Squawk Alpha 7000
 

Hi

Have recently overheard GA traffic when leaving CAS being told to squawk 'Alpha 7000' by ATCOs.

Is there a specific reason why this request has been introduced when traffic is leaving CAS? Recent aticles in GASIL and similar have been advising to leave Mode C selected at all times enable TCAS to work effectively.

Cheers

It's a little bit old fashioned I think. I stand to be corrected, but I believe that the "Alpha" part of the transponder signal is the code, and the "Charlie" bit of the signal is separate. In other words, squawking "XXXX Alpha", means squawk that number and does not mention the "Charlie" bit.

I have been told to "Squawk xxxx Alpha" in RVSM airspace, where you are supposed to squawk charlie all the time.

JR

Charlie is altitude.

7000 in the UK is a "conspicuity" code.. Manual of ATC says:

Conspicuity Code

4.7.1 The conspicuity code, 7000, together with Mode C should be displayed by all suitably equipped aircraft unless:

a) they have been assigned a discrete code;
b) they are flying in an aerodrome traffic pattern below 3000 feet; or
c) they are transponding on one of the special purpose codes or on one of the other
specific conspicuity codes assigned in accordance with the UK SSR Code Allotment Plan.

4.7.2 Subject to the above, pilots are required to squawk 7000 when operating at and above
FL 100 and are advised to when below FL 100. Both the special purpose and the
conspicuity codes, together with the associated Mode C data, must be considered as
unvalidated and unverified.

It's confusing isn't it? Most of us think of Modes as being mutually exclusive states of a user interface i.e. you're either in Mode 1 or Mode 2 or Mode N. So an autopilot is either in altitude mode or vertical speed mode etc. It can't be in both.

For SSR, the Mode refers to the type of interrogation and reply, so it's entirely possible for a transponder to reply to a Mode A interrogation (with its 12 bit code) as well as replying to a Mode C interrogation (with its encoded altitude). It should do exactly this when the switch is in the ALT position.

Although there are a couple of examples of the use of the word "Alpha" in CAP 413, it's not on the list of standard phrases in MATS Part 1 (except as "Stop squawk alpha" which is impossible with most transponders except as "Stop squawk"). The word is redundant and IMHO should not be used.

Well, to some pilots it probably wouldn't be - they would see this instruction to mean turn off the Mode C, (perhaps thinking that the controller they are working is no longer interested in the alt read out as they are off the edge of his/ her airspace and therefore the height info is of no benefit to the controller, but not considering that other units or equipment are still interested in the Mode C data). However if the instruction simply means 'squawk 7000 but leave the Mode C selected' then why not just say 'squawk 7000' - so you're right in this respect it could be confusing for some pilots who take everything literally! :confused:

This is another example of the almost wanton obfuscation and obscurity in aviation terminology. Transponder equipment in aircraft is marked 'ON' and 'ALT', not 'Mode A' and 'Mode C'. Some are placarded 'No Height Information'. But you won't find those terms used by ATC.

Yesterday I was trying to explain to a student (in the air) why we turn the transponder to 'ON' as we pass 1000ft and 'ALT' as we leave the zone - to minimise TCAS alerts when inside CAS. But by the time I'd finished, with all those mentions of 'TCAS' and 'Mode Charlie' he was completely maxed out and hadn't a clue what I was on about. Some refinement of instructing skills required perhaps, but it's surely also time to stop talking about 'Alpha'? Military units seem to be OK with this - generally saying 'squawk 7000 and freecall...'

To minimise TCAS alerts ??????

More likely your actions will provide a lot more spurious Traffic Advisories and also prevent a life saving Resolution Advisory being given to a TCAS equipped aircraft if something goes wrong (e.g a level bust).

Most of us younger ATCO's use the term 'squawk 7000' as this is what is now taught at the colleges, however, some of my more experienced colleagues still use 'squawk Alpha 7000'.

Hi ATCO 1979,

Do they still teach, "Squawk seven zero zero zero"?

:D

What if you were told to squawk Alpha Midnight??

ATCO Two

Do I infer that you have a problem with "seven zero zero zero", i.e. correct phraseology, being taught?

