Aerodynamics Discuss the physics of flight revolving around the aerodynamics and design of aircraft.

Aileron Differential

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Old 07-25-2013, 02:23 PM
  #26
fred985
 
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Default RE: Aileron Differential

a coordinated turn requires all 3 controls. areilon to roll, rudder to control yaw and elevator to turn. thats how i kept myself alive for a 1000 hours of flying real airplanes such as cubs and stearmans. these aircaft had absolutely no aerilon efect at stall, only rudder and elevator control. go to most any local country airport and see if you can find a cub that you can measure the airelon angles. i just set them at 3 to 1 ratio or 2 1/2 to 1 and my scale oldeys seem to like that.,,,,just dont forget the elavator and rudder........
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Old 07-25-2013, 02:34 PM
  #27
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i set the diff by where i hook up the servo linkage.the down will be about 8 oclock , the up will be about 4 oclock,,,...this shortens and lengtins the travel of the likage,,,,no comp radio mum-bo-gumbo. hell i have enough trouble working the comp much less these new fangled radios ! both servos turn the same way,,,works for me.
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Old 07-25-2013, 04:35 PM
  #28
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Default RE: Aileron Differential


Quote:
ORIGINAL: rmh

Quote:
ORIGINAL: wingstrut

I need to clarify something, When I say that I apply a little opposite aileron I mean a little, less than a 1/4 inch deflection which is nothing in this aircraft.
It helps to stabilize the plane to make a much smoother controlled turn.
I get a lot of positive comments on how my turns make the aircraft look like the full size and not a model.
If I gave it a lot of left aileron as in a flat turn and opposite rudder than I would have a stall.

I posted this question because I wasn't familiar with Differential ailerons, after reading all the great explanations now I know that I don't want it.
I love flying these ww1 planes and I will never mix controls in the radio, I can fly the plane better than the radio mix can.


Thank you all for the great explanations and for taking your valuable time in doing so..........Ron
Your comment about corrective aileron tells me you have it set close to perfect.
In model flying we don't have instrument panel - we watch and correct as required
When setting up models for aerobatics - we also found a setting such as you have is -"about right

IF you held the initial turn -the setting would result in a tightening spiral-
the very slight reverse aileron held against the rudder applied - kept the model in a predictable turn-
going further into MODEL flying
The right setup for predictable flying is still the best
When we fine tuned designs for predictable very slow rolls - the amount of dihedral would always be such that the application of rudder in final section of the roll- would SLOW the roll rather than increase it
much easier to control
Apparantly some feel full scale practice always applies to our models - it doesn't always apply but in this case it is about the same.
some models turn with no bank or very little - depends on what designs one flies -if you poo poo all types you just limit your knowledge.
Just curious about your comment above. are you saying that in a Left roll, you are applying right rudder during the final part of the roll?

The real aircraft I did most of my aerobatics in was a Robin 2160 (Da da... hence the RCU name - I owned the red Robin in the pic for 12 years) This was a small 2 seat aircraft with dihedral and a large rudder.. During a slow roll you had to make constant correction for the effect of dihedral... IE in the first quarter of the roll you needed extra aileron to combat the slow down effect of "top rudder" similarly, in the last quarter you needed to back off the ailerons significantly to counter the increased roll rate caused by top rudder..

I agree there is a very big difference in flying real aircraft or models, because in models we lack the seat of the pants "feel" and our only feedback is visual and aural, not tactile at all..

Certainly what may look great when viewed externally in a model could feel incorrect in a real aircraft.

Turning with rudder and holding off on aileron is a NO NO in "Real" flying because it can kill an inexperienced pilot in some aircraft types.

Also some students inevitably end up flying swept wing jet aircraft. Turning with rudder and holding off aileron is going to get very untidy very quickly in anything with a swept wing..

There was a story about a 727 captain who kept reporting severe vibration during flight.. subsequent pilots flying the same aircraft could not observe it..

After more similar reports a senior check pilot flew with this captain and it turns out he was leading with rudder in turns and holding off so much aileron that the roll spoilers on the opposite side would deploy and hence the vibration.. I can't verify the story, it may be an urban myth but makes a good story at "Beer O clock"

Hence we demonstrate this type of turn during training to help students recognise dangerous practice and therefore avoid it. I have seen experienced pilots at airshows turn aircraft fully with rudder and no angle of bank at all, so I agree it is entirely possible.. I find models are generally (and I mean very generally) more forgiving aerodynamically.. I have tried this demonstration in many of my RC models and most of the time nothing bad happens,

Makes an interesting discussion though..
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Old 07-25-2013, 04:59 PM
  #29
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Default RE: Aileron Differential

No, when I do a right hand roll I use right rudder to get it through. when I do a right banked turn I use elevator ailerons and rudder, I use a very minute left aileron to apply slight drag to the aircraft to stabilize it so it won't continue to turn or drop off from the rudder effect. That is the only time that I use opposite aileron in a normal turn and it is very slight you can barely see my thumb move the stick, actually I don't move the stick I just lean on it. I don't do flat turns.
Now reverse all this for a left turn.


