Question about how to make minimum separation
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aucatc,
most of Europe uses the 4DME principle. Many times there's a NAV AID (a marker) just there... And as others stated, 160kts is also a widely recognized speed control down to 4DME, when traffic hits your face...
More or less the 4DME speed control comes from the ICAO rule - no speed control after passing 4DME from the threshold.
(let's forget about wake turb. separation and meteo conditions for a while)
Now, if you need 3NM separation all the way to the threshold, you should try with a "buffer" as mentioned. Maybe 4, 4.5NM and locked on 160kts 'till 4DME?
Different type of aircraft can also be funny... A good turboprop with it's 200+ until 4DME can "run away" or "close up" if you really need. But should be done with pilots concurrence and not by default. A320 family with CONF0,1,2,3,4 is also known to be able to reduce significantly on final approach phase. Not very professional to force them anyway...
Spitoon as well wrote about the "reduced visual" after 4DME. Depends on your rules of course.
most of Europe uses the 4DME principle. Many times there's a NAV AID (a marker) just there... And as others stated, 160kts is also a widely recognized speed control down to 4DME, when traffic hits your face...
More or less the 4DME speed control comes from the ICAO rule - no speed control after passing 4DME from the threshold.
(let's forget about wake turb. separation and meteo conditions for a while)
Now, if you need 3NM separation all the way to the threshold, you should try with a "buffer" as mentioned. Maybe 4, 4.5NM and locked on 160kts 'till 4DME?
Different type of aircraft can also be funny... A good turboprop with it's 200+ until 4DME can "run away" or "close up" if you really need. But should be done with pilots concurrence and not by default. A320 family with CONF0,1,2,3,4 is also known to be able to reduce significantly on final approach phase. Not very professional to force them anyway...
Spitoon as well wrote about the "reduced visual" after 4DME. Depends on your rules of course.
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kiwikid...as a quick note, I have looked at Dubai for several entities, mostly for the parallel ops, but in general, isnt overspeed/overrun a significant issue?
upperATC,
What is interesting is that while ICAO doesnt require speed control inside 4DME, it does still require min sep to threshold..something that appears to be missed.
upperATC,
What is interesting is that while ICAO doesnt require speed control inside 4DME, it does still require min sep to threshold..something that appears to be missed.
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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.
Ultimately any aircraft can do any speed it wants and ATC will compensate, there's a bit more to it than just quoting facts and figures from a text book.
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FlightPathOBN
was there anything like "separation not important" after 4DME in my post?
Quite the opposite, methinks; buffer + speed control = required minimum until touchdown (hopefully)... If not, an SMS to the tower, with a "go around" text, possibly with a pukey smiley face at the end...
But I see, you, again, are running an inquisition against LHR special procedures... Well, Good luck.
was there anything like "separation not important" after 4DME in my post?
Quite the opposite, methinks; buffer + speed control = required minimum until touchdown (hopefully)... If not, an SMS to the tower, with a "go around" text, possibly with a pukey smiley face at the end...
But I see, you, again, are running an inquisition against LHR special procedures... Well, Good luck.
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NY Tracon - EWR area controller here. We have a waiver that allows us to run 2.5 miles on final inside 10nm for like types that don't involve wake turbulence separation. on a nice VFR day if we run visuals, its not uncommon to allow them to get as close as 2 miles as long as they're able to get off the first high speed taxi exit. On perfect conditions like that, we run 38 to 41 rate depending of course, of the number of inbound heavies and 75's.
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Originally Posted by FlightPathOBN
What is interesting is that while ICAO doesnt require speed control inside 4DME, it does still require min sep to threshold..something that appears to be missed.
It is correct that separation must be maintained to the threshold, one could go further and include the aircraft when they're on the runway too. Maybe it is better to simply accept that separation between aircraft that are required to be separated has to be maintained at all times. That's one of the main reasons that ATC is there. In practice, when minimum separation and speed control is being used to separate aircraft until 4 NM from the threshold, the only way to maintain separation after the 4NM point is to use 'reduced separation in the vicinity of the aerodrome' - in most cases this will be achieved by the controller watching the aircraft (no doubt the pilot of the following aircraft will be watching closely too, but it is the controller watching that is providing the separation).
