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Old Feb 20, 2013, 10:24 AM
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Spin recovery varies -depending on the type craft
The idea is to break out of the revolving situation. (rimshot!)
in a very flat spin - slow revolving and slow descent - you have to do SOMETHING to get the nose down
I n one instance the test pilot on a canard actually stepped out of the cockpit and leaned forward -trying to shift cg enough to stop the spin. he ended up riding it down - injured but not killed .
Adding power (if there is enough) - works on some planes - but getting the nose down to pick up flying speed is the typical approach
On our own models most of em stop spinning as soon as control deflection is relaxed - they just fly out of it in a diving attitude.
But in a deep flatspin- juggling the power and elevator settings can reduce downward speed to zero- Just a nice round n round spin with the fuselage almost level to the ground.
Your Cub won't do this
Nor will my FunCub.
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Old Feb 20, 2013, 10:38 AM
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Adding power might introduce gyroscopic precession effects to the spin that can end up aggravating it, so depending on the direction of the spin adding power might make matters better or worse. Sometimes it's hard to properly detect the direction of the spin from within the cockpit, things get confusing pretty fast, so it's generally better to just bring the power to idle, try to drop the nose down and wait for the plane to exit the spin on its own. On some planes even applying opposite rudder can cause trouble, because the pilot might be in an inverted spin and not able to understand the spin direction. Seems crazy, but not unheard of.
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Old Feb 20, 2013, 10:41 AM
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I don't recall adding power being a part of any light aircraft spin recovery procedure. A bit off-topic, but for most jets, adding power is not recommended in a spin (if you still have power).

F-18 Out of Control Flight Procedures (including inverted/upright spins)
1. Controls - Release, Feet - Off Rudder Pedals
2. Speedbrake - Check In
-If still out of control
3. Throttles - Idle
4. Altitude, AOA, Airspeed and Yaw Rate - Check
-If command arrow present
5. Lateral Stick - Full With Arrow
-When command arrow removed
6. Lateral Stick - Smoothly Neutral
-When recovery indicated by yaw rate tones removed, side forces subsided and airspeeed accelerating above 180 knots
7. Recover
-Passing 6,000' AGL and dive recovery not initiated
8. Eject

It's pretty hard to get the F-18 to spin either upright or inverted.
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Old Feb 20, 2013, 10:44 AM
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Here's a nice article about spin recovery in a pitts special, but the same considerations apply to pretty much any plane: http://www.aopa.org/training/article...0603spins.html
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Old Feb 20, 2013, 10:49 AM
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Spin recovery varies from craft to craft-
always has
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Old Feb 20, 2013, 01:32 PM
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What kind of model design would promote a more aggressive type of spin that's hard to come out of?

Wing loading low high or medium?

Wing aspect ratio low or high?

Fuselage to wing span ratio?

Tail to wing separation?

Fuselage side area and shape?
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Old Feb 20, 2013, 03:50 PM
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Quote:
Originally Posted by grant31781 View Post
What kind of model design would promote a more aggressive type of spin that's hard to come out of?

Wing loading low high or medium?

Wing aspect ratio low or high?

Fuselage to wing span ratio?

Tail to wing separation?

Fuselage side area and shape?
What do YOU think is the worst case?
or -is it possible to have this problem in any of the types you listed .
what experiences have you had to qualify your thoughts ?
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Old Feb 20, 2013, 06:26 PM
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The jet I posted the video of has an aggressive spin however its tailess. Even though it spins well it is actually hard to get into the spin.

In my experience conventional planes with very little fuselage side area and short coupled always seem to spin fast and flat and have a little harder time coming out of a spin. For example a typical spad style gutter stick plane.

Fuselage length 30" with motor and rudder 34" Wing 12.5X48" H tail 8" root 5.5" tip X16" span. V stab 8" root 5.5" tip span 8". Distance between wing TE and Stab LE is 6.5". Fuselage 2.5 tall tapered starting at the TE of the wing to 1/2" tall at tail.

Longer coupled models always want to spin slow and nose down and recover easily.

