A drink from the Aerobatic fire hose

[Bill]

Well, yesterday was aerobatic lesson #2 in the Citabria, and this one was alot more interesting. As you learned from my first lesson writeup (what, you didn't read it??? ), my instructor is an ex-Navy jet pilot. His take on teaching aerobatics is do it the military way, which must mean throw you to the wolves.

We sit down for the pre-flight lesson, and he says we'll go practice steep turns, this time working up to nearly 90 degree knife edge turns. Then we'll go practice a combination of maneuvers. We'll line up on the road, pitch down 30 degrees, then at 140mph, pull back smoothly for a nice loop, coming out of the loop, pitch up 30 degrees, then he'll call an aileron roll, left or right. After the aileron roll, I'm then to stand the plane on its tail and do a zoom climb, followed by a 0G forward pitch arriving at level flight right above stall speed. Then, do a knife edge turn 180 degrees to pick up the road again, and repeat the sequence. Whew!

So out we go, this time I'm in the front seat. Being 6'2", my knees nearly are into the bottom of the dash, and I feel like a kid in a kiddie car. We do the takeoff roll, and I do the dance, and do a decent takeoff.

In the practice area, we start with 60 degree turns, and he wants me to be really aggressive in the left right transitions, using nearly all of the control travel on the reversals. Then, we move on to nearly 90 degree turns, but I have a hard time keeping the nose on the horizion.

Question for you acro experts: How DOES one keep the nose on the horizon? Looking at the vector diagram, nearly all the lift is horizontal, I don't really see what keeps the airplane in the air on a 90 bank turn.

So, we then start the combination, and the loop goes well, 30 degrees up, and he calls a left aileron roll, and I do the classic newbie mistake. I dial in full left stick, and forget the rudder. Horrible adverse yaw, and the plane does a sick tumble thru the air and then I fall out of the maneuver. Ending up with a windshield full of ground, I figure out how to get the wings level and then pull out of the dive. John says to try some rudder on the next one .

So, we do this pattern 4 more times over, and by the end I'm really getting a nice fast full control deflection aileron roll, but I'm still pushing too hard forward on the pitch out from the zoom climb, giving negative G's, and John doesn't like that. Gotta work on that some.

After that, he asks how I'm feeling, and I say I'm still doing fine. He asks if I want to try the snap roll, so we do. We discussed this before on the pre-flight lesson, and he said to come out of the snap, you need to basically do a spin recovery. Rudder opposite to the rotation, and firm stick forward.

So, power back in level flight to 85mph, and then snap! At the same time, power goes full, full left rudder, and stick hard back full. And, AROUND we go...yeeehaaaa!!!!!! I do the recovery, and end up pitch down with the engine at idle. He asks why I pulled the engine, and I said I guess I thought about doing a spin recovery, and all the books said you wanted no power so you didn't get into a flat spin. Correct, he says, but for the snap, he says to leave full power in for the full maneuver. So, we do several more snaps in each direction, then head for the ranch.

The airport is a grass strip (Sky Ranch near Knoxville, TN), and is on a river, so the approach is strange. You come in over land, go across the water, then onto land again, and you get several baubles. I ended up ballooning the flair, but John put in a quick burst of power, and I came down on a fairly nice 3 point, and then started chasing the tail. John asked if I wanted to try the brakes, and I took a shot at pumping the heel brakes while doing the dance on the rudder. It worked out pretty well, and thus endeth my second lesson.

This guy worked me hard, I was sweating more than I ever did during my private, but I had a wonderful time. This was the first time I've ever used full control deflections in flight, and it is good to get a feel for the airplane. He says as we progress we'll work up to using (and going beyond) the full capabilities of the aircraft.

Lastly, snap rolls RULE! What a blast, SNAP, and zing you go around.

It is gonna be hard to give this up at the end of the class.

