Transponder code
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Transponder code
Hi
In flight - Entering a different FIR - Controller asks for a squawk change
Do we have to select STBY while changing the code as taught in some books or we can straight away change the code (especially in modern equipment installed in B777 etc)
Someone told me that during a code change it automatically stops and there is no need to put it into standby mode
regards
In flight - Entering a different FIR - Controller asks for a squawk change
Do we have to select STBY while changing the code as taught in some books or we can straight away change the code (especially in modern equipment installed in B777 etc)
Someone told me that during a code change it automatically stops and there is no need to put it into standby mode
regards
Transponder code
Hi Haroon,
It all depends ob your type of equipment.
Old school turnknobs - better switch to standby or you might transmit an emergencycode…
New ones - change is normaly possible without standby but its all written down in the appropriate documentation, which should be available to the pilot…
It all depends ob your type of equipment.
Old school turnknobs - better switch to standby or you might transmit an emergencycode…
New ones - change is normaly possible without standby but its all written down in the appropriate documentation, which should be available to the pilot…
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Actually I've wondered this too although everyone leaves it in TA/RA while changing it and some airports like Stansted say in the jepp brief to set it to 2000 before selecting Standby. From flying school though you got your hand chopped off by an instructor if you tried to change the code before selecting Standby first though.
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Do not select standby! ATC will immediately lose you on their screen. You should know your equipment well enough that you don't select an emergency code while switching transponder codes.
This quote is from TC AIM RAC 1.9.1:
The only time you select 'standby' is when ATC says "SQUAWK STANDBY" or after landing.
This quote is from TC AIM RAC 1.9.1:
ATC radar units are equipped with alarm systems that respond when the aircraft is within radar coverage and the pilot selects the emergency, communication failure or hijack transponder code. It is possible to unintentionally select these codes momentarily when changing the transponder from one code to another. To prevent unnecessary activation of the alarm, pilots should avoid inadvertent selection of 7500, 7600 or 7700 when changing the code if either of the first two digits to be selected is a seven. For example, if it is necessary to change from Code 1700 to Code 7100, first change to Code 1100, then Code 7100, NOT Code 7700 and then Code 7100. Do not select “STANDBY” while changing codes as this will cause the target to be lost on the ATC radar screen.
Last edited by italia458; 20th Mar 2013 at 15:09.
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The only time you select 'standby' is when ATC says "SQUAWK STANDBY" or after landing.
As Flying Bull pointed out, it depends on your equipment. But unless it looks like it still relies on valves, it probably won't cause a problem. In the old days it was SOP to go to STBY primarily to avoid setting off alarms on the radar displays but equipment manufacturers - of both transponders and radar processors - soon started building in what are often called 'slugs', slight delays before believing that a changed code really was the next selected code and transponders effectively switched themselves to STBY while code selections changed. In practice it means that a controller using modern kit will not see the new code until the system detects that it's stopped changing.
Just to make things a bit more complicated - not that it changes anything in practice - a modern radar tracker may use inputs from multiple sensors and has all sorts algorithms going on inside the black box to ignore questionable tx'der responses amongst other things.
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thanks everyone
thats what i was interested in.
started building in what are often called 'slugs', slight delays before believing that a changed code really was the next selected code and transponders effectively switched themselves to STBY while code selections changed.
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Spitoon,
Pro tip: Don't select an emergency code when changing transponder codes! I promise you that no alarms will go off if you follow that advice. 
Read the last sentence of the quote from TC AIM RAC 1.9.1 I posted above.
In the old days it was SOP to go to STBY primarily to avoid setting off alarms on the radar displays
Read the last sentence of the quote from TC AIM RAC 1.9.1 I posted above.
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Haroon,
Be careful about just believing that your equipment will do what Spitoon said. I talked to an IFR controller and he told me that your XPDR code will indicate when you are switching through numbers, as Spitoon said it would, but he said as soon as you select an emergency code it will show up, there is no delay.
To avoid setting off alarms you need to follow the advice of TC AIM RAC 1.9.1. I will paraphrase it: DO NOT SELECT AN EMERGENCY CODE! It's as simple as that.
