Wake Vortex Separation Query

[No_Speed_Restriction]

This has probably been answered to death so apologies in advance to the thread police.

If a medium aircraft lines up on a runway from the start end (runway length apx 3000m) and a heavy lines up ahead and takes off from an intersection (lets say a quarter/fifth of the way down), how much timing would you apply?Also, would you start your stopwatch the second the heavy aircraft starts its takeoff roll or would you start timing at that aircraft's rotation?

[Gonzo]

In the UK,

We would apply the same as if they both departed from the threshold. We would only increase the separation if the second, lighter a/c departed from the intersection and the first, heavier a/c departed from the full length.

We apply separation rotation to rotation.

[No_Speed_Restriction]

Cheers for that Gonzo!

[dixi188]

On the subject of wake turbulence, why do some airports say "caution" even when there's 20 knots of crosswind blowing?
It it an "elf'n'safety" thing? i.e. ass covering.
Just wondering.

[Gonzo]

We are not permitted to reduce wake turbulence separations (distance for inbounds, time for outbounds) for any reason, although reducing inbound spacing in periods of high crosswind/headwind is being worked on.

So, whenever the separation degrades to less than the minimum, we have to warn the a/c involved.