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Learning the Flatspin

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Learning the Flatspin

Old 12-05-2009, 07:23 AM
  #1  
gauravag
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Default Learning the Flatspin

Hello everyone,
I have a pattern-like airplane - Javelin-90 that is a 66" wingspan, 67" fuse and got a Saito 125 in the front.
Now i am trying to do the inverted flatspin ( heard that planes like this better than upright ), and need some help.
Here is how i am attempting this .
1. I take the plane high up as much as i can, and invert it, then reduce throttle and keep increasing the down elevator, till the plane stalls.
2. At the stall break, i give FULL Down elevator and FULL Left rudder. Plane gets into a tail spin
3 Then i give opposite aileron ( sticks on the same side as rudder ) , and add throttle,

However the plane does not really flat spin , and the nose is always pointed down, and comes rapidly towards ground in a tailspin kind of manoever.

The CG is quite aft, as i can do KE without any elevator inputs.
I tried giving more throttle but that did not really help, the plane instead came towards the ground faster.
I also tried giving more opposite aileron, though it tried to flatten the plane, it did not really perform a good flatspin.

Elev. throw is at the max on the servo arm/control horn. This is around 20-30 degrees. Servos are Hitec Digitals . Twin on Elevator.
Elevator is more than 50% of the stab, and so quite big.

Please help me learn this manoever.
Thanks !
-Gaurav
Old 12-05-2009, 09:10 AM
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ro347
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Default RE: Learning the Flatspin

need more throw.
Old 12-05-2009, 09:46 AM
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Jezmo
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Default RE: Learning the Flatspin

On my AeroWorks Extra 260 I have 45 degs of elevator travel and 50 degs of rudder. It takes all of both inputs and a little opposite aileron with the throttle slightly higher than idle to get a decent flat spin. My CG is also far enough aft that the plane needs NO stick input to maintain level flight while inverted. It tucks slightly to the gear on knife edge so it's quite tail heavy but it does beautiful waterfalls, knife edge spins, etc. It does awesome elevators, harriers, and also hovers quite nice. Point of all of this is the CG needs to be pretty far back with a bunch of control travel to get a good flat spin. The ratio of elevator area to horizontal stab surface area is important too as while in the spin the relative wind will tend to push up on the stab and attempt to push the nose down causing it to break out of the spin. This is why some planes flat spin well and others don't.
Old 12-05-2009, 10:26 AM
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daveopam
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Default RE: Learning the Flatspin

A couple things to try. First this is how I get into one. I go vertical and get plenty high, then cut the power with the plane still pointing up. When it stalls, I give full down, full right rudder and full left aile with the engine at idle. After the first few spins I start to bring the aile back to center as I add a little power. The amount of opposite aile and throttle is different on every plane. You need to find the sweet spot. Some planes need 100% opposite aile and some need centered aile. Same on throttle, some need 1/3 power some need full. I have an Ult that will go flat at idle. So experiment.
Second thing you might try is going into a flat spin from a blender. To do this climb out and point the nose straight down. After the plane gains a little airspeed, give the inputs I described above. This can be a very violent maneuver, so increase the airspeed a little at a time.
Also,like Jezmo said CG is a big part of it. You have your CG perfect for pattern. This does not mean it is right for a flat spin. If you still cant get it flat this is where you need to look. Finally, the plane you have is not the best for a flat spin. Pattern ships are designed to be stable. The long tail is hurting you to a certain extent. You may never get it totally flat.

David

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