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flight idle?

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Old 05-07-2010, 01:02 PM
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tripower222
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Default flight idle?

Im new to electric so this may be a elementry question but. I purchased a Eagle 580 50" EP (Matt Chapman) and it flies great but I dont like its glide ratio when the throttle is chopped it drops like a rock. Is it common to throw a mix in off a switch or dial and have a flight Idle position?
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Old 05-07-2010, 07:06 PM
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1320Fastback
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Default RE: flight idle?

I set the throttle trim on my electrics to keep the propeller moving at low stick, usually to where the ESC just makes the motor work and no higher.
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Old 05-07-2010, 11:31 PM
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Default RE: flight idle?

I have no idle position on my any of my planes.  Off is off.   If I want some throttle, I just move the stick.  Idle is an IC concept because you can't turn the motor off.  There is no place for it in electrics. 

Actually an "idle" motor, turning slowly actually induces drag which will just make the plane drop faster.

Leave the concept of Idle for your glow planes.
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Old 05-08-2010, 03:08 PM
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1320Fastback
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Default RE: flight idle?

Exactly I use it to get some of my faster planes to slow down, if your plane is dropping then you need to add throttle regardless of whether its at a complete stop or windmilling.
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Old 05-08-2010, 08:34 PM
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Default RE: flight idle?


ORIGINAL: tripower222

.....it flies great but I dont like its glide ratio when the throttle is chopped it drops like a rock.
This RCU review states it glides well:
http://www.rcuniverse.com/magazine/a...rticle_id=1121

Nose heaviness may be the cause of your situation; how does it fly inverted when the throttle is chopped?
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Old 05-09-2010, 07:39 AM
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Default RE: flight idle?



If you do want good gldier performance, if your ESC has a brake, setthe brake.   A windmilling prop acts like an air brake.  Stop the prop and you greatly decrease the drag. 

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Old 05-09-2010, 09:28 AM
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Default RE: flight idle?

Yes, I was very surprised by how much drag a windmilling or slow-turning prop induces. My light planes glide much better with the motor completely off and fully braked. Try some dead-stick approaches and see if you notice any improvement in the glide. I suppose it would matter less with a heavier plane.
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Old 05-09-2010, 12:16 PM
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Default RE: flight idle?

I disagree on two points made. I am new to this too, so please tell me if I am wrong!
1) Idling increases drag and has no place in electrics
2) Using the break to stop the prop will add to the gliding performance of the airplane
An idling GLOW engine will produce drag as the propeller will idle at a fixed speed. Any wind trying to accelerate the prop will fail to do so, and thus increase the resistance. With an electric motor without the break set, the propeller is free to spin up faster since there is no compression holding it back, and thus the windmilling propeller is not creating any drag. The break on an ESC will apply a resistive force to the propeller (like compression), so a stopped propeller will create more drag than a free spinning propeller. The break settings on some ESCs are variable, so you can adjust the amount of resistance to the spinning prop. A high break setting will/should stop it completely, whereas a lower break setting will let the prop spin but at a fixed rate.

Having an idle RPM is beneficial in many maneuvers, such as snaps and stall turns. The prop wash over the tail will help the plane through these maneuvers. Full scale planes have an idle RPM and use that to their advantage in many instances. Of course there are times when the idle RPM can be a negative thing, such as trying to land on a short field. The beauty of electric flight is that we have full control of this throughout the flight.

In precision aerobatics, we use the break function to slow the plane down on down lines, when gravity is trying to accelerate the plane in a vertical dive, or a similar attitude. If you want to the plane to glide, you want to turn off the break function and let the propeller spin naturally with the wind. Any force you apply in resistance to that natural spinning of the prop will work against the forward motion of the airplane.

I just started flying my electric pattern plane. I tried with the break on at first, as it was suggested in the forums related to my airplane. While it really does slow the plane down in a vertical dive, or coming down the back side of a loop, it also slows the plane down when gliding through the air. It was later suggested to me to leave an idle rpm until I got used to the feel of the plane and of electric flight, then I could start playing with no idle and playing with the break. Subsequent flights have really given me the benefit of flying the plane in a manner that I'm used to, and getting to learn the characteristics of the plane before having to learn the characteristics of electric flight.
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Old 05-09-2010, 01:38 PM
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Default RE: flight idle?


ORIGINAL: gaRCfield

...With an electric motor without the break set, the propeller is free to spin up faster since there is no compression holding it back, and thus the windmilling propeller is not creating any drag.
In order to increase RPM, the propeller needs rotational force applied from some source. With the plane at rest, the only source is provided by the motor. As it gains flight speed, airflow induced by forward flight can also induce prop rotation if the motor is stopped. The energy required to spin the propeller up with the motor off is going to be subtracted from the forward flight speed.

The same process is at work in helicopter auto rotation which allows for a soft landing in the event of engine failure. Helicopters have a free-wheeling unit that effectively disconnects the blades from the motor if it should fail and allows the blades to spin up and create enough lift to allow for a controlled, soft landing. If the blades were inhibited by the engine compression and transmission, it would fall like a brick.
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Old 05-09-2010, 08:56 PM
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Default RE: flight idle?

That's right, it does have more drag with the prop freewheeling. If it is slowing the plane down to much, crank up the throttle a bit till you get that glide speed that you want for decent approach, just above stall speed. Use your throttle as an elevator control.
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