Demise of the biplane

[TB2]

This may sound naive, but why was the biplane phased out and single-wing a/c adopted? My only guess would be that two wings were necessary to provide more lift area 'cuz the engines weren't that powerful. Am I right?

[majortomski]

This may sound naive, but why was the biplane phased out and single-wing a/c adopted? My only guess would be that two wings were necessary to provide more lift area 'cuz the engines weren't that powerful. Am I right?

Partly right. The principle driver behind a biplane is strength The two wings, and the associated wirirng and struts form a warren truss beam. The same type of beam used to support railroad trains. It gives lots of bending strenght for very little weight. The power factor comes in if you try to make a monoplane with the same area to fly as well on the same amount of power. The early monoplane wing gets too big and heavey to be effective. Drawback to biplane is the associated drag of all those parts. Starting with Fokker and Dornier's work with thick canteliver wings the designers learned to get nearly the same strenght out of a monoplane and picked up speed with the loss of all those draggy parts.

[Old Man]

A conflict between two schools of fighter design in the 30s, seems to have had a lot of influence in the matter. Just about as long as there have been fighter planes, there have been some that were designed for advantages of speed and some designed for advantages of manouverability. Biplane design offered advantages to the former class, because of lower wing-loadings and shorter wingspans, while monoplane design offered advantages to the former class because of better streamlining. Soviet fighter design and procurement in that period provides an excellent illustration of the debate, as does Italian.

Improvements in engineering cantilever wing structures, particularly the all metal stressed skin construction pioneered in civil aviation designs aimed at the expanding market for airliners in the mid-thirties, went a long way towards sealing the predominance of the monoplane. The new construction method made it possible to effectively exploit greater engine power, and give the monoplane designs decisive advantages in speed, which with tactics aimed at exploiting that advantage in hit and run style made it immaterial how manouverable a slower biplane might be.

No one seems to have attempted a biplane fighter in the new construction style, which might have perhaps dispensed with interplane struts and the like. Probably the most advanced of the biplane fighters was Polikarpov's I-15ter, which had a retracting landing gear and was, in one model, fitted with a motor of 1,000 horsepower, with which it managed a top speed in the 300mph range, and retained superior manouverability. It was still built with old style composite construction wings, however, that required interplane bracing, and still fell short of the speed of the opposing Messerschmitts by thirty to forty miles per hour.

The Japanese, valueing manouverability above all else, succeeded in building monoplane fighters with wing loadings comperable to biplane designs constructed in the new methods, but managed this only by making the structures so light as to make the machines very vulnerable to combat damage

Edited July 6, 2006 by Old Man

[The Loggie]

Other Biplane problems were A) less visibility from the cockpit and minimum separation distance between wings dictated by one wings airstream distorting the others. The only modern biplanes that I can name are the Pitts Special and the Christian Eagle - both small compact stunt biplanes.

George, out...........

[Skyking]

All the technical reasons stated in the previous posts are correct as far as the technical aspects of why aircraft have evolved from biplanes to monoplanes. However from a purely asthetic point of view, you can't beat the biplane for looks, no matter what argument you give. There's something about a biplane that just looks "right", that it is meant to fly and that it is meant to be in the air. Granted there are some very nice looking monoplanes, but the romance and the "wind in your hair" feeling of flying in an open cockpit, 2500 AGL on a clear evening, is something that you don't just "do", you experience it. As long as dedicated people keep them flying, biplanes will hardly be "demised", but live on to remind us of flying in simpler times, when a few instruments and a compass were all you needed. Keep your glass cockpits, your GPS, your computer assisted fly by wire controls and your need for speed with your tail feathers on fire from some shrieking afterburner. For me, I'll take a big round engine making a mechanical symphony of noise and an open cockpit, a few instruments to help me stay straight and level, and a clear VFR evening, and I will be in my hog heaven.

The keys to a beauty such as this Waco UPF7 wouldn't hurt either.

Cheers

Mike

Edited July 10, 2006 by Skyking

[TB2]

Totally agree, Mike. Although I haven't had the privilege of flying in one, they are something to behold. A few months ago I heard what sounded like the drone of a radial engine in the sky. Looked up and saw a large, unfortunately unidentifiable, bi-plane. The sight of her (at the risk of sounding sappy) struck a romantic cord in my heart. What a beauty!

[Edgar]

The problem; it's called a built-in headwind. The more bits, and pieces, that stick into