A drink from the Aerobatic fire hose

[IamBull]

Why not? If an airplane can go straight up, why cant its fuselage genereate enough lift to keep it flying?

Trust me on this, it's physically impossible regardless of aircraft.

 

[jason]

Trust me on this, it's physically impossible regardless of aircraft.

Thank God you cleared that up. To think that all of these other pilots thought that it might be a possibility.

Thankfully we have you around to keep us from dropping out of the air like flies.

 

[CJones]

Why not? If an airplane can go straight up, why cant its fuselage genereate enough lift to keep it flying?

Even if the fuse isn't generating a ton of lift, one would think that with the rudder lower than the engine, some of the thrust would be converted to vertical (in reference to the ground) lift. When I see guys doing knife-edge maneuvers at airshows, the tail is never level with the engine, the tail is always lower than the engine which leads ME to believe that a portion of the thrust created by the prop is actually acting as lift.

I'm not an Aero Engineer... but I am a thinker....

 

[Patch]

Although, he probably has more hours than the flight team combined.

Doubt it.

 

[Patch]

Sure it can. That's exactly what happens during knife edge flight. The aerodynamics discussion is whether you can then make a level turn while maintaining that 90 degrees of bank. We know that in coordinated flight, no aircraft can achieve this because of the G required to make it happen.

The question is, can it be done in uncoordinated flight? I can't see it being done since every description seems to point to the aircraft losing altitude or rolling out of the bank (or into more bank).

Why not? If an airplane can go straight up, why cant its fuselage genereate enough lift to keep it flying?

 

[BudRiggs]

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.

I saw a guy make such a turn. Perfectly level turn to the left, didn't gain or lose an inch of altitude.

The entire time he was in this 360 deg left turn, he was rolling the airplane to the right...to the outside of the turn.

I didn't believe it when I saw it, and still can't get my mind around how he was moving the controls to get that result.

It was an airshow at Roswell, NM, 1980's. It may have been part of Leo Loudenslager's routine.

 

[Tristar]

Don't worry Jesse, I think these "millitary hot shots" are compensating for something with thier jets.

 

[IamBull]

Thank God you cleared that up. To think that all of these other pilots thought that it might be a possibility.

Thankfully we have you around to keep us from dropping out of the air like flies.

You welcome . Just saying the question has been asked and answered 6-9 times already. Reminds me of the part in Zoolander where the hand model guy explains for like 5 minutes why male models are the perfect killers and then Zoolander asks "...so why male models?"...

 

[IamBull]

You military hotshots crack me up. Thanks for the entertainment.

You want the truth? You can't handle the truth! Son, we fly in a MOA filled with Cessna jockeys who are trying to kill us. And those MOA's are occupied by the mighty T-38. Who's gonna fly the mighty Talon? You? You, Jesse? I have a greater responsibility than you can possibly fathom. You fly your mighty skyhawk and curse the jet jockies. You have that luxury. You have the luxury of not knowing what I know: that flying formation at 300knots with an IP in the backseat trying to wash you out builds skill that you cannot possibly imagine. And my flying, while at a mindblowing 6 miles per minute saves lives...You don't want the truth. Because deep down, in places you don't talk about at parties, you want me in that jet. You need me in that jet.
We use words like formation integrity, flight discipline, honor...we use these words as the backbone to a life spent flying at supersonic speeds. You use 'em as a punchline. I have neither the time nor the inclination to explain myself to a man who flies at the speed of one half mile a minute! I'd rather you just said thank you and went on your way. Otherwise, I suggest you strap on a parachute and g-suit. Either way, I don't give a damn what final approach course you think you're entitled to go blowing through!

