On reading the previous posts and links about wake turbulence, I wondered: How can the vortices from the wings of a 747 travel about 4-6 nm? I would have thought that the vortices would have dissipated after a mile or so, and become weak by one and a half miles
They are very strong cyclonic winds that are generated from the air pressure building in front of the wing and then spilling off the wingtips. Where you encounter them and how strong they may be is a function of not only the speed and weight of the aircraft that generated them but also of ambient wind conditions. In dead-still air, you can expect the vortices to spread outward from the flight path of the wing in each direction and to descend as well. If there is a cross wind, both vortices will move in the direction of the wind and descend. The stronger the ambient wind, the more quickly wake turbulance will dissipate.
Someone in another post asked if this had actually ever caused a crash. The most recent one I am aware of was 3-4 years ago when a Lear-jet type aircraft on final to John Wayne-Santa Ana airport encountered wake turbulence at about 800 feet AGL about 3-4 miles behind the aircraft that generated it. The turbulance was so extreme the light jet went inverted and crashed before the pilot could make a recovery. Wake turbulence is nothing to fool around with and I have aborted a number of landings where I felt I was landing too soon behind an airliner for my comfort zone.
If you have to land close behind a transport (and I cannot image why you should have to), the correct technique is to make sure you stay above the flight path of the aircraft ahead and to land futher down the runway than that aircraft did. The reason for staying above the flight path is that such vortices descend. The reason for landing long is that wake turbulance ceases to be generated when the wing is no longer generating lift.
Interesting Don, thanks.
Lets hope this can be modeled in the next FS release.
I believe I am right in saying the AA Airbus (A300 or was it 310) that crashed shortly after 911 happened in part due to wake turbulence created by a 747 which departed shortly before the "bus". Severe turb... the pilot tried to correct put in too much rudder full left to full right (rudder reversal) causing the tailplane to break off. Forgive me for not giving full detail but I simply can't remember in full!
You are right PH rudder reversal was the cause of the tail failure
Here is the NTSB report with a sim video of how and what happened ➡
Thanks everyone 😀