5NM Vs. 3NM seperation inside TMA

[Short Approach?]

In Copenhagen we have always had some additional rules which specified when 3NM seperation was sufficient.

We are renewing thoose rules now, and I'm interested in hearing from you:

* If you have such additional rules, and how they work.

* If you donīt have such rules, and can use 3NM inside the TMA no matter what.

Kind regards.

Feel free to use PM

[radar707]

If you do a search on Pprune you should find all the answers you need as this has been discussed before.

Where I work 3 miles is allowed if the aircraft are within 40 miles of the radar head and below FL245

[Over+Out]

I work LTCC.
We are allowed 3 miles between all aircraft controlled by Controllers operating in the same room, which is Approach (LL, KK, SS, KB, LC, GW), TMA and Area Control, providing we are within 80 miles of the radar head.

[Eva San]

I don't really the point of that thread.
I mean that your spacing and whatever restriction that goes with it is radar depending (hardware and software). It's a technical subject and I think one should trust radar specialists enough not to discuss their findings ... ?

[GroundBound]

I'm curious how the < 40 or 80 miles from the radar head is applied in today's multi- radar tracking sytems.
If the radar tracking is based on a mosiac, then I assume you can know, in a given display area, which radar (head) is being used for the radar display.
However, with true multi-radar tracking, where the displayed position is made from a composite a several radar returns, how can you know whether you are within 40/80 miles of any particular head?
As far as I remember, the idea of using 3nm separation at less than 40 miles from the radar head was applicable to (usually) primary (approach) radar, on the basis that the resolution from such a radar would ensure relative accuracy between nearby returns. It was not TMA related, apart from the fact that approach controllers often had a TMA around their airports.
GB

[BOBBLEHAT]

We use 3nm in the London TMA using a single source radar.

[discountinvestigator]

Originally Posted by Short Approach?

In Copenhagen we have always had some additional rules which specified when 3NM seperation was sufficient

* If you donīt have such rules, and can use 3NM inside the TMA no matter what.

The CPH TMA rules were relatively complex at one stage. However, the reduction from 5 to 3 nm was carried out for the final approach stage after some work I did there in the late 90s, from memory.

The rules relating to radar separation minima come from different sources. Of course, you also have to add in the wake vortex minima as well, and I seem to remember that you have a problem with 500 feet IFR/VFR separations, or at least did, as that did not give wake vortex separation as well.

The minimum radar separation depends on the accuracy of the radar, the latency of the radar data processing system and display system, the rotation rate of the radar, the use of multi-radar trackers or single radar display, the use of primary-only, secondary-only or combined plots, the use of normal data processing or fall back data processing system, the ability of the system to handle reversion to procedural control in the event of surveillance failures as well as some elements of radar location/flightpath location.

One of the reasons that final approach separations could be reduced was that the range accuracy was better than the angle accuracy and if the radar head was at the airport, then effectively you were range separation and not angle or angle/range separation.

There should be an engineering safety case for your whole surveillance system, and that should impose the engineering limits on your service. The operational limits may be slightly different and you have to take the worst of both worlds. The operational limits should be defined in your unit operational safety case. It is Danish legal expectation that all current operations have been the subject of risk assessment. Therefore, if you are not undertaking any major equipment changes, you should have historic documents demonstrating what you have is OK. The risk assessment and subsequent safety assurance documentation will give you good guides as to the risk optimisation/mitigation measures that were put into place and why.

PM if you need it.

[Spitoon]

This from Eurocontrol might give a few pointers. Section 4 is of particular interest - but it depends whether CPH is considered to be a "Major Terminal Area".