Mode C when squawking 7000 in open FIR?

[topunicyclist]

When flying in Class G airspace and squawking 7000 under VFR without Radar Information Service, but on an appraoch frequency that has radar (e.g. Blackpool App), is it preferable to have Mode C switched on as well?

I seem to remember reading some posts on a similar topic a while ago, but I would be intersted to hear some more opinions, particularly from ATCOs.

Thanks.

[Spoonbill]

:)The short answer is yes.
Where ever you are flying, if you have mode C available it is very helpful if you leave it switched on. This applies whether you are working an ATC unit or not.
Although the height readout cannot be used as a verified altitude, (unless we cross check it with you), it gives us some idea of what height you are operating at and other traffic can be informed accordingly.
If you get the opportunity to visit an SSR equipped radar unit, (especially on a weekend), you should do so. You'll then see for yourself the difference having height readout selected makes! :)

[Cough]

Yes you should - Every TCAS equipped airliner flying at 35,000' above you will get a traffic warning within about 2nm of you. Very annoying.

[HEATHROW DIRECTOR]

The short answer is absolutely NO. Nobody has verified the information so it cannot used and might be dangerously misleading. Picture this - an airliner takes TCAS avoiding action against an unverified Mode C read-out. The transponder on the clockwork-mouse is busted and reading 2000 ft too high and the airliner takes an avoiding-action climb.... staright into something else.

I've seen potentially that situation so often...

[PPRuNe Radar]

Or the alternative HD.

Somebody (Mode C equipped but switched off) blunders into your zone. You don't tell BirdSeed 01 anything because as the intruder has no Mode C it HAS to be clear of Controlled Airspace, right ?? Oh, and BirdSeed 01 is a freighter, no TCAS needed. Big bang over London, but all the intruders fault, and the ATCO can sleep easy at night.

Me ?? I'd much rather take the chance with the few whose Mode C is corrupt and increase workload avoiding them spuriously than not knowing that those few who do enter without permission are actually wandering around in conflict with heavy metal.

I also think your argument sort of falls down a bit since if the airliner takes avoiding action based on TCAS, then the majority of guys above him will also have it and take co-ordinated action, or if they don't then at least they will also be shown on his display and he is unlikely to want to fly too close towards a known target.

Pains me to say it but I actually agree with the CAA line (must be mellowing). Their instruction in the legal document, the UK AIP, is that below FL100 pilots should squawk, and that pilots shall squawk Mode C if available at all times when Mode A is selected, except for those circumstances where use of a transponder is not required (remaining within the circuit, etc).

So topunicyclist, according to the legal document (ENR 1-6-2-1), you should squawk 7000 in the circumstance you describe. If you choose to do so, then you shall squawk Mode C if it is available.

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PPRuNe Radar
ATC Forum Moderator
[email protected]

[ATC Watcher]

Cough : where can I buy this wonderful TCAS that can detect other transponders 35.000 Ft below ?
To the orginal question, if you carry Mode C use it , it might save the day, one day, even at 1500 Ft , even in Class G.

[BombBay]

http://www.pprune.org/ubb/NonCGI/frown.gif Heathrow - suggest that you read the post before replying in such vitriolic terms!
I dont know where you work, but it appears that you are probably within controlled airspace.
I work in exactly the sort of airspace that Topuni describes, and I wholeheartedly agree with those who say yes.
Although many of the aircraft I handle each day are tcas equipped, I've yet to hear anyone complain about recieving alerts from such transponding aircraft, indeed they are grateful that we can also give them some idea of heights, albeit unverified.
End of rant!
http://www.pprune.org/ubb/NonCGI/cool.gif

[Warped Factor]

topuni,

PPRuNe Radar has given you the definitive reply.

HD, sorry, simply put....you're wrong.

WF.

[Findo]

Topunicyclist - squawk all you've got as often as you can except in the circuit. Eventually even the military will have a TCAS type device and you might save being mown down by a Tornado going about its lawful business at 500kts with limited cockpit visibility in haze.

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Go with the flow ... or you'll miss your slot.

[eyeinthesky]

I have to agree that if you've got it, use it! Chances are that if it's corrupt then at some point you will be talking to a radar unit who will tell you!

HD: Can't believe the naivety of your reply. You don't do our profession any favours!!!



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"Take-off is optional, Landing is mandatory"

[Bagheera]

HD,
Ive seen some mis-informed replies ,but that one wins the Chisholm prize!

[This message has been edited by Bagheera (edited 19 April 2001).]

[10W]

Bagheera,

Shouldn't you be asleep ?? ;)

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10 West
UK ATC'er
[email protected]

[HugMonster]

HD, that is without a doubt the single most stupid, uninformed and DANGEROUS post I have seen on these boards in the entire time I have been PPRuNeing.

You should be ashamed of yourself.

[Skycop]

Please cross-refer to my request as a police pilot on "Private Flying" regarding spurious TCAS alerts from non-Mode C 7000 squawkers.

Not using "C" does cause TCAS users problems in the open FIR.

SC

[Findo]

Not using mode C also has the effect of cluttering up radar displays on sectors you do not need to be seen on. The typical filter for a high level sector is based upon a height band. Non mode C traffic shows through because radar does not know what height the aircraft is and shows the mode A. Typical example is the weekend traffic around Newcastle. Newcastle get them all to squawk same squawk and lots don't have mode C. Result can be radar clutter on the sectors working 25,000ft above.

If you've got a transponder use it all.




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Go with the flow ... or you'll miss your slot.

[fragul]

Yep, agree with most - and of course in the area you mention it's Warton's playground. Even given that the mode C info is unverified, it may help them not to hit you with a Hawk/Tornado/Typhoon !!

[topunicyclist]

Thanks for all replies......I've also been keeping an eye on the similar thread on the Private Flying forum, which I discovered a day or two after starting this thread.

[stopbar]

Yes, Yes, Yes if you've got it use it, might save yours and ours bacon one day. I'm speaking as a Class G controller.

[ukatco]

Yes you should use mode c if you have it. An ATCO providing a radar advisory service in class G needs to provide 5nm seperation from you if you have no mode C. With mode C he doesn't need 5nm as long as he has 3000ft vertical seperation from your C readout.