Question about how to make minimum separation

[caucatc]

I heard that in busy airports, controllers wish to make two aircraft approaching on same runway with minimum separation when preceding aircraft touchdown.
But I still could not find the right way to make sure two aircraft will not less than the minimum, because that is too close to minimum, for example, 3miles is minimum, but 2.9 is an incident. I know to tell pilots maintain certain speed to certain position, I always tell pilots to maintain 180Kts to 7 miles touchdown, but after 7 miles some pilots reduce speed slowly, some reduce speed to minimum very very fast, that is unable for me to predict.
Can somebody give me some advice about it?
Appreciate

[HEATHROW DIRECTOR]

Try using speed control to 4nm from touchdown. That may help. A great deal of experience is needed to achieve constant minimum separation.

[LoserGill]

As stated by Heathrow Director, experience is key.

Often times, on a particular runway, there may be a tailwind at 500 feet AGL with a headwind on the runway itself causing speed changes that you were not expecting unless you have seen them before (or someone tells you about it).

[caucatc]

Thank you guys, but if the minimum separation is 3NM, will you trying to make it as 3NM not 3.5NM or 4NM? Because 3NM change to 2.9NM is very soon.

[Glamdring]

As stated above experience is key.

If you use speed control to 4nm and have an appreciation of the Aircraft's final approach speed and the wind then it's just a matter of vectoring a little wide so that the catch up on final approach gets you your separation.

[Spitoon]

And remember that if wake turbulence separation is not an issue you can also use reduced separation in the vicinity of the aerodrome inside 4 NM if your rules and the weather are suitable.

[Blockla]

Try 160Kts to 4 miles, works for most types and operators.

180K to 7 miles may be too hot for many types/operators, which is why you get sudden reductions, they may be very keen to slow down ASAP.

[caucatc]

160 Kts to 4NM? Can pilots do that? I normally do not give speed restriction after 7NM to touchdown.

[Gulfstreamaviator]

YES we can

160 to 4nm is actually how most of our FMS or hand flyers are "designed" to operate.

I only fly corporate Gulfstream aircraft, and we operate with 160 to final flap selection, and 4 miles is above 1000ft (a typical stable or go missed height).

We also would be very happy with 180 to 7 or 8. Again that is how our systems are designed to work..... next flap setting point.

good luck

glf

[HEATHROW DIRECTOR]

<<160 Kts to 4NM? Can pilots do that?>>

They do it all day at many major airfields.

[Talkdownman]

Seems to me that BeiJing needs to send its ATCOs to nats CTC for an advanced APS course, just as ROMATSA has been doing for several years. They keep coming back for more and Bucharest ATC seems all the better for it.

[caucatc]

What we talk to are the pilots from all over the world with different operating skills, someone
can bu someone cannt I asked some pilots, most of them said it is a little bit difficult.

[HEATHROW DIRECTOR]

ATC at most major airports talk to pilots from all over the world, but it all works OK. Some aircraft types need slightly different speeds on final approach but as long as pilots tell ATC in advance it is very easy to fir them in to the landing stream. What sort of landing rate are you achieving?

[Talkdownman]

Have a look at this link to see what 160 kts to 4D achieves at Heathrow. Allow time to load then replay to your heart's content. At Heathrow it is very unusual for a crew to refuse 160 to 4. Most of them know that their IAS is being watched on enhanced Mode S too, so speed control compliance has improved significantly.

[caucatc]

rate of descent? around 700ft/m, descend via glide slope.
Mode S to monitor speed is a good method.
Where is the link?

[FlightPathOBN]

You should probably look at the CAAC standards. What NATS does is not the only standard. The FAA std is completely different. FAA req's min sep from threshold to 5nm, and with RECAT (Memphis so far) from threshold to 10nm.
Min radar sep is 3nm, and wake sep varies, and with RECAT, there is no visual sep allowed.

With regards to speeds, there is the CAT speed of the aircraft approach. CAT C is 140 kts for the final segment. You wont have aircraft like A380's at 160 kts on final either...

Not sure where you are located, but 160kts at Lhasa or Linzhi would be entertaining for everyone!

[Warped Factor]

You wont have aircraft like A380's at 160 kts on final either...

All the A380 operators at LHR do 160kts to 5dme on final.

[HEATHROW DIRECTOR]

I note that FPOBN is an engineer!!!!!!!

[FlightPathOBN]

Well, I dont find anywhere else in the world where sep or speed ends at 5DME! As noted, the FAA standard is to threshold. Losing min sep to threshold is an incident for a controller in the US.

With coded procedures, such as RNP and GBAS, the CAT speed is always for an entire leg, from wherever the FAF is coded in, sets the minima based on FAS +momentary descent as to not cross the MDA and to make the missed approach. So a CAT C approach is max 140 kts from FAF to threshold, that is both ICAO and FAA std.

The A380's are crossing threshold around 120kts.

[Kiwikid]

DXB regularly requires 180kts to 10nm final and 160kts to 4nm. We get plenty of A380's here and they don't often complain about those requirements. Sure they do slow down a lot from 4nm and some other types don't slow down much at all but you just learn to compensate for that.
I believe that LHR has the extra benefit of only having to apply sep til the first aircraft gets to 4nm which would make life easier though.