 

[Diana]

Hey Bill, sounds like you had an exciting lesson today. Which Citabria is it? The 7GCAA? Does it have inverted fuel and oil?

and he calls a left aileron roll, and I do the classic newbie mistake. I dial in full left stick, and forget the rudder. Horrible adverse yaw, and the plane does a sick tumble thru the air and then I fall out of the maneuver. Ending up with a windshield full of ground, I figure out how to get the wings level and then pull out of the dive. John says to try some rudder on the next one

Yes, this may start one of those very long and controversial discussions about how much rudder to use in an aileron roll in a Citabria.........I'm still experimenting with that one.

He asks if I want to try the snap roll, so we do. So, we do several more snaps in each direction

Is this the owner of the airplane? Snaps in Citabrias can be really tough on them. I refuse to do snap rolls in mine.

He says as we progress we'll work up to using (and going beyond) the full capabilities of the aircraft.

Bill, I wonder what he means by going beyond the full capabilities of the aircraft? That would concern me a little bit.

Anyway, I'm glad you had a great time. Citabrias are fun!

 

[citationxjl]

Our maintenance at UND didnt like us to do snap rolls in the decathalon either. Something about the fuel lines or something.

 

[Bill]

Hey Bill, sounds like you had an exciting lesson today. Which Citabria is it? The 7GCAA? Does it have inverted fuel and oil?

The plane does not have inverted fuel and oil, which is probably why he didn't like the negative G's when pitching over from the zoom climb. Looking at the G-meter, we did +2.7 and -0.5 for the lesson.

Yes, this may start one of those very long and controversial discussions about how much rudder to use in an aileron roll in a Citabria.........I'm still experimenting with that one.

He wanted full control deflections, so I was using full stick and full rudder for the aileron rolls. Dunno if this is how others do it???

Is this the owner of the airplane? Snaps in Citabrias can be really tough on them. I refuse to do snap rolls in mine.

He is the owner of the plane, which just went through a very thorough firewall forward rebuild with top notch everything. He also said snaps were stressful on the aircraft, and a clipped wing plane would be better for snaps. That said, he still wants students to know how to do the maneuver. What happens to the plane if it is snapped too much? What kind of plane do you have to move into to be able to do snaps without aircraft damage?

Bill, I wonder what he means by going beyond the full capabilities of the aircraft? That would concern me a little bit.

He told me that every student will leave the class knowing the full performance capabilities of the aircraft, and we will exceed them a few times so students know how to recover from unusual/adverse attitides.

I hope I'm not painting the picture of a madman here, this guy seems to be very good. Very down to earth, very concerned that his students really learn how to fly. He didn't hotdog, and didn't do snazzy demos or anything like that. In fact, the only time I could tell he was on the controls was the takeoff and landing. For the rest, he let me figure it out with his coaching.

Anyway, I'm glad you had a great time. Citabrias are fun!

Indeed! I'm somewhat concerned that Citabrias are not well suited for snaps, makes me wonder what I might have to look at if I decided to buy...I *like* snaps.

 

[Toby]

Hi Bill,

I posted a reply earlier, because I was trying to answer one of your questions, but I was not quite awake yet so I deleted it. Will try again!

Your lesson sounded very intense. What a workout! Yes, it will be hard to quit acro when you come to the end of the course. Don't count on doing so. ;-)

We have not done any snaps in the Decathlon, so I haven't experienced one of those yet.

About your question below (Lance can explain this better than I):
"Question for you acro experts: How DOES one keep the nose on the horizon? Looking at the vector diagram, nearly all the lift is horizontal, I don't really see what keeps the airplane in the air on a 90 bank turn."

I can't answer it, but there is a great illustration and explanation of lift on pages 106-07 of Alan Cassidy's book, Better Aerobatics. He is talking about a 60-degree banked turn, though, not 90. The wings are still producing a lot of upward lift in a turn, and at 60 degrees the elevator does, too. The elevator also pushes you around the turn with sideways lift. (btw, are you sure you were at 90 degrees?)

