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« on: August 17, 2012, 07:49:56 PM »
girishsarwal
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Ok, I recently learnt about A/R mixing on trainer planes (higher drag and lower speed) to avoid adverse yaw. I also learnt that there are two school of thoughts, one who advocate A/R mixing (U.S. Flight - David Scott) and others who feel it is unnecessary.

I tried A/R mixing on my radio and found that the plane was harder to control and would lose altitude faster. So I have two questions where I seek help from seniors:

1) Does A/R mixing make a high drag plane easier to handle?
2) I do not understand why it should be losing height faster. Am I missing something grossly? Is it because the rudder partly behaves as a down elevator when banking


Look forward to inputs
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« Reply #1 on: August 17, 2012, 08:07:13 PM »
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I normally fly most of my planes with a little
A/R mixing - that way I use the rudder by just moving the aileron stick.

Turns are more coordinated and yes the plane tends to lose altitude - the
obvious solution is to mix or feed in a little up elevator as well.


There is a school of thought which discourages A/R mixing and advocate
that the pilot learn to coordinate his turns manually - it is said to
make him a better pilot - true no doubt .

another mix which I tend to use a lot is - elevator / throttle
i.e full throttle - a little down elevator with elevator moving incrementally up as I
reduce throttle.

The above are purely personal preferences based on my style of flying - which is take off, fly circuits
in the traffic pattern - an odd loop and roll and then rejoin the circuit to do touch and goes and close passes
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« Reply #2 on: August 17, 2012, 08:55:37 PM »
anwar
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Flying the plane yourself is always more fun than using radio mixes Wink

Aileron-to-rudder and other mixes all feel like cheating !
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« Reply #3 on: August 17, 2012, 11:11:06 PM »
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Let me be a little scientific about it,

For example

How does an aeroplane turn ? by banking, lift vector is tilted , you have two vectors one which supports the weight and the other providing necesary centripetal force to turn the aeroplane. the why do we need fin/rudder ?

whenever you bank the aeroplane slips into the turn, it is prevented broadly by the the (a) Sweep back (B) position of wing (c) and the fin. If their contribution is more than the ensuing slip then  when the aeroplane turns it skids away from the turn. skid is more discernable in a glider, so in a glider like aeroplane, there is always a requirement of in-turn rudder. how much of rudder depends upon the (a) rate of turn (b) speed. therefore it only makes sense to mix aileron to rudder in such an aeroplane, because this skid could cause spin especially when you roll reverse.

Another example is when lowering flaps, most aeroplane's nose goes down. again mixing Flaps to Elevator here only makes sense

These are just examples, even in the real aeroplane designed to be so agile and pull 9 gs are designed for such mix

(a) It is no non-pilot like or cheating if you mix (b) It is aeroplane specific, more you can perceive minute variations in the aeroplane's flight path backed up by theory, more informed decision you will take as far as mixing is concerned

http://www.centennialofflight.gov/essay/Theories_of_Flight/Performance_Class2/TH25G5.jpg
A/R mixing or not
« Last Edit: August 18, 2012, 05:31:11 AM by rcpilotacro » Logged

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« Reply #4 on: August 18, 2012, 05:54:49 AM »
rcpilotacro
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1) Does A/R mixing make a high drag plane easier to handle?

Girish it is not high drag plane, it is in fact Adverse Aileron Yaw, depending on the characteristic of your aeroplane you may require In-Turn or Out-Of-Turn Rudder (Whether she is yawing away or yawing into the turn more ), start you mix with (a) perceiving how much is the adverse yaw or sideslip (b) start the mix with less % and increase as you go along

For explanation on adverse aileron drag read http://www.rcindia.org/rc-general-topics/basic-aerodynamics-for-rc-flying/msg112476/#msg112476

2) I do not understand why it should be losing height faster. Am I missing something grossly? Is it because the rudder partly behaves as a down elevator when banking
if the adverse yaw is preventing the aeroplane from turning you will need to mix (a) In-turn rudder and (b) back elevator mix to aileron. this adverse yaw can be a cause for the spin esp when you quickly reverse your direction of roll
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« Reply #5 on: August 19, 2012, 09:40:24 PM »
shadman_alam
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A/R mixing on trainer!!! what will you train if u hav mixed everything already.. I hav seen ppl do it on scale planes where it makes sense...
Raw untuned flights teach alot.. Mixing comes in picture in f3a n precision flying.. Sometimes after a repair we feel the need of A/R mixings when the model dips too much at slow turns.. But even then.. Use this opprtunity to horne ur rudder skills.. Its will always payoff.. Another imporant thing is with A/R mixing your rolls will never be axial especially in the second half.. You will end up making barrels..
But you can definitely give a try n experiments new things.. Im sure u will agree with us after few flights of A/R mix..
Shadman
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« Reply #6 on: August 20, 2012, 08:22:08 AM »
girishsarwal
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Many thanks all for the inputs.

saikat - never head of the ele/thr mixing, but you mix so many things, may we call you the flying DJ Cheesy. Thanks for the inputs sire

rcpilotacro - I love the scientific rationale, makes most sense to know what one is doing rather than just following. Got a couple of new things to learn

anwar - I think if one knows what it exactly does, it wouldnt be cheating, but not knowing and simply following surely is cheating oneself Smiley. Its like driving an automatic car vs a manual transmission.

shadman_alam - I agree, that's not training but the whole point of asking this question was to bring out more views. I now feel that A/R mixing should be introduced at advanced stages rather than earlier ones, so I will stick to the desi school of thought. I fly the boomerang so its more of a sports trainer.

updates: I tried automatic mixing at the filed and manual mixing as well. This is what I realized:

1) The aileron initiates the turn while the elevator executes it, if we mix the aileron with the rudder, the nose orientation is only being corrected at the start of the turn and little thereafter, not while executing it. So a manual mixing between the elevater and ruder (only while turning in air) made most sense, esp on slower planes with lower WL.

2) Manual mixing does make a better pilot as one really gets to understand the controls.

3) Knife edge is a no no...

So I've now broken A/R mixing into two parts as such (for my understanding only)-
A/R mixing (yes or no) - slight aileron + ruder at initiating a turn, followed by elevator + rudder - yes
Automatic mixing or manual mixing - automatic makes most sense if done for a specific set of maneuvers and manual is applicable in almost all situations
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« Reply #7 on: August 20, 2012, 02:23:57 PM »
shadman_alam
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Oh man.. You getting in too deep with it... There is so much to be done n learnt with those two sticks.. They are your best pals.. N its not old skool thought.. With all the mixing on.. U ll be busy flipping switches through the flight.. One for inverted, one for harrier, one for knife edge n one for turning n you will have to mix throttle with aileron for the torque effect.. When will you fly?Huh?? ... there can be soo many mixing possible..doesnt mean you have to put everything on to make it fly best. .IMHO
Just trim out your plane with properply.. Thats more than enuff..
Shadman
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« Reply #8 on: August 20, 2012, 04:11:56 PM »
girishsarwal
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Quote
Just trim out your plane with properply.. Thats more than enuff..
  Hats Off

That indeed is the best advice sire...
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