Vortex issues

[throw a dyce]

I'm interested in people's opinion on this.As a Radar controller would you provide minimum vortex spacing to inbounds to the threshold of the runway,or until 4 miles when you can't apply speed control anymore?
Also what would be the minimum vortex for a small departing from an intersection,followed by a light from the full length,in minutes.UK only.

[radar707]

I apply vortex to 4 miles as I believe is the norm for most units.2 minutes for a light behind a small

[Defruiter]

We only apply to 4nm, as specified in our Part 2

[mr.777]

Until 4 DME...if the gap is closing considerably, tower can apply a further speed reduction. One of the main reasons 160 to 4 is so important...(I'll quit now while I'm ahead).

[loubylou]

At my current unit it is provided to 4DME, the thinking being that the second aircraft will also slow down in a similar manner.
But I add a bit extra if I think it may warrant it ( nothing in this manual blah blah!)
But at my previous unit, vortex was provided to touchdown, but after this was raised, then after a ring around of all the units, it was discovered that the majority of units all did vortex sep to 4D.
Dep - I would give 2 mins separation - 3 if it was the other way around.

louby

[Jerricho]

Certainly a UK thing. Here in Canada, it's to the threshold (and different spacing required)

[Spitoon]

I'd apply it to the threshold - if we do vortex spacing because it keeps the aircraft safe, what is different inside 4 miles. Arguably, because the aircraft are closer to the ground and in landng configuration they are less able to manage an upset in this situation.

Assumptions that the following aircraft will also slow down is not really applying the spacing.

I'd like to see the safety case for not applying wake vortex spacing inside 4 miles. Anybody care to share.....?

[2.5 miles]

"Assumptions that the following aircraft will also slow down is not really applying the spacing."

We apply spacing and speed control to 4nm. Unfortunately, whilst we may apply them, speeds or clearance limit (4nm) are not always adhered to. When we apply the speed we are assuming that it will be flown, mandatory compliance with an instruction. Different types will slow at different rates and generally larger aircraft are slower to slow due to momentum, as are slippery A319's. 757's slow a lot inside 4 DME, Virgin 346's don't! Personally, I try to take all of the characteristics into account when applying the "correct" spacing. In the main speed compliance is good and most crews are aware enough to tell us early if their speeds are going to differ greatly from what we would expect.
The other point here is that these are "recommended spacings" in the UK not separation standards (check MATS part 1 definition and phraseology). Light blue touch paper...............

2.5

[ADIS5000]

TAD,

Reference Vortex Spacing Requirements; MATS 1 states (Sect 1 Chap 3) "...the spacing listed below is to be applied between aircraft on final approach."

It also defines Final Approach - Instrument (Glossary page 4) as (paraphrasing) ...From the time that the aircraft has crossed the final approach fix .... until either it has landed or can continue the approach visually or goes around.

Therefore, I believe that vortex spacing applies until the threshold. Especially as we know that the most intense vortices are generated when the wing of the aircraft is working at its hardest ie: at low speeds and high AoA.

I also think that morally the mighty 'duty of care' would tend to imply that after 4DME you wouldn't effectively say "that's it fellas all vortex spacing bets are off!" Otherwise, using my interpretations above, at EGPD you would only be applying vortex spacing from the ADN until 4DME ie: A total distance of 3nm!!

Edited slightly 'cos I don't think 2.5s post is strictly correct!!

Regards, ADIS

[airac]

2.5 miles BANG:ok:

9.3.1 Where flights are operating visually (IFR flights operating under the reduced minima in the vicinity of aerodromes, VFR flights, or a mixture of the two), pilots are to be informed of the recommended spacing.
9.3.2 For other flights the spacing listed below is to be applied between successive aircraft
on final approach.

'shall', 'is to', 'are to' and 'must'
mean that the instruction is mandatory.

[2.5 miles]

Airac,
A suggested in my original post, I apply and adhere to the recommended spacings. However, please read on;

9.3.1 Where flights are operating visually (IFR flights operating under the reduced minima in the vicinity of aerodromes, VFR flights, or a mixture of the two), pilots are to be informed of the recommended spacing.

The table at 9.3.2 also states that spacing between successive medium aircraft is 3nm. Why then are Heathrow and Gatwick permitted to reduce this to 2.5 miles?

Attachment to Appendix E Phraseology: "Caution vortex wake. The recommended spacing is (distance) miles."

I accept that this is specific to the scenarios listed as per 9.3.1 and specifically for aircraft joining visually. Heathrow Tower have similar phraseology (where are you Gonzo), which warns pilots where recommended spacing has been eroded by greater than 1/2 mile, incorporated in their Part 2 I believe!

2.5

[airac]

incorporated in their Part 2 I believe!

Then there is your answer.:ok:

I believe the boys in blue can disregard vortex spacing if the cross wind component is greater than a specific amount .
Doesn't answer the question I know, but interesting and Logical
But when has logic ever prevailed:ugh:

[throw a dyce]

I used to think it was to 4DME as well.However the latest thinking here on helis(small) against fixed wing (small or light) seems to apply to the threshold,and beyond.We already factor in a catch up on radar for fixed wing following helis.However you still can't be certain that vortex can be achieved to half way down the runway,if the first one slows to 60kts inside 4DME and has vanished from radar.They can sit hovering on the runway while the gap is just reducing rapidly.Just have to make a belt and braces much much bigger gap.
Also the departure profiles of the small heli intersection departure,followed by a light fixed wing full length,means that the light is rotating just were the heli has lifted.There is not much in Mats part1 to cover this,but I would go for 3 mins rather than 2mins.That should slow things up a bit as well.
I also think that some to these helis,S92 and EC225 in particular should be in the medium category.They generate a hell of a draught just sitting on the ground.

Incorporate into Mats 2 as suggested.:uhoh: