Wake Turbulence reports to ATC for different weather conditions

[Julian Hensey]

Yes, another question....

I am interested for the guys at the major airports queuing traffic with the standard separation how many reports they get of wake turbulence from the aircraft in front?

I would be also very interested if they find the number of wake turbulence reports from pilots goes up or down in different weather conditions? I think, if I am right, that still weather with no winds, encourages wake turbulence, and windy weather can lower the risk of it? Is this true from practical reports by pilots?

J

[HEATHROW DIRECTOR]

I'll be interested to hear from my ex-colleagues about the current situation. Certainly when I was working Vortex wake reports were fairly unusual given the amount of traffic involved. Guess you are aware that ATC separations take account of Vortex wake?

[Julian Hensey]

Yes I realise the whole idea of the distance between aircraft is to stop wake turbulence reports, but I have heard reports before, and I am wondering whether they are particularly prevalent during certain weather conditions.

[the dean]

having trained for many years at a major airport...and behind everything you care to mention...i can tell you in brief you are partly right...in that in still air it is very likely that wake will hang about longer and more importantly possibly remain in the vicinity of the runway rather than break up and move away...

but remember it also depends on the type of aircraft causing the wake...how heavy they are...and perhaps more important what type...

some types have the reputation of leaving more dangerous wakes than others for lighter traffic..

so if you had a succession of say 757s which have that reputation..then it could be that ( conditions apart ) the air may be more disturbed that arriving after a succession of 737s....

and of course if one arrives in something light not knowing how many or what has arrived ahead then one may not suspect..

the time lapse between arrivals of course has a lot to do with it..

arriving in something light it is always best to assume the worst and plan to stay higher than the glide slope all the way down...in that way any wake will always be below.

departing is a little different...since one has been at the field one will have seen the departing traffic ahead and can make plans accordingly...

hope thats of some help..

the dean.

[Tarq57]

My aerodrome is hardly major, and we generally don't hear wake turbulence reports...we see 'em. (Tower controller.)
Quite common to see a distinctive roll, usually only about 10 degrees, characterized by its abruptness. Usually, as stated above, in light or no wind, or especially a very light crosswind. Worst for landings: about a 10kt tailwind down to (almost) touchdown. Hard to stay above it. Seen one light aircraft crash landing close behind an Argosy that rotated early on takeoff. Know of two other major crashes, lighties behind mediums on takeoff. Aircraft munted, nobody killed. Lucky.
This was before the current vortex separations were introduced/or the pilots asked for a waiver.
Heaviest a/c that routinely operates here is a 757. Occasional 767, very occasional 74 or 77. (Diverts, usually.)
It's often fairly windy here, so isn't too much of a problem. The separations are provided, regardless.

[the dean]

in fact markjoy reminds me...it was the 767 not the 757 that we regarded as needing more respect for wake avoidance....

correction...

the dean.

[kphx]

Take a look in Flight International (1-7 May) Page 26 - good article: Wake Vortices - Closing the Gap. Food for thought.:)

[Julian Hensey]

Report is here.

http://www.flightglobal.com/articles/2007/05/01/213562/wake-up-call.html

And a report about the future of A380 separation....

http://www.flightglobal.com/articles/2007/05/01/213561/further-reduction-in-a380-separation-likely-by-year-end.html

[tomcrespel]

Vortex Wake is more of a problem on still days you are correct but caution must always be applied in all vortex situations. vortex wake starts as soon as the nosewheel of any aircraft leaves the ground to the minute it touches the ground now discretion can be used sensibly to get around the vortex wake delay before the second aircraft is released if you are using runway 27 and you have a strong cross wind 360degrees then the vortex wake will be dissipated therefore reducing the amount of time needed before releasing the following aircraft. There are laid down times example a light behind a small requires two mins vortex wake before launching it provided its departing from the same point on the runway!!! if its an intersection departure after a full length departure 3 mins must be applied!!! touch and go is classed as an intersection departure! i work as an ATCO at a busy airfield and apply vortex wake separation to the book even if it is busy because if something happens and they find in a subsequent enquiry i let it go to early guess who is out of a job!!!! i hope this helps

[tomcrespel]

new A380 is in a class of its own as far as vortex wake and will be a Super Heavy.
all separation for arriving traffic has vortex wake taken into account and if the following aircraft is above and behind the leading aircraft then vortex wake should not affect it vortex wake is a twisted pair of cylindrical air masses that flow downwards and out

[canuck slf]

Are there any new opinions/experience on the A380 vortex seperation now that it has been in service for a few months?
Also, having watched video of a landing and seeing the vortices from the engine nacelles I am interested as to whether the turbulence problem is generated from the wings or the nacelles?

[duknweev]

Still required to give 6/8/10NM sep behind a380/super. No reports of turb yet here at yssy.

Only pilot reports I've had are all >10NM behind heavies in clam conditions below 5000. Earlier this year a DHC8-400 reported severe wake turb crossing 15NM behind 747 on descent ~FL150 quote "headsets thrown off and coffee all over cabin". eeek!