If you do, why do you not put a case to SRG for the pronunciation to be changed? Then there will be no discrepancy with what is, correctly, taught and what is done "in the field" (though for no good reason apart from idleness).

To be honest, any time I've said "Squawk sev-en zero zero zero" I've had the reply "Say again?".
I think most pilots know what is being asked of Squawk 7000.

There is no problem with "thousand" being used in altitudes, why not with Squawks?

2 sheds,

Aha, so you admit that there is a discrepancy? I rest my case. I'm with Stupendous Man on this one.

Stupendous

To answer your question... because an SSR code is not a value of hundreds and thousands, but is a set of four code digits. E.g. I am sure that you would not refer to an aircraft with radio failure as "squawking seven thousand, six hundred"?

ATCO Two

My point is that if you think that the "operational" habit is more pertinent, put up a case to SRG, get CAP413 changed, and the whole subject will be sorted out formally. Otherwise, the colleges remain obliged to teach precisely what is intended by both ICAO and the UK CAA. If they do not adopt this principle, then that is the start of a very slippery slope.

Okay, from a mil point of view and not wishing to offend anyones CAP413, we say simply "Squawk 7000!" No seven-zero-zero-zero, no squawk alpha etc etc. As far as I was aware it was recognised and taught practice to pronounce it seven t-ousand anyway!

All for an easy life me!:ok:

PPRuNe Radar:Interesting point, hadn't thought of that. However because it's inside a Class D zone all IFR traffic is given traffic information on us VFRs and the ATC phraseology is usually "traffic you may see on TCAS is...". The procedure I describe was instigated at the behest of the local ATSU so I have to presume they know what they want. It's very rare for us not to have 1000ft vertical separation on IFRs because of the organisation of lanes etc and in effect what the IFRs get inside the zone is like Class C. If they operated it strictly according to Class D rules then there would certainly be potential for a conflict between the Class D rules and TCAS criteria but I can't see the current modus operandi creating a problem. Then again, I don't suppose pilots of most IFRs know that ****** Approach always applies 1000ft vertical or 3nm horizontal separation between them and any VFR traffic - except in the circuit or when confirmed visual.

PS never heard anyone say squawk seven tousand

Surely if you are flying in Class D even VFR you should be allocated aSquawk as it is a known traffic environment. As to hundreds and thousands. FL ONE HUNDRED, FL TWO ZERO ZERO, etc.

NorthSouth

Feel free to point your ATS provider at this document :ok:

It may highlight the gaps in their knowledge and show that they are operating under some misconceptions. :}

Eurocontrol ACAS II Bulletin 4 - TCAS II and VFR Traffic

Quite a decent read for GA VFR pilots too and shows how you can help improve safety by operating your transponder correctly - at no extra cost.

As for any ATS provider who ignores the safety lessons after the Swiss tragedy (regardless of the difference in their operations from the actual incident), they will be crucified if they are giving advice to pilots which could prevent the means of avoiding a mid air collision, and rightly so.

:uhoh:

You are depending on everyone sticking to their correct levels with no one making a Level Bust. Experience in the UK shows that these incidents do happen far too often, with the occasional close call. There is a widespread campaign to raise pilot awareness and to get both pilots and ATC alike to think of the problems which can occur.

You can read the report by the CAA Working Group here:

UK CAA On The Level Final Report

I think that SRG would be very concerned by any unit who was not aware of either of these documents, and even more so if they were not doing all they could to embrace the safety lessons within them, but were making recommendations which actually go against them ....... still, a Class D Zone narrows the culprits down a little !!!

I'm shocked, and I'm entirely with Radar.

Why should we give a flying duck about what the local ATSU wants? TCAS isn't there for their benefit. Worth pursuing with ATS Standards, I think.

Also, an increasing amount of GA traffic is employing TCAS and using it when operating outside CAS. We have a Police Helicopter based which is TCAS equipped, so it makes sense to keep the Mode C selected at all times.

I think I'm right in saying that units with processed radar can choose not to display Mode A & C data on traffic operating above/below selected levels, so I guess it dosen't cause much clutter?