Airspeed when Slipping to landing

Ok. But from a slip, wouldn't the plane drop the high wing and spin toward the yaw?

I thought the skid-to-spin scenario people cite as a common base-to-final turn scenario also had to do with load factor from the bank raising the stall speed, but not the matching of the bank to the yaw direction. Why would bank independent of yaw have anything to do with AoA and affect the spin/stall, except for load factor?
 
Jaybird180 said:
In a stalled slip, are the wings at equal AoA?
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Probably not exactly, but not nearly as far apart as in a skid. Again, try to get a real stall from a full slip. Think about slipping with right rudder and left aileron - yaw to the right generally increases the AoA of the left wing, but left aileron reduces the AoA of the left wing, which has an opposing effect.

Jaybird180 said:
Is it your statement(s) that the airplane will NOT spin?
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Most of the folks who argue that airplanes will spin out of a slip have never actually tried it properly. I think there are airplanes that will, but it's less common. I've only tried it in four different aircraft types, but never could get a spin (or even a real breaking stall) from a full slip.
 
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Jaybird180 said:
Is it your statement(s) that the airplane will NOT spin?
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I'll say that in the decathalon I used, the nose dropped in a mush, but the wing didn't drop. By contrast, when we were simulating the dreaded base-to-final skid, it flipped right over.

I need to think more about the aerodynamics. It may have something to due with the difference between aileron and rudder authority and what you run out of first.
 
TMetzinger said:
But if you're in a slip (with the ball on the inside), and you pull up to stall, you don't spin.
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I would rather say, "But if you're in a slip (with the ball on the inside), and you pull up to stall, you probably won't spin." It really is possible to spin out of that move if you're aggressive enough and the airplane has sharp enough stall characteristics. And even if it doesn't really spin, it can still be lethal. However, with that over-the-top entry, it isn't as lethal as a skidded turn stall at low altitude where the nose's first move is down.
 
Ron Levy said:
I would rather say, "But if you're in a slip (with the ball on the inside), and you pull up to stall, you probably won't spin." It really is possible to spin out of that move if you're aggressive enough and the airplane has sharp enough stall characteristics. And even if it doesn't really spin, it can still be lethal. However, with that over-the-top entry, it isn't as lethal as a skidded turn stall at low altitude where the nose's first move is down.
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I agree. Probably the best is to say you are much less likely to enter a spin from a slip (where your nose is already down) than a skid.
 
BayAreaFlyer said:
Ok. But from a slip, wouldn't the plane drop the high wing and spin toward the yaw?

I thought the skid-to-spin scenario people cite as a common base-to-final turn scenario also had to do with load factor from the bank raising the stall speed, but not the matching of the bank to the yaw direction. Why would bank independent of yaw have anything to do with AoA and affect the spin/stall, except for load factor?
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In a slip where the flight path is straight, the angle of attack on each wing will be equal. In a skid, the problem is that the flight path isn't straight; it's curved, and in a descending turn (the base-to-final scenario) the angle of attack is higher on the inside wing even if the airplane is coordinated. Skidding it increases the differential enormously and if that inside wing stalls it will flick over into a spin. Slipping in a descending turn decreases the AoA differential and increases safety.

It all has to do with the helical flight path each wing takes. The inside wing is descending at the same rate as the outside wing, but it is doing it on a smaller radius; therefore, the helix is steeper on the inside and the relative wind is striking the wing at a higher AoA.

If you go to this POA page... http://www.pilotsofamerica.com/forum/showthread.php?t=40070&page=4
...and scroll about two-thirds of the way down the page you will see pictures of an AoA demonstrator I built. A straight slipping turn could be shown on the straight/descending rails of this device and you'd see that the AoA is the same on both wings; in the descending turn the AoA differential gets worse in a skid and better in a slip.

Dan
 
BayAreaFlyer said:
Ok. But from a slip, wouldn't the plane drop the high wing and spin toward the yaw?

I thought the skid-to-spin scenario people cite as a common base-to-final turn scenario also had to do with load factor from the bank raising the stall speed, but not the matching of the bank to the yaw direction. Why would bank independent of yaw have anything to do with AoA and affect the spin/stall, except for load factor?
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The load factor is only a contributing factor. It makes the stall occur at a higher airspeed. But it won't spin if you are coordinated. The spin part only occurs when the pilot tries to force the plane around the turn by using more rudder without increasing the bank thus causing the inside wing (the low wing in a skid) to go slower and lose lift sooner.

As for the "can't slip to a spin" issue, think about it this way: You're in a slip with left wing low and full right rudder. You get slow enough to enter a stall. The high wing drops but you maintain full right rudder. Now the plane is trying to turn right because the bank has changed and you are still holding right rudder - in other words, you are now skidding and could quickly enter a spin.

You don't enter the stall from the slip. You enter it from the skid that occurred immediately after the wing dropped and the slip "ended". If you immediately released/reversed the rudder as the upper wing started to drop then you would never enter a skid. You might still be stalled but you wouldn't spin.

The real question is "how fast does the high wing drop". From everything I've heard, it's relatively slow on most of the small planes I'd be flying. On some planes it may happen so fast you don't have time to react so do it at altitude if you want to check it out in your own plane.
 
dbman5 said:
As for the "can't slip to a spin" issue, think about it this way: You're in a slip with left wing low and full right rudder. You get slow enough to enter a stall. The high wing drops but you maintain full right rudder. Now the plane is trying to turn right because the bank has changed and you are still holding right rudder - in other words, you are now skidding and could quickly enter a spin.
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Which airplane have you done this in?
 
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