Why 1177 for everyone?
Joined: Aug 2010
Posts: 224
Likes: 113
From: UK
I assume it's so that London Info know who is and who isn't listening to them, but, again an assumption, you only set it when told to
(all assumptions because i stopped flying some years ago due to medications not being on the CAA approved list [and din't like the idea of cheating by self certifying and getting a lower privilege license])
Joined: Apr 2001
Posts: 1,827
Likes: 7
From: Sometimes north, sometimes south
It's a conspicuity code. It tells any radar controller seeing that squawk that it's an aircraft talking to London Info. If that radar controller wants to know more about the aircraft's intentions s/he phones London Info.
Joined: Oct 2007
Posts: 1,831
Likes: 16
From: Moray,Scotland,U.K.
Is it that each ATC is assigned a group of codes, for IFR and for VFR traffic? So they allocate you whichever of those available is considered most suitable.
The local code assigned to circuit aircraft is different from the one for off-circuit VFR traffic. IFR get their own personal (discrete) squawk. When going to a different service, I either get one of their squawks, or am told to use 7000.
The local code assigned to circuit aircraft is different from the one for off-circuit VFR traffic. IFR get their own personal (discrete) squawk. When going to a different service, I either get one of their squawks, or am told to use 7000.
Joined: Sep 2004
Posts: 1,684
Likes: 3
From: Down at the sharp pointy end, where all the weather is made.
I'm sure we all understand how the code is used. A few pilots I've spoken to mistakenly think that because they're being allocated a code, they're getting a radar service, which of course they're not!
I think what Sam is asking is why 1177 was chosen, against any of a range of other possibilities. The real question here, is there a clever scheme working in the background where 1177 is a better choice for some reason or is it rather a random choice by a clerk just picking a spare code that has no more or less significance than, say, using 0013 for the Luton conspicuity code or down our way, Newquay having 17XX, Exeter 04XX and Culdrose 40XX? My guess is that there is no clever system, it's just random. It probably represents a convenient random gap in the groups of codes allocated to different ATC units.
Sam, we'll probably never know unless the person working in the office that allocates codes is reading this - odds against, I'd say!
It'll all get washed away when the UK mandates ADS-B OUT and IN - bring it on, I say.
TOO
I think what Sam is asking is why 1177 was chosen, against any of a range of other possibilities. The real question here, is there a clever scheme working in the background where 1177 is a better choice for some reason or is it rather a random choice by a clerk just picking a spare code that has no more or less significance than, say, using 0013 for the Luton conspicuity code or down our way, Newquay having 17XX, Exeter 04XX and Culdrose 40XX? My guess is that there is no clever system, it's just random. It probably represents a convenient random gap in the groups of codes allocated to different ATC units.
Sam, we'll probably never know unless the person working in the office that allocates codes is reading this - odds against, I'd say!
It'll all get washed away when the UK mandates ADS-B OUT and IN - bring it on, I say.
TOO
Joined: Jun 2008
Posts: 519
Likes: 16
From: Luton
The UK assignments of SSR codes are documented in the UK IAIP at
NATS | AIS - Home
The relevent part of it is the En Route Information ENR 1.6
EG_ENR_1_6 paragraphs 2.2.2 through 2.6
Re. 1177:
Use: London AC (Swanwick) FIS
Remarks: Aircraft in receipt of a Basic Service from London Information. Shall only be selected with ATC direction.
It tells other controllers with which ATS unit the aircraft is communicating.
NATS | AIS - Home
The relevent part of it is the En Route Information ENR 1.6
EG_ENR_1_6 paragraphs 2.2.2 through 2.6
Re. 1177:
Use: London AC (Swanwick) FIS
Remarks: Aircraft in receipt of a Basic Service from London Information. Shall only be selected with ATC direction.
It tells other controllers with which ATS unit the aircraft is communicating.
Joined: Nov 2005
Aviation Qualifications: PPL
Posts: 12,458
Likes: 368
From: Wildest Surrey
I'm sure we all understand how the code is used. A few pilots I've spoken to mistakenly think that because they're being allocated a code, they're getting a radar service, which of course they're not!