What is interesting is that the NATS slide that is reproduced clearly states that up to 1/2 mile of the minimum wake turbulence separation can be lost before ATC will tell the pilot. I don't know what the ATC book of rules says the controller might/must also do but it seems to me that this needs more consideration.
PANS-ATM (para 5.8.1.1) says 'The ATC unit concerned shall not be required to apply wake turbulence separation:
a) for arriving VFR flights landing on the same runway as a preceding landing HEAVY or MEDIUM aircraft; and
b) between arriving IFR flights executing visual approach when the aircraft has reported the preceding aircraft in sight and has been instructed to follow and maintain own separation from that aircraft'.
And later (para 8.7.3.2) says 'The radar separation minimum in 8.7.3.1 may, if so prescribed by the appropriate ATS authority, be reduced, but not below:
.
.
v) distance-based wake turbulence separation minima in 8.7.3.4, or as may be prescribed by the appropriate ATS authority (e.g. for specific aircraft types), do not apply.
So, for the procedures shown on the NATS slide to be consistent with PANS-ATM, (all?) aircraft must be making visual approaches and the pilot of the following aircraft the aircraft must have reported the preceding aircraft in sight and been instructed to follow and maintain own separation from that aircraft'. Does this happen.....
In the more likely situation, where ATC is providing separation, the book clearly says that reduction in separation cannot be applied where wake turbulence separation is prescribed. So it seems that NATS/UK are not applying this part of PANS-ATM. I don't have the books to hand to check but I guess there must be a difference filed on this particular topic. Although I don't recall having procedures to do this when I last did aerodrome control in the UK.....
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We normally assign speeds to maintain to FAF, or 5DME. I find it interesting to see my European colleagues use 4DME. What is your typical transfer of control point from approach to tower? 4DME?
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I am really appreciate for all your replies, I was just try to get some skills or experiences from seniors controllers about how to handle good separations on final.
I do learn a lot here, and I will try more in the real work, but of course will not lose minimum separation.
I do learn a lot here, and I will try more in the real work, but of course will not lose minimum separation.
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N90-EWR, yes at Heathrow we have formally stated that transfer of control from Approach to Tower takes place at 4 DME. If separation begins to reduce after 4 DME the Tower is able to apply "reduced separation in the vicinity of an aerodrome". Outside 4 DME Approach is responsible for separation. Transfer of communication takes place when the aircraft reports established on the ILS, MLS or RNAV.
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Just out of interest, is the MLS used often?
On a serious note, I believe it was the case that it was only the BA Airbus fleet that used the MLS. That may have changed however.
Last edited by Glamdring; 29th Mar 2013 at 18:53.
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N90-EWR, yes at Heathrow we have formally stated that transfer of control from Approach to Tower takes place at 4 DME. If separation begins to reduce after 4 DME the Tower is able to apply "reduced separation in the vicinity of an aerodrome".
In making the assumption that between like aircraft, there is no sep requirement, you appear to assume that aircraft do not make a wake, therefore there is NO sep required between like aircraft, ie a 737-800 hitting the wake from a 737-400 has no effect at 300 feet above threshold.
That is the point of the illustration....
Last edited by FlightPathOBN; 29th Mar 2013 at 22:14.
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We have a letter of agreement with EWR tower that sets the transfer of control point at 8 DME. This is because it is not unusual to have traffic landing on rwy 04R/22L, while at the same time some traffic (usually regionals) landing on rwy 11/29, and departing rwy 04L/22R simultaneously. Even though we still assign speeds to the FAF, the tower local controller will sometimes adjust the speed if there is any potential conflicts involving a no LAHSO aircraft. They do notify us if they have to slow an aircraft before the FAF, so that we can adjust with the traffic behind as well.
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speed reduction
"Even though we still assign speeds to the FAF, the tower local controller will sometimes adjust the speed"
Could you elaborate on this, please. By what means does TWR manipulate with a/c speed? Isn't it too late for that, as we've read in previous posts? I presume that radar display is required for that.
Could you elaborate on this, please. By what means does TWR manipulate with a/c speed? Isn't it too late for that, as we've read in previous posts? I presume that radar display is required for that.
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EWR tower has a BRITE radar display. Since we're switching aircraft around 8 DME they sometimes adjust speeds if needed to maintain spacing, specially if there is wake turbulence involved.