"He wanted full control deflections, so I was using full stick and full rudder for the aileron rolls. Dunno if this is how others do it???"

That's how I do it. Without rudder, I get adverse yaw and veer off to the side. The technique seems to be different in different aircraft, from what I've read.

About stressing the plane, we are pretty careful about how much we impose. The structure can be weakened with repeated stress, and you won't be able to see it. Just a thought, because you mentioned going beyond. Maybe that's not what your instructor meant. I have noticed that when I do rolls correctly, there's a smooth and balanced sensation, and I don't feel a lot of g-force, which I'm pretty sure means less stress.

 

[Diana]

He wanted full control deflections, so I was using full stick and full rudder for the aileron rolls. Dunno if this is how others do it???

Well, this is where it gets controversial. I was originally taught to use full rudder (all the way around) in the Citabria. Then I read where that's not how it is usually done in other airplanes. Then I got into heated discussions with some people (fought like cats and dogs with the fur flying!). I posted this question on the AOPA board and on the YahooCitabria forum. You might enjoy reading that, btw. You can do a search there or ask that group.

http://groups.yahoo.com/group/CitabriaPilots/

Too bad we can't access that very long discussion on the AOPA WebBoard about aileron rolls in a Citabria.

He told me that every student will leave the class knowing the full performance capabilities of the aircraft, and we will exceed them a few times so students know how to recover from unusual/adverse attitides.

I'll be interested in hearing about what you exceed.

I hope I'm not painting the picture of a madman here, this guy seems to be very good.

Well, his approach may work well with you. It probably wouldn't with me because I'm timid and like to get in the water "one toe at a time."

I'm somewhat concerned that Citabrias are not well suited for snaps, makes me wonder what I might have to look at if I decided to buy...I *like* snaps.

Hopefully some of the more experienced aerobatic pilots will chime in here. I'm thinking maybe Pitts or Skybolt, something like that, depending on what price you're talking about. Were you thinking of buying, or renting?

Whatever you do, have fun!

 

[Bill]

http://groups.yahoo.com/group/CitabriaPilots/

Thanks, I'll take a look in there sometime soon!

Well, his approach may work well with you. It probably wouldn't with me because I'm timid and like to get in the water "one toe at a time."

He claims this is the military way, they start acro on your first lesson in an airplane. He says that is the only way to have new pilots flying supersonic fighters at 50 hrs.

He uses this for ALL of his students. His private stu's must take the first four arco courses before he lets them solo, and they must complete the last four before he OK's them for their checkride.

He charges twice as much (not for this course) as the prevailing rate in the area, and caters his teaching and program for more professional clients. He and his two partners have 40 students right now, with a pretty good waiting list of people waiting to fly with them.

Everyone I've flown with who trained with John has shown to be an exceptional pilot.

Hopefully some of the more experienced aerobatic pilots will chime in here. I'm thinking maybe Pitts or Skybolt, something like that, depending on what price you're talking about. Were you thinking of buying, or renting?

Whatever you do, have fun!

I AM having fun, and buying is still about 17 months out. I belong to a club that has three nice planes (172P,PA-28-181,206), so I'm thinking of maybe buying an acro taildragger for fun, and renting the club planes for travel.

Renting an acro plane? Most places want 200hrs in taildragger before they'll rent you one, so you have the chicken and the egg...

Dunno, though, 17 months is a long time...

 

[Ken Ibold]

Well, this is where it gets controversial. I was originally taught to use full rudder (all the way around) in the Citabria. Then I read where that's not how it is usually done in other airplanes. Then I got into heated discussions with some people (fought like cats and dogs with the fur flying!). I posted this question on the AOPA board and on the YahooCitabria forum. You might enjoy reading that, btw. You can do a search there or ask that group.

