Aerobatics - why biplanes?
Thread Starter
Aerobatics - why biplanes?
So, to the aerobaticists amongst you, why are biplanes quite common for aeros?
The only time I see them flying near my house, they're all over the place. And very entertaining too.
The only time I see them flying near my house, they're all over the place. And very entertaining too.
A little less conversation,
a little more aviation...
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Why biplanes?
Fundamentally, because prior to the advent of carbon spars, stubby wing biplanes with wooden spars...where all of the strength came from the flying wires...was seen as the way to go.
Wooden spar techniques did move along - the Cap 10, Cap 21 and 231 are examples, but at the end of the day, longevity is still an issue. The One-Design, essentially a monoplane Pitts with a wooden spar, is a different and robust development - frankly, if the worst happens and the North Koreans start dropping instant-sunshine on our heads, then I'm going to hide under a One-Design - the spar can survive pretty much anything.
But if you've got the funds, and the time, you do your time in a Pitts, and then buy an Extra.
Ultimately, the Pitts is a 200 BHP Caterham, and the Extra is a 300 BHP+ Porsche. Take your pick, but set your budget accordingly.
Fundamentally, because prior to the advent of carbon spars, stubby wing biplanes with wooden spars...where all of the strength came from the flying wires...was seen as the way to go.
Wooden spar techniques did move along - the Cap 10, Cap 21 and 231 are examples, but at the end of the day, longevity is still an issue. The One-Design, essentially a monoplane Pitts with a wooden spar, is a different and robust development - frankly, if the worst happens and the North Koreans start dropping instant-sunshine on our heads, then I'm going to hide under a One-Design - the spar can survive pretty much anything.
But if you've got the funds, and the time, you do your time in a Pitts, and then buy an Extra.
Ultimately, the Pitts is a 200 BHP Caterham, and the Extra is a 300 BHP+ Porsche. Take your pick, but set your budget accordingly.
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Its to give it more wing area for lugging the beer bellys in the air.
By having a bi plane it moves the centre of pressure up nearer the C of G (the belly) thus decreasing the stability and improving handling.
Well thats my theory
By having a bi plane it moves the centre of pressure up nearer the C of G (the belly) thus decreasing the stability and improving handling.
Well thats my theory
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Another factor might be that the wings don't have to span that far outwards for the same chord, wing loading and surface area. This means better roll rates.
But aerobatics is fun and there's a definite "wow" factor involved as well.
But aerobatics is fun and there's a definite "wow" factor involved as well.
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Biplanes provided a very strong wing structure by using flying wires bracing a very light box structure. As Ed says, until the 70's the monoplane spars were not strong enough for high G loads without being very heavy. Nowdays the use of carbon biber has changed this and the monoplane wings win out because of reducd drag.
So your title could have been " why are old aerobatic aircraft Biplanes".
There is also an aesthetic argument. The Biplane boys and girls love them. The Monoplane men and women think that there are just too many wings!!
ZA
So your title could have been " why are old aerobatic aircraft Biplanes".
There is also an aesthetic argument. The Biplane boys and girls love them. The Monoplane men and women think that there are just too many wings!!
ZA
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They are also relatively slow and have high drag, which means they perform compact manoeuvres and don't pick up speed quite so quickly when pointed downwards.
Compare the size of a loop flown by the Reds with one flown by a Tiger Moth and you get the picture. OTOH unless they have a big engine like a Pitts they run out of energy fairly quickly.
Compare the size of a loop flown by the Reds with one flown by a Tiger Moth and you get the picture. OTOH unless they have a big engine like a Pitts they run out of energy fairly quickly.
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Another factor might be that the wings don't have to span that far outwards for the same chord, wing loading and surface area. This means better roll rates.
But aerobatics is fun and there's a definite "wow" factor involved as well.
But aerobatics is fun and there's a definite "wow" factor involved as well.
As I understand, a biplane with struts and braces weighs a lot less than a monoplane of the same wing area. Thus allowing a heavier engine to be installed which provides better performance as compared to a monoplane with similar weight.
Can someone give a clarification?
