ATC question
Thread Starter
Joined: Jun 2010
Posts: 31
Likes: 0
From: socal
ATC question
Greetings, just a quick question regarding transponder emergency codes 75,76, and 7700... with ads-b, if you insert one of these codes into your transponder, will atc see this distinct code or will they only see a nonspecific code where in you will have to verbally tell them what your actual emergency is? If the answer is the latter, it would be difficult if you've inserted 7600. Thanks to all in advance for offering your many insights.
fly safe,
fly safe,
Joined: Apr 2009
Aviation Qualifications: Non-Aircrew
Posts: 1,601
Likes: 704
From: DM33
ADS-B Out transmits the same squawk code as set on the transponder. There is no "non-specific" code.
Mode S transponders with ADS-B Out use the code directly in their extended squitter. UAT ADS-B Out typically captures the code by receiving the transponder signal and decoding the squawk code.
ATC can't see any code other than the one you set.
Mode S transponders with ADS-B Out use the code directly in their extended squitter. UAT ADS-B Out typically captures the code by receiving the transponder signal and decoding the squawk code.
ATC can't see any code other than the one you set.
Pegase Driver
Joined: May 1997
Aviation Qualifications: ATCO
Posts: 4,456
Likes: 1,171
From: Europe
You might confuse SSR A codes and Mode S selective address codes . . As EXDAC said, ADS-B out will transmit the A codes set in the transponder . , Now the display of that code on the controller may vary from system to system , some will show the actual code ,most modern systems will automatically translate A7700 as " EMER" , "EMERGENCY" or some eye catchy symbol . As to your question regarding 7600, obviously you can't transmit the reason , but it does not really matter ,the procedures to follow is fixed for the controller to follow for each code . Remember that in n some real emergency cases , there is also no communications for a while until the event is over or under control , It's Aviate well before Communicate .
Joined: Aug 2007
Posts: 818
Likes: 117
From: Cardiff
Greetings, just a quick question regarding transponder emergency codes 75,76, and 7700... with ads-b, if you insert one of these codes into your transponder, will atc see this distinct code or will they only see a nonspecific code where in you will have to verbally tell them what your actual emergency is? If the answer is the latter, it would be difficult if you've inserted 7600. Thanks to all in advance for offering your many insights.
fly safe,
fly safe,
From the difficulty they had trying to get the signal lamp out of the door I concluded that it had been a very long time since someone had landed at Birmingham with radio failure.
Joined: Jun 2021
Posts: 14
Likes: 1
From: West Mids
In answer to Slim75’s question - it may be dependent on the ATC unit’s equipment - squawking an emergency code will flash red and highlight your aircraft data block on the screens we use, but we will still see your original details (eg callsign converted if you were on an airways squawk, or original squawk code if not).
In response to the second poster’s comments on the lack of use of an Aldis lamp during radio fail at Birmingham - the unit does not physically have one to use.. and has not had one for many years. It would be interesting to see if many modern towers have one available- my suspicion is larger modern units won’t have, unless specifically mentioned in the AIP?
In response to the second poster’s comments on the lack of use of an Aldis lamp during radio fail at Birmingham - the unit does not physically have one to use.. and has not had one for many years. It would be interesting to see if many modern towers have one available- my suspicion is larger modern units won’t have, unless specifically mentioned in the AIP?
Joined: Apr 2005
Posts: 1,652
Likes: 138
From: 50+ north
In UK the following will apply.
Setting 7500 will result in a discrete enquiry from ATC “(Callsign) confirm you are squawking assigned code (code assigned by ATC that it would otherwise be squawking).”
Setting 7600 will merely indicate a comms loss with the expectation that you will will follow any published comms loss procedure.
Setting 7700 will require verbal explanation of the nature of the emergency and any resultant requests/intents.
Setting 7500 will result in a discrete enquiry from ATC “(Callsign) confirm you are squawking assigned code (code assigned by ATC that it would otherwise be squawking).”
Setting 7600 will merely indicate a comms loss with the expectation that you will will follow any published comms loss procedure.
Setting 7700 will require verbal explanation of the nature of the emergency and any resultant requests/intents.
Thread Starter
Joined: Jun 2010
Posts: 31
Likes: 0
From: socal
Thanks to all for your insights. I was able to get this question in with Los Angeles Center last week while airborne. The controller told me that regardless of the emergency code entered into the transponder (ads-b), his screen will only see the aircraft's callsign and a nondistinct code other than what was originally assigned but not anything specific. He further stated that operators need to verbally tell the controller the nature of the actual emergency since their ground systems can not distinguish the specific code entered into the transponder. i guess i'll go with that. thanks again.
stay safe,
stay safe,
Joined: Dec 2020
Aviation Qualifications: ATPL
Posts: 179
Likes: 81
From: Amsterdam
Quick one for those who look after us in the tower:
Delivery tells me to squawk 7502 in my clearance.
My transponder is set 1000.
If I start from left to right, my transponder will very shortly read 7500 (until I change the last 0 to a 2).
Does ATC see this pop up (7500) whilst I'm setting 7502?
I was told to always set the transponder from right to left.
Delivery tells me to squawk 7502 in my clearance.
My transponder is set 1000.
If I start from left to right, my transponder will very shortly read 7500 (until I change the last 0 to a 2).
Does ATC see this pop up (7500) whilst I'm setting 7502?
I was told to always set the transponder from right to left.
Joined: Apr 2005
Posts: 1,652
Likes: 138
From: 50+ north
Quick one for those who look after us in the tower:
Delivery tells me to squawk 7502 in my clearance.
My transponder is set 1000.
If I start from left to right, my transponder will very shortly read 7500 (until I change the last 0 to a 2).
Does ATC see this pop up (7500) whilst I'm setting 7502?
I was told to always set the transponder from right to left.
Delivery tells me to squawk 7502 in my clearance.
My transponder is set 1000.
If I start from left to right, my transponder will very shortly read 7500 (until I change the last 0 to a 2).
Does ATC see this pop up (7500) whilst I'm setting 7502?
I was told to always set the transponder from right to left.
Joined: Dec 2020
Aviation Qualifications: ATPL
Posts: 179
Likes: 81
From: Amsterdam
Thanks for the input but the question reads like an ATPL question. You have to really read the question.
Will ATC be able to see the 7500 code whilst I'm turning the knobs of the transponder?
Will ATC be able to see the 7500 code whilst I'm turning the knobs of the transponder?
Joined: Apr 2005
Posts: 1,652
Likes: 138
From: 50+ north
Pegase Driver
Joined: May 1997
Aviation Qualifications: ATCO
Posts: 4,456
Likes: 1,171
From: Europe
In addition , quite a few ATM systems have a filter that needs at least 2 returns to confirm an anomaly , especially on the mode C ., to avoid garbling and false alerts , in this case no chance for ATC to see your "intermediate " codes.
@Dixi188 :
Always used to select STBY before changing squawk.
, a bad habit today as most ATC systems run on SSR only and you will then briefly disappear from view, it will also delay TCAS reactions . ,and on the ground, multilateratuion protections from vehicles depends on having your transponder on at all times..( for those airports equipped)
