Wake Turbulence Seperation and Opposite Runways

[Prop Job]

Good day,

I am hoping to get some advice regarding wake turbulence separation requirements.

We operate out of some airports that are quiet enough to accommodate operations from opposite runway ends. Lets assume the airport has a single runway - 18/36. If a Heavy lands on runway 36 and we depart off 18 in a Medium, what separation (if any) is required?

The only reference I could find was this:

A separation minimum of 2 minutes is required between a LIGHT or MEDIUM aircraft and a HEAVY aircraft and between a LIGHT aircraft and a MEDIUM aircraft when the heavier aircraft is making a low or missed approach and the lighter aircraft is:

• using an opposite-direction runway for take-off or
• landing on the same runway in the opposite direction or
• landing on a parallel opposite-direction runway separated by less than 760 m (2,500 ft).

Nowhere can I find a reference dealing with landings, only low of missed approaches.

Any help would be greatly appreciated. Thank you!

Prop Job

[missy]

Originally Posted by Prop Job

Good day,

I am hoping to get some advice regarding wake turbulence separation requirements.

We operate out of some airports that are quiet enough to accommodate operations from opposite runway ends. Lets assume the airport has a single runway - 18/36. If a Heavy lands on runway 36 and we depart off 18 in a Medium, what separation (if any) is required?

The only reference I could find was this:

A separation minimum of 2 minutes is required between a LIGHT or MEDIUM aircraft and a HEAVY aircraft and between a LIGHT aircraft and a MEDIUM aircraft when the heavier aircraft is making a low or missed approach and the lighter aircraft is:

• using an opposite-direction runway for take-off or
• landing on the same runway in the opposite direction or
• landing on a parallel opposite-direction runway separated by less than 760 m (2,500 ft).

Nowhere can I find a reference dealing with landings, only low of missed approaches.

Any help would be greatly appreciated. Thank you!

Prop Job

There's a couple things in play here.
1/. if the heavy is on profile then they should touch down at the landing threshold (and wake ceases at that point).
2/. A heavy is likely to take 60 seconds to vacate the runway (from threshold to the exit taxiway)
3/. Once you enter the runway then more than 60 seconds will have lapsed since the heavy crossed the threshold
4/. You will take 30-45 seconds to get airborne (once cleared for take-off)
5/. You'll become airborne well before the touchdown point of the heavy (and if you don't then you've probably more things to worry about than wake turbulence)
6/. You'll out climb the profile of the heavy (and if you don't then you've probably more things to worry about than wake turbulence).

[Flying184]

No defined procedures.(always takes a while to get your head around it!)

But common sense says if you believe the flight paths will cross then apply the appropriate wake turbulence separation timings.

With reference to your example, more caution would be needed if one runway had a displaced threshold etc.... there would be more chance of the flight paths crossing! Also aircraft types would be important.... yes a helicopter might get airborne before the point of touchdown of the heavy... but how can you ensure he will not fly through the approach profile (and hence wake!) of the heavy lander......

Again.... common sense needs to be applied. If in doubt - apply the separation.

[Pera]

ATC would probably apply a time standard but if it's uncontrolled then it's up to you. The second post makes sense but if you're unsure, wait a few minutes.

[Prop Job]

Thank you for the replies.

Am I correct in saying there also won't be a wake separation requirement if there are two departures from opposite runway ends? Reason being that we'll rotate past the point on the runway where they rotated.

Thanks!

Prop Job

[underfire]

Am I correct in saying there also won't be a wake separation requirement if there are two departures from opposite runway ends? Reason being that we'll rotate past the point on the runway where they rotated.

Well, the ac does not generate wake until after rotation, and out of ground effect. It would be unlikely that even if rotation points were before each other, that a wake would be encountered. I do not see any reference to this scenario as it is a bit unusual to have simultaneous DEP operations. Must play hell with the ILS for the arr.

In your other examples, are runways parallel of perpendicular to each other?

[Flying184]

Originally Posted by Prop Job

Thank you for the replies.

Am I correct in saying there also won't be a wake separation requirement if there are two departures from opposite runway ends? Reason being that we'll rotate past the point on the runway where they rotated.

Thanks!

Prop Job

No - you cannot *assume* this because what if a heavy (e.g. B773) is taking off on an empty repositioning flight, and an A321 is taking off on a max take-off weight from the opposite end.

As before - the question needs to be "will the *flight* paths cross - if so then wake separation timings must be applied.

Hope this helps!

[Prop Job]

Hi underfire,

Sorry for only replying now. The airport in question has parallel runways, but most of the night only one runway is used for departures and arrivals. There are times at night where the airport allows opposite direction departures on that one runway, traffic dependant of course.

Thanks again for everyone's input.