I thought that ATC was under the obligation to apply turbulence category separation
I too thought that, until Athens who cleared me to take off “when ready”, immediately after a departing 737. I waited 2 minutes and did my best to get airborne early and stay upwind, but didn’t think afterwards waiting just 2 mins was a good idea. I wasn’t sure if the ATCO was smart or made a mistake, and that procedure would have caused an accident to somebody who didn’t know about vortices (many/most UK PPLs, probably).
And I was IFR.
ATC usually does do that. It can be a two sided sword however. Strict wake compliance has halved the slots at ZRH…
BTW, you don’t need a heavy iron for that. Recently in Germany it was found that an Antonov 2’s wake turbulence caused the crash of a light airplane.
I too thought that, until Athens who cleared me to take off “when ready”, immediately after a departing 737. I waited 2 minutes and did my best to get airborne early and stay upwind, but didn’t think afterwards waiting just 2 mins was a good idea. I wasn’t sure if the ATCO was smart or made a mistake, and that procedure would have caused an accident to somebody who didn’t know about vortices (many/most UK PPLs, probably).
I was under the impression that ATC were duty bound to advise wake separation requirements when applicable?
There are things you can do to minimize the effect of vortices. Keeping the velocity up is a good thing, too have as good aileron authority as possible. Accelerate while in ground effect and make a longer flare (in ground effect), instead of simply climbing (at low speed) once the wheels are off the ground and making a low speed final. Vortices dissipate fast when hitting the ground, but can stay around “forever” higher up.
I think the most important thing is to be prepared for them. If they get you off guard, they are deadly, but if you are prepared (and have enough velocity), you have your reaction and responses on alert, which makes all the difference.
Peter wrote:
I too thought that, until Athens who cleared me to take off “when ready”, immediately after a departing 737.
I had a similar experience last year at Karlsruhe. Cleared for take off behind an A320. ATC simply told me where on the runway it had rotated and left it to me. I waited a full three minutes. I don’t think it made me very popular with ATC, but they didn’t complain – just a deafening silence! What made me particularly nervous was that I was departing on a SID that required climbing on runway heading for several miles – no chance to deviate right or left. I took off without incident – looks like I was just lucky.
I think the most important thing is to be prepared for them. If they get you off guard, they are deadly, but if you are prepared (and have enough velocity), you have your reaction and responses on alert, which makes all the difference.
I think that’s great advice and is true for most things in flying. If you have speed then you have control, etc and if you are expecting trouble your reaction time is much better.
Same when flying approaches when turbulence is expected or known.
But it seems the wake from a 737 sized plane will flip a 1500kg GA plane upside down pretty well…
What surprises me is how localised the wake is. A few metres off and there is absolutely nothing. I have also got this flying near Gatwick, just below the base of CAS. Say at 2400ft, with the jets being as low as 3500ft. Their wake will be below CAS in about 2 minutes, and you get a really nasty bump.
Just advise ATC of your requirements if there is any doubt. Also remember there is a difference between the wake categories promulgated by ICAO and those in use in the UK – see AIC Pink 001/15. ICAO Medium can mean anything from 7-136 tonnes!
In the Learjet, we are ICAO Medium but UK Light and take separation against Medium on takeoff. I have hit 737 wake in the flare and we end up going around at around 20ft and it was no fun at all. A colleague hit a 767 wake around 7 miles behind in the London TMA and ended up rolled almost 90°.
Peter wrote:
If you have speed then you have control, etc
Too much speed surely isn’t too good, as this A300 crew must have found out…
Reading this report on an encounter between a Challenger 604 and an A388 and operating in an area with plenty of A38x movements has worried me – just how much extra spacing should a light aircraft apply if a Challenger can be so badly affected ?
Not sure I would worry too much about the wake turbulence bouncing off the ground. There it should dissipate rather fast.
But in the air along the glidepath, add a little cross-wind component and it can subside right on the glideslope for a quite long time.
Also, extending the downwind does might not help as much as you’d hope. If you start your descent from underneath his glidepath and intend to land after his landing point, evidently you have to go through the glideslope somewhere, and hit that turbulence.