I have not noticed wing loading making a large difference. I do not think it is possible to make my big 60 inch cub like plane go into a uncontrolled spin. I think the large box shaped slab side fuselage has a very strong anti spin effect. The plane does spin with full left or right rudder input and some up elevator. Remove either one and it stops immeadiatly. Spins are always nose down and moderate in speed and decent rate.
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Old Feb 20, 2013, 07:17 PM
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Thanks for sharing -
I have a background which includes many designs which were required to do and be judged on spin entry and exit - upright and inverted ,plus models which had to do snap rolls and yet exit on line -
Oher models types we flew also would sometimes proove to spin very easily or not spin at all.
The Cub you noted ( had a few different sizes of these) could and would snap easily under some conditions and having snapped would enter a spin - easily recovered tho ONCE speed increased.
The single factor in all types which caused unwanted spin and or snap- was high weight (wingloading.)
short or long high or low aspect ratio.
those which were virtually snap proof (spinproof) had extreme low aspect ratios ( 2-1)- you simply could not get a significant speed difference on wing panels
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Old Feb 20, 2013, 08:05 PM
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That is interesting. How high of a wing loading are you talking?

My 60 inch cub plane has an extremely low wing loading. 7.2 WL 3.72 cubic.

The 40 sized spads with the same dimensions has about a 22 oz WL with an 11 cubic.

Now the jet however had a wing loading almost identical to the 60 inch cub.

I am guessing the higher WL creates a stronger rotational force to sustain the spinning?

What type models did you build that did the best spins?
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Old Feb 20, 2013, 09:12 PM
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Quote:
Originally Posted by grant31781 View Post
That is interesting. How high of a wing loading are you talking?

My 60 inch cub plane has an extremely low wing loading. 7.2 WL 3.72 cubic.

The 40 sized spads with the same dimensions has about a 22 oz WL with an 11 cubic.

Now the jet however had a wing loading almost identical to the 60 inch cub.

I am guessing the higher WL creates a stronger rotational force to sustain the spinning?

What type models did you build that did the best spins?
Large scale aerobatic types - Edge-Sukhoi- Extra - 10-40 pounds
Th e spins could be entered at will- and slowed , speeded up by changing elev/power settings. here are a couple
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Old Feb 24, 2013, 08:08 PM
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I build two airplanes over the weekend to do some testing. 1st plane had a 24 inch 1.5 wing by .25 inch tall piece of popular for the fuselage. I built tail feather to fit the 60 X 9" wing used on the cub that doesn’t want to spin.

I really thought the wing would spin well however even with this plane it would not spin well. It would go into a fast rotation flat spin and i guess un stall and tumble then fall right out of the spin. The cub would not flat spin.

I got to thinking about the wing loading. The loading was ridiculously low so I cut the wing down to a 35 inch span. So 35 X 9 inch. I also resized the tai feathers.

Mixed results with this one. Changing the chord of the vertical tail made the plane spin. The wider chord tail would not let the plane spin no matter what I did. It would just spiral down. When I cut off a inch or so of the leading edge of the stab, the plane would spin easily.

So this made me figure the vertical tail has to stall out to allow the plane to keep spinning. Then i cut a new tail with the same area but with a high Aspect ratio. It was 2.5" X 8". This tail would really let the plane spin. The higher A/R stalls at a lower AOA so it worked well.

With neutral sticks the plane would keep spinning 8 or more turns before stopping. I cut some off the top of the tail and got into an unrecoverable flat spin. This was my final testing with the stick plane.

My new plane is a scaled down a Spad DPS to have a 31" X 8 inch chord wing and a 20 inch fuselage. Tail surfaces 18% H stab and 9% V stab of wing area. Cubic wing laoding is equivalent to a 46 powered DPS.

This plane is quite fast and fun and will spin extremely well and keep spinning hands off. Up elevator seems to be the easiest way to stop the spin. That is very strange but it works on this plane. Down makes it worse.

So the only thing I can think of that would cause the other planes not to spin well would be the fuselage side area is keeping the Vertical tail from stalling and the wing loading is so low that the wing unstalls easily.
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Old Feb 25, 2013, 06:55 AM
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If the elevator control surfaces are really large, up elevator might just un-stall the elevator and allow the plane to recover from the spin. On the Panavia Tornado the manual calls for up elevator to recover from a spin, which makes sense since it's a flying tail design without active stabilization.
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Old Feb 25, 2013, 08:40 AM
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The H tail is 4.5 X 10.25. Elevator is 2" wide.
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Old Feb 25, 2013, 11:14 AM
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2" on a 4.5" chord can mean a rather large change in pitch for the overall tail section with something like a 30° deflection
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