What it boils down to, IMO, is that there is not really any one-size-fits-all "proper" use of rudder in an aileron roll. Instruction in aerobatic maneuvers typically follows the competition judging criteria, and the aileron roll is not a competition maneuver. And so you get myriad opinions as to the "right" way to do them.

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.

 

[Bill]

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.

OK, my instructor said that you cannot always follow Kershner exactly, as the 152 needs some non-standard control inputs to do some of the maneuvers. He says if you do some of those control inputs in the Citabria, you will not get the expected results. I need to sit down with him and find out what maneuvers (in his opinion) these are.

That said, my instructor gave me a copy of the Citabria manual and says do the maneuvers per the manual.

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

Understood. He said we may do a couple more snaps, but no more. In his experience, it is easier to teach spins and spin recoveries after students have tried the snap roll. Maybe phychological?

Also, he contends that the stresses are minimal if you enter the snap at the recommended speed of 85mph. He says where people really stress the plane is doing snaps at cruise speed, etc.

Bunk or truth?

 

[Ken Ibold]

That said, my instructor gave me a copy of the Citabria manual and says do the maneuvers per the manual.

What manual is this?

 

[Bill]

What manual is this?

I don't know where this came from, but I assume it was written by American Champion.

OK, well, I tried to upload a pdf of the information, but I keep getting a "The page cannot be displayed" error when trying to attach.

If you want to see it, PM me with your e-mail and I'll send it off.

 

[gismo]

What it boils down to, IMO, is that there is not really any one-size-fits-all "proper" use of rudder in an aileron roll. Instruction in aerobatic maneuvers typically follows the competition judging criteria, and the aileron roll is not a competition maneuver. And so you get myriad opinions as to the "right" way to do them.

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.

You're right there's really no "right" way to do an "aileron roll". But then, the easiest way is to do the whole thing on a ballistic arc. When the airplane is ballistic (0 g) you don't need any rudder because there is no adverse yaw. Almost as easy is to start the roll and pullup at the same time which requires that "bit of coordinating rudder", in fact more rudder than you would need for the same aileron deflection if you weren't pulling up. The closer you get to 0 g before rolling the less rudder you'll need.

Bill, WRT to your question about keeping the nose up in a very steep turn, there are two ways. One is to use inertia. If you pull the nose above the horizon as you enter the turn it will be a while before it falls below the horizon. The other is to use top rudder which makes the turn very uncoordinated. You can also combine the two. You can maintain altitude in a coordinated 80 degree bank by pulling 6 g's, but then there's no margin for error and the nose has to be very high (about 15 degrees above the horizon). The bank angle vs g force is very sensitive at these angles. Reduce the bank to 75 and you need less than 4 g's.

 

[Diana]

I don't know where this came from, but I assume it was written by American Champion.

OK, well, I tried to upload a pdf of the information, but I keep getting a "The page cannot be displayed" error when trying to attach.

Bill, is this the one you have?

 

[Patch]

Thread revival. (Saw this on the bottom pane of another thread, figured I'd chime in)

In the practice area, we start with 60 degree turns, and he wants me to be really aggressive in the left right transitions, using nearly all of the control travel on the reversals. Then, we move on to nearly 90 degree turns, but I have a hard time keeping the nose on the horizion.

Question for you acro experts: How DOES one keep the nose on the horizon? Looking at the vector diagram, nearly all the lift is horizontal, I don't really see what keeps the airplane in the air on a 90 bank turn.

Can't be done in any aircraft. The amount of G required to hold level flight at 90 degrees of bank is infinite.

 

[SkyHog]

Thread revival. (Saw this on the bottom pane of another thread, figured I'd chime in)




Can't be done in any aircraft. The amount of G required to hold level flight at 90 degrees of bank is infinite.

Just a theoretical, but what about those aircraft which generate lift with the fuselage side?

Then wouldn't top rudder kind of work as elevator?

 

[Patch]

Just a theoretical, but what about those aircraft which generate lift with the fuselage side?

