Savannah VG - Rolling Left

[Xavier]

Hi,

 

3 months ago when the ferry pilot brought my Savannah VG from North QLD to Darwin he told me that the Left Wing is flying low and he was annoyed during the X-country flight that the aircraft was rolling to the left.

 

He could not release the stick for too long.

 

I am now almost at the end of the X-Country endorsement and I start to find it quite annoying too.

 

I would like to get some advice on how to get this fixed.

 

Fixed trim pad on one aileron ?

 

Aileron adjustment only ?

 

The Savannah is a VG model with the 912UL 80HP

 

Thank you for your help.

 

Xavier

 

 

[rick morawski]

Hi Xavier,

 

A friends Sav had a turn to the left as well, very annoying, he always flew left wing low. So I fixed it for him with a trim tab on the middle of right inner aileron bent slightly down. Size was about 200 X 50 plus 19 for overlap on the trailing edge of the aileron. Remove the small rivets at the trailing edge of the aileron and replace them fixing the trim tab as well.

 

Fly's straight and level now.

 

Cheers

 

Rick

 

 

[Rastus]

I had the same issue with a Cherokee 180 that I used to own.

 

The fix, as detailed in the Flight Manual, was to raise the flap on the high wing by 1/2 a turn on the rod end until she flew straight. I guess, if you can't raise the flap on the high wing, you could lower the flap on the low wing.

 

It took a couple of adjustments to get it right, but it is a lot easier than adding a tab.

 

Worth considering?

 

Robert

 

 

[rgmwa]

This might help, even though you have a different aircraft: http://vansaircraft.com/pdf/Wing_Heavy.pdf

 

rgmwa

 

 

[rankamateur]

Ian Ellis, former NSW distributor, also had a small trim tab on the aileron of his VG.

 

 

[Yenn]

I would think very carefully before using the Vans method. The RV ailerons are different from Savannahs and you could end up in all sorts of problems, bearing im mind that it is easy to squeeze the trailing edge, but not so easy to get back to the starting point if it doesn't work. Trim tabs are easy to make and with a pop rivetted plane easy to attach. They are also easily adjusted with just a slight bend.

 

 

[Guest Maj Millard]

Generally a slight raising of the opposite flap will solve a heavy wing problem. That's why they put adjustable rod end connections on control surfaces. Fixed trim tabs on anything are a last resort.

 

 

[rankamateur]

Hi,

Just out of interest have a look across the top of the wings to see if the rivet lines on one wing line up with those on the opposite wing. Being 6'3" tall I check every one I approach and have only seen two where the lines don't line up by about 20mm. The one with the trimtab I referred to above was one of them. I have no idea how you could build one with one wing effectively in front of the other by 20mm if you wanted to try, but at least two builders have succeeded

 

 

[Xavier]

Thank you for all your answers,

 

I will have a close look at raising the opposite flap and see if I can get a LAME to do the proper adjustments for me.

 

 

[rotax618]

Check the nosewheel adjustment with reference to the rudder, the nosewheel is in the prop slipstream and can have quite an effect on roll. The fact of the matter is that the VG Savannah doesnt have enough dihederal and any slight out of adjustment will cause an annoying roll.

 

 

[rotax618]

The neutral roll stability of my VG annoyed me and when I did the 560kg upgrade I was able to increase the dihedral because of the new longer strut ends. The Sav is now a dream to fly, I can fly hands off even in thermally conditions. Can open out maps, get a drink and something to eat without having to immediately grab the stick because of unwanted roll. Just compare the dihederal of the standard Sav with, skyfox,foxbat, jabiru etc etc.

 

 

[Guest Maj Millard]

There's also the rolling effect in the opposite direction to prop relation, induce by the prop at full power. (P factor). This could be amplified with a 100 Hp engine and beefy props on the SAV..all though certainly not limited to those, and of course certainly not limited to the SAV aircraft either.

 

As a remote example many of the high-powered WW2 fighters including the P-51 Mustang would exihibit the bad habit of dropping a wing if pulled off the ground too early at full power, before having sufficent airflow over ailerons and rudder, therefore rendering those control surfaces incapability of exercising adequate control .

 

I know of two such occurrences that happened in Queensland with 100 HP Savs, both resulting in crashes after a left wing drop right after liftoff. One aircraft was written off and the other was repaired. One pilot was very experienced but could not get the wing back up, nor was he able to reduce power due to the low altitude and obstacles.

 

I have a good amount of time in a VG 100 HP SAV and have never experienced this myself even though I do operated in STOL mode when flying that aircraft.

 

There may be a problem here or there may not, and other more experienced SAV drivers may have something to add, however if your aircraft shows a tendency to carry a heavy left wing, I think I'd be onto correcting that pronto !.........

 

 

[facthunter]

You could have a twist in one wing or even the rudder bias can produce the effect you describe.

 

Note this post has sat for nearly a day so may be out of context with other posts. Nev

 

 

[rankamateur]

You could have a twist in one wing or even the rudder bias can produce the effect you describe. Note this post has sat for nearly a day so may be out of context with other posts. Nev

You can't get a twist in a Savannah wing, all the holes are computer cut full size, you could build a straight wing on the front lawn. Unless of course you twist it after installation!

