Base to final spin

E_Dawg

Moderator
In the situation of base turning final, overshooting, jam on bottom rudder and stall / spin: does the bottom wing stall first or do both wings stall at the same time with the bottom wing more stalled?
 
Why does this seem like a loaded, baited question?
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In the situation of base turning final, overshooting, jam on bottom rudder and stall / spin: does the bottom wing stall first or do both wings stall at the same time with the bottom wing more stalled?

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I've always thought the bottom wing stalls first. If you have an appreciable roll rate, it may just be enough to push the relative wind on the "inboard" wing past its stalling AOA. Also, the outboard wing is moving a little faster through the air, so it may have just a hair more freestream energy to keep the flow attached.

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Also, does stall speed rise when flying uncoordinated?

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I'm gonna go out on a limb and say, "no." Break the relative wind into two components: perpendicular and parallel to the chord of the wing (not counting swept wings here). The lift keeping the plane in the air is generated from the flow perpendicular to the wing. The airspeed should measure only the chord-wise component of the flow, so the indicated stalling speed shouldn't change.

The spanwise flow, that doesn't generate any lift but lengthens the path could become a factor in extreme cases. After the flow over the wing has traveled a certain distance ("characteristic length"), it is apt to transition from laminar to turbulent. Because its flowing diagonally compared to the lifting surface, the flow may become turbulent at a shorter distance along the chord and effectively reduce the efficiency of the wing and generate less lift.

Maybe I'm full of it?
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Why does this seem like a loaded, baited question?

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Nah, if I knew the answers I wouldn't have asked
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Thanks for the post, what you said is pretty much what I was thinking... anyone else?
 
I think the explanation was very clear and correct...

The spin is a very stable maneuver, and it has been known to save lives a couple of times: flying VFR aircraft, being caught above the layer (relatively high ceilings), the pilot did a spin from above, recovered when he was in the clear below, everything went fine.
 
If you go out and do crossed control stalls, you will find that you will get stall horn and buffet well above normal stall speed. In a Cherokee, it is possible to get a good buffet above 60 knots in the clean configuration. In the Arrow, this increases to close to 70 knots.

Based on this, I would say that it is possible to stall an uncoordinated aircraft on the base to final turn at a much higher speed than would otherwise be expected. This is one of the reasons it is the most dangerous of stalls. It happens at a speed the pilot considers safe, and since the aircraft is uncoordinated and then stalled, it will spin. Once in a spin there is really no chance of recovery since the pilot was caught by suprise and the altitude is so low.
 
ananoman thanks, I'm trying to fill out a written test... some of these questions are tough; so you're saying an aircraft can NOT fly at published stall speed in a slip?
 
When you are talking about stall speed, remember that it varies. The constant is the AOA at which the a/c will stall.

You will not be able to fly a forward slip at the critical AOA, since the wing will be in a stalled condition.

For the slip, I ask my students to carry a little extra speed, doesn't hurt; Plus it might even help you, since you increase the parasite drag when the airspeed increases, therefore you are loosing altitude faster (if altitude is what you want to loose).
 
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The spin is a very stable maneuver, and it has been known to save lives a couple of times: flying VFR aircraft, being caught above the layer (relatively high ceilings), the pilot did a spin from above, recovered when he was in the clear below, everything went fine.

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Are you kidding me?! Sounds like a prime candidate for the Darwin awards. What kind of a moron would do something like that?

Lets see, did he:

-Declare an emergency? I hope so, since he broke about half a dozen regs. Well..maybe I hope not...probably shouldn't have a license anyways.

-Take into account that their might be a mountain...or traffic in the clouds below?

-Think of maybe using, oh I dunno....BAI instead?

say_speed, you come up with some "out there" stuff, man.

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For the slip, I ask my students to carry a little extra speed, doesn't hurt; Plus it might even help you, since you increase the parasite drag when the airspeed increases, therefore you are loosing altitude faster (if altitude is what you want to loose).

