posted 05-14- 08:44 AM               

I heard once that any plane will spin, some easier than others. Is this true? If so, why is it so hard to get a plane (FM wise) to spin? I tried to get my SE5a to spin with no luck. BTW, I have never got my R/C glider to spin...

What is the trick to get OpenPlane aircraft to spin? What keeps these planes so stable? I heard once that pushing out mass to the outside would help keep the momentum of a spin. I made the Ailerons of my SE5a very heavy. I also made the tail heavy and countered that by squishing the engine inertia box ahead by the prop. If anything, this seemed to fight a spin! Now the plane would just stall foward and recover.

When the weight is is set back the way I had it, the plane will start to spin, but if you let the controls go neautral it recovers to stright flight very quick. Any roll or yaw momentum is instantly disposed of.

So can anyone gice me some insight on what keeps a plane spinning and how do I implement this for my plane? Or would a real SE5a never spin?

Thanks.

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-Sv =FC=

WWI in SDOE!

posted 05-14- 10:07 AM               

For sure man, Whats up with the planes.

I know that they do spin OCCASSIONALY But thats it. And I dont' think I have ever had a inverted flat spin and thats supposed to be one of the things you have to watch out for during inverted manuvers at low speed.

Heck I do that all the time but never spin.

Also most of the planes have REALLY gentle stalls. Some are hard in a banked turn and flick onto there back but thats about it.

Most of the time if you decrease your speed and pull back gently you can keep it falling just fine it never actually seems to stall or if it does one wing just slips down and you go down in a gentle spiral till over stall speed again.

Is that how its supposed to be?

posted 05-15- 05:48 AM               

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C/O Jagdgeschwader 5 'Eismeer'

posted 05-15- 09:28 AM               

Jerry, Yeah I have gotten them to spin lots but not by trying. Most just in a fight and yanking the stick around to much I guess.

I have been stuck in them and crashed a couple times.

Mosty I find some planes like to flick on there back in a banked turn or in a loop.

posted 05-15- 10:28 AM               

I'll make a deal with ya ...

You help me with my DOF problems with lining up my control surfaces on my F86 and I'll get your SE5a to spin ...

posted 05-15- 10:49 AM               

I am a good DOF-liner-upper

posted 05-15- 01:06 PM               

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Tony "Razer" Martin

http://www.fshangar.com

posted 05-15- 01:32 PM               

Yeah some will spin. Most will spin. BUT they never spin inverted which is supposed to be why you should avoid inverted manuvers at low speed.

Also they stall really gentle most of the time. They never really start to fall right out of the sky it seems.

posted 05-16- 12:01 PM               

If you want more info on the stall e-mail me or look on a aerodynamic book...

posted 05-16- 01:04 PM               

What is a stall really? Is is not just a sudden drop in lift produced by a wing? A point a which the wing loses most of its abilty to produce lift? A wing may still be producing lift but be "stalled", right? I am not sure of what a stall really means, is it not also typicaly associated with loss of laminer flow as well? Or is this just another qualification?

Still, the stall is only part of the spin. I have been hearing more lately that many spins are a result of the wing blocking airflow (or causing turbulance) to the stabalizer - this eleminates the stabilty of the aircraft and therefore its ability to counter the spin. Is this the only cause of an uncontrolable spin?

posted 05-16- 01:49 PM            

The lift is produced by an area of lower pressure above the wing. The stall occurs when the airflow over the wing, that produces this low pressure area, becomes turbulent, thus collapsing the lifting area. Some lift may still be produced, but it should be very little. To really guess, I think the buffeting you notice just before a stall is the tendency for the airflow to collapse the area, but then it rebuilds again (maybe because the AOA is reduced just little enough??)

I think the publised stall speed is when you're at level flight, not zero AOA. In fact, you'd probably have quite a high AOA. This stall speed must be at some weight of the plane too. Make it heavier and you need higher AOA to keep lift, thus stalling at lower speed (compare to accelerated stall, it's the same effect.)

posted 05-16- 01:57 PM            

never tell a flight instructor a plane stalls at different AOA. Mine would have killed me
Seriously, a plane always stalls at a certain AOA and it can stall at any airspeed.
The reason is the following equation

lift = ½ r V² × coefficient of lift × area
coeffecient of lift = function of AOA

as lift has to balance gravity and the coefficient of lift is related to the AOA, you need a certain AOA for a certain airspeed for straight and level flight. If you reduce airspeed you need a greater angle of attack. The airspeed where you reach the critical AOA is your minimum stall speed. But e.g. in a 4g turn you need 4x more lift to balance your weight, therefore you reach the critical AOA at 2x the minimum stall speed.

Check the following section for a good explanation about what is a stall
http://www.monmouth.com/~jsd/fly/how/htm/spins.html#SECTION002110000000000000000

and how you enter a spin http://www.monmouth.com/~jsd/fly/how/htm/spins.html#SECTION002150000000000000000

posted 05-16- 03:15 PM               

I see what you are saying bakunin. That all makes sense to me except the part about accellerated stalls, I get confused a bit here. The extra g-force is created by the extra lift of the wings at a higher AOA in a turn. This lift is accelerating the plane upwards, or in a turn, around the turn.

Isn't an accelerated stall the result of pushing past critical AOA at high speed? I am guessing here, but wouldn't the critical AOA be less at higher speed? Just the way the air flows over a wing at certain speeds, at higher speeds with a given AOA, might laminer flow break into turbulance earlier than at slower airspeeds? If this is so, then there is a simplification made in these sims, right now the lift coef is static over airspeed... is this really true?

An example: A wing in a wind tunnel at 30 degree AOA and a 40 mph airspeed. We have laminer flow and a high lift coef. Now the same wing at the same AOA with 150 mph airspeed. Might this result in seperation and turbulance and therefore a significantly lower lift coef?

I am guessing today too LOL. But it is fun

posted 05-16- 03:21 PM               

If a plane loses lift in a turn (below the G induced weight as you suggest), wouldn't this just cause the plane to lessen its turn and not completely stall? You seem to imply by referencing the lift equation that a stall is anytime the lift is less than the weight. If this were the case, then any aircraft in a decent would be in a stall.

It seems that that "stall" is more an event that has to do with laminer flow and seperation, is it not? If a wing could keep laminer flow (and therefore its lift making abilities) at very high AOA, there would never be a stall, right? The curve would be expodential with the slope increasing as the AOA increases. Of course this is impossible as it would mean infinite lift at 90 degrees AOA, but keeping laminer flow is impossible as well...

Just more thinking aloud...

posted 05-17- 12:00 PM               

Other thing, the stall is a heavy drop of lift caused by the lost of laminar flow. But the wing continue to make a little bit of lift. In fact 75% of the lift is make by the suction of the air at the top of the airfoil (extrados) and the left 25% is create by the air deflected by the bottom of the wing (intrados). When the airfoil stall you lost nearly all of the 75% of lift.

posted 05-17- 03:27 PM            

sorry sv for not responding, but I am bit busy right now. I am off for holiday. 3 weeks flying around california