Flexwing microlight radar signatures

[Mr_Bigchopper]

Hi,

I was wondering if any ATC LARS officer could give me some idea of what kind of signatures they get from microlight aircraft.

While flying 'round and about it's difficult to really judge whether or not I could expect to be within range of a radar system.

I realise of course that this is subject to many variables, but I was after an approximation... say within 10nm, 15nm, 5nm?

cheers
Andy

PS I am talking UK here..More specifically, midlands and southern England

[Standard Noise]

Well we can certainly see microlights on our screens. It's a good job since we talk to quite a few out of Hewish, Weston Zoyland etc
The return depends on many things, mainly your altitude/distance. In theory we should be able to see you at 1000' out to ten miles, 2000' out to 20 miles and so on, but this also depends on the atmospheric conditions eg if you are flying into a decent headwind or there is a bit of WX clutter, the return may be filtered out.
Most of the time though, you will show up. Our particular problem at Bristol is that lower aircraft are masked by the Mendip ridge, however, if you were to fly down the coast from say Slimbridge in Gloucs to Hinckley Point, we'd prolly see you all the way even at 1000', but then again that won't help you much when you're flying in Cambridgeshire, will it?

[tribekey]

On a good day with no weather clutter and a radar that's just been 'tweaked' by the tels guys we can see you at similar range/distances mentioned by standard noise. If you fly at a tangent to the radar head you'll disappear,so if you fly between EGHH and EGHI fom say stoney cross to the lymington araea or vice versa you won't show up.If there's weather showing on the radar you'll be lost in the clutter and if we use filters to improve the picture you may disappear as well. Microlight pilots who call for a FIS and give position reports sometimes don't match with any discernible return.Given the amount of pax jets etc now flying around the solent/new forest area i'd advise you always to call up (obviously you must within class d anyway but there are areas between the two airports that are outside controlled airspace).

All this is primary radar, get a transponder and you'll be seen unless you are very low.

[2 sheds]

Mr Bigchopper (nothing like being modest, eh?)

It would be useful if you qualified your question to indicate whether you are thinking in terms of receiving a radar service or the ATC unit detecting your aircraft with a view to passing radar-derived traffic information or avoiding action to other aircraft under service. Either way, it would make a huge difference if you were transponder-equipped.

[AlanM]

Of course, around the LTMA you are unlikely to be seen with the processed radars.....even at 4000ft in a transponding aircraft.

[eyeinthesky]

AlanM
If you're referring to what I think you are, then youmay have a point about the construction of the aircraft and where the transponder aerial is sited having an effect upon their conspicuity to radar.

However, to use a radar head which is miles away when controlling at relatively low level and when you have other radars available is also tempting fate...

To answer the original question: if ATC have 'filtered out' the primary returns (as they may do if there is a lot of clutter), then you are invisible.

[Mr_Bigchopper]

Hi all,
Thanks for your info. While flying around I have always wondered this, even while on FIS. Of course it's not the sort of thing you can just spark up a conversation about with Essex radar while skirting around the northern side of Stansted class D.

2Sheds,

I was thinking merely of what is the likelihood of you seeing the primary return. I realise that you can of course still provide a service independant of what return you get.

A transponder is not really too practical for me at the moment since it's like the old joke "How do you double the value of a skoda - fill the tank with petrol", springs to mind! Well at least with my machine anyway,..



cheers
Andy

[London Mil]

You don't necessarily need a plastic aircraft close to the theoretical limits of radar coverage to reduce the chance of being seen. Word has it that excesive speed or indeed a rather stealthy Tornado complete with big fin and lots of dangly bits can confound the latest systems.
eyethinksy, since when has the position of a transponder aerial had a negative effect on the performance of radar? Call me a bluff old traditionalist, but surely the PSR and SSR processing should be completely separate?

[Mr_Bigchopper]

"Mr Bigchopper (nothing like being modest, eh?)"...

I have a helicopter.. what were you thinking about then?

Thanks for your information, all.

Fitting a transponder isn't entirely practical for my flexwing, believe me! So, primary it is....


" eyethinksy, since when has the position of a transponder aerial had a negative effect on the performance of radar?"...

Well, all antennas have a specific radiation pattern... that is, they radiate more in one direction than another.. this can be made worse depending on how it is mounted to the aircraft itself.. this compromises radar system performance, since the transponder has reduced receive and transmitt performance related to the direction in question. Antennas used for transponders are intended to be reasonably omnidirectional.. that is... until they are mounted adjacent to an aircraft fuz, rather than perpendicular.


cheers
Andy

[av8boy]

You could always adopt a low-tech approach...



See 'em on boats all the time. The drag shouldn't cost you but five or ten knots...

[London Mil]

bc, thanks for the lesson in SSR theory. Let me refresh the question: since when does the location of a transponder aerial affect the primary radar (ie non-SSR) return?

[Mr_Bigchopper]

"since when does the location of a transponder aerial affect the primary radar (ie non-SSR) return?"

If your question was always intended as primary, then apologies, I agree with you . But I had read and interpreted your previous question as SSR, since it was in the context of the use of transponders.

Cheers
Andy

[SpotterFC]

SSR

BC

Kinetic Avionics are currently testing something that might fit the bill for you. URL is the company name as one word with .co.uk and the product is LAST.

Not connected in anyway with them - just might be useful...

[chevvron]

With processed primary radars (including Watchman) its the groundspeed of the target that decides whether it will be displayed on a radar screen; if you're flying below the threshold speed you'll be automatically deleted 'cos the stupid processor doesn't know you're an aircraft, and assumes the controller doesn't want to see you. With Watchman, the controller can select 'background video' which allows view of non-processed radar, but the newer ASR10 does not have this facility.
Positioning of an SSR aerial on an aircraft CAN affect the response characteristics, for instance, it the aerial is close to the fin, then in 'tail on' aspect to the radar head, the reply can be masked leading to loss of the SSR label from the display. Chinooks seem to be particularly prone to this phenomenon.

[Widger]

I will back up previous comments. I remember seeing contacts in the Westonzoyland area on Watchman and this was confirmed by an aircraft passing at the time. However, with more advanced processing, that blip, that the human eye, thinks might be a flock of birds or you in your microlight, may well get deleted.

Get a transponder and stay alive!

[eyeinthesky]

London Mil et al:

I was referring to SECONDARY radar performance in my comment about the location of the transponder aerial. Apologies if it led to confusion..