London TMA VFR traffic under control?

[fly4fud]

Had a flight into LCY this afternoon. Splendid weather, unlimited vis. Vectors for rwy 10. Flying at 3000, twice TA on our ACAS (happens quite often in the London TMA and is very annoying). Spotted light VFR (?) traffic 1000 below, first a Cherokee, second unidentified target.
- is there a positive control on those traffic?
- how come is this traffic not transmitting mode C?

Thanks for all replies

P.S.
and did the lost student pilot (heard on 21.5 at around 1300Z) make it alright to Cambridge?

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* cut my wings and I'll die *

[Warped Factor]

f4f,

The traffic you refer to will be flying in the open FIR below the TMA.

As such they will not be under any sort of control, if only because there are no radar units in the SE of England (apart from Farnborough) willing or able to provide a radar service to GA traffic operating outside CAS.

But anyway, as the airspace is uncontrolled by definition, there is no need/requirement for any form of control.

As an aside, we vector IFR traffic to the base of CAS +500ft in the London area, so there may be occasions where light aircaft will only be just over 500ft below you.

There's no requirement in the FIR below the TMA for a transponder to be carried, never mind Mode C. I myself fly a lovely old aeroplane from an airfield just west of Heathrow and which lies below the TMA. No transponder on board and, possibly controversial viewpoint here, I hope we are never forced into installing one.

WF.

[Numpo-Nigit]

Within the UK, and outside controlled airspace, carriage of mode C is only mandatory above FL100 (gliders are exempt).

Edited to include exemption!!!

[This message has been edited by Numpo-Nigit (edited 14 January 2001).]

[fly4fud]

Thanks for your answers. I understand those aircraft are outside (below) the TMA. But why is the xponder only on mode A?
We get annoying TAs (no RAs), and as we don't get any altitude from the conflicting, are not able to reassure ourselves as to the vertical separation. As it is, we then much prefer no sqwak at all, and then are not worried about traffic we don't see!

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* cut my wings and I'll die *

[Chilli Monster]

f4f

At the flying school I learnt at the transponders on their basic training aircraft were all mode 'A' only - no 'C' whatsoever. This is probably the case with the aircraft you are talking about. Commercially you will be fitted with it, but bear in mind at the other end of the spectrum it is NOT a requirement - as warped factor has already pointed out. I would say that's a probable reason.

CM

[The Fat Controller]

Basic transponder (mode A) = one box and one antenna.
Mode C capability = above plus encoding altimeter = more expense !!!
There's one reason why lots of people who fly regularly below FL100 don't have mode C.
Also, from the controllers perspective we prefer to see traffic squaking 7000, especially if it is in the vicinity of controlled airspace, because it's then pretty obvious from it's track history that it is a "low and slow" below CAS, NATS area radars are pretty poor at reliably tracking primary only targets at low levels.


[This message has been edited by The Fat Controller (edited 15 January 2001).]

[Dan Dare]

F4F how can you ask people to switch off their transponders? Surely you are better to be worried about traffic you cant see than to hit traffic which shouldn't be there, but didn't squawk because you would prefer them not to.

Have to agree with Warped factor on the issue of mandatory transponders. Some of us don't even have a radio!


[This message has been edited by Dan Dare (edited 16 January 2001).]

[fly4fud]

Again, thanks for you answers!
First, let me say that I'm in no way attacking light aircraft owners (I'm also one...) or operators!

The Fat Controller, mode C capability needs not be that expensive. I just installed an encoder (not the encoding altimeter, this one is dear) that I bought a couple of years ago in the U.S. for 125 US$. Of course the xponder itself must be designed to also handle mode C, which most are.

Dan Dare, I implied no squawk for aircrafts not equipped with mode C. Why are those aircraft flying with the xponder ON, while outside of controlled airspace and ATC that doesn't give a f...? It only gives us alarms (TAs), quite often when still in IMC and during busy approach times, and we sure could do without those ;)

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* cut my wings and I'll die *

[10W]

f4f,

Whilst some equipment can be bought cheaply, it may be an expensive mod in the CAAs eyes if not approved or proven by them. Lots of paperwork and folding money has to change hands in those cases http://www.pprune.org/ubb/NonCGI/frown.gif

Also, the transponder requirements are currently established for ATC needs, not for TCAS. We would much rather see that a target is likely to be a VFR tiddler (squawking 7000) and likely below our airspace, than just see (if we do at all) a primary contact edging it's way across the screen. Depending upon the circumstances we may have to take action if we have no information on it.

The TCAS issues are obviously growing as more aircraft become fitted with it, however the needs and wants of pilots need to be expressed somehow through a relevant industry group so that they can be addressed. As I say, the current procedures and requirements are not designed with TCAS as a consideration.

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10 West
UK ATC'er
[email protected]