flat spins..?
06-19-2006, 12:28 AM
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flat spins..?
Hey all,
I've come up with 2 methods of preforming a flat spin at my club. I know which works best on my plane (oviosly not flat with a trainer) but I'm wondering what the correct method is. Or if it's just a style thing. Quite a few members hold to Ailerons and rudder in same direction. This will spin my plane but no where near flat. Kinda like repeated snap rolls straight for the ground. The method that atleast on member uses, and works far better on my plane (probably can get it to 45 degrees from level) is rudder and aileron in opposite directions. Anyone?
-John
I've come up with 2 methods of preforming a flat spin at my club. I know which works best on my plane (oviosly not flat with a trainer) but I'm wondering what the correct method is. Or if it's just a style thing. Quite a few members hold to Ailerons and rudder in same direction. This will spin my plane but no where near flat. Kinda like repeated snap rolls straight for the ground. The method that atleast on member uses, and works far better on my plane (probably can get it to 45 degrees from level) is rudder and aileron in opposite directions. Anyone?
-John
06-19-2006, 01:45 AM
#3
RE: flat spins..?
You wont really be able to flat spin a trainer very well. They just are not made for it. But you can play with the control inputs and get a little bit of a spin out of them, as you say it is going to spin with the nose pointed downward and just will not flatten out.
Flat Spin
When you want to "flat" spin upright you use full up elevator and full rudder in the same direction, and then you only use enough aileron in the same direction
to get into the spin. Once the plane enters the spin you get off of the ailerons (as needed) to flatten it out. Throttle also plays a big roll in flat spins. Too much throttle and you will pull the nose up too high and can even flip the plane over backwards, not enough and you cant get it to really flatten out and the nose will ride pointing downward a little through the spin. It also helps to be a little tailheavy to get a really good flat spin.
For an inverted flat spin you input full down elevator and the rudder and aileron inputs are opposite. ie. left rudder and right aileron or vice versa. Same rules about centering the ailerons and adjusting the throttle to flatten out the spin apply.
Normal Spin
Normal spins are basically the same inputs as flat spins, but you dont use any throttle, you spin at idle. The planes spins with the nose pointing downward somewhat. Depending on the CG and control throws the amount the nose points down will vary.
The perfect spins (we are talking RC here all of you aerodynamic experts) will descend vertically at the CG of the plane, as if the cg were affixed to a line on a plumb bob (with the exception of wind drift) and the nose and tail will rotate conically around the CG. The plane sortof looks like it is "sitting" as it spins. It should not barrel roll and it definitely should not aileron roll.
Ideally you enter a spin by stalling the airplane. You get up real high and chop the throttle. The plane will slow down to a stop and stall either by falling forward or by dropping a wingtip and falling forward at the nose at the same time. Most folks start to discretely feed in up elevator as the plane comes to a stop which will stall the plane more visibly and cause the nose and one wingtip to drop more dramatically. But thats cheating.
Flat Spin
When you want to "flat" spin upright you use full up elevator and full rudder in the same direction, and then you only use enough aileron in the same direction
to get into the spin. Once the plane enters the spin you get off of the ailerons (as needed) to flatten it out. Throttle also plays a big roll in flat spins. Too much throttle and you will pull the nose up too high and can even flip the plane over backwards, not enough and you cant get it to really flatten out and the nose will ride pointing downward a little through the spin. It also helps to be a little tailheavy to get a really good flat spin.
For an inverted flat spin you input full down elevator and the rudder and aileron inputs are opposite. ie. left rudder and right aileron or vice versa. Same rules about centering the ailerons and adjusting the throttle to flatten out the spin apply.
Normal Spin
Normal spins are basically the same inputs as flat spins, but you dont use any throttle, you spin at idle. The planes spins with the nose pointing downward somewhat. Depending on the CG and control throws the amount the nose points down will vary.
The perfect spins (we are talking RC here all of you aerodynamic experts) will descend vertically at the CG of the plane, as if the cg were affixed to a line on a plumb bob (with the exception of wind drift) and the nose and tail will rotate conically around the CG. The plane sortof looks like it is "sitting" as it spins. It should not barrel roll and it definitely should not aileron roll.
