In 2012, there was a deadly accident during an airfield festival 15 min from my place. A DR-400 with a very experienced pilot started 40 seconds after an AN-2, got into its vortex and turned upside down and crashed with one fatality and several injured.
Back then it was not officially known that an aircraft like the AN-2 can create a vortex that is stronger than what the control surfaces of an airplane can handle. Therefore an depth investigation was performed by the BfU together with the German aerospace research center DLR. The video is rather interesting although German only:
First they simulated it on computers and calculated a vortex about the diameter for a DR400. Then they tested it with smoke and confirmed the calculation. Lastly, they flew an AN-2 and a DR-400 at safe altitude with measurement equipment and positioned it inside the vortex of the AN-2. On several occasions they confirmed that an AN-2 vortex will turn a DR-400 upside down with no way for the pilot to counteract.
Unfortunately the report was only published in German
Contrary to previous belief, even small aircraft like a AN-2 can create deadly vortices and wake separation needs to be applied.
I remember a documentary type film on Swedish television from years ago, mid 90-ies where the pilot of an AN-2 explained the dangers of taking off behind him. Thinking about it, it’s a pretty heavy aircraft that takes off at very low speed with a massive prop up front. It seems likely that it will create a big stir – as proven by the DLR.
In the documentary a bunch of classic aircraft were flying from Sweden to France and one of them got caught in the AN2 wake, almost flipping it over (Tiger Moth or similar) but narrowly escaped.
Three dead and one injured no? Stahlkopf… Better have one when you test stuff like that :-)
We had a similar incident when 2 friends of mine were flying a DR220 taking off after an AN2. They had a sudden wing drop on take-off and, while picking up that wing the other wing dropped, touched the ground and they ended up facing backwards in a wire fence by the airfield perimeter.
Officially there is no wake turbulence separation required for that size of aircraft, experience tells us otherwise.
When I trained on the AN2 in Bulgaria many years ago I was told that the Aeroclub always kept a 2 min separation even between 2 AN2’s.
For gliders and light planes rhey kept their distance.
Very interesting video … and a tragic accident.
Not quite the same, but I still recall landing a Cirrus and nearly ending up inverted on short final. Fortunately the passenger had snapped the crucial photo sequence just before of the Hercules doing full power run ups just off the threshold with PWs best giving a most interesting crosss wind – wake turbulence of a sort.
AT apologised profusely and no harm was done; I had no idea what was about to happen not having spotted the Hercules but it was more than attention grabbing.
Reminds me of this. A video of a Cirrus getting caught in the wake of a departing Blackhawk.
Video on wake vortices from the German air investigators (now EN language)
Hi All, long-time reader but first time poster here.
The following video on wake vortices (the An-2 / DR-400 vortex accident) has been referenced on here a few times over the years as “German only”. It seems to now be available with an English voice-over so may be worth another look.
Good video – many thanks for posting it, and welcome to EuroGA @mkfly
One big point they are making is that when the vortex diameter is big enough to cover the wingspan of the affected plane, its ailerons become ineffective. I don’t get that because surely the ailerons still have the same relative airflow over them. It is just that they don’t have enough power to overcome the vortex – in the same way as a plane may not have enough climb capability to overcome a downdraught.
I wonder if using the rudder also would help in such a case? Best to not do that on an Airbus though… somebody broke one of them doing that.
Their server is slow and one has to pause it every so often to let the download catch up.