90 bank turn (Merged)
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Re: 90 bank turn (Merged)
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Re: 90 bank turn (Merged)
Well if you are trying to maintain a level 90° banked turn the world will stop. As G forces = 1/Cos AoB you will see that above 60° g increases exponentially. At 60° g~2 at 75° g~5 etc.
I make it at 89° you will be pulling somewhere in the region of 58g
Of couse, if under Va the aircraft will stall in an interesting manner as mentioned, if over your wings may well part company with the rest of your airframe.
If you are not maintaining height during this turn, it is possible to pull zero g. A 75° "Lazy 8" and you can have the ASI reading zero yet still not be stalled, as there is no load on the wing.
(a few assumptions are made here, like ignoring lift from the fusalage, but the principles are the same and g levels would be approximately similar)
I make it at 89° you will be pulling somewhere in the region of 58g
Of couse, if under Va the aircraft will stall in an interesting manner as mentioned, if over your wings may well part company with the rest of your airframe.
If you are not maintaining height during this turn, it is possible to pull zero g. A 75° "Lazy 8" and you can have the ASI reading zero yet still not be stalled, as there is no load on the wing.
(a few assumptions are made here, like ignoring lift from the fusalage, but the principles are the same and g levels would be approximately similar)
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Re: 90 bank turn (Merged)
Originally Posted by englishal
Well if you are trying to maintain a level 90° banked turn the world will stop. As G forces = 1/Cos AoB you will see that above 60° g increases exponentially. At 60° g~2 at 75° g~5 etc.
I make it at 89° you will be pulling somewhere in the region of 58g
Of couse, if under Va the aircraft will stall in an interesting manner as mentioned, if over your wings may well part company with the rest of your airframe.
If you are not maintaining height during this turn, it is possible to pull zero g. A 75° "Lazy 8" and you can have the ASI reading zero yet still not be stalled, as there is no load on the wing.
(a few assumptions are made here, like ignoring lift from the fusalage, but the principles are the same and g levels would be approximately similar)
I make it at 89° you will be pulling somewhere in the region of 58g
Of couse, if under Va the aircraft will stall in an interesting manner as mentioned, if over your wings may well part company with the rest of your airframe.
If you are not maintaining height during this turn, it is possible to pull zero g. A 75° "Lazy 8" and you can have the ASI reading zero yet still not be stalled, as there is no load on the wing.
(a few assumptions are made here, like ignoring lift from the fusalage, but the principles are the same and g levels would be approximately similar)
If you accept that knife edge level flight is possible (it is), you won't suddenly get crazy g by adding some elevator to the equation.
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Re: 90 bank turn (Merged)
Originally Posted by goose67
Slim Slag,
Like the FCI link. I'm doing the 3-day 5-mission course there in a few weeks' time. Have to ask them to demo it
Like the FCI link. I'm doing the 3-day 5-mission course there in a few weeks' time. Have to ask them to demo it
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Re: 90 bank turn (Merged)
Cheers paulo. I'll certainly do that. Only problem is, I doubt the C152 share I have will seem quite so appealing when I come back home. Have to see if the other guys fancy upgrading...
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Re: 90 bank turn (Merged)
If you accept that knife edge level flight is possible (it is), you won't suddenly get crazy g by adding some elevator to the equation.
Even if you add a bit of elevator you will turn and as you say and the G forces won't nescessarily be massive as the lift is still being generated by the fusalage. If you try to maintain a level 90° banked turn in a typical GA or other non-aero's aircraft you need the upward vector of lift to be generated by the wing, and hence you'll soon come a cropper........
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Re: 90 bank turn (Merged)
The knife edge spin is purely a gyroscopic figure. The rudder and the engine precession try to hold the nose up, while the full forward stick creates the "tumble" appearance. In fact you are pitching around the main axis of the wing. Great for dramatic height loss, and short crankshaft life......
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Re: 90 bank turn (Merged)
I think the original question posed was a more basic one regarding how aircraft turning at what looks like 90 degrees maintain level flight. The knife edge with some elevator to cause the the nose to turn is a very esoteric and abnormal manoeuvre which can only be performed by a few specialist aerobatic aircraft, eg the Extra 300.
The answer to what I think was asked is that the aircraft isn't actually at 90 degrees of bank maintaining level flight, it just looks like that. And no aircraft would be using top rudder to maintain a level balanced turn, even at high angles of bank. If you stuck a bootfull of rudder in a hawk, for example, in a 7g level turn, you'd either break the tail off or spin into the ground.
The answer to what I think was asked is that the aircraft isn't actually at 90 degrees of bank maintaining level flight, it just looks like that. And no aircraft would be using top rudder to maintain a level balanced turn, even at high angles of bank. If you stuck a bootfull of rudder in a hawk, for example, in a 7g level turn, you'd either break the tail off or spin into the ground.
Re: 90 bank turn (Merged)
Learned this long ago, sorry if it's a bit incomplete...
In level flight the required g force will be the inverse of the sine (or was it cosine) of the bank angle. Sine 60 = .5 so g = 2. 75 degrees will produce 4g. 30 degrees about 1.4. The stall speed is multiplied by the square root of the g force, so at 60 degrees (2g) stall speed increases by about 40%,75 degrees (4g) the stall speed is double normal. Which is why most aircraft are Va at around double the stall speed.(normal category limit +3.8g)(which means the structure may fail at around 5.7g..50% safety factor)
Knife edge flight impossible in most ga aircraft: they lack the rudder authority and power. Tried a vertical sideslip in a Cherokee when learning to fly.Just once. It doesn't work.(It does produce high speed, rapid height loss, possible overstress, and high pulse.)If an A300 tail can fail in overload, I guess a lighty tail can too. Not to be encouraged.