 

[jesse]

You want the truth? You can't handle the truth! Son, we fly in a MOA filled with Cessna jockeys who are trying to kill us. And those MOA's are occupied by the mighty T-38. Who's gonna fly the mighty Talon? You? You, Jesse? I have a greater responsibility than you can possibly fathom. You fly your mighty skyhawk and curse the jet jockies. You have that luxury. You have the luxury of not knowing what I know: that flying formation at 300knots with an IP in the backseat trying to wash you out builds skill that you cannot possibly imagine. And my flying, while at a mindblowing 6 miles per minute saves lives...You don't want the truth. Because deep down, in places you don't talk about at parties, you want me in that jet. You need me in that jet.
We use words like formation integrity, flight discipline, honor...we use these words as the backbone to a life spent flying at supersonic speeds. You use 'em as a punchline. I have neither the time nor the inclination to explain myself to a man who flies at the speed of one half mile a minute! I'd rather you just said thank you and went on your way. Otherwise, I suggest you strap on a parachute and g-suit. Either way, I don't give a damn what final approach course you think you're entitled to go blowing through!

I hope that's a joke.

 

[tonycondon]

http://www.youtube.com/watch?v=VPgOQRixuHc&mode=related&search=

 

[jason]

I hope that's a joke.

A Few Good Men

 

[jason]

You want the truth? You can't handle the truth! Son, we fly in a MOA filled with Cessna jockeys who are trying to kill us. And those MOA's are occupied by the mighty T-38. Who's gonna fly the mighty Talon? You? You, Jesse? I have a greater responsibility than you can possibly fathom. You fly your mighty skyhawk and curse the jet jockies. You have that luxury. You have the luxury of not knowing what I know: that flying formation at 300knots with an IP in the backseat trying to wash you out builds skill that you cannot possibly imagine. And my flying, while at a mindblowing 6 miles per minute saves lives...You don't want the truth. Because deep down, in places you don't talk about at parties, you want me in that jet. You need me in that jet.
We use words like formation integrity, flight discipline, honor...we use these words as the backbone to a life spent flying at supersonic speeds. You use 'em as a punchline. I have neither the time nor the inclination to explain myself to a man who flies at the speed of one half mile a minute! I'd rather you just said thank you and went on your way. Otherwise, I suggest you strap on a parachute and g-suit. Either way, I don't give a damn what final approach course you think you're entitled to go blowing through!

Touché

 

[IamBull]

Dude. My last post was clearly a joke to lighten things up. Perhaps you were too young to remember "A few good men."

Here's the movie quote....

"Son, we live in a world that has walls, and those walls have to be guarded by men with guns. Whose gonna do it? You? You, Lt. Weinburg? I have a greater responsibility than you could possibly fathom. You weep for Santiago, and you curse the marines. You have that luxury. You have the luxury of not knowing what I know. That Santiago's death, while tragic, probably saved lives. And my existence, while grotesque and incomprehensible to you, saves lives. You don't want the truth because deep down in places you don't talk about at parties, you want me on that wall, you need me on that wall. We use words like honor, code, loyalty. We use these words as the backbone of a life spent defending something. You use them as a punchline. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the blanket of the very freedom that I provide, and then questions the manner in which I provide it. I would rather you just said thank you, and went on your way, Otherwise, I suggest you pick up a weapon, and stand a post. Either way, I don't give a damn what you think you are entitled to."

 

[CJones]

Dude. My last post was clearly a joke to lighten things up. Perhaps you were too young to remember "A few good men."

Here's the movie quote....

"Son, we live in a world that has walls, and those walls have to be guarded by men with guns. Whose gonna do it? You? You, Lt. Weinburg? I have a greater responsibility than you could possibly fathom. You weep for Santiago, and you curse the marines. You have that luxury. You have the luxury of not knowing what I know. That Santiago's death, while tragic, probably saved lives. And my existence, while grotesque and incomprehensible to you, saves lives. You don't want the truth because deep down in places you don't talk about at parties, you want me on that wall, you need me on that wall. We use words like honor, code, loyalty. We use these words as the backbone of a life spent defending something. You use them as a punchline. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the blanket of the very freedom that I provide, and then questions the manner in which I provide it. I would rather you just said thank you, and went on your way, Otherwise, I suggest you pick up a weapon, and stand a post. Either way, I don't give a damn what you think you are entitled to."

