Minimum jet separation on final

[autoflight]

In the absense of departures and cross runway operation, what is the minimum distance or time between arriving medium jets? Is 4 nm enough? Should following aircraft make small speed adjustments based on TCAS to achieve optimum separations? Assume there is a high speed exit for around 40 kts or more, how far from the approach end should the exit begin?

What would be the procedure for A320 and B737 or heavier types? To be more sure of making the exit, would auto brake medium be selected for landing and then released ASAP for any required manual braking when nominated high speed exit is assured?

Departures would have to be considered at some stage. How would that work on a single runway or with 2 rwys at Brisbane? Without a parallel runway are we destined to have the same holding delays in a few years when traffic increases further?

With 3 runways in operation at Zaventem, X rwy long sequences of landings have been observed, all at 3.75 - 4 nm separation, but it was very very tight if preceeding aircraft made an exit at a slower than necessary speed. A go-around was inevitable if the landing aircraft missed the high speed.

Much experience with low separation will be on airfields with wide spaced parallel runways. Anyone have low separation experience on other busy sub-standard airfields like Brisbane?

[Ollie Onion]

Heathrow seperation between medium jets was 2.5nm. Quite impressive to watch really. You would be at 10nm final and have two in front with another just touching down. That was the true meaning of 'minimum runway occupancy'.

Worked a treat, I had only one go-around in 6 years due to the aircraft ahead not making its turnoff. Off course there was also strategic use of 'land after' clearances and 'expect late landing clearance' instructions.

On the 320 'minimum runway' occupancy meant MED autobrake and FULL reverse EVERY landing and you would often turn to see an aircraft in the flare as you cleared the runway. I guess that is what happens when the airport is at 100% capacity.

[4Greens]

There are variations due aircraft type.

[Keg]

Worked a treat, I had only one go-around in 6 years due to the aircraft ahead not making its turnoff.

Much better high speed turn offs at Heathrow. Better placed, don't have 120 degree turns immediately after exiting the runway, etc. EG, the high speed exits for SYD 34L are crap- way too far in although you do have the benefit of not having the hard turn back. The SYD 16R turn offs are too close on the domestic side and too far on the international side...... and both still have the hassle of having to hang a 120 degree turn not long after you're off the runway.

[HEATHROW DIRECTOR]

<<Should following aircraft make small speed adjustments based on TCAS to achieve optimum separations?>>

Definitely not. The controller is the only one who knows what spacing is required for many reasons so just follow his instructions. If you make your own adjustments by slowing down it might have serious effects on the one behind if the controller is providing wake turbulence separation. If you have a different final approach speed requirement from "usual" let ATC know in good time so they can accommodate you.

[Conductor]

Should following aircraft make small speed adjustments based on TCAS to achieve optimum separations?

Not even possible on the 767. The TCAS display is so small and so inaccurate when showing relative aircraft positions.

[Ultergra]

"On the 320 'minimum runway' occupancy meant MED autobrake and FULL reverse..."

Max reverse or idle reverse... Autobrake provides a decelleration RATE. If you use idle rev it will brake accordingly to achieve a rate and max reverse same.. Brakes will vary accordingly to achieve a decel rate...

Min runway occupancy is med autobrake.. Idle or max rev
You'll still pull up at the same decel rate...

The only think affected is brake temperature.

[lemel]

TCAS is not to be used to separate yourself from other aircraft as ATC would do in a radar environment.

It's a collision avoidance system, not a traffic separation system.

As with all controlled airspace (assuming your IFR), let ATC control your spacing and speed. That is why they have a job, otherwise the entire Australian FIR would be a CTAF.

[1Charlie]

The minimum spacing on final in a single runway mixed mode environment depend on aircraft type, weather (vis, base, headwind) and normal occupancy time for the arrivals and departures. You use Brisbane as an example. If you have 2 turboprops arriving and are to depart a turboprop in the gap, you're going to want a 4nm gap. If they're jets you'll need 5. And if they're heavies (apart fr the mighty 767) you want 6nm. In good weather the arrival rate will be about 24 per hr. One every 150 seconds. This equates to about 6nm gaps, and allows for one heavy, or perhaps two turboprops. In this configuration you have 24 arrivals and maybe 26 or 27 departures given a reasonable traffic mix for a total movement rate of 51 or 52 per hr.

[Oxidant]

Definitely not. The controller is the only one who knows what spacing is required for many reasons so just follow his instructions. If you make your own adjustments by slowing down it might have serious effects on the one behind if the controller is providing wake turbulence separation. If you have a different final approach speed requirement from "usual" let ATC know in good time so they can accommodate you.