 

 

[Guest Maj Millard]

 

I've trimmed up a lot of aircraft in my time and I feel I'm pretty good at it by now. If I have to put a fixed trim tab on anything but a rudder I consider it a failure. You should be able to achieve wings level trim on most aircraft by adjustments to either aileron or flap or a combo of the two.

 

Rudders have to contend with a twisted airflow from the prop which often rotates around the fuselage as it travels back striking the rudder on one side only. Pretty hard to get around that one, unless your in a glider.

 

Of course I have run into some pretty badly constructed wings also, which will cause all sorts of out of trim stuff, and are always a challange.

 

My last trimming effort was on the WAC Spirit aircraft in the photo. During final inspection it was pretty obvious the builder had no idea where things should be, so I had to rerig the whole thing, particularly the ailerons and flaps.

 

Bill Grieves from SE Qld performed the initial flight ( having flown a Spirit before) then conducted training in it for the owner. His comments a week later " Rarely do I find an aircraft straight out of a build that flew so nicely and almost hands off ". The Spirit by the way is the latest out of the States by World Aircraft and is sort of like a super Savannah, having much in common together with many improvements. Three kits were imported into Australia and as far as I know two have been completed and flown, with the third under construction. Unfortunately the increased price of this lovely aircraft now in the U.S. ( around $140k US) will probabily mean we don't see too many more out there in this country.

 

 

 

 

[Geoff13]

[ATTACH=full]36352[/ATTACH] [ATTACH=full]36350[/ATTACH] [ATTACH=full]36351[/ATTACH]

I've trimmed up a lot of aircraft in my time and I feel I'm pretty good at it by now. If I have to put a fixed trim tab on anything but a rudder I consider it a failure. You should be able to achieve wings level trim on most aircraft by adjustments to either aileron or flap or a combo of the two.

 

Rudders have to contend with a twisted airflow from the prop which often rotates around the fuselage as it travels back striking the rudder on one side only. Pretty hard to get around that one, unless your in a glider.

 

Of course I have run into some pretty badly constructed wings also, which will cause all sorts of out of trim stuff, and are always a challange.

 

My last trimming effort was on the WAC Spirit aircraft in the photo. During final inspection it was pretty obvious the builder had no idea where things should be, so I had to rerig the whole thing, particularly the ailerons and flaps.

 

Bill Grieves from SE Qld performed the initial flight ( having flown a Spirit before) then conducted training in it for the owner. His comments a week later " Rarely do I find an aircraft straight out of a build that flew so nicely and almost hands off ". The Spirit by the way is the latest out of the States by World Aircraft and is sort of like a super Savannah, having much in common together with many improvements. Three kits were imported into Australia and as far as I know two have been completed and flown, with the third under construction. Unfortunately the increased price of this lovely aircraft now in the U.S. ( around $140k US) will probabily mean we don't see too many more out there in this country.

Not sure which ones you know of that are flying Maj, but the one at Caboolture has been for a month or so now. Beautiful aircraft it is to.

 

 

[Guest SrPilot]

I would think very carefully before using the Vans method. The RV ailerons are different from Savannahs and you could end up in all sorts of problems, bearing in mind that it is easy to squeeze the trailing edge, but not so easy to get back to the starting point if it doesn't work. Trim tabs are easy to make and with a pop riveted plane easy to attach. They are also easily adjusted with just a slight bend.

I am certainly no expert, but I have built an airplane, completed another one, and have helped others build theirs. Some used the "Van method" to fix issues back when we were building or flying RVs. (I still think my RV-3A was a great airplane.)

 

From my experience in using the Van method, I surmised that most errors arose from either doing to much or doing it on the wrong trailing edge. The "squeeze" as I remember it was to tighten the arc of a trailing edge that was simply too fat. The squeeze was almost nothing. Just a pound or two of squeeze - "a little squeeze" - enough to make an imperceptibly tighter arc but not enough to even see the metal move. Then a test flight. Then another squeeze if necessary. To fatten the arc if the arc was already too tight or if we squeezed a mite too much, we placed a 2x4 (50mm x 102mm) piece of lumber against the trailing edge and lightly tapped along the edge to "push" the trailing edge forward thereby (hopefully) fattening the arc. Better though to get the trailing edge curvature correct during the build process.

 

On some airplanes, such as the Glastar, that process is not available because the trailing edge has no arc. The top and botton skins are riveted along the trailing edge.

 

 

With this method, if the rivets are driven too hard, it may ripple or turn the trailing edge up or down. Those issues may be addressed by carefully straightening the trailing edge with sheet metal pliers.

 

Better, though, not to induce bending or waving by squeezing or driving the rivets too hard in the first place. Neither of these procedures are easy or quick, and they can raise other issues such as tool-hardening of the sheet metal, cracks, etc. Plus, it doesn't compute to attempt to fix an improperly aligned wing or stabilizer by bending ailerons, elevators, or the rudder.

