing codes. If they WERE suggesting standby, then there'd be no need to remind us about the potential for momentary excitement should we run through any of these codes (assuming, of course, that this was carefully thought through!).
I, for one, have seen "momentary false alarms" come from inadvertent emergency codes, and although it got my attention, it pretty quickly became obvious that the pilot was simply cycling through the code on his or her way to the assigned code (and if in doubt, I asked...). I've come to expect this from time to time, in the same way that I've come to expect to see a pilot cycle through a code assigned to an aircraft that was just about to depart--resulting in the computer tagging the aircraft I was identifying with the data block of the aircraft which had not yet departed. Perhaps this would mean that I would have to suspend the track of the departure until he/she really DOES depart, but again, not the end of the world. In the long run I'd prefer to see that secondary target associated with the primary as the code was being changed.
For instance, assume you're VFR squawking 1200 with Mode C and you call me up for some radar service. As I dig up a code for you I'm looking for your 1200 code where you said you were at. If you go to standby to enter the code, then your secondary target and altitude go away. In most cases this is probably not an issue. However, if I see a target start changing codes, there is the possibility I can help both of us out. It helps me because I can start to plan--obviously you're not identified until we dance the dance, but I've got a pretty good clue that I'm looking at you. This helps YOU because I may be working or observing traffic near you and as I see you come out of 1200 I can say something like "possible VFR traffic twelve o'clock less than a mile opposite direction altitude indicates 3200." If you go to standby, I don't know whether you are my customer or whether the Mode 3/A on a VFR target has simply gone away (as is so often the case). In that case, I can see the guy that's going to hit you, but I can't see you (well, maybe a primary, but you get the drift).
Of course, these are just MY thoughts. Give an old guy a break. I'm retired.
Dave
Quick observation having to do with the US regs and the AIM: 91.215 says that when you're in airspace requiring a transponder, the transponder has to be "operated." Ok. Cryptic.
So, looking at the AIM (4-19(e)(1)) we find:
*********
When making routine code changes, pilots should avoid inadvertent selection of Codes 7500, 7600 or 7700 thereby causing momentary false alarms at automated ground facilities. For example, when switching from Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to 7700 and then 7200. This procedure applies to nondiscrete Code 7500 and all discrete codes in the 7600 and 7700 series (i.e. 7600-7677, 7700-7777) which will trigger special indicators in automated facilities. Only nondiscrete Code 7500 will be decoded as the hijack code.
**********
Of course, the AIM is NOT regulatory. Still, I get the impression that the FAA's position on this is that you shouldn't go to standby when changing codes. If they WERE suggesting standby, then there'd be no need to remind us about the potential for momentary excitement should we run through any of these codes (assuming, of course, that this was carefully thought through!).
I, for one, have seen "momentary false alarms" come from inadvertent emergency codes, and although it got my attention, it pretty quickly became obvious that the pilot was simply cycling through the code on his or her way to the assigned code (and if in doubt, I asked...). I've come to expect this from time to time, in the same way that I've come to expect to see a pilot cycle through a code assigned to an aircraft that was just about to depart--resulting in the computer tagging the aircraft I was identifying with the data block of the aircraft which had not yet departed. Perhaps this would mean that I would have to suspend the track of the departure until he/she really DOES depart, but again, not the end of the world. In the long run I'd prefer to see that secondary target associated with the primary as the code was being changed.
For instance, assume you're VFR squawking 1200 with Mode C and you call me up for some radar service. As I dig up a code for you I'm looking for your 1200 code where you said you were at. If you go to standby to enter the code, then your secondary target and altitude go away. In most cases this is probably not an issue. However, if I see a target start changing codes, there is the possibility I can help both of us out. It helps me because I can start to plan--obviously you're not identified until we dance the dance, but I've got a pretty good clue that I'm looking at you. This helps YOU because I may be working or observing traffic near you and as I see you come out of 1200 I can say something like "possible VFR traffic twelve o'clock less than a mile opposite direction altitude indicates 3200." If you go to standby, I don't know whether you are my customer or whether the Mode 3/A on a VFR target has simply gone away (as is so often the case). In that case, I can see the guy that's going to hit you, but I can't see you (well, maybe a primary, but you get the drift).
Of course, these are just MY thoughts. Give an old guy a break. I'm retired.
Dave
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Bendix King have published pilot guides for their products online (pdf format).
http://www.bendixking.com/static/catalog/index.jsp
Doesn't answer the question at hand, but might be useful for people who rent aircraft and want to get some more info on the kit installed.
http://www.bendixking.com/static/catalog/index.jsp
Doesn't answer the question at hand, but might be useful for people who rent aircraft and want to get some more info on the kit installed.
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On the A320/A321 the transponder automatically holds the last squawk for 20 seconds after you turn the dial, then it changes to the new one. So you do not need to set it to SBY to chage it. Horray!
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Blue Eagle - I am surprised. On a similar visit to LATCC the D+D controller told me to select sby first to avoid the setting off of the alarms for the usual codes, but also to avoid the 'others' which set off alarms which we as pilots are usually unaware of. (such as 0030 for 'London FIR lost', (I might have the number wrong)).
He said that if 7700 is recieved, it might be the last thing a pilot is able to do in an emergency, so they still call the services out. He said that it had happened and left them in a real dilemma.
I can see airmanship points on both sides of the arguments however.
Seems the answer is not at all clear and depends on the fit in your aircraft.
He said that if 7700 is recieved, it might be the last thing a pilot is able to do in an emergency, so they still call the services out. He said that it had happened and left them in a real dilemma.
I can see airmanship points on both sides of the arguments however.
Seems the answer is not at all clear and depends on the fit in your aircraft.