One more reason might be that, in aerobatics, a basic disadvantage of a biplane is less relevant. A biplane has poorer aerodynamics than a monoplane, especially a cantilever monoplane. However for aerobatics neither cruise speed nor fuel efficiency are prime factors.
By having the wing's centre of gravity closer to the craft's axis, reducing the wing's momentum
(hope I worded and spelt that right).
But how does small wing span provide better roll rates?
(hope I worded and spelt that right).
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Comparing a Pitts with a C152 is misleading.
Comparing a Pitts S1T with 200 HP against an Laser 200 would be a better comparison. They have similar roll rates, the Pitts is slightly lighter but has more drag. If you compare the Pitts to an Edge 360 then the Monoplane has better performance all round
As was said earlier the newer wooden or composite monoplanes are very light for their strength.
Roll rate is a consequence of the size of the aileron not the short or long wingspan. Having aileron further away from the fuselage gives more "leverage" but aileron near the fuselage gives faster roll at low speed when its in the prop slipstream. There is also a limit due to the strength of the wing that the aileron attaches to. Again, modern composites are stronger which has allowed bigger ailerons and therefore faster roll rates.
Nowadays people have moved on to 300+ HP and all the new competition aircraft are composite. There are no biplanes competing in internationals at Advanced or Unlimited...or Red Bull for that matter.
So, Curtis Pitts aircraft were brilliant and allowed a very light structure to be very strong. However nowadays they have been overtaken by modern composites.
Comparing a Pitts S1T with 200 HP against an Laser 200 would be a better comparison. They have similar roll rates, the Pitts is slightly lighter but has more drag. If you compare the Pitts to an Edge 360 then the Monoplane has better performance all round
As was said earlier the newer wooden or composite monoplanes are very light for their strength.
Roll rate is a consequence of the size of the aileron not the short or long wingspan. Having aileron further away from the fuselage gives more "leverage" but aileron near the fuselage gives faster roll at low speed when its in the prop slipstream. There is also a limit due to the strength of the wing that the aileron attaches to. Again, modern composites are stronger which has allowed bigger ailerons and therefore faster roll rates.
Nowadays people have moved on to 300+ HP and all the new competition aircraft are composite. There are no biplanes competing in internationals at Advanced or Unlimited...or Red Bull for that matter.
So, Curtis Pitts aircraft were brilliant and allowed a very light structure to be very strong. However nowadays they have been overtaken by modern composites.
Last edited by Zulu Alpha; 30th Jan 2012 at 15:53.
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Aside from the performance comparisons I think the Pitts has a certain something that is immediately evident as soon as you leave the ground; it's definitely a rewarding aircraft to fly. It's also reasonably affordable, particularly if it's kept on a permit, and you can homebuild some models too. The design is quite old now but they do seem to last once their built with a reasonable amount of care. I think that is why there are still so many kicking about today and hence their popularity as a cost effective competition ship.
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The monoplane Yak 18 placed 1st, 2nd, 3rd, 4th and 7th at the 1966 World Aerobatic Championship, and was followed by the Yak 50 and 55, none of which used CF in their construction.
Nice photos by the way. Where's the aeroplane?
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Comparing a Pitts with a C152 is misleading.
Comparing a Pitts S1T with 200 HP against an l@ser 200 would be a better comparison. They have similar roll rates, the Pitts is slightly lighter but has more drag. If you compare the Pitts to an Edge 360 then the Monoplane has better performance all round
As was said earlier the newer wooden or composite monoplanes are very light for their strength.
Comparing a Pitts S1T with 200 HP against an l@ser 200 would be a better comparison. They have similar roll rates, the Pitts is slightly lighter but has more drag. If you compare the Pitts to an Edge 360 then the Monoplane has better performance all round
As was said earlier the newer wooden or composite monoplanes are very light for their strength.
Roll rate is a consequence of the size of the aileron not the short or long wingspan. Having aileron further away from the fuselage gives more "leverage" but aileron near the fuselage gives faster roll at low speed when its in the prop slipstream. There is also a limit due to the strength of the wing that the aileron attaches to. Again, modern composites are stronger which has allowed bigger ailerons and therefore faster roll rates.
Flightlab Ground School 9. Rolling Dynamics
Last edited by aditya104; 12th Feb 2012 at 08:24.
