1:1 rudder aileron mix !

[PB]

I've followed the rudder aileron mixing debate on these forums. It's a subject which attracts some pretty diverse opinins, from 'you should be flying the plane, not the transmtter' to '..a real pilot can feel sideslip and apply rudder accordingly, I can't feel sideslip so it's legitimate to counter it digitally' and to 'I need all the help I can get'.......I'm in the last category !!

All those opinions accepted and respected, if we do use rudder aileron mixing there's usually a debate about how much rudder to mix, and it tends to be around 3% to 5%. Well, quite by accident I came across this whilst looking for something else:

**LINK**

Page 6 of this interesting tutorial says that a 1:1 mix should be used which I assume means travel and not percentage, ie, not 100% rudder to 100% aileron but, say, 10mm of rudder to 10mm of aileron. In which case if the rudder has, say, 20mm of travel and the aileron 10mm this would represent a mix of 50%

I'd be interested in a discussion and debate of this American RC Flight School document.

[Stevo]

Interesting link!

Note that the 1:1 means degrees of deflection, and as the rudder has a wider chord you will have to adjust accordingly. Should the wind die down, I'm off to the field to give it a go...

And yes,I'm in the last category!

[Steve Hargreaves - Moderator]

H'mmm...interesting.

Personally I set up about 10% mix & adjust until I'm happy....that said I only have one model that uses CAR.....I like to use the rudder as intended & rely on my left thumb!!!

[Frank Skilbeck]

Looks like an old article as it advocates the use of a Y lead for doing the mixing, every aircraft will be different and the amount of mix will be aircraft dependent.

[Biggles' Elder Brother - Moderator]

People with an evangelical zeal about anything always make me nervous - they begin from the premiss that they have some "magic bullet" that if it is applied universally will solve all the world's ills! The guy that wrote this comes across to me as having this view about aileron/rudder mixing.

I'm very scaeptical that 1:1 mixes on the rudder of every trainer is a universally good idea. I've flown a lot of trainers and to be honest I've never come across one where the adverse yaw was so severe that it got in the way of the student learning. True I've seen a few that, to a practiced eye, don't look pretty in a turn - but they do turn fine - they just point their nose out a bit! I've also come across trainers that hardly exhibit the effect at all! And whether the trainer does or doesn't adverse yaw in my experience most beginners don't even notice! So, I'd conclude that a bit of adverse yaw is not a significant problem in most cases - and certainly not a barrier to progress for any learner.

The article also advocates possibly the least desirable solution method. We correct adverse yaw in the air using the rudder because we don't have an alternative. But if it is a problem with a model I believe its far better, safer - and probably simpler - to fix it via differential aileron throw if at all possible rather than mix in rudder.

Why safer? Well there is a factor here that this chap (who rather disparagingly refers to the rest of us as "recreational instructors" - as opposed to him being a "professional" I assume!) has overlooked - trainers have loads of dihedral. Its this that makes them resist banking - and hence turning - far more than adverse yaw. The dihedral has another effect - because it is constantly trying to pick up the low wing and right itself, when turning a trainer you have to hold the ailerons in all the time. This of course is very different from a model with little or no dihedral where the aileron is only used to initiate the bank. So our trainer, with his "magic bullet" implemented, is turning with ailerons constantly on and a whole load of "bottom rudder" to boot. That's going to require a matching load of up-elevator to maintain height - already this doesn't sound good - in a steep turn it could be receipie for disaster!

Don't get me wrong - I'm not anti rudder/aileron mixes - on the right models they have their place. But I wont be advising any learner I'm instructing any time soon to put that much rudder mix in a trainer! I don't need the spin recovery practice!

BEB

Edited By Biggles' Elder Brother - Moderator on 29/04/2013 13:14:09

[Johnny Kirkham]

I think its all down to the type of model as to what percentage is used......for example I fly a WW1 Bristol monoplane, it wont turn on aileron/elevator alone and it needs a good portion of rudder to kick the back end round. At the moment ive got a aileron to rudder mix of 20% but it really needs more as im still using quiet a bit of rudder stick when i turn.....I will increase this percentage bit by bit untill it flys scale like.

Johnny

[Simon Chaddock]

PB

I rather agree with BEB on this one.

You say you cant 'feel' the side slip but then as a ground based pilot you cant feel any of the other things a full size pilot can.

You have to rely on 'seeing' everything and learning to interprete what you see is a key part of flying be it RC or full size.