Do you apply wake turbulence separation when a VFR arrival is followed by IFR arrival

[ramzez]

Hi all,

At your aerodrome do you apply wake turbulence separation minima between an arriving heavier category VFR aircraft followed by a lighter category IFR aircraft?

Example situations could be:
1) a Medium category aircraft is flying VFR in traffic circuit and a Light category IFR aircraft is making an instrument approach.
2) a Medium category aircraft VFR crosses final in front of a Light category IFR aircraft making an instrument approach.

[B2N2]

One issue with your question, the IFR aircraft is in VMC conditions hence responsible for their own ‘see and avoid’.
Now they will get a caution from either the Approach or Tower controller.
Something to the extent of:
” Three miles in trail of a C130, caution wake turbulence cleared for the ILS approach runway 33R”

[Gonzo]

VFR heavy/medium followed by IFR medium/light, on an instrument approach (I.e. not a visual)?

Yes, wake turbulence separation must be applied in this situation, rare as it is.

[Equivocal]

One issue with your question, the IFR aircraft is in VMC conditions hence responsible for their own ‘see and avoid’.
Now they will get a caution from either the Approach or Tower controller.What is more important for which ATC procedures are are applied is the flight rules and clearances issued to the aircraft. Under the generally applied (ICAO-based) procedures, an IFR flight that happens to be in VMC will still be an IFR flight (albeit it could be making a visual approach). And if it has been cleared for a visual approach and has reported the preceding aircraft in sight and been instructed to follow and maintain own separation from that aircraft, then wake turbulence separation will not be applied by ATC and a caution will be issued. I don't know if this is what the US procedures require.

[mike current]

One issue with your question, the IFR aircraft is in VMC conditions hence responsible for their own ‘see and avoid’.
Now they will get a caution from either the Approach or Tower controller.
Something to the extent of:
” Three miles in trail of a C130, caution wake turbulence cleared for the ILS approach runway 33R”

Only if they are making a visual approach. If they make an instrument approach they will be vectored by Approach so that the minimum wake turbulence distance is achieved.

[ramzez]

Thanks for the replies. I specifically mean a complete instrument approach, not a visual approach.

VFR heavy/medium followed by IFR medium/light, on an instrument approach (I.e. not a visual)?

Yes, wake turbulence separation must be applied in this situation, rare as it is.



What kind of procedures do you have in place to accomplish this?

I understand that it is easy when TWR has coordinated with APP that a medium VFR will make an approach. Then APP can vector and speed control the light IFR so that there is distance-based wake turbulence separation between the medium VFR and the light IFR.

Can it be done the other way around so that TWR makes the decision? Say that you have transferred the light IFR on a long final to TWR, can TWR assess the situation and put the medium VFR in front?

[10 DME ARC]

You have to provide vortex! I used to be a Manager of airspace where one airport had this happen almost daily, mostly VFR Heavy or VFR Super(A380's) circuits and lesser grouped arriving IFR's and got involved with many a 'problem' between tower and approach! Basically lots of coordination between TWR & APP and probably bigger gaps than sequencing successive IFR's as training airliners tend to slow more than norm, empty and training, this with the 380 could be interesting as anyone who works them regular knows they're mighty slow inside 4nm anyway!
Yes if you can heavier VFR aircraft put behind IFR arrival works if you have a gap!

[mike current]

Thanks for the replies. I specifically mean a complete instrument approach, not a visual approach.





What kind of procedures do you have in place to accomplish this?

I understand that it is easy when TWR has coordinated with APP that a medium VFR will make an approach. Then APP can vector and speed control the light IFR so that there is distance-based wake turbulence separation between the medium VFR and the light IFR.

Can it be done the other way around so that TWR makes the decision? Say that you have transferred the light IFR on a long final to TWR, can TWR assess the situation and put the medium VFR in front?

Yes. If the Tower controller has an ATM (radar screen in the tower) they can judge and measure the distance that way.

If it's visual control only I have no idea, but my guess would be time based with a degree of extra spacing to allow for errors.

Either way, if you have an A380 doing visual circuits I don't think it's a situation that came out of nowhere, so it's probably thoroughly planned and coordinated!

This situation is fairly normal at military airfields and places like Aberdeen (UK) where you can have large VFR helicopters ahead of light IFR aircraft. (Or C130s, C17s etc doing circuits)
Ultimately you can't fully control VFR aircraft, it's down to judgement and you either apply extra distance on the side of caution, or you get it bang on cause you're good/lucky, or you end up too tight and have to send the IFR around.