In level flight the required g force will be the inverse of the sine (or was it cosine) of the bank angle. Sine 60 = .5 so g = 2. 75 degrees will produce 4g. 30 degrees about 1.4. The stall speed is multiplied by the square root of the g force, so at 60 degrees (2g) stall speed increases by about 40%,75 degrees (4g) the stall speed is double normal. Which is why most aircraft are Va at around double the stall speed.(normal category limit +3.8g)(which means the structure may fail at around 5.7g..50% safety factor)
Knife edge flight impossible in most ga aircraft: they lack the rudder authority and power. Tried a vertical sideslip in a Cherokee when learning to fly.Just once. It doesn't work.(It does produce high speed, rapid height loss, possible overstress, and high pulse.)If an A300 tail can fail in overload, I guess a lighty tail can too. Not to be encouraged.
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Re: 90 bank turn (Merged)
The B-52 (I had a link but lost it - horrifying video) was banking too steeply at too low speed/alt. Since the B-52 uses spoilers for roll, they have no effect in that situation, so they couldn't roll wings level without dropping the nose. Result: Splat! It had a lot to do with an arrogant commander as well.
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Re: 90 bank turn (Merged)
Originally Posted by markjoy
Knife edge flight impossible in most ga aircraft: they lack the rudder authority and power. Tried a vertical sideslip in a Cherokee when learning to fly.Just once. It doesn't work.(It does produce high speed, rapid height loss, possible overstress, and high pulse.)If an A300 tail can fail in overload, I guess a lighty tail can too. Not to be encouraged.
Edit: Actually, err, retract... I did all sorts of daft things learning. Nearly similar. The high speed and rapid height loss sound familiar. I got back to "base" a little shaky after some steep turns got a bit too steep.
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Re: 90 bank turn (Merged)
Paris Dakar, I recall that clip. I believe it was on the B52 documentary which occasionally surfaces on Discovery Wings. I believe the programme mentioned that the crew were show boating as they were transfering to another airfield. Sadly, it really was their last visit
Paulo
Yes, of course it was youthfull exuberance, and ignorant and ill advized. Fortunately most ga aircraft have their limits well above what most pilots are prepared to try.
For those interested in the b52 vid ; http://www.alexisparkinn.com/photoga...52%20Crash.mpg
videopage of source site, a goody!
http://www.alexisparkinn.com/aviation_videos.htm
Enjoy.Some of them are cool, some funny, some quite shocking.
Yes, of course it was youthfull exuberance, and ignorant and ill advized. Fortunately most ga aircraft have their limits well above what most pilots are prepared to try.
For those interested in the b52 vid ; http://www.alexisparkinn.com/photoga...52%20Crash.mpg
videopage of source site, a goody!
http://www.alexisparkinn.com/aviation_videos.htm
Enjoy.Some of them are cool, some funny, some quite shocking.
Any decent aerobatic plane can be flown in a stable knife-edge - for example the Decathlon does it. Lots of top rudder and a bit of forward stick. The lift is all coming from the fuselage, so you need some speed too. You can turn using the elevator.
It is possible to fly a turn which starts normally and transitions into a knife-edge turn as the bank angle increases, with careful blending between rudder and elevator. Taken through a full roll this is called a rolling turn, and is a standard advanced aerobatic manoeuvre (though very hard to get really right).
The knife edge spin is an intriguing manoeuvre - I once did one inadvertently and plan to try flying them intentiionally soon. However what my instuctor (and Alan Cassidy) call one doesn't seem to be what the video shows, which is what my instructor calls a Zwiebelturm. That is definitely a tumble and pretty seriously disorientating the first few times. In theory, if you do it right, you end up in an inverted spin, right way and going upwards, which is a bit mind boggling even to think about.
n5296s
It is possible to fly a turn which starts normally and transitions into a knife-edge turn as the bank angle increases, with careful blending between rudder and elevator. Taken through a full roll this is called a rolling turn, and is a standard advanced aerobatic manoeuvre (though very hard to get really right).
The knife edge spin is an intriguing manoeuvre - I once did one inadvertently and plan to try flying them intentiionally soon. However what my instuctor (and Alan Cassidy) call one doesn't seem to be what the video shows, which is what my instructor calls a Zwiebelturm. That is definitely a tumble and pretty seriously disorientating the first few times. In theory, if you do it right, you end up in an inverted spin, right way and going upwards, which is a bit mind boggling even to think about.
n5296s
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During a slow roll the aircraft experiences S&L flight at all bank angles, I managed to hold a Robin 2160i in the knife edge position, though with alot of rudder force, which my old aerobatic instructor attributes to the fuselage shape effectively being a wing in its own right. But unless you are flying aero's, why try? you will just end up in a spin.
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Originally Posted by paulo
Make sure you get some snap rolls in too... they are quite mad... in very fast "whooaa!! what happened there?" kind of way.
On the last flight I got to fly a knife edge spin up. It's surreal looking down your left wing tip at the corkscrew created by the smoke while you're gaining height. 
The outside loop was a bit uncomfortable though. My head looked like a beetroot 
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Enough to say that a 90 degree banked, level and balanced turn is absolutely impossible for a conventional winged aircraft. Anything much over 80 degrees and your wings are designed to fail under excessive load.
