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« Reply #25 on: September 20, 2017, 10:24:31 PM »
K K Iyer
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@swapnilnimbalkar,
Thats not the end of the story though.
When you are in a left bank, the plane slips to the left.
When you are in a left yaw, the plane slips to the right.
Both result in extra drag as the plane is flying a bit sideways.
Balancing these two is called a 'coordinated turn'

Stopping here as we are quite far from the heading of this thread...
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« Reply #26 on: September 21, 2017, 05:54:16 AM »
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 Salute Iyer sir. Unretired fully now, I trust
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« Reply #27 on: September 21, 2017, 07:11:58 PM »
swapnilnimbalkar
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@swapnilnimbalkar,
Thats not the end of the story though.
When you are in a left bank, the plane slips to the left.
When you are in a left yaw, the plane slips to the right.
Both result in extra drag as the plane is flying a bit sideways.
Balancing these two is called a 'coordinated turn'

Stopping here as we are quite far from the heading of this thread...

Understood. Thank you Sir.

Now consider this imaginary situation.

I am in a level flight, now I move stick to the left for a left turn,
Left aileron has moved up and the right one down,

Now here's the twist,  suddenly the left aileron servo stops working and puts the aileron at its place i.e. at "0" position.
But the right aileron is down.

What will happen next?
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« Reply #28 on: September 21, 2017, 09:56:43 PM »
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@swapnilnimbalkar,
Let me share a true story.
I was flying my Dynam Tiger Moth slowly.
So slow that it was just about moving forward.
Its possible to fly her like that due to her low wing loading.
I gave left aileron, and she started turning right!
I really thought that the controls had somehow got reversed, but they had not.
So what's the explanation?

You need to look at a typical lift and drag curve graph to find out.
The clue lies in the fact that the airspeed was low, hence the ...... Huh???
I think you'll feel really happy on discovering the answer!
All the best.

image.jpg
Re: Props - Diameter and Pitch
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« Reply #29 on: September 22, 2017, 05:02:28 PM »
swapnilnimbalkar
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So this is what I feel,

consider a metal rod with two wheels on either end attached to it.

lets say the whole assembly is moving forward;

suddenly you apply brake on right wheel, still the left wheel is free to move, so what will happen?

left wheel will keep on moving and the whole assembly will take right turn.

In the Dynam Tiger example the right aileron which had moved down acted as a brake and left aileron was neutral so your plane turned (actually yawed) right, instead of rolling.

This is what I can think of. 

Expecting your views.
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« Reply #30 on: September 22, 2017, 06:27:33 PM »
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Left aileron was NOT neutral.

The problem needs to be viewed in aerodynamic terms, not mechanical engineering terms!


You need to look at a typical lift and drag curve graph to find out.

The clue lies in the fact that the airspeed was low, hence the ...... Huh???
I think you'll feel really happy on discovering the answer!
All the best.
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« Reply #31 on: September 24, 2017, 08:14:19 PM »
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I thought a lot about it.

It seems that,

when the plane was turned to left the (i.e. right aileron was down) it increased the Lift on right wing

but increased lift came with a penalty of increased drag.  Since the plane was just above stall speed it could not overcome the drag produced by the right wing.

Hence it turned to the right.

Correct  Head Scratching
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« Reply #32 on: September 24, 2017, 10:33:48 PM »
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I thought a lot about it.
It seems that when the plane was turned to left the (i.e. right aileron was down) it increased the Lift on right wing but increased lift came with a penalty of increased drag.  Since the plane was just above stall speed it could not overcome the drag produced by the right wing. Hence it turned to the right.
Correct  Head Scratching

@swapnilnimbalkar
Was wondering why no response for over 48 hours. Obviously you were thinking about the problem!

In scientific enquiry, one has to be careful in statements. You said:
"Since the plane was just above stall speed it could not overcome the drag produced by the right wing."
Remember that the lift and drag directions are at right angles.
So the lift cannot play any role of 'overcoming' drag.

Did you look at any lift curve and drag curve graphs?

The Tiger Moth, when at low airspeed, had to be flying at high angle of attack

In the lift drag curves, you will see that at high angles of attack near stall, an increase in the angle of attack produces negligible increase in lift, but a significant increase in drag. (right aileron down)
Similarly at high angles of attack near stall, a decrease in the angle of attack produces negligible decrease in lift, but a significant decrease in drag. (left aileron up)

Is this true when flying at higher airspeed, ie, at lower angle of attack?

I'll be very happy if you find the answer by looking at a graph of lift and drag vs angle of attack.
Enjoy your research!

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« Reply #33 on: September 25, 2017, 11:45:59 AM »
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Iyer Sir,

Did you look at any lift curve and drag curve graphs?
> Yes I did (but didn't understand),

But your statement,

"In the lift drag curves, you will see that at high angles of attack near stall, an increase in the angle of attack produces negligible increase in lift, but a significant increase in drag. (right aileron down)
Similarly at high angles of attack near stall, a decrease in the angle of attack produces negligible decrease in lift, but a significant decrease in drag. (left aileron up)"


made it clear.

What I assumed is that, lets say your wing is at an angle of attack of 10, I thought it means whole wing is at that angle of attack.  But when you deflect the ailerons your angle of attack is different on both the sides of the wing (correct?), I didn't know that.

"Is this true when flying at higher airspeed, ie, at lower angle of attack?"

>No, it's not true. At higher airspeed the angle of attack is decreased and CL will decrease but CD will decrease too!
Also at higher speeds L/D is most favorable.

It seems to be an interesting topic to explore.  I will try to find out more information on this.

Thank you!

Swapnil N.
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« Reply #34 on: September 27, 2017, 01:17:33 AM »
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At higher airspeed the angle of attack is decreased and CL will decrease but CD will decrease too!
Also at higher speeds L/D is most favorable

As I said earlier, have to be careful in your statements!
"At higher airspeed the angle of attack is decreased and CL will decrease but CD will decrease too!"
That was not the point.
What I wanted you to see was that the effect on the lift and drag, of a change in the AOA, at low AOA was different from that at high AOA.

"Also at higher speeds L/D is most favorable"
L/D is highest at a specific speed, not just 'higher speeds'
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