Wake turbulence separation in the cruise

[Jwscud]

I was wondering how you controllers separate the Heavies from the rest of us at altitude.

I recently had a rather unpleasant encounter in a 737 with what can only have been a heavy or super's wake in the climb around FL380 that involved some nasty roll excursions and some serious buffeting and wondered how this is dealt with. On this occasion the controller couldn't see an obvious offender on his scope so the wake is clearly seriously persistent.

Obviously separation in the climb is harder as you can't predict our rates as to where we might pass through the level of a cruising heavy or the propagation of the vortices but I would be interested in some controller input about how you handle it.

[Rossoneri]

From an en-route perspective, the simple answer is we don't use any form of wake vortex separation. It's 5 miles or 1000ft outside the TMA (with the odd 10nm exception at the edge of radar range). With a/c in trail most people tend not to go much tighter than 8nm with both on speeds. With climb-throughs on crossing tracks, you'll normally pass laterally by 7nm+ (adding a bit of room, just in case), and if you're close enough to the guy in front to be troubled by his wake, you'd probably be on a parallel heading to facilitate the climb just in case you started catching up.

If you encounter wake, we'll always offer you to offset from your track, or try a different level if you'll be following the cause of the turbulence for a while. It's not just the 'little' folk either, I remember a B744 encountering the wake of one of his colleagues ahead of him, also in a B744. (The fact he chose to ignore the speeds I'd imposed is a different story)....

[Jwscud]

Thanks - we weren't following anyone that I'm aware of. The nature of the encounter we had suggested it was closer to perpendicular.

We filed a report about it so hopefully we will hear something back when they play the tapes back to see where the nearest culprit could have been. It was in a particularly busy patch of NW European airspace so tracks of aircraft could have been anywhere rather than the well-defined airway corridors.

[Vortex Issues]

Have a look at the recently published AIC from the CAA. It should tell you everything you need.

http://www.ead.eurocontrol.int/eadbasic/pamslight-DFD849CEA44A3EB7644655947C11CCCD/7FE5QZZF3FXUS/EN/AIC/P/003-2014/EG_Circ_2014_P_003_en_2014-02-20.pdf

[Jwscud]

Thanks - the stuff about minimising the possibility of upset is particularly interesting.

I would NOT want to encounter a Super's wake on the limit of 5 miles though!

[Una Due Tfc]

If the limit is 5 miles then in very busy airspace you are going to be very close to that limit most of that time. I usually throw in an extra mile or 2 separation behind a super for the wife and kids, but I only see a handful of them a day. Over London I'm sure that's far harder to achieve