Ron
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Old 07-25-2013, 05:10 PM
  #30
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Default RE: Aileron Differential


Quote:
ORIGINAL: wingstrut

No, when I do a right hand roll I use right rudder to get it through. when I do a right banked turn I use elevator ailerons and rudder, I use a very minute left aileron to apply slight drag to the aircraft to stabilize it so it won't continue to turn or drop off from the rudder effect. That is the only time that I use opposite aileron in a normal turn and it is very slight you can barely see my thumb move the stick, actually I don't move the stick I just lean on it. I don't do flat turns.
Now reverse all this for a left turn.


Ron

Thanks Ron, I understand..

If you are doing a slow left roll, at the 90 degree point (IE the first quarter with the right wing vertically up) do you apply any right rudder at all here to stop the nose from dropping?

We generally call this "Top rudder"

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Old 07-25-2013, 05:19 PM
  #31
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Default RE: Aileron Differential

What we are describing is actually a "Skidding Turn"

Lots of good info about it online..

here is a good link.. the 2nd Paragraph explains what I was trying to say...

http://en.wikipedia.org/wiki/Skid_%28aerodynamic%29

Another really good article, gives a nice example in a real aircraft of a student being "caught unawares"

http://www.av8n.com/how/htm/snaps.html
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Old 07-25-2013, 05:54 PM
  #32
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Default RE: Aileron Differential

Rob, No I don't, because the pup doesn't drop until you get it on it back, then I give it a little down elevator to keep it from dropping and that is when she hesitates to roll anymore, that is when I use rudder to bring her over.
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Old 07-25-2013, 06:23 PM
  #33
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Default RE: Aileron Differential

Flying a model with equal lateral and horizontal surface areas - is interesting -to say the least
What happens is that the roll -typically used in aircraft for years - simply establishes a banked angle but NO change in heading -
However if one simply -in level flight applies rudder - the model turns -the side area of the fuselage provides the proper lift -during the turn
Yu have to fly the setups to appreciate how it works
Why do it?
unlimited aerobatics have changed the picture of aerobatics .
Yesterday's nice aerobatic craft is hopelessly outclassed when trying to do the power hungry -and strange attitude maneuvers in the new sequences
flying and climbing in knife edge is common now.
Hence the need for very neutral airframes.
First full scale craft I flew-an Ercoupe - early version - low power and limited responses .
but I was smitten with how easily it did what I wanted it to do
It was as easy to fly as driving a car - as long as you just wanted to maintain a constant altitude
It also landed nose in the wind and flight direction down the runway-
But this method of flying did not appeal to the "purists".
Too bad -
Time changes all
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Old 07-26-2013, 05:12 AM
  #34
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Default RE: Aileron Differential


Quote:
ORIGINAL: wingstrut

Rob, No I don't, because the pup doesn't drop until you get it on it back, then I give it a little down elevator to keep it from dropping and that is when she hesitates to roll anymore, that is when I use rudder to bring her over.

Yes, that does make sense.. thinking through what you described....

It makes perfect sense why she hesitates on the roll when you apply down elevator.

Follow me through this..

1. When upright and with positive G - the aircraft has dihedral so any rudder input will cause roll in the same direction.. IE left rudder gives left roll..

While the wing has positive G the differential ailerons are working as intended..

2. When you apply down elevator you are creating negative G - now freeze the aircraft inverted here and see what we have...

With negative G on the wing - effectively we now have an aircraft with Negative dihedral (anhedral) - reverse differential ailerons.. (the down going aileron is deflected down more than the upgoing aileron) and we have rudder opposite to the direction of roll.

Imagine rolling left, with left rudder applied.. freeze the aircraft inverted and with negative g on the wing.. effectively our aircraft is flying as an aircraft attempting to roll left with "right" rudder, the instant you changed from positive to negative G on the wing, the secondary effect of your rudder changed direction..

If you apply more rudder at this point and ease back to neutral on the elevator it will keep rolling in the direction intended as neutral elevator position in your transmitter will be 1 positive G (approximately) in the aircraft...


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Old 07-26-2013, 05:28 AM
  #35
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Default RE: Aileron Differential


Quote:
ORIGINAL: rmh

When we fine tuned designs for predictable very slow rolls - the amount of dihedral would always be such that the application of rudder in final section of the roll- would SLOW the roll rather than increase it
much easier to control
Sorry, disregard my previous question.. I misunderstood what you had written.. My bad.. I understand your comment now.. You were actually designing the aircraft for the desired effect.