Then wouldn't top rudder kind of work as elevator?

It's a discussion of where your lift vector is. In level flight, at 90 degrees of bank (knife edge), some aircraft create enough lift (and have enough rudder authority) to hold that attitude. Your lift vector is still essential up, even though you're in a bank.

In turning flight, you change the amount of G required based on your lift vector. At 60 degrees of bank, it takes 2 Gs to sustain level flight. At 80 that number goes up to around 6 Gs. At 90, it's infinity because your lift vector is entirely in the horizontal with none being in the vertical so the nose will just fall.

 

[tonycondon]

this discussion is always confusing as hell because some people consider lift to be the vertical force produced by the aircraft and others consider lift to be the force created by the wings.

 

[Diana]

Thread revival. (Saw this on the bottom pane of another thread, figured I'd chime in)

This is like a trip down memory lane.

Patch, what are you flying right now? It would be nice to hear more about you.

 

[Patch]

this discussion is always confusing as hell because some people consider lift to be the vertical force produced by the aircraft and others consider lift to be the force created by the wings.

Those people don't think in 3d.

 

[tonycondon]

Those people don't think in 3d.

which ones? seems to me you think that lift is the force caused by the wings.

 

[Patch]

which ones? seems to me you think that lift is the force caused by the wings.

Lift is the force that opposes gravity. Your lift vector is what I'm referring to.

 

[skimanjim]

keeping the airplane level in a 90 degree turn is, as mentioned before, a matter of top rudder, hence the name 'knife edge flight' if you have enough energy, you can maintain level flight with top rudder.

As far as snaps, in thoery, you can do them all day provided you keep below manuevering speed, but then you get into fatigue issues and all that jazz... all being said and done, snaps are usually hard on any airplane, but most accidents come from doing them at higher rates of speed (which give you higher roll rates) but is much much harder, since you are likely putting too many g's somewhere on the aircraft

Jim

 

[Patch]

keeping the airplane level in a 90 degree turn is, as mentioned before, a matter of top rudder, hence the name 'knife edge flight' if you have enough energy, you can maintain level flight with top rudder.


Jim

Straight and level - yes. In a turn, it's mathematically impossible.

 

[wbarnhill]

It's a discussion of where your lift vector is. In level flight, at 90 degrees of bank (knife edge), some aircraft create enough lift (and have enough rudder authority) to hold that attitude. Your lift vector is still essential up, even though you're in a bank.

In turning flight, you change the amount of G required based on your lift vector. At 60 degrees of bank, it takes 2 Gs to sustain level flight. At 80 that number goes up to around 6 Gs. At 90, it's infinity because your lift vector is entirely in the horizontal with none being in the vertical so the nose will just fall.

So let me try to get this straight...

As long as you've got the energy and rudder authority, you can turn the aircraft on its side with no problem and maintain "level flight", but the moment you try to commence a turn, you're going to lose some form of energy and have to provide back pressure to attempt to maintain level flight, and that back pressure requirement will increase as the bank angle increases (to the point that you can't meet the requirement and the nose falls)?

Please correct me if I'm wrong, this is awfully interesting

 

[jesse]

So let me try to get this straight...

As long as you've got the energy and rudder authority, you can turn the aircraft on its side with no problem and maintain "level flight", but the moment you try to commence a turn, you're going to lose some form of energy and have to provide back pressure to attempt to maintain level flight, and that back pressure requirement will increase as the bank angle increases (to the point that you can't meet the requirement and the nose falls)?

Please correct me if I'm wrong, this is awfully interesting

I think it'd be awfully tricky to put an airplane on a 90 degree bank and attempt to hold altitude without changing heading. I guess I've never attempted to hold altitude or heading at 90 degrees or greater. Once you roll past 70 degrees unless you fight like hell you are coming down. I've found it's a very nice way to come down.