Be careful about just believing that your equipment will do what Spitoon said. I talked to an IFR controller and he told me that your XPDR code will indicate when you are switching through numbers, as Spitoon said it would, but he said as soon as you select an emergency code it will show up, there is no delay.
To avoid setting off alarms you need to follow the advice of TC AIM RAC 1.9.1. I will paraphrase it: DO NOT SELECT AN EMERGENCY CODE! It's as simple as that.
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apart from triggering an alarm through an emergency code one can also pass through someone else's code. Dont know how much of a nuisance that can create but perhaps that is also to be avoided as I think I read somewhere.
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Haroon,
Don't worry about passing through someone else's code. This isn't rocket-surgery! How on earth are you supposed to know all the other codes that airplanes, being picked up on the same radar screen as you are, would be squawking? And then if you did know them, to move your dials so as not to end up squawking the same code as any other airplane! It's ridiculous!
When ATC says to squawk a code, change to that code immediately and don't select an emergency code. The end.
Don't worry about passing through someone else's code. This isn't rocket-surgery! How on earth are you supposed to know all the other codes that airplanes, being picked up on the same radar screen as you are, would be squawking? And then if you did know them, to move your dials so as not to end up squawking the same code as any other airplane! It's ridiculous!
When ATC says to squawk a code, change to that code immediately and don't select an emergency code. The end.
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its not about "knowing" the codes but "inadvertently" passing through them..
anyway i am not sure if thats an ATC concern or not. i just read it somewhere which i cant remember.
forget about the squawk and please throw some light upon "Rocket-Surgery" is it something like "Brain-Science"
anyway i am not sure if thats an ATC concern or not. i just read it somewhere which i cant remember.
forget about the squawk and please throw some light upon "Rocket-Surgery" is it something like "Brain-Science"
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Haroon,
Come on man! It's 2013... we've had transponders for decades. This isn't a problem!
It's a combination of rocket science and brain surgery, which means it's double-intense! Very similar to a double-rainbow.
its not about "knowing" the codes but "inadvertently" passing through them..
forget about the squawk and please throw some light upon "Rocket-Surgery" is it something like "Brain-Science"
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Transponder
What I find strange is that after all these years we only have three emergency codes. I think separate codes for engine fire, hydraulic failure, cargo fire, passenger problem, low fuel, smoke in cabin etc etc would be most helpful. Why are humans just like lumps on a log? We need some thinkers among us.
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What I find strange is that after all these years we only have three emergency codes. I think separate codes for engine fire, hydraulic failure, cargo fire, passenger problem, low fuel, smoke in cabin etc etc would be most helpful. Why are humans just like lumps on a log? We need some thinkers among us.
The 3 codes puts a big ring around you and alerts all ATC units that can pick you up on secondary. If ATC then need to start looking up codes then they're more likely to lose their eye off the main issue and that is more likely to lead to a mistake.
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737aviator
Can I just point out what the UK AIP, ENR 1.6.2.2.1 (e) tell us:
I believe it's something to do with automatically logging-off the Mode S system. Any ATC people here to explain?
some airports like Stansted say in the jepp brief to set it to 2000 before selecting Standby. From flying school though you got your hand chopped off by an instructor if you tried to change the code before selecting Standby first though.
Code 2000. When entering United Kingdom airspace from an adjacent region where the operation of transponders has not been required; or by Mode S transponder equipped aircraft on the aerodrome surface when under tow, or parked and prior to selecting OFF or STDBY - unless otherwise instructed by ATC.
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Flying Bull:
I started with 64 code transponders then after a few years we went to 4096 with Mode C. The company told us to never go to standby when switching codes. Instead, if assigned a code with a leading "7" use your brain to not select, 7500, 7600, or 7700.
Really not exactly rocket science.
Hi Haroon,
It all depends ob your type of equipment.
Old school turnknobs - better switch to standby or you might transmit an emergencycode…
New ones - change is normaly possible without standby but its all written down in the appropriate documentation, which should be available to the pilot…
It all depends ob your type of equipment.
Old school turnknobs - better switch to standby or you might transmit an emergencycode…
New ones - change is normaly possible without standby but its all written down in the appropriate documentation, which should be available to the pilot…
Really not exactly rocket science.