A drink from the Aerobatic fire hose

I just love assjacks that show up on a forum telling everyone else hey are idiots and have no clue what they are talking about.
 
Ed: I'm not calling anyone an idiot, I'm just stating the facts.

Ok, thread revival: Bill, do you guys ever take a camera up when you fly? :)
 
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You military hotshots crack me up. Thanks for the entertainment.
 
Patch said:
You have some of the basic concepts down, but you're confusing them. You are correct in describing the concepts behind knife edge flight, but that is not how a level turn works. Adding top rudder to your turn will only create a rolling moment that will decrease the angle of bank. A great example of this is turn reversals.
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Theoreticall, in knife edge flight, there is no turning moment becuase both wings are at 0 alpha. Addition of top rudder in knifed edge flight in a flat bottom wing whihc could creat lift can be offset with aileron, and a heading change its done with elevator, in effect creating a turn, although not in the traditional sense of being coordinated, simply you have a heading change while maintaining level flight with all the lift being generated by the fuselage.
 
skimanjim said:
Theoreticall, in knife edge flight, there is no turning moment becuase both wings are at 0 alpha. Addition of top rudder in knifed edge flight in a flat bottom wing whihc could creat lift can be offset with aileron, and a heading change its done with elevator, in effect creating a turn, although not in the traditional sense of being coordinated, simply you have a heading change while maintaining level flight with all the lift being generated by the fuselage.
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When you use the elevator in that condition, what do you think the alpha is on the wing?
 
skimanjim said:
Theoreticall, in knife edge flight, there is no turning moment becuase both wings are at 0 alpha. Addition of top rudder in knifed edge flight in a flat bottom wing whihc could creat lift can be offset with aileron, and a heading change its done with elevator, in effect creating a turn, although not in the traditional sense of being coordinated, simply you have a heading change while maintaining level flight with all the lift being generated by the fuselage.
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Generated by the fuselage or by the "angle of attack" and thrust essentially pointed downward? Meaning, you're banked 90 right and the nose is pointed up toward the left side of plane. Thrust is pointed down. That's all I see at work here. Am I missing something?
 
Folks, let's not let this get personal. The discussion is fine, the personal comments are not.
 
Patch said:
Believe me, I am. And it can't be done. :)
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Problem is, if I am to believe you then I have to believe I've done the impossible. You can turn a plane in knife edge flight, it's just not a coordinated turn.
 
Jeez, who to believe. The experienced aerobatic guys on the board or the two guys who just showed up out of left field. But the new guys have JETS in their avatars, they must be experts!!!

Saying things wrt aviation like "It can't be done" is not to wise btw.
 
KennyFlys said:
Question: If lift is generated by the difference in pressure between the two surfaces of the wing of differing camber (if you will), how is it you're going to get lift from the side of a plane when both sides are identical?
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Kenny: There are two effects that produce lift with a wing. You're thinking of Bernoulli lift (lower pressure due to air traveling farther, blah blah blah). You're forgetting Newtonian lift ("every action has an equal and opposite reaction") which is pushing air downward and thus pushing the airplane upward.

In knife edge flight, you'll be developing strictly Newtonian lift from the side of the fuselage being at a positive angle of attack (in a way) and pushing air down.
 
flyingcheesehead said:
Kenny: There are two effects that produce lift with a wing. You're thinking of Bernoulli lift (lower pressure due to air traveling farther, blah blah blah). You're forgetting Newtonian lift ("every action has an equal and opposite reaction") which is pushing air downward and thus pushing the airplane upward.

In knife edge flight, you'll be developing strictly Newtonian lift from the side of the fuselage being at a positive angle of attack (in a way) and pushing air down.
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That's pretty much was I later described. High angle of attack on the side but it can only be maintained with substantial thrust pointing downward.
 
Patch said:
That's not the point. At 90 degrees of bank, it is impossible to sustain a level turn.
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What Chip said.

What happens if you're in knife-edge flight and you move the elevator? (along with the other necessary control inputs to sustain it) I'm pretty sure you're gonna turn...
 
Patch said:
At 89 degrees of bank, the amount of G required to hold level flight is pretty high, but not insurmountable as you still have some vertical vector.
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I do not think there has ever been an airplane built that could withstand the 57.3 G's you'd have in a level coordinated 89-degree banked turn, not to mention there has certainly never been a pilot built who could fly such a turn.

That's why in instrument nose high recoveries, we go to 90 degrees of bank to slice back down to the horizon.
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"we" do WHAT??? What on earth are you talking about?

That's the discussion on turning. When you talk about knife edge flight, you're not talking about turning.
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Are you saying it's impossible to turn when knife-edge?
 
KennyFlys said:
That's pretty much was I later described. High angle of attack on the side but it can only be maintained with substantial thrust pointing downward.
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thrust would only be required to hold altitude. just like wings level flight. my gliders got quite a large side area and a very effective rudder. bet i could hold it in knife edge. maybe i could thermal knife edge :):)
 
lancefisher said:
Problem is, if I am to believe you then I have to believe I've done the impossible. You can turn a plane in knife edge flight, it's just not a coordinated turn.
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I guess the discussion then becomes coordinated or uncoordinated. For coordinated, you just have to do the math - it's division by zero. For uncoordinated, I'm having trouble picturing the aircraft that wouldn't lose altitude or roll out of bank with top rudder at 90 degrees of bank and back pressure. How are you doing this?
 