Some airplanes (few) would have enough thrust and rudder to hold altitude at 90 degrees. Hell some airplanes almost have enough thrust to hover. I'm willing to bet you could/would change heading in these airplanes.

With enough energy in almost anything I'm sure you could hold altitude (for a short amount of time) at 90 degrees.

I've never really flown anything that I'd dare attempt to hold altitude at such a bank. So my words are pretty much worthless.

 

[wbarnhill]

I think it'd be awfully tricky to put an airplane on a 90 degree bank and attempt to hold altitude without changing heading. I guess I've never attempted to hold altitude or heading at 90 degrees or greater. Once you roll past 70 degrees unless you fight like hell you are coming down. I've found it's a very nice way to come down.

Some airplanes (few) would have enough thrust and rudder to hold altitude at 90 degrees. Hell some airplanes almost have enough thrust to hover. I'm willing to bet you could/would change heading in these airplanes.

With enough energy in almost anything I'm sure you could hold altitude (for a short amount of time) at 90 degrees.

I've never really flown anything that I'd dare attempt to hold altitude at such a bank. So my words are pretty much worthless.

C'mon Jesse, we're aware of your antics... you know you've put the DA-20 in a 90 degree bank. Waiting for the video....

 

[tonycondon]

sure but could he hold altitude and not change heading??

 

[jason]

sure but could he hold altitude and not change heading??

Hell, I can barely do that in straight and level flight.

 

[tonycondon]

Hell, I can barely do that in straight and level flight.

neither can jesse

 

[skimanjim]

Straight and level - yes. In a turn, it's mathematically impossible.

Theres no difference in knife edge flight on heading or changing heading. The top rudder simply provides enought lift to keep the airplane level. The side of a citabria will develop quite a large amount of lift when its on its side. So the combinations of the lift from the fuselage and the wing will mean that the airplane holds altitude and changes heading, hench a 90 degree competition turn. It is the same concept as doing a pure slow roll... you combine the control inputs to make no altitude change throughout the roll, unlike the aileron roll, which involves a pitch up at the start.

 

[jesse]

C'mon Jesse, we're aware of your antics... you know you've put the DA-20 in a 90 degree bank. Waiting for the video....

I think one too many lawyers played a roll in writing the Diamond DA-20 POH

Permissible Utility Category Maneuvers:
Steep turns in which the angle of bank does not exceed 60°

Which means, you know, I'd never have a video exceeding 60 degrees..Yeah that's it--and I'd uh--never post it on a public forum even if such a video were to exist--not that it does.

 

[Patch]

So let me try to get this straight...

As long as you've got the energy and rudder authority, you can turn the aircraft on its side with no problem and maintain "level flight", but the moment you try to commence a turn, you're going to lose some form of energy and have to provide back pressure to attempt to maintain level flight, and that back pressure requirement will increase as the bank angle increases (to the point that you can't meet the requirement and the nose falls)?

Please correct me if I'm wrong, this is awfully interesting

You are correct. It's all about where your lift vector is (in theory, the vector perpendicular to the aircraft). If you are in 60 degrees of bank, you still have some component of lift in the vertical and some in the horizontal. It requires 2 Gs to hold that turn level (without losing altitude that is). It doesn't matter what the aircraft - it'll always take 2 Gs to hold 60 degrees of bank.

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. When you hit 90, you reach infinity (division by zero) as there is no vertical component. That's why in instrument nose high recoveries, we go to 90 degrees of bank to slice back down to the horizon.

That's the discussion on turning. When you talk about knife edge flight, you're not talking about turning. You're talking about sustaining flight through lift generated by the fuselage. You keep the nose up with rudder and your vertical component of the lift vector is now parallel with the wingline. "Level flight" in this case is now 90 degrees of bank. This type of flight is much easier to do with a symmetric airfoil since it creates zero lift at zero alpha.