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The goal of the forward slip is to lose altitude without increasing airspeed. If you let the airspeed build up, you then have to lose it somewhere. If you end up floating down the runway, that throws any quick descent you did out the window.
 
I don't mind gaining 5 kts or so on the IAS seein' how as the old peter tube ain't facin' direct in the wind no more...

Dave
 
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I would say that it is possible to stall an uncoordinated aircraft on the base to final turn at a much higher speed than would otherwise be expected.

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True, true ... there is the consideration of load factor. So your stall speed is gonna be roughly = 1g stall speed / cos(bank angle)
 
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The spin is a very stable maneuver, and it has been known to save lives a couple of times: flying VFR aircraft, being caught above the layer (relatively high ceilings), the pilot did a spin from above, recovered when he was in the clear below, everything went fine.

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I thought when a VFR pilot gets caught in IMC he tries to AVOID getting into a spin?
 
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Are you kidding me?! Sounds like a prime candidate for the Darwin awards. What kind of a moron would do something like that?

[/ QUOTE ]Perhaps a little history is in order. In the early days of aviation (WWI era) it was common practice to "spin through the overcast." There was no such thing as instrument flying. Not much of ANYBODY flying for that matter. Even post WWII, a lot of planes were designed with spins in mind. Take a look at all of the taildraggers built prior to the 1960s. All have very large vert stabs with wide cord rudders.

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Lets see, did he:

-Declare an emergency? I hope so, since he broke about half a dozen regs. Well..maybe I hope not...probably shouldn't have a license anyways.


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To who? No radios. No regs either.

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-Take into account that their might be a mountain...or traffic in the clouds below?

[/ QUOTE ]No such thing as IFR flying yet.

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-Think of maybe using, oh I dunno....BAI instead?

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No attitude intruments. Only things in the cockpit were a wiskey compass, tach, airspeed, and altimeter.

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say_speed, you come up with some "out there" stuff, man.

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OK, sorry.

I wasn't thinking back in the 40's. I assumed he meant more modern-day, which may as well be suicide given the lack of spin training thats required now. Guess thats what I get for assuming.
 
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True, true ... there is the consideration of load factor. So your stall speed is gonna be roughly = 1g stall speed / cos(bank angle)


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This will not work for an uncoordinated stall. The 1g stall speed assumes smooth, even airflow over the entire aircraft.
 
ESF, look at the spin in comparison to a spiraling dive. In all honesty, the spin is easier to control and stablize than the ever spiral. One thing that is really amazing about the spin is that the sink rate is very stabilized. My spin training was with an aerobatic instructor, former F-18 driver and Top Gun instructor. He really hammered home the differences between the two. We all typically fear the spin because no one does them and they are said to be so difficult to recover from. But, in the proper plane and properly loaded (hence the 1940's planes fitting this cat.) the spin can be pretty benign.

Also, Ed (E.G). the spin always goes towards the yaw. So if you are slipping in straight ahead with full right rudder and you pull the nose up and stall, the right will will drop, or more importantly, the left will fly up and over the top of the fuselage and enter you into the spin. But to the pilot, it would seem as though you spin backwards. -C



.
 
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ESF, look at the spin in comparison to a spiraling dive. In all honesty, the spin is easier to control and stablize than the ever spiral. One thing that is really amazing about the spin is that the sink rate is very stabilized.

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Yeah, I see what you're saying. It just sounded like he was touting a spin as a way to recover from being stuck above an overcast, but I admit, I jumped the gun a little.

Hows the instructing going, by the way?
 
It is going really well. I am learning tons and working my butt off. The only problem has been a lack of freetime. I am finally working on my multi and hopefully get the MEI done soon. I have been wanting to do that so some time now but I never have the time to myself. It is a great position to be in considering that many CFI's are out there waiting for studs all the time. I have managed to log over 150hr dual given in less than 90 days!
 
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