Quite right H.D. Woe betide those who ignored the instructions of speed & heading & felt the wrath of the young lady at the other end of the radio :eek:

[Oxidant]

The minimum spacing on final in a single runway mixed mode environment depend on aircraft type, weather (vis, base, headwind) and normal occupancy time for the arrivals and departures. You use Brisbane as an example. If you have 2 turboprops arriving and are to depart a turboprop in the gap, you're going to want a 4nm gap. If they're jets you'll need 5. And if they're heavies (apart fr the mighty 767) you want 6nm. In good weather the arrival rate will be about 24 per hr. One every 150 seconds. This equates to about 6nm gaps, and allows for one heavy, or perhaps two turboprops. In this configuration you have 24 arrivals and maybe 26 or 27 departures given a reasonable traffic mix for a total movement rate of 51 or 52 per hr.

Never been to EGKK then, have you........

[1Charlie]

Final spacing at Gatwick during normal operations is 6nm (1 in 1 out). It's even published in their unit instructions

[autoflight]

I am very impressed with the responses. Thank-you.

[adc123]

Some aerodromes is Australia operate on 4nm arrival spacing

[HEATHROW DIRECTOR]

<<Final spacing at Gatwick during normal operations is 6nm (1 in 1 out). It's even published in their unit instructions>>

Do you have any first hand experience of Gatwick 1Charlie? Yes, 6nm is employed but ATC will adjust that spacing as necessary top provide the best utilisation. If it's quiet with departures (rare, I know) they may pack a few with 3nm spacing.

[FlightPathOBN]

autoflight,

Each airport/runway has its own characteristics and aircraft types. Brisbane is currently single runway, but a parallel is getting there. That new runway will support simultaneous ARR and DEP operations.

Brisbane has quite a bit of heavy traffic. This makes it a bit more of a challenge for closer spacing options. The high speed exits currently in place (DC-9 era) offer little relief.

Environmentally, getting a new track approved is a very big challenge.

One scenario that may help at Brisbane is a batched diverse DEP. The DEP procedure can really only be optimized over the bay, so it would be weather dependent, but going to 400/500 feet and turning left and right, combined with a batched departure, would add a few more slots...IF environment would approve.

[1Charlie]

I'm aware Gatwick TCU is able to adjust the spacing on final to suit how many departures there are. A flexibility not enjoyed by most Australian airports as the sequence was locked in 200nm away. This standard terminal arrival setup where delay is absorbed en route was at industry request and is becoming more common. The question was how big should the arrival spacing be if there are departures in between. Do you not agree with the numbers?

[FlightPathOBN]

One would batch arrivals, just as you batch departures. In the morning at YBBN, if you batch DEP, then in 10 mins, you could have 10 DEP with div departure, in another 10 min, 8 ARR. If you blend DEP/ARR with the heavies, the spacing will get you far fewer movements.

This gives ac less time in terminal airspace (heavy fuel burn) and less taxi time for ac in DEP...

push 'em back, and let 'em go....

[autoflight]

FPOBN,

Do you actually need environmental approval? If you do, can you go ahead anyway and force them to challenge your operation? Of course previously the ducks would have needed to be lined up for max advantage.

[Sue Ridgepipe]

Definitely not. The controller is the only one who knows what spacing is required for many reasons so just follow his instructions. If you make your own adjustments by slowing down it might have serious effects on the one behind if the controller is providing wake turbulence separation.
The controller may know what spacing is required, but unfortunately they are not always capable of providing it. I've lost count now of the number of times I've been told to maintain 180kts on approach when it's quite obvious form the TCAS that we are at the minimum 5 mile separation from the preceeding heavy and he has already slowed down more than us. Of course as soon as we change to tower, the first thing they say is "caution wake turbulence" for being too close. So now I just slow down when I need to to maintain the required separation, if it messes up their flow well that's their fault for not separating us properly in the first place.

[C441]

Once followed an Jet Blue A-320 down final on 31R at JFK in a 744, gradually closing until when he touched down we were at 2nm ....maybe. We're thinking Canarsie go-round. The controller wasn't and told him "I need ya off as soon as ya can. I gotta seven-forty-seven up ya ass at 2 miles". The A-320 skipped off at "E", a near right angle taxiway, about 750m from the displaced threshold. Had he not made it at "E" we were off on another Long Island scenic! Thanks passed on for the nice work by them!! :D
...........probably don't need to do that all the time though.....

[FlightPathOBN]

af,

Do you actually need environmental approval?

Look how many RNP procedures there are for each airport that are permanently NOTAM'd out...

These have been approved in every respect, from design, ops and flight val, BUT...