[10 DME ARC]

Either way, if you have an A380 doing visual circuits I don't think it's a situation that came out of nowhere, so it's probably thoroughly planned and coordinated!

Ha! You ever worked in the Middle East?

[parishiltons]

Hi all,

At your aerodrome do you apply wake turbulence separation minima between an arriving heavier category VFR aircraft followed by a lighter category IFR aircraft?

Example situations could be:
1) a Medium category aircraft is flying VFR in traffic circuit and a Light category IFR aircraft is making an instrument approach.
2) a Medium category aircraft VFR crosses final in front of a Light category IFR aircraft making an instrument approach.
It's done by the book (MATS), not according to individual whim or with different rules at any given aerodrome. See Section 10.6 at https://www.airservicesaustralia.com/mats/docs/nos-saf-2000.pdf

[Tarq57]

This happens reasonably often at my aerodrome.
The only wake turbulence tower is allowed to apply is time-based. Where a lighter aircraft is shortly to make an instrument approach, and we have a heavier VFR ahead, we ask the approach controller to provide the appropriate spacing (provided that's straightforward). If it's very straightforward ie: the lighter aircraft is well over two minutes flying time from the track of the heavier VFR, we can confidently apply the time spacing.
It's very unusual that it can't be catered for by an appropriate method, but should that happen, the VFR aircraft would be instructed to hold clear of the approach, then visually follow the lighter IFR aircraft.

[parishiltons]

This happens reasonably often at my aerodrome.
The only wake turbulence tower is allowed to apply is time-based. Where a lighter aircraft is shortly to make an instrument approach, and we have a heavier VFR ahead, we ask the approach controller to provide the appropriate spacing (provided that's straightforward). If it's very straightforward ie: the lighter aircraft is well over two minutes flying time from the track of the heavier VFR, we can confidently apply the time spacing.
It's very unusual that it can't be catered for by an appropriate method, but should that happen, the VFR aircraft would be instructed to hold clear of the approach, then visually follow the lighter IFR aircraft.
Wouldn't APP be sequencing the consecutive arrivals anyway? Or are you referring to a VFR in the circuit, rather than an arriving flight? Why can't you use surveillance gear to establish and monitor a distance WT standard? Or don't you have surveillance in your tower? Also why would you delay the leading VFR aircraft just because the other one is IFR - is there something in NZ AIP that gives it priority?

[Tarq57]

Wouldn't APP be sequencing the consecutive arrivals anyway? Or are you referring to a VFR in the circuit, rather than an arriving flight? Why can't you use surveillance gear to establish and monitor a distance WT standard? Or don't you have surveillance in your tower? Also why would you delay the leading VFR aircraft just because the other one is IFR - is there something in NZ AIP that gives it priority?
In NZ, Tower has been delegated the resposibility for sequencing VFR arrivals and departures, as well as circuit traffic.
We are not permitted to use a radar-based wake turbulence standard; the only method permitted for tower controllers is time-based.
Where it's a problem, and time permitting, I'll ask the approach unit to provide WT separation - in effect, it amounts to myself using the 6nm standard clearly observable on radar, but the approach unit owning the responsibility for same. Heavens knows why this archaic procedure is in effect, but it is. There are other situations where a radar-based distance is permanently delegated to tower for effecting separations between arrivals/departures, and successive arrivals, I don't know why stretching that delegation to WT spacing is so dangerous.

Priorities are a different ball game. RPT flights capable of a particular performance are normally accorded priority. If the arriving VFR is one of those (rare) it takes its turn in the landing sequence, same as everyone else. Should that landing sequence have one or more light IFRs in it, we'd normally ask the approach unit to provide a WT-sized gap for the M or H arrival.

[parishiltons]

In NZ, Tower has been delegated the resposibility for sequencing VFR arrivals and departures, as well as circuit traffic.
We are not permitted to use a radar-based wake turbulence standard; the only method permitted for tower controllers is time-based.
Where it's a problem, and time permitting, I'll ask the approach unit to provide WT separation - in effect, it amounts to myself using the 6nm standard clearly observable on radar, but the approach unit owning the responsibility for same. Heavens knows why this archaic procedure is in effect, but it is. There are other situations where a radar-based distance is permanently delegated to tower for effecting separations between arrivals/departures, and successive arrivals, I don't know why stretching that delegation to WT spacing is so dangerous.

Priorities are a different ball game. RPT flights capable of a particular performance are normally accorded priority. If the arriving VFR is one of those (rare) it takes its turn in the landing sequence, same as everyone else. Should that landing sequence have one or more light IFRs in it, we'd normally ask the approach unit to provide a WT-sized gap for the M or H arrival.
Thanks Tarq