Class C - Separation by target resolution

[soaringhigh650]

Hi there,

Aircraft Separation. Separation is provided within the Class C airspace and the outer area after two-way radio communications and radar contact are established. VFR aircraft are separated from IFR aircraft within the Class C airspace by any of the following:

1. Visual separation.

2. 500 feet vertical; except when operating beneath a heavy jet.

3. Target resolution.

Can someone tell me what is target resolution?

[RAC/OPS]

Sounds like a fancy way of saying radar separation to me. Thought resolution had something to do with how big blips are at a certain range, which is dependent on the rotation speed of the antenna I think. Hence X miles separation from the centre of the blips provided the blips don't touch etc

[malecontrol]

Target resolution means targets or radar blips should not touch each other. No touching no, over-lapping.

[soaringhigh650]

Thanks. What happens if they touch? Does that mean a collision?

[Arkady]

No, the target on the radar is far, far bigger than the actual size of the aeroplane, hence, in theory, if the blips do not merge the aircraft will not hit each other. If the blips do merge, they might!

[soaringhigh650]

I see. How big is it? I take this increases the further away the aircraft is from the radar?

[cossack]

The size of the radar target to be used is published in unit procedures (so no using a really small target size when they get close together:= ) and in our case its only within 7 miles of the airport so no worries about distance from the radar source causing issues.

[BaldEd]

soaringhigh650:
Size of Target: Depends on whether it is displayed on an old analogue screen (circular, with rotating sweep, primary radar only, like the now obsolete Marconi 264S) - in this case the radar blip will vary in size, being larger at the edge of the screen and getting smaller as it approaches the center. Most radars in use today have digital screens where the targets are synthetically generated and displayed on the screen. They all thus appear at the same size on the screen - though there are normally a range of sizes that the controller can set (for ease of reading the target labels). The so-called 'blips' on modern radar screens are processed into different shapes according to how the radar information was obtained: from primary radar only, from secondary radar only, or from both primary and secondary radars. The controller can thus readily determine from where an aircraft's radar return came.

The controllers job is to see that they do not let their 'controlled' targets get closer than the minimum separation (either lateral or vertical) distances. The targets can pass over each other if vertical separation exists.

[peuce]

Some more questions for those using this procedure:


Is using "target resolution" an approved procedure?
Between which category of aircraft can you use it?
When can you use it? That is, when do you go down from the normal 3nm separation to target resolution?


Thanks

[alwaysdirect]

As a Scandinavian controller, trained in England,
I would say target separation is:
"Two controlled primary targets, who met the defined separation minima, and deconflicted"(Or its some RAF separation minima standard)

I would guess you´re flying VFR G space, and would never encountered this rule.

[Spitoon]

I guess this discussion really only applies if you're using primary radar displayed in fairly 'raw' form. As BaldEd points out, often these days the radar data is heavily processed and aircraft are represented by regular sized position symbols. The relationship between the location of the position symbol, the raw target and the actual aircraft has plenty of approximations already - I certainly wouldn't want to put primary position symbols closer than the required separation.