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Old 07-26-2013, 10:14 AM
  #36
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Default RE: Aileron Differential


Quote:
ORIGINAL: Top_Gunn


Quote:
ORIGINAL: rmh

in some cases - that works
Some aircraft us rudder ONLY for turning - the use of ailerons not required nor is banking needed
The rules change as the airframes evolve.
Yes, if you're talking about weird planes usually made of slabs of foam. The OP has a WWI biplane. Like most planes, it turns by banking and the rudder is used to prevent adverse yaw. ''Nearly all cases'' would be a lot less misleading than ''some cases.''
The first generation of RC models were neither "weird" nor were they made.of foam. A good pilot with the right rudder-only plane can do some remarkable aerobatics.

Jess
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Old 07-26-2013, 11:35 AM
  #37
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Default RE: Aileron Differential

Quote:
The first generation of RC models were neither "weird" nor were they made.of foam. A good pilot with the right rudder-only plane can do some remarkable aerobatics.

Jess
I believe you're talking about ordinary R/C planes without ailerons (two- or three-channel today, usually; one-channel back in the day. They turn by banking, with the bank induced by using rudder. Hanson is talking about planes that turn without banking, not the "first generation of RC models." Some of them are not made of foam, to be sure. Whether they're weird is, I suppose, a matter of taste. Why they was worth bringing up in a thread on aileron differential I don't know.
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Old 07-29-2013, 02:18 PM
  #38
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Default RE: Aileron Differential


Quote:
ORIGINAL: Top_Gunn

Quote:
The first generation of RC models were neither ''weird'' nor were they made.of foam. A good pilot with the right rudder-only plane can do some remarkable aerobatics.

Jess
I believe you're talking about ordinary R/C planes without ailerons (two- or three-channel today, usually; one-channel back in the day. They turn by banking, with the bank induced by using rudder. Hanson is talking about planes that turn without banking, not the ''first generation of RC models.'' Some of them are not made of foam, to be sure. Whether they're weird is, I suppose, a matter of taste. Why they was worth bringing up in a thread on aileron differential I don't know.
First full scale craft had no ailerons -
some gliders use NO ailerons - they use spoilers
Foamies are not the only models which don't use ailerons
Being different is not weird- just different
Once one understands WHY these models -and full scale- do not us ailerons - the correct use and design of ailerons becomes easier to understand.
That is why I mentioned it -
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Old 07-29-2013, 04:11 PM
  #39
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Default RE: Aileron Differential

OK Guys, I increased my aileron throw now the ailerons work great except for the increased drag on the outside turning wing.
I dialed in some aileron differential and now have a much more controllable airplane, I did not take away the need for using rudder in the turns but I greatly reduced the adverse yaw in the aircraft.
The plane flies like a ww1 aircraft, you have to use all controls to get it around the field, by applying the differential it has helped smooth out the turns and puts a little more confidence in those tight turns where the plane wanted to wallow or stall because of the extreme drag.
I reduced the down aileron throw half of what the up aileron throw is.
I have over three inches of travel in the ailerons from neutral which sometimes is needed in gusty conditions when the aircraft slows down for landing, plus these 1/3 scale bipes you have to really have large throws just to get them to react.
I love my pup!
Thanks to all the great info, I really appreciate the help everyone has given.

Ron
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Old 07-29-2013, 05:01 PM
  #40
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Default RE: Aileron Differential

Quote:
First full scale craft had no ailerons -
some gliders use NO ailerons - they use spoilers
Foamies are not the only models which don't use ailerons
Being different is not weird- just different
Once one understands WHY these models -and full scale- do not us ailerons - the correct use and design of ailerons becomes easier to understand.
The first full-scale planes used wing warping, which the patent litigation between Curtiss and the Wrights held to be the same thing as ailerons. But you forgot to mention the jets and rockets that use thrust vectoring to change direction. That's about as useful a contribution to a discussion of turning with ailerons as the rest of these examples.
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Old 07-29-2013, 08:34 PM
  #41
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Default RE: Aileron Differential


Quote:
ORIGINAL: Top_Gunn

Quote:
The first generation of RC models were neither ''weird'' nor were they made.of foam. A good pilot with the right rudder-only plane can do some remarkable aerobatics.

Jess
I believe you're talking about ordinary R/C planes without ailerons (two- or three-channel today, usually; one-channel back in the day. They turn by banking, with the bank induced by using rudder. Hanson is talking about planes that turn without banking, not the ''first generation of RC models.'' Some of them are not made of foam, to be sure. Whether they're weird is, I suppose, a matter of taste. Why they was worth bringing up in a thread on aileron differential I don't know.
Top, as indicated by this and your subsequent post your singularity of focus is the equal of a fine microscope.

I expect that if you carefully read the post to which I was replying the intent of my post will become clear. If not do not worry, the matter is of no great social or political import.

If I might be so bold as to make a suggestion, perhaps if you find a post of no interest simply skip over it and not waste your valuable time in formulating a reply, though Ii always find your posts informative and interesting.

Jess
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Old 08-22-2013, 07:02 PM
  #42
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