What is up with the F-35’s wingtip vortices?

sdd_f35testb_047I have next to no knowledge in the field of aerodynamics- I stumble to explain the two competing theories of how a wing works, how coupled and uncoupled canard-deltas differ – even the simple equations of Energy Management have me stumped (not even sure this last one solely exists in aerodynamics). So I’m hoping that some bright aerodynamic engineer can help me with this one – ideally using simple language. Why does the F-35 produce such distinctive vortices from the wingtip/flap edge – and are they intentional, and positive in effect? Agile fighters – with strakes or canards – display visible vortices on the inner section of the wing- presumably where it’s wanted. I thought that wingtip vortices caused induced drag and were best avoided? Yet, the F-35 seems to stream them like a ’70s airliner. Educated comments in the reply section are VERY welcome. US_Navy_110606-N-DR144-314_An_F-A-18E_Super_Hornet_assigned_to_Strike_Fighter_Squadron_(VFA)_81_maneuvers_over_the_Nimitz-class_aircraft_carrier_US.jpg

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  1. Guerry

    I have a friend who used to fly for the Marines. I will pass this to him and see what he has to say. He is a smart guy.

  2. Steven

    Its actually an optical illusion that these are wing tip vortices. One of them is and the other is a vortices coming off the flaperon. This is because the plane has its gear down meaning it also has trailing edge flaps down creating a 2nd vortices which interacts with the one produced by the wing tip causing them to mix and give a spiralling appearance.

  3. Capt-Select Somebody (@overdesigned)

    Steven is right–also, reducing vortices is desired for efficiency reasons but eliminating them entirely is basically impossible. The geometry requirements of stealth/low-observable probably also mean that using standard methods (winglets, missile rails) to reduce them aren’t feasible.

    Solution was probably just deal with a little aerodynamic inefficiency and put a bigger engine on it.

  4. Mike

    I can’t tell you why the contrails look like that, but what I can say is, look at the F-35 in that photo.
    Than landing gear is down, the horizontal stabs are in idle position, the lift fan is open, the swivel doors for the engine nozzle is open.

    this F-35B is not trying to maneuver at all.

    Recent airshow appearances of the F-35 specially those made by the Royal Norwegian air force have shown that the F-35 is very capable in the turn and burn department, despite what the critics have to say

  5. ptitz

    Wingtip vortices are unavoidable. They arise whenever a lifting surface is placed into a stream of air at an angle. This produces higher pressure at the bottom and lower pressure at the top. At the wing tips this results in spillover of air upwards. The magnitude of drag that it’s responsible for depends mainly on aspect ratio of the wing, i.e. chord/span ratio. As such, something like a 70s airliner would probably produce less induced drag than any figher out there because of higher aspect ratio. In the picture of F-35 you see both the vortices originating from the wingtips and from the edge of the aileron, which in itself acts as a small wing. In F/A-18 the leading edge extensions produce massive vortices, because they act as tiny wings with tiny aspect ratio. Overal there is no *right* amount of induced drag to have. It’s a trade-off between aerodynamics and structural integrity of the wing.

    • Steven

      Ptitz, unfortunately you are wrong. The vortices aren’t both originating from the wingtips. Only one of them is. The other is coming from the flaperon. They are swirling together because of the pressure difference causing the spiral of the two separate vortices.

  6. mrmalaya

    I have raised the same issue on the net since the F35 appeared in the UK this summer. The point is, the vortices are very visible whilst the aircraft manoeuvres as well as when it is flying slow and straight in photo ops. It is not simply a feature of flying slow and dirty with flaps deployed and undercarriage down and they hang around too!
    I’m not knocking the aircraft, but that can’t have been intentional.

  7. Simone Hochgreb

    Vorticity generation is necessary for lift. At the wingtips, the vortices merge, and the pressure at the centre of the vortex is sufficiently low for moisture condensation to take place. That is why it is possible to visualise them with the naked eye. They are then convected downstream by the inviscid flow around the frame. This happens in all airfoils, but it is only visible in certain situations (see pressure issues above).
    What is the copyright on the figure, please?

  8. Vasco Ribeiro

    I have the same question, not about flap vortices, but looks like the last generation stealth aircraft is most of the time generating visible wing tip vortices or “contrails”. I have the knowledge that in most normal aircraft the incidence of the wing changes across its lenght, at the wing tip pointing down (lower incidence). This is clearly visible on the F-16 or F-18 wingtip, and generally is intended to make the tip the last part of the wing to stall to give roll control and to reduce drag at cruise speed. Even the wing of the Spitfire was design like this. With this, looks like that the F-35 wing tip is most of the time at an high AOA, the likely reason being optimized for high speed, when AOA gets very low.

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