Redhill and Gatwick: transponders off, mode A or mode C?

[ModernDinosaur]

Hi!

As a regular flyer from Redhill Aerodrome, I have always been advised by my elders and betters (i.e. almost everybody!) that I should keep the transponder off whilst in the circuit, 7000A only while under the Gatwick CTA and 7000C outside the CTA.

At first this seemed sensible - Redhill is right under many of the SIDs from Gatwick, and I can well imagine that our ATPL friends aren't too keen on getting TCAS alerts from PPL pilots on climb-out directly underneath them, but the more time I spend reading posts here the more I'm starting to question this advice.

So - what would the controllers at Gatwick like us to do? Have I been doing it "right" all along? Should I stick Mode C on unless it's a circuit detail? Mode C all the time?

On a related note, I sometimes fly a track around the edge of the Gatwick CTA, just out of controlled airspace, with 7000C selected. Usually I talk to Farnborough Radar down the western side of Gatwick, Shoreham for FIS on the south and and switch back to Redhill for FIS on the eastern and northern edges. Would Gatwick prefer me to identify myself to them so they know who the blob is just outside their zone?

All comments welcomed!

MD.

[HugMonster]

If I'm flying over the top of you I want to see your Mode C response on my TCAS.

Dunno about the vicinity of LGW, but just about everywhere else, it appears to make more work for ATC if there is only Mode A - "XYZ123, popup traffic, slow moving left 10 o'clock - no height information"

They then have to keep an eye on you just in case you're in my way, and I (or my FO) are worriedly looking outside just in case we bang into you at exactly the time when we're really rather busy on the flight deck, when confirming via Mode C that you're well below us is simple and saves an awful lot of worry.

I've always trained my students ALWAYS to squawk mode C. It gives more information. It can help. It can never do any harm. Why not do it?

[HEATHROW DIRECTOR]

I'm not Gatwick.... but just a point that Mode C is useless info to ATC unless it has been properly verified. If you saw some of the transponders on light a/c you might be surprised... I've seen as high as FL 120 and as low as a minus number, coming from duff transponders on a/c at low level. Minus altitudes are really baffling and lead us to comment about submarines, etc!

[Warped Factor]

I am Gatwick.....

Transponder off in the circuit is recommended practice. At all other times, including when under the CTA, if you have Mode A and Mode C please select them both. Both for the benefit of the TCAS equipped airliners and as further usefull info for ATC. Your level may not be verified, but it is still usefull to see.

As for speaking to Gatwick on the route you mentioned, my advice would be feel free. Sadly with the demise of Dunsfold there's no suitable LARS unit around the S and SE of the Zone. But if you call Gatwick you'll get a FIS and subject to primary workload you may be offered a RIS. Ideally listen out to see how busy it is first, and if it is busy when you call keep the r/t as crisp and, err, um, ahhh concise as you can :)

WF.

[HEATHROW DIRECTOR]

I guess we all have our own opinions.. but, WF, have you noticed how many of our colleagues immediately de-select 7000 as soon as they sit down? I do the opposite, having seen more "wildies" than I've had hot dinners!

[Spitoon]

MATS Part 1, the controllers bible says 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.The AIP is not quite so clear but paras 1.2 and 2.2 of ENR 1.6.2 (http://www.ais.org.uk/uk_aip/aip/pdf/enr/2010602.pdf) explain it.

[sennadog]

Good question ModernDinosaur. From what I've read so far it's best practice to use Mode C when flying around Gatwick CTA and there is a strong chance of receiving at least a FIS if not a RIS from Gatwick according to Warped Factor.

If this is the case and given that there is a lot of GA traffic around the eastern end of Gatwick CTA I can see this veering towards a dramatic increase of GA aircraft asking for a service of some sort from Gatwick as it's long been a concern for pilots such as myself that there is no service offered around that area.

My gut feeling says that it would be great to be offered a "local" service in that area but given that Bewl Water is a major routing point, isn't this going to lead to Gatwick being overstretched?

[Hippy]

Taking the topic slightly broader, I would just like to say that an un-verified Mode C can actually be alot more helpfull than no Mode C at all. When providing RAS we have to provide 5 miles seperation from non-mode C returns, but with an un-verified mode C we are able to take 3000ft and a gap. Can save a lot of track miles in busy airspace.

[bookworm]

Spitoon raising an interesting point, in that the AIP is slightly at odds with the quoted MATS Pt 1.

It says that pilots should select 7000 A/C except when remaining in the aerodrome traffic pattern.

On a normal arrival, as opposed to a circuit detail, I wouldn't consider switching off my transponder until I was on the ground (unless requested otherwise), even if I were flying a full circuit.

[Capt Pit Bull]

Personally, as somebody who overflys redhill a couple of times most working days, I'd vote for either:

Standby

or

On with Altitude Reporting.



On without altitude reporting causes us to receive unnecessary Traffic Advisories.

CPB

[Warped Factor]

HD,

I guess we all have our own opinions.. but, WF, have you noticed how many of our colleagues immediately de-select 7000 as soon as they sit down? I do the opposite, having seen more "wildies" than I've had hot dinners!

It may be common practice to de-select the 7000 squawks at the Heathrow end of the room, but they don't do it on any of the other approach units in TC. Pop down the other end and have a look sometime :)

Heathrow probably only gets away with filtering out the 7000's because they have Thames and SVFR keeping an eye on what's happening at the lower levels around the Zone most of the time. If these units weren't there filtering 7000's would not be such a good idea.

sennadog,

If this is the case and given that there is a lot of GA traffic around the eastern end of Gatwick CTA I can see this veering towards a dramatic increase of GA aircraft asking for a service of some sort from Gatwick as it's long been a concern for pilots such as myself that there is no service offered around that area.

Just bear in mind that Gatwick is not a LARS unit and any service offered will be subject to workload. And if it's busy, a reasonable standard of r/t would be appreciated. Sadly, the PPL community (of which I'm one) often do themselves no favours. But then that's probably a topic for another thread.....

WF.

[Flyontrack]

There's a similar discussion going on at the Infringement project website which you might find interesting!

It's at www.flyontrack.co.uk

All opinions welcome - it's an open forum but you can go private if you prefer.