Mixing aileron or rudder in with throttle advice

[RPatrick]

After switching over to brushless motors, it has become very noticeable that my planes will not fly straight and level throughout the entire speed range. If I set the trim at high speed, the plane will roll at slow speed and vice versa.

I have decided to try mixing in aileron movement with the throttle channel on my Hitec Eclipse Tx to try to keep things straight throughout the entire speed range.

Has anyone had good experiences doing this? Any advice on the best method for determining how much to mix in?


RPatrick

[Viper Pilot]

Never heard of such a thing!!!
Good luck!!!

VP

[Sparky Paul]

De-warp the wing, set the fin straight.. then worry about this mix. The need will go away.

[Dan H.]

In addition to the factors Paul mentions, there are probably thrust line issues affecting your plane. If it's rolling to the left at full throttle you may need to add a degree or two of right thrust at the firewall. Adding rudder trim or rudder offset might help too. There's also propwash effect--when you go full throttle a big corkscrew-shaped cylinder of propwash surrounds the fuselage and usually runs smack into the left side of the tail fin, inducing a little left yaw.

You probably don't want to try to correct this with aileron input but rather with rudder changes if possible.

[RPatrick]

Thanks for all the advice !

I was not aware that this was caused by all those factors. I was thinking along the lines of the torque forces increasing disproportionately with the air flow over the surfaces.

The plane in question is a Hobby Lobby foam Diablotin. The fuseloge is very slightly less than straight, but it is foam so I'll have to live with it.

I did take the plane out for more test flying today, and set the trims at half throttle. The problem is now barely noticeable, if at all. I'll stay away from the throttle mix as suggested. By the way, the plane flies great! :D

take care,

RPatrick

[DaveW]

RPatrick

Welcome to the high power world.

All the little misalignments that don't bother low power models start to rise up and bite when the speed / power goes up.

Some hints:

From slow level flight, at half throttle or less, go to full power suddenly. If it veers to the left and rolls, thats motor torque.
Use right thrust to correct this.

If it pitches up or down, adjust the up / dn angle of the motor to compensate.

If the problem gets worse with speed, thats airfame misalignment, not motor angle.

A straight airplane is essential for high speed models if you don't want a lot of trim change with speed.

A little sawing and re-gluing to fix alignment problems can turn a dog into a delight!!

However, I also have an Eclipse :) and it is possible to mix out bad tendencies.
The Pattern flyers all do it to fine tune their $5000 precsion planes! Don't be afraid to mix in a little ailieron with throttle.

You can always turn off the mix in flight using the appropriate switch if it is wrong and try again until you find the best point.

Perfectly acceptable when its not feasible to change structure like in your case.

Cheers,
DaveW




Good Luck
DaveW

[Tony Oliver]

This may provoke an argument, as I'm not too technically on this.

My impression is that torque is an acceleration force and when the speed is constant that's the end of it. Only on acceleration and deceleration do any effects show up.

More often than not a model shows odd flight characteristics due to the presence of warps, misaligned thrustlines, inconsistently built wings etc as already mentioned in the earlier posts.
But what about the 'spiral airflow' reputed to hit surfaces they run into? For example the airflow from a large prop could hit the underside of the starboard wing and the topside of the port one, while the tail could get the opposite effect depending on the moment arm length. I hate to think what the sum of all these can do.

I've yet to be convinced that there is a problem, but certainly it would show up at higher rather than lower speeds.
Anyone got any facts or thoughts on this?

Tony

[Mr.RC-CAM]

I had very good luck taming my little Soarstar with throttle mix. It had a tendency to yaw, as well as gain a bit of alitude, at high throttle speeds.

I dialed in a little throttle-to-rudder and throttle-to-elevator mix. It now flys straight as an arrow throughout the throttle range. The flight mode switch can be used to disable the mix.

The mixing features were available on my computer radio, so it seemed like a simple way to handle the deed. I started with about 10% mix and tweak until perfect. Took about five minutes to get it right.

This electronic band-aide might not have been the "right" way to fix it, but it sure worked well for my slow park flyer.

[Kevin Murray]

RPatrick - What brushless motor are you useing in your HL Tiger ?

Would you mine posting your power set-up ?
motor, cells, prop

[RPatrick]

I wanted my HL Diablotin to be light yet powerful. I like those super slow float-by passes that can be done with a light plane.

I put in an Astro 020 sensorless. I still used the recommended MPJet gearbox, though I had to make an adapter to fit the 020.

I have been flying with 10 X 600AE cells using a 10 x 4.7 APC prop. My flying weight is 20.3 ounces.

On launch the thing goes straight up like a rocket. It wants to hover for the first 2 minutes, if only the pilot could do it! What surprised me most about this set-up is that I am getting 8 minute flights on 600 mah packs! That works out to averaging a 4.5 amp draw. I am still in disbelief that the plane can do all that for 8 minutes at 4.5 amps! I'll call it 10 cell magic...

I am going to bump the prop size up to 11 x 4.7 next flight.

I am only using about 50% of what this motor is capable of, one could easily change batteries and prop size to get it all!

RPatrick

[Kevin Murray]

Thanks. I have the Diablo version. It's getting an 020 also. Sendored type. Will be useing the MP Jet planetary 3.3:1
And CP1300 by either 8 or 10 cells