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flyingcheesehead said:
I do not think there has ever been an airplane built that could withstand the 57.3 G's you'd have in a level coordinated 89-degree banked turn, not to mention there has certainly never been a pilot built who could fly such a turn.
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True, but at least it's a tangible number. Infinity is pretty hard to achieve. ;)
 
"we" do WHAT??? What on earth are you talking about?

Roll 90 degrees to the nearest horizon? Absolutely! You need to have gyros that won't tumble and a bit of training and confidence but this is one potentially lifesaving manuever. The bank angle will unload the wing and letting the nose fall back through the horizon get's you on the way to correcting your altitude. I attended upset recovery training (URT) two years ago with these folks http://www.calspan.com/ and it made a believer out of me. It's not totally intuitive but if you think about the aerodynamics of it you'll see the value and practicality.
 
Patch said:
I guess the discussion then becomes coordinated or uncoordinated. For coordinated, you just have to do the math - it's division by zero. For uncoordinated, I'm having trouble picturing the aircraft that wouldn't lose altitude or roll out of bank with top rudder at 90 degrees of bank and back pressure. How are you doing this?
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Anyway, going back to this discussion, the aerodynamics of this are a bit confusing to me.

Assuming a symmetric airfoil, at 90 degrees of bank with no elevator input, there is no load on the wings, zero AoA, and therefore no lift. You are being kept airborne by the alpha of the actual airframe. You maintain altitude (and alpha) by rudder.

Adding elevator increases the load on the wing - thus creating lift. You are now introducing a horizontal component. Because the nose is up, you're not coordinated which puts one wing more forward into the relative wind than the other, creating drag. This also creates a rolling moment if left unchecked. So then you're rolling out of your 90 degrees of bank.

If you counter that with aileron, are you not just slipping at that point? It seems to me you'd need a pretty high thrust to weight ratio to make that happen cross controlled without losing altitude. Maybe I'm just not completely understanding what's being described here.

In almost every airplane I've flown, completely level knife edge flight is challenging. I can't imagine making a level turn in such a cross-controlled configuration without losing/gaining altitude and maintaining perfectly 90 degrees of bank without rolling at all. :dunno:
 
Yea, you are essentially slipping the airplane, and where they place the turns, at least in a competition sequence, you still have plenty of energy to play with. for a short period of time, 90 to270 degree turn... the most you would likely see in a comptition, there is still enough energy available to maintain alitidude, and since you are not actually moving your wings forward/backward, it is in steady state, this not much difference in airflow and not a whole lot of roll created.
 
skimanjim said:
Yea, you are essentially slipping the airplane, and where they place the turns, at least in a competition sequence, you still have plenty of energy to play with. for a short period of time, 90 to270 degree turn... the most you would likely see in a comptition, there is still enough energy available to maintain alitidude, and since you are not actually moving your wings forward/backward, it is in steady state, this not much difference in airflow and not a whole lot of roll created.
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Not if you're exactly at 90. Ask any aeronautical engineer. It doesn't matter if you're doing 69 knots in a Cessna or in full AB in an F-16. You cannot maintain level flight if you try to turn the aircraft at EXACTLY 90 degrees of bank, period dot.
 
Fast n' Furious said:
"we" do WHAT??? What on earth are you talking about?

Roll 90 degrees to the nearest horizon? Absolutely! You need to have gyros that won't tumble and a bit of training and confidence but this is one potentially lifesaving manuever. The bank angle will unload the wing and letting the nose fall back through the horizon get's you on the way to correcting your altitude.
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I've never tried this, but it sound perfectly logical (and scary). You get quickly back to nose level without potentially putting a bunch of negative G's on the wings.
 
Bill Jennings said:
I've never tried this, but it sound perfectly logical (and scary). You get quickly back to nose level without potentially putting a bunch of negative G's on the wings.
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Negative G's are tough. I'm surprised that Mig I showed up was able to withstand a 4G negative dive.
 
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jesse said:
Negative G's are tough. I'm surprised that Mig I showed up was able to withstand a 4G negative dive.
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You were in a 4g inverted dive with a MiG28? At what range?
 
FlyNE said:
You were in a 4g inverted dive with a MiG28? At what range?
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Um, about 2 meters.
It was actually about 1 and a half I think. It was 1 and a half, I've got a great Polaroid of it, and he's right there, must be 1 and a half.
Was a nice picture.
 
jesse said:
Um, about 2 meters.
It was actually about 1 and a half I think. It was 1 and a half, I've got a great Polaroid of it, and he's right there, must be 1 and a half.
Was a nice picture.
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what were you doing there?
 
Bill Jennings said:
I've never tried this, but it sound perfectly logical (and scary). You get quickly back to nose level without potentially putting a bunch of negative G's on the wings.
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That's the idea! URT isn't acro but I think it's some of the most practical training a pilot can get. It may save your life.
 
FlyNE said:
:confused::dunno:
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You know, the finger!!
smiley_finger.gif
 
Ya know I have horses at home and jesse has a motorcycle. I feel a Top Gun scene comming on...cuz we all know he can't fly an F-18. ;)

Although, he probably has more hours than the flight team combined.
 
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IamBull said:
Not if you're exactly at 90. Ask any aeronautical engineer. It doesn't matter if you're doing 69 knots in a Cessna or in full AB in an F-16. You cannot maintain level flight if you try to turn the aircraft at EXACTLY 90 degrees of bank, period dot.
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Why not? If an airplane can go straight up, why cant its fuselage genereate enough lift to keep it flying?
 
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