Ideally you enter a spin by stalling the airplane. You get up real high and chop the throttle. The plane will slow down to a stop and stall either by falling forward or by dropping a wingtip and falling forward at the nose at the same time. Most folks start to discretely feed in up elevator as the plane comes to a stop which will stall the plane more visibly and cause the nose and one wingtip to drop more dramatically. But thats cheating.
06-19-2006, 08:58 AM
#4
RE: flat spins..?
I did my first Flat Spin about a week and a half ago. It was with a customized SPAD with rediculous control throws and a less than perfect CG. I did it completely on accedent. I took the plane high and chopped the throttle/split the sticks/full up elevator. I expected an ever accelerating nose down downward spiral but saw a near perfect flat spin with a slow decent. Well I perfomed this maneuver 3 times succesfuly and had 2 succesful recoveries
So give yourself some room and don't stare at it to long after you get it right.
So give yourself some room and don't stare at it to long after you get it right.
06-19-2006, 09:47 PM
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RE: flat spins..?
Thanks all,
I've done osme googling too. I think next time I go up I'm gonna try how, from what I gathered, full scale does it. Enter a nomal spin by approaching stall and just before stalling shoving sticks to buttom same side corner. After normal spin established advancing throttle and feeidn in opposite ailerons. I'm quite curious what happens. What suprised me about when I enter spin by going wot straight up and shoving sticks opposite corners is the plane does not self recover with neutral. Well, atleast not in 2 spins where I kicked it out with opp. rudder. I would have thought a trainer would have corrected faster.
-John
--edit--
a Hypothesis. Thinking about it, my guess on what's gonna happen when I try the above is: Sprial dive towards ground. As soon as I easy up on ailerons and start feeding in throttle it's gonna start coming out of the spin. I am guessing the trainer is gonna self correct to fast to maintain the spin into power and opp. ailerons.
I've done osme googling too. I think next time I go up I'm gonna try how, from what I gathered, full scale does it. Enter a nomal spin by approaching stall and just before stalling shoving sticks to buttom same side corner. After normal spin established advancing throttle and feeidn in opposite ailerons. I'm quite curious what happens. What suprised me about when I enter spin by going wot straight up and shoving sticks opposite corners is the plane does not self recover with neutral. Well, atleast not in 2 spins where I kicked it out with opp. rudder. I would have thought a trainer would have corrected faster.
-John
--edit--
a Hypothesis. Thinking about it, my guess on what's gonna happen when I try the above is: Sprial dive towards ground. As soon as I easy up on ailerons and start feeding in throttle it's gonna start coming out of the spin. I am guessing the trainer is gonna self correct to fast to maintain the spin into power and opp. ailerons.
06-19-2006, 10:20 PM
#6
RE: flat spins..?
That is precisely how its done strider. A plane will not upright spin correctly if you input cross controls. The reason cross controls work in an inverted spin is because although the control inputs are opposite, the rudder is actually causing the plane to spin in the same direction as the ailerons did when they initiated the spin. You want to talk about not recovering, wait until you get an Ultimate Biplane into a true inverted flat spin.. You talk about non recovery. Its almost impossible to get it out of the spin without considerable forethought.
Your hypothesis is what will happen. Mainly because a trainer is going to want to self correct. Its almost impossible to get a trainer to maintain a stall condition. As soon as the nose drops its going to start flying again. As a matter of fact as soon as it develops any forward speed whatsoever it will start flying again.
Heres a video we shot of my 2nd flight on my new 35% Extra. At the 3 minute mark I did an inverted flat spin into an upright flat spin. This was just a test and trim flight and pretty conservative so there isnt much to it so dont expect a dazzling display. The angle is a little deceiving and it looks like the nose was pointing down just a little but it wasn't. It was flat.
http://kenvids.com/videos/Extra260-2ndFlight.wmv
Your hypothesis is what will happen. Mainly because a trainer is going to want to self correct. Its almost impossible to get a trainer to maintain a stall condition. As soon as the nose drops its going to start flying again. As a matter of fact as soon as it develops any forward speed whatsoever it will start flying again.
Heres a video we shot of my 2nd flight on my new 35% Extra. At the 3 minute mark I did an inverted flat spin into an upright flat spin. This was just a test and trim flight and pretty conservative so there isnt much to it so dont expect a dazzling display. The angle is a little deceiving and it looks like the nose was pointing down just a little but it wasn't. It was flat.
http://kenvids.com/videos/Extra260-2ndFlight.wmv
