Dreadful accident - should have been avoided
 

There was a terrible accident in Backnang-Heiningen in Germany back in 2012. The relevant air authorities made a video explaining what happened, which is only available in German.

I edited it into a shorter version with English explanations.

Please have a look, it contains valuable information for anybody flying light aircraft:
https://www.youtube.com/watch?v=KXlv16ETueU

Wow, thanks!

Correct me if I am wrong, the 2-minute wake turbulence separation is applicable to landings as well.

Another grave danger is helicopters (downwash).

Well done, good post, surprisingly strong vortices generated from an aircraft that I would not intuitively consider presented such a high risk.

Wow, that is quite shocking, thanks for posting.

I'm surprised an AN2 produces such strong vortices.

Good point about helicopters. In Lausanne we've just had the addition of a bunch of helicopter hangars, it can make life interesting. Two minutes is not all that long

ISTR 757s produced extremely strong vortices that flipped fairly large jets.

757s were notorious - I think they are better now they have winglets. I remember seeing them go over Mobberley on short final for (the then) 06 at EGCC, and several seconds afterwards came the most eerie whistling and cracking sounds of the vortices. No other jet, even 747s, did that.

It's £6 to a rental pilot.

(But yes, when ATC tell me to wait for vortex separation I'm perfectly happy to do so.)

It has happened before. I well remember this accident.
https://assets.digital.cabinet-offic...pdf_500836.pdf

I used to operate a Chipmunk from a major airport, so vortices were always a threat. ATC would say to me (holding on base, 1 mile out) "cleared to final behind the landing 737. Recommended spacing is 6 nautical miles". If I'd trundled downwind away from the airfield and then turned base to allow that 6 nautical miles spacing, I'd have lost my place in the queue to the next instrument inbound down the ILS.

Vortices are generated at the wingtips, while the wing is at a positive AoA. They move outwards and downwards (and of course move laterally with the surface wind). So, if you join final above the flight path of the 'heavy' (easy 'cause they are on a 3 degree glidepath and I can come in much steeper) and remain above their flightpath, and touch down after their touchdown point, you won't encounter vortex. So that's what we did. It often resulted in a 'land after clearance' on short final!

I brought this over from our local discussion forum - a very scary stunt, where an An-2 tows 5 gliders onto an airshow. THe 5th pilot at the rear is constantly swearing about the lack of sufficient aileron authority due to the wing vortices.
I believe this stunt was only possible as the gliders wings reach out from the vortex, giving them a little bit of control authority / stability.

Yeah, but the time is still going in your logbook...

I was once flying somewhat line astern in my 150, behind a buddy in his 150. His vortex stood me hard on my wingtip, and spit me out - I learned! Same weight aircraft is all it takes to put you over. If not "at altitude", you're in big trouble!

Vortex avoidance is one thing which a good crosswind greatly aids. Many has been the time I have satisfied myself as to the direction that the vortex has been blown, and I've operated well to the upwind side, with no problem. In the video clip, it is apparent that there is little to no wind, so the vortexes will just hang there stationary, until the dissipate - probably in £6 or so..... ;)

It's interesting to observe while a pax in a window seat, behind the wing on an airliner, that once a whole lot of flap is extended, the vortex is generated off the outboard end of the flap, rather than the wing tip. This has negligible bearing on avoidance though....

Lesson from the past
 

Way back when I was going through Navy flight training I had a wake turbulence experience that could have ended badly. The solution used to counter that problem applies well to a wide range of aircraft, so please take note:

I was number 6 in a flight of 6 aircraft on an air to air gunnery mission in T-2A jets. The first four aircraft took the runway in echelon 1000 feet down the runway, and the last two aircraft remained at the runway end in echelon. Per the briefing, the individual aircraft rolled at 10 second intervals.

When it was my turn as #6, I applied full power and performed a normal take off, raising the gear and accelerating. At 50 feet above the runway, the aircraft began to roll until it was standing on its right wing tip despite application of full left aileron and a bootfull of left rudder.

What do I have left I asked myself? Ejection was out of the question with the older ejection seats. The aircraft was not going to fly many seconds more in that attitude.:eek:

I pulled back on the stick which turned the aircraft away from over the runway and in seconds I was in control again.

The fix was simple. All I had to do was throw out the mental concept of remaining over the runway. I hope this little story helps others.

Dear god, that looks scary. You say that was for an airshow but it couldn't be a one off, they'd have to practice, so did the team ever lose a glider getting snarled up in another tow wire?

Not at all a 'heavy' but I once was surprised by the strength of the vortex off a friend's Condor.

The AN2 is a nasty case because it has a very short takeoff run so any following takeoff is going to be below it and in the falling vortices.
Add that to the fact that it weighs in at around 5 tons and you really need to leave a good 2 or 3 minutes before following.

What a good thread,

Wake turbulence and ground air current are something that all of the PPL Pilots FW and Rotary should read up on and fully understand, I trained initially on R22/R44 and they are really twitchy when being even 3 mins behind anything else..

Good videos as well, well done for the attention this needs.:ok:

I flew a Citabria at a helicopter training field and came back when a Schweizer trainer was doing hover practice 50 yards to the side of the runway.

There's quite the wake, even from a small helicopter.

Try 9 gliders on tow.
Vortices from that lot?
http://www.liveleak.com/view?i=ab9_1372010278&comments=1

Jeez, that's insane! :) Even thought the Turbo Cmelak is under 2 tons, so creates slightly weaker turbulence than an Antonov-2 biplane.

It's good to see the formation from the side-view. The first 6 appears to be above the wake and the last 3 (with the greatest distance) suffer the most from it.

I guess the music is put on to supress the swearing and cursing and F-words :)