 

I agree that one should think carefully before using such methods. Personally, before doing too much bending of control surfaces, I'd consider alternatives. I remember visiting a friend who was building a Midget Mustang - long, long ago. I noticed some parts in a trash can. Several parts, all the same part. I picked one up and asked "what are these?" He pointed to a part on his airplane and said "faulty examples of this." Ah, an alternative. Build another one.

 

You also might want to read about aileron snatch if you're not familiar with the phenomenon. Trailing edge shapes affect performance. And for every fix of one problem, there's always the possibly of inducing a different problem. (Mr. Murphy's law).

 

Aileron snatch conversation here: http://www.vansairforce.com/community/showthread.php?t=24980

 

When I built my GlaStar, I ended up with a hands-off, straight-flying airplane. That happens when you're really, really good!

 

Or, in my case, when all the errors equaled out.

 

Trim tabs, anyone?

 

 

[bobcharl]

Xavier.

 

This does seem to be a common problem with many Savs, and while there are various theories as to the cause I don't think there has been a definitive answer.

 

My homebuilt VG XL did the same thing, and I had expected it so when doing the last of the painting I made and painted a trim tab, very similar in dimensions to Ricks in post #2 with a row of holes to facilitate bending as used on the rudder trim tab, just to have on hand. After a few flights I was annoyed as you are by the "heavy" wing so fitted the trim tab, a few more flights to get it set and WOW, the difference is stunning.

 

A few comments on some of the above posts.

 

I agree that fixed tabs are not the most desireable bits of gear. they look bad and probably fix the effect rather than the cause. But hey, they work.

 

I know that Maj has had much more experience than I, but if he is suggesting (and I am not sure he is ) that the flaperon actuation rods be adjusted to raise or lower a flaperon, proceed with caution.This will only have the effect of changing the position of both flaperons when in the neutral position as measured by the jig supplied in the kit by ICP. Because the flaperons are responsible for some lift, altering their common position would have an effect on the longitudinal balance in flight. As this was getting way ahead of my skill levels, I left it well alone.

 

Rotax618, I am intrigued by those longer strut ends. I have done the 600kg mod but still using the same strut ends. Tell me more.

 

Regards,

 

Bob

 

 

[Ultralights]

My Savannah had a slight roll to the right, but mainly due to the fact it has 3 fuel tanks. 2 on the right hand side, and once both are full its noticeable, but not to bad. the roll is fixed with a fixed trim tab on the right aileron.

 

Another change i noticed with the roll stability was the change from the small standard nose wheel to the larger 6.00x6 tyre. this tyre is a lot taller but the same width, but its change was noticeable and required a change to the trim tab.

 

 

[rotax618]

The upgrade Im talking about was the early VG savannah to 560kg. It consisted of thicker wing root mainspar fittings and doubling the outer mainspar strut attachment, fitting 2 extra bulkheads to the rear fuselage and doubling the lower rear fuselage angles. I fitted the VG leading edge at the same time as suggested by ICP - the leading edge made very little difference from the old profile , slats off and Stollspeed VGs.

 

ICP supplied new chrome moly outer main strut fittings which were undrilled. Pretty simple to change the dihedral, doesnt need a big increase but +1 - 2 deg gives a vast improvement to lateral stability.

 

Dont modify anything unless you are sure you know what you are doing, having first discussed it with the importer Reg Brost.

 

 

[Xavier]

Thank you all for your advice, I now have different options and will make a decision soon.

 

 

[Kyle Communications]

You can't get a twist in a Savannah wing, all the holes are computer cut full size, you could build a straight wing on the front lawn. Unless of course you twist it after installation!

Mine flew perfect no trimming required on any surface. Since the repair though after the nosewheel folded and the right wingtip smacked the deck the plane has got a ever so slight roll to the left when flying straight and level. It doesnt take much twist to give you a slight roll. It isnt too annoying at the moment but I will fix it. I think a half turn on the flaperon ball link will probably fix it.

 

 

[rankamateur]

Unless of course you twist it after installation!

 

 

[Kyle Communications]

Got to tell you Steve...the twin sticks are such a pleasure to fly with now....absolutely chalk and cheese for comfort or me...and you being a long stringbean if you have any dramas should consider it.....when you FINALLY get back to working on yours

 

 

[rick morawski]

Mine flew perfect no trimming required on any surface. Since the repair though after the nosewheel folded and the right wingtip smacked the deck the plane has got a ever so slight roll to the left when flying straight and level. It doesnt take much twist to give you a slight roll. It isnt too annoying at the moment but I will fix it. I think a half turn on the flaperon ball link will probably fix it.

Please correct me if I'm wrong, but to my thinking, adjustment of the aileron linkage will ultimately just move the position of the control stick. When the ailerons move to a point of least wind resistance they will be in the same position they were before the adjustment, but the control stick will have moved over one side or other, and you will still have your unwanted roll. I can't get past this idea so please let me know the theory of the adjusting of the aileron link.

Cheers

 

Rick