[autoflight]

The environmental people seem to have a strangle hold on operational efficiency refinements. Maybe they have been allowed excessive veto powers that are overdue for a calculated challenge. If the problem is actually political, then so is the solution. . . . .

[FlightPathOBN]

Enviro is listening to all of the people who complain about noise....

[SHRAGS]

Witnessed at holding point recently. "So and so are you ready for immediate?" Affirm is response and cleared for immediate takeoff. Puts the power up and looks to be in position to do a nice rolling start and then proceeds to SQUARE OFF the line up taking at least 20 seconds. International told to go round. ATC says thanks for immediate takeoff and a happy "your welcome" was response. Not a clue. If we want better separation standards we all need to play the game.

[Capn Bloggs]

Witnessed at holding point recently. "So and so are you ready for immediate?" Affirm is response and cleared for immediate takeoff. Puts the power up and looks to be in position to do a nice rolling start and then proceeds to SQUARE OFF the line up taking at least 20 seconds. International told to go round. ATC says thanks for immediate takeoff and a happy "your welcome" was response. Not a clue. If we want better separation standards we all need to play the game.
They complied with AIP. If you want them to do something else better/faster, educate them, redo AIP so it's more obvious what is expected.
A clearance for immediate take--off may be issued to an aircraft before it enters the runway. On acceptance of such clearance the aircraft shall taxi out to the runway and take off in one continuous movement.

[adc123]

If thats the attitude capn bloggs, then atc should do away with immediate departures. They do it for your sake, not theirs. SHRAGS is spot on. Everyone needs to play the game.

[Capn Bloggs]

SHRAGS is spot on. Everyone needs to play the game.

OK, tell me exactly why you think that crew did a squared-up, slo-mo takeoff. Because they thought, FU, I can't be stuffed doing a whizzy or, I have to comply with my lineup allowance, but I can keep it rolling, as per AIP, so yes, I'm ready immediate...

I'll put it another way. Tell everybody what the "rules" are and then everybody will play the way you think they should. :cool:

[1Charlie]

What I find retarded is the fact distance remaining for departure is published for a square turn onto the runway when the line is curved. Why the hell isn't distance remaining calculated from where the lead in line meets the RWY centreline???? Luckily some pilots use discretion and follow the line on an immediate departure because it makes a big difference compared to the affectionally nicknamed 'woosy backtrack'.

[Capn Bloggs]

Luckily some pilots use discretion and follow the line on an immediate departure
The yellow line is for exiting the runway, not taking off. ;)

Why the hell isn't distance remaining calculated from where the lead in line meets the RWY centreline????
It probably is. Have a look at the typical lineup allowance and you'll understand why some crews don't just give it the gun along the yellow line to blast off.

As usual, front-liners are arguing, when it is the responsibility of the AsA bosses and company performance departments to get talking to give me the performance data I need to do "proper" rolling takeoffs. I can assure you that I am not going to expose myself by cutting the corner on lineup/roll just because somebody wants me to gun it, if my performance does not allow it.

[Showa Cho]

If you can't do a rolling departure without a mini-backtrack, when asked the 'ready immediate' question, say no. Quite easy really. If your performance data allows for it, say yes. Or run the figures for worst-case departure - rolling without backtrack with 5 knots up the clacker, and taxi for that intersection. Seen it done, helps everyone out.

[1Charlie]

Exactly.
Performance data needs to calculated based on distance remaining after a curved line up. Theres 2689m from A7, surely 50m can be spared. Everyone wins.

I know it seems trivial, but when the place is rockin you have only a few seconds between legal and go-'round.

[Capn Bloggs]

If you can't do a rolling departure without a mini-backtrack...
You guys are telling me nothing I don't already know and do. Tell your masters to tell those things to the operators ie companies. Education is the key, and not ACE rush thru your checks, slam on the brakes to get off the runway ASAP and so on... Real education breeds commonsense. Commonsense breeds an efficient but safe operation.

[neville_nobody]

If we want better separation standards we all need to play the game

Including CASA. The attitude has to change from what is legally correct to what is practical. Until that happens nothing will change. It will only take one FOI see you cut the corner lining up on a 4000m runway and your airline investigate you for the whole 'helping out' mentality to fail. Just have a read of the Pac Bro court case in Queenstown

If we built more runways in this country this would be a redundant topic.

[TIMA9X]

I know it seems trivial, but when the place is rockin you have only a few seconds between legal and go-'round. In this clip the thought did cross my mind when I decided to film it, although not shown, (I was a bit late) the MD11 took a little longer than usual to start to roll.. possible the 738 crew may have discussed a GA for a few seconds, anyway was an interesting moment.

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