I think what Sam is asking is why 1177 was chosen, against any of a range of other possibilities. The real question here, is there a clever scheme working in the background where 1177 is a better choice for some reason or is it rather a random choice by a clerk just picking a spare code that has no more or less significance than, say, using 0013 for the Luton conspicuity code or down our way, Newquay having 17XX, Exeter 04XX and Culdrose 40XX? My guess is that there is no clever system, it's just random. It probably represents a convenient random gap in the groups of codes allocated to different ATC units.
Sam, we'll probably never know unless the person working in the office that allocates codes is reading this - odds against, I'd say!
It'll all get washed away when the UK mandates ADS-B OUT and IN - bring it on, I say.
TOO
I think what Sam is asking is why 1177 was chosen, against any of a range of other possibilities. The real question here, is there a clever scheme working in the background where 1177 is a better choice for some reason or is it rather a random choice by a clerk just picking a spare code that has no more or less significance than, say, using 0013 for the Luton conspicuity code or down our way, Newquay having 17XX, Exeter 04XX and Culdrose 40XX? My guess is that there is no clever system, it's just random. It probably represents a convenient random gap in the groups of codes allocated to different ATC units.
Sam, we'll probably never know unless the person working in the office that allocates codes is reading this - odds against, I'd say!
It'll all get washed away when the UK mandates ADS-B OUT and IN - bring it on, I say.
TOO
Joined: Oct 2006
Posts: 896
Likes: 0
From: Strathaven Airfield
Good question Sam!
With regards to telephone numbers, when I worked on The Scotsman newspaper there was "outrage" when the new switchboard came in and we got a whole new range of phone numbers, and....
Out went the 225 part of the number (i.e. 0131 225 xxxx), since it referred to the old CALedonian exchange.
The same principle went for the area codes like Dartford 01322 (01 DA 2), and Inverness 01463 (01 IN 3).
And main roads are numbered clockwise from London and Edinburgh.
And in aviation - to get back on topic! - danger areas etc are number by the second part of their northing. So at 53N an area would be D3xx and at 54N it would be in the D4xx sequence.
So it would be fun to know if there was such a system for squawks!
ps. To answer the "who cares" argument: Maybe useful if there were two numbers in there whose letters match the station using them?
pps. Why my interest? I use words to generate my PINs!
With regards to telephone numbers, when I worked on The Scotsman newspaper there was "outrage" when the new switchboard came in and we got a whole new range of phone numbers, and....
Out went the 225 part of the number (i.e. 0131 225 xxxx), since it referred to the old CALedonian exchange.
The same principle went for the area codes like Dartford 01322 (01 DA 2), and Inverness 01463 (01 IN 3).
And main roads are numbered clockwise from London and Edinburgh.
And in aviation - to get back on topic! - danger areas etc are number by the second part of their northing. So at 53N an area would be D3xx and at 54N it would be in the D4xx sequence.
So it would be fun to know if there was such a system for squawks!
ps. To answer the "who cares" argument: Maybe useful if there were two numbers in there whose letters match the station using them?
pps. Why my interest? I use words to generate my PINs!
Joined: May 2000
Posts: 712
Likes: 17
From: SE England
1177 is only a tidy representation of the real transmitted code: 001001111111, which I think also looks pleasing. Use that as the basis for a PIN? Incidentally, 1177 is too complex for Swanwick controllers to remember so it appears as FIR.
Joined: Nov 2005
Aviation Qualifications: PPL
Posts: 12,458
Likes: 368
From: Wildest Surrey
Economy of use; no reason why other units sufficiently far apart shouldn't have the same code.
Joined: May 1999
Aviation Qualifications: ATP+Mil
Posts: 27,399
Likes: 857
From: Quite near 'An aerodrome somewhere in England'
1177 is easily selected by those who fly squawking 7000 and also means that setting 7700 is both straightforward and unlikely to be set when not needed.