"Did you order the Code Red?!"
"You're G.D. right I ordered the Code Red!!!"
"Your honor, I request an immediate Title [something] and immediate move to court martial. General [something] has rights."

 

[Patch]

Dude, he was padlocked..

1554

Dude. My last post was clearly a joke to lighten things up. Perhaps you were too young to remember "A few good men."

Here's the movie quote....

"Son, we live in a world that has walls, and those walls have to be guarded by men with guns. Whose gonna do it? You? You, Lt. Weinburg? I have a greater responsibility than you could possibly fathom. You weep for Santiago, and you curse the marines. You have that luxury. You have the luxury of not knowing what I know. That Santiago's death, while tragic, probably saved lives. And my existence, while grotesque and incomprehensible to you, saves lives. You don't want the truth because deep down in places you don't talk about at parties, you want me on that wall, you need me on that wall. We use words like honor, code, loyalty. We use these words as the backbone of a life spent defending something. You use them as a punchline. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the blanket of the very freedom that I provide, and then questions the manner in which I provide it. I would rather you just said thank you, and went on your way, Otherwise, I suggest you pick up a weapon, and stand a post. Either way, I don't give a damn what you think you are entitled to."

 

[N6399A]

OK Bull............ that was great . I thought I was the only one that knew those lines by heart. Or did you look them up?

 

[KennyFlys]

"Did you order the Code Red?!"
"You're G.D. right I ordered the Code Red!!!"
"Your honor, I request an immediate Title [something] and immediate move to court martial. General [something] has rights."

Come on Chris... get it right. It was an Article 38, I think. That's assignment of counsel. But, I keep thinking it was a 32 which is investigation. Either way, he was no dang general other than a general jerk. He was a bird brain.. oops, I mean Full Bird Colonel.

 

[gismo]

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?

With top rudder, 90 degrees of bank and back pressure (actually just a lessening of forward pressure unless you are trimmed for zero g, a common aerobatic practice).

IIRC knife edge flight requires no aileron even though the top wing is significanty blanketed by the fuselage because the wings are generating no lift if you're not turning. Aileron would be required to counter the difference in lift between the wings and at some (fairly high I believe) g load you would run out of aileron when turning in knife edge flight but there's plenty of control for a noticeable turn rate.

Other than causing the fuselage to blanket the top wing, the rudder doesn't directly generate any rolling force in a knife edge turn or straight flight.

As to the thrust required, with most planes, it's more a function of the greatly increased drag of knife edge flight that demands a lot of power to hold altitude. This is true whether you are turning or going straight.

Something else already mentioned is that even though you migbt not have enough thrust to balance the high drag, you can use inertia (energy). That would lilmit the duration of a knife edge turn, but not the possibililty of one.

 

[flyingcheesehead]

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

You wouldn't be coordinated whether or not you added elevator. Knife edge is by definition uncoordinated.

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 there's any dihedral, the down wing would also be generating lift due to a higher AoA. So, you counter any of the rolling effects with aileron.

If you counter that with aileron, are you not just slipping at that point?

As you have been the entire time, yes.

It seems to me you'd need a pretty high thrust to weight ratio to make that happen cross controlled without losing altitude.

Yep. However, I think that the real reason you'd need a high thrust-weight ratio is simply due to the loss of lift from the wings. Presumably, the lift available from the fuselage when in knife-edge flight is lower than that from the wings in level flight, you'd need a larger vertical thrust component to maintain level flight. In addition, knife-edge is a high-drag configuration simply because the AoA of the fuselage must be much higher than the wings normally would be to have any effect. The addition of aileron isn't going to add much drag above what's already there.

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.

I'd think that maintaining 90 degrees of bank is more difficult than maintaining altitude, since you're not significantly altering anything that's keeping you in the air to begin with. However, the higher the rate of turn, the more drag would be introduced, which would require higher thrust and/or more rudder to compensate, which would change the rolling tendencies and... I think my brain just overloaded.