 

[Patch]

I think it'd be awfully tricky to put an airplane on a 90 degree bank and attempt to hold altitude without changing heading. I guess I've never attempted to hold altitude or heading at 90 degrees or greater. Once you roll past 70 degrees unless you fight like hell you are coming down. I've found it's a very nice way to come down.

Roll any amount of bank without back pressure and the nose will drop. At 90, your "elevator" is now the rudder. Not every aircraft can do it, but some generate enough lift with their fuselage and have enough rudder authority to do it.

Some airplanes (few) would have enough thrust and rudder to hold altitude at 90 degrees. Hell some airplanes almost have enough thrust to hover. I'm willing to bet you could/would change heading in these airplanes.

That's not the point. At 90 degrees of bank, it is impossible to sustain a level turn.

With enough energy in almost anything I'm sure you could hold altitude (for a short amount of time) at 90 degrees.

You hold altitude by generating Gs. You can't generate an infinite amount of Gs.

I've never really flown anything that I'd dare attempt to hold altitude at such a bank. So my words are pretty much worthless.

 

[Patch]

Theres no difference in knife edge flight on heading or changing heading. The top rudder simply provides enough lift to keep the airplane level. The side of a citabria will develop quite a large amount of lift when its on its side. So the combinations of the lift from the fuselage and the wing will mean that the airplane holds altitude and changes heading, hench a 90 degree competition turn.

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.

There's an Advanced Handling Exercise that demonstrates an aircraft's handling under G. In this turn reversal exercise, you begin a loaded turn (60 or more degrees of bank). On the first turn, you unload, roll the aircraft using aileron, then get back on the G (with the controls centered of course, careful not to get an asymmetric over-g). On the second, you keep the aircraft loaded and roll the aircraft using top rudder. The aircraft will reverse the direction of the turn. The first method will reverse the direction of the turn much more quickly, at the expense of not turning for the few seconds while you unload.. The second will reverse turn directions more slowly, but will keep you turning the entire time. Where is this important? BFM, but that's another discussion unto itself. The bottom line here is that top rudder in a loaded turn will roll the aircraft and will not allow you to sustain your 90 degree turn.

 

[jesse]

Roll any amount of bank without back pressure and the nose will drop. At 90, your "elevator" is now the rudder. Not every aircraft can do it, but some generate enough lift with their fuselage and have enough rudder authority to do it.

Exactly. Elevator is now the rudder.

You hold altitude by generating Gs. You can't generate an infinite amount of Gs.

That might make sense. If you're only thinking about the lift from the wings. You must consider the lift from the rudder and fuselage along with the airplane's thrust and inertia.

 

[Patch]

That might make sense. If you're only thinking about the lift from the wings. You must consider the lift from the rudder and fuselage along with the airplane's thrust and inertia.

Believe me, I am. And it can't be done.

 

[KennyFlys]

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?

 

[Patch]

How does a symmetric airfoil generate lift?

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?

 

[IamBull]

Hell, I can barely do that in straight and level flight.

Perhaps you should find a new hobbie

Theres no difference in knife edge flight on heading or changing heading. The top rudder simply provides enought lift to keep the airplane level. The side of a citabria will develop quite a large amount of lift when its on its side. So the combinations of the lift from the fuselage and the wing will mean that the airplane holds altitude and changes heading, hench a 90 degree competition turn. It is the same concept as doing a pure slow roll... you combine the control inputs to make no altitude change throughout the roll, unlike the aileron roll, which involves a pitch up at the start.

No aircraft can hold level flight at exactly 90 degrees of bank in a turn. Can an aircraft roll to 90 and turn? Yes, but you will lose altitude. However, you can roll to 90 in some aircraft, without putting AOA on the jet (which is fancy talk for applying backstick pressure), put in some top rudder and not lose altitude. You gotta think 3 dimensionally and in terms of lift vector young padawan .

 

[gibbons]

That's not the point. At 90 degrees of bank, it is impossible to sustain a level...

coordinated

...turn.