Improving low speed authority of ailerons?

[Enigma]

Vortex generators improve low speed airflow over the wing enhancing a wings performance in slow flight. A benefit of this is a lower stall speed, but at a much less advertised cost (usually) of less stall warning. Of greater benefit (in my opinion) is that the vortex generators improve the aileron authority deeper into the slow flight regime.

 

I am interested in experimenting with vortex generators only affixed to the outboard section of the wings so as to enhance the low speed authority of the ailerons while leaving the inboard section of wing to stall at it's normal angle of attack.

 

It seems likely that others may already have experimented with this idea and I am wondering if any information is available?

 

I am especially curious if a second row of vortex generators closer to the ailerons has been experimented with and if it has proved to be beneficial or not? Also how far forward of the ailerons would a second row be placed to maximize aileron performance?

 

Thank you.

 

 

[djpacro]

They'll only improve aileron authority if there is any degradation in that authority due to separated flow so the first thing to do is to put tufts there and look at what is going on.

 

 

[JG3]

[quote=Of greater benefit (in my opinion) is that the vortex generators improve the aileron authority deeper into the slow flight regime.

 

I am interested in experimenting with vortex generators only affixed to the outboard section of the wings so as to enhance the low speed authority of the ailerons while leaving the inboard section of wing to stall at it's normal angle of attack.

 

It seems likely that others may already have experimented with this idea and I am wondering if any information is available?

 

I am especially curious if a second row of vortex generators closer to the ailerons has been experimented with and if it has proved to be beneficial or not?

 

Thank you.

 

Yes, VGs only in front of the ailerons has been tried many times and is effective in increasing aileron authority at lower speeds. Jabiru 200 series have particularly noticed this.

 

There is unlikely any benefit placing a second row of VGs farther back near the aileron, due to the thickening boundary layer at that point. The vortexes once generated by the VGs at the front of the wing are very persistent and stream right back to the trailing edge.

 

 

[SDQDI]

There was a huge thread on this site some time ago about vortex generators which would be worth a read. I will try and look it up in a minute.

 

Leaving the middle section to stall is a thing that is done by quite a few different people.

 

Just be careful if doing your own testing as while vg's can improve your planes performance they can also change it for the worse. for example your plane may have had a mild stall before vgs but after it may have a viscous wing drop which if unsuspected could cause trouble. What I am trying to say is just be prepared for these things. Having said that I have had only good experiences with them but that isn't always the case.

 

 

[SDQDI]

Do vortex generators really work.

 

There is a couple of threads but this one would be a start

 

 

[F10]

Most military aircraft I have come across in my career,have vortex generators located on the outer leading edge, ahead of the ailerons. They are located on the leading edge radius, in a position where they will only come into play as such, at high angles of attack, where the greater upwash will cause more airflow across them, generating vortices and so energising the boundary layer at low speeds. 

[facthunter]

Ailerons operate at the dirtiest part of a wing, Don't expect them to do much near a stall, because there's NO  good airflow near either. Washout on the wing helps, Like a single Cessna has but there's a limit to anything. If your wing drops lifting it with aileron will make it worse. Just "forget" aileron near a stall. That takes a bit of doing as when flying normally it's second nature and you get used to it. 

  Pulling the stick back  to raise the nose is normal too but bad news near a stall. It's exactly what you don't want..  Nev . 

[Ian]

Has anyone been playing with vortex generators recently? It would be nice if someone had the time and inclination to characterize the change in flight characteristics of a particular plane with and without.

[facthunter]

I think there were approved kits on Piper Chieftains.   Light twins are the sort of thing that responds to such fitments.  Also GAP seals. Nev

Edited December 17, 2021 by facthunter

[onetrack]

Ian - John Gilpin ("JG3" on this forum) is your go-to man for VG's ....

 

https://www.stolspeed.com/

[RossK]

Our Sportstar came without VGs and we fitted them (from JG3) shortly after getting it.

Stall is more benign, less yawing before the stall.

Clean stall is 40kts now. I have seen lower speeds but it's just losing height holding it's nose in the air.

We've lost about 3 knots off the cruise as a result. 

We didn't do empirical testing, and it's an approved mod from Evektor.

[Geoff_H]

4 hours ago, facthunter said:

I think there were approved kits on Piper Chieftains.   Light twins are the sort of thing that responds to such fitments.  Also GAP seals. Nev

My Mooney had gap seals. They appear to work very well.

[facthunter]

On the rudder of a twin they can reduce Vmc(a) Getting it officially recognised would be another matter but who cares if it works. Nev

[skippydiesel]

On 17/12/2021 at 3:21 PM, Geoff_H said:

My Mooney had gap seals. They appear to work very well.

I agree on the gap seals - must be correctly installed.