This is what makes the good aerobatic performers all that much more amazing - They can think about this stuff while pulling 6 G's and rolling two turns per second. I thought a hammerhead was a pretty simple maneuver til I did one! I'd never thought of all the interesting effects the various forces had until then. What an eye-opener! But, the second one got better, and the third better yet, and... Oh man, I need some Vitamin G now.

 

[flyingcheesehead]

IIRC knife edge flight requires no aileron even though the top wing is significanty blanketed by the fuselage because the wings are generating no lift if you're not turning.

Wouldn't that only be true of a symmetric airfoil with zero dihedral?

 

[CJones]

Come on Chris... get it right. It was an Article 38, I think. That's assignment of counsel. But, I keep thinking it was a 32 which is investigation. Either way, he was no dang general other than a general jerk. He was a bird brain.. oops, I mean Full Bird Colonel.

Whatever.. I'm not a military brat, nor do I play one on TV.

 

[KennyFlys]

Whatever.. I'm not a military brat, nor do I play one on TV.

You should consider staying at a Holiday Inn Express!

 

[wsuffa]

Folks,

Let's not turn this thread into a personal wetting-match, please. Some of the posts here are approaching the line where they might be considered insults and personal attacks, both of which are contraty to the RoC.

Thanks.

 

[jesse]

Folks,

Let's not turn this thread into a personal wetting-match, please. Some of the posts here are approaching the line where they might be considered insults and personal attacks, both of which are contraty to the RoC.

Thanks.

All of which stopped several pages ago.....

 

[N50909]

Myself, I follow the method Bill Kershner teaches in his Aerobat: a stab of coordinating rudder at the initiation of the roll, neutral rudder through the middle, a stab of coordinating rudder at the rollout. If it's good enough for Bill then, by gum, it's good enough for me.

I do not snap my Citabria. And if someone else snaps it and I find out about it, they never fly my airplane again.

That's the way I was taught to fly an aileron roll in the Super Decathlon, so I'm sticking to it. YMMV.

As for snaps, I asked, he said Nope, end of story.

EDIT: Sorry, I came late to this party. Didn't mean to go back to page 1... you guys can go back to sharks vs jets antics.

 

[jason]

EDIT: Sorry, I came late to this party. Didn't mean to go back to page 1... you guys can go back to sharks vs jets antics.

So fitting when you think about it...

"When you're a Jet you're a Jet all the way...."

 

[gismo]

Wouldn't that only be true of a symmetric airfoil with zero dihedral?

I don't think airfoil symmetry matters here other than it's effect on the pitch attitude required for zero lift. I doubt that dihedral has any bearing either but I can't say for sure right now. The only airplanes I've flown on knife edge were biplanes with little or no dihedral.

 

[flyingcheesehead]

I don't think airfoil symmetry matters here other than it's effect on the pitch attitude required for zero lift. I doubt that dihedral has any bearing either but I can't say for sure right now. The only airplanes I've flown on knife edge were biplanes with little or no dihedral.

I'm thinking back to Stick and Rudder where he talks about the effect of dihedral in a skidding turn, which is what knife edge is albeit flipped onto the side 90 degrees. Let's say you're knife-edge to the left in a Cessna or something like that with plenty of dihedral. Actually, think about it from the viewpoint of the relative wind. You're looking at the left-hand side of the fuselage. Say the fuse needs a 45-degree AoA. What does a Cessna wing look like if you're standing forward and to the left at a 45-degree angle looking at the plane? You're looking at the bottom of the left wing, and the top of the right wing... And that's exactly what the wind is affecting. So, there should be more lift from the left wing, requiring left aileron to counter it.

I guess you're right about the symmetric airfoil not mattering, I was thinking in terms of bernoulli lift on a non-symmetric airfoil, but a reduction in the wing's AoA would take care of that.

 

[N50909]

The only airplanes I've flown on knife edge were biplanes with little or no dihedral.

Don't most modern biplanes have one wing with zero dihedral (typically the top) and one with some dihedral?

I'm thinking Stearmans don't have any dihedral on either wing but I don't know if I've ever seen one knife edge either.

 

[gismo]

I'm thinking back to Stick and Rudder where he talks about the effect of dihedral in a skidding turn, which is what knife edge is albeit flipped onto the side 90 degrees. Let's say you're knife-edge to the left in a Cessna or something like that with plenty of dihedral. Actually, think about it from the viewpoint of the relative wind. You're looking at the left-hand side of the fuselage. Say the fuse needs a 45-degree AoA. What does a Cessna wing look like if you're standing forward and to the left at a 45-degree angle looking at the plane? You're looking at the bottom of the left wing, and the top of the right wing... And that's exactly what the wind is affecting. So, there should be more lift from the left wing, requiring left aileron to counter it.

With or without dihedral, I think you need some aileron to counteract a roll force in knife edge flight simply due to the fuselage blocking the airflow over some of the upper wing. And I also think your imagined view of the bottom of one wing and the top of another is flawed (assuming the chords of the wings are parallel). I don't believe that you can see the upper surface of one wing and the lower surface of the other from any viewing position. You could confirm this by looking at an airplane on the ground from various viewoints.

 

[flyingcheesehead]

And I also think your imagined view of the bottom of one wing and the top of another is flawed (assuming the chords of the wings are parallel). I don't believe that you can see the upper surface of one wing and the lower surface of the other from any viewing position. You could confirm this by looking at an airplane on the ground from various viewoints.

Sure I can. It's a piece of cake on the 182.

Let's say the height of the top of the wing at the fuselage is x, and the height of the bottom of the wing at the tips is y. Put a camera, Mark I Eyeball, or other viewing device at a height of x+((y-x)/2) a couple of feet in front of the leading edge of the left wingtip. You will see the bottom of the left wing and the top of the right.

Hmmm, I think I just got an excuse to go to the airport and take a picture. Thanks.

Edit: This *does* assume sufficient dihedral that the wingtips are higher than the wing roots by at least the thickness of the wing.

 

[flyingcheesehead]

Let's say the height of the top of the wing at the fuselage is x, and the height of the bottom of the wing at the tips is y. Put a camera, Mark I Eyeball, or other viewing device at a height of x+((y-x)/2) a couple of feet in front of the leading edge of the left wingtip. You will see the bottom of the left wing and the top of the right.

Hmmm, I think I just got an excuse to go to the airport and take a picture. Thanks.

Well, I forgot my regular camera at home and had to use my phone, and the lighting inside the hangar kinda sucked, but here's the pic. If the relative wind is coming from this viewpoint, the close wing has a positive AoA and the far wing is negative.

 

[gismo]

Well, I forgot my regular camera at home and had to use my phone, and the lighting inside the hangar kinda sucked, but here's the pic. If the relative wind is coming from this viewpoint, the close wing has a positive AoA and the far wing is negative.

Well I can see more of the top on the right wing and more of the bottom of the left wing, but I can't see anywhere near all of both. Now what were we arguing about?

 

[flyingcheesehead]

Well I can see more of the top on the right wing and more of the bottom of the left wing, but I can't see anywhere near all of both. Now what were we arguing about?

Well, it'd be impossible to see all of either without being pretty much directly above or below, technically...

I'm just sayin' that if there's dihedral, there will be an additional aerodynamic tendency for the airplane to roll upright, that's all. I don't think we're arguing.

 

[gismo]

Well, it'd be impossible to see all of either without being pretty much directly above or below, technically...

I'm just sayin' that if there's dihedral, there will be an additional aerodynamic tendency for the airplane to roll upright, that's all. I don't think we're arguing.

Well as I pointed out before my only experience with knife edge flight is in a biplane with no dihedral so I can't say for sure. But I really doubt that dihedral would matter (or at least nowhere near as much as the shadowing of the wing furthest from the ground). When you use rudder to raise a wing in "normal" flight, the extra lift on the rising wing comes from the higher airspeed that results from being on the outside of the turn. In knife edge flight there is no turn so the airspeed that each wing sees is the same. As to the AOA on each wing, I believe that it's just as equal on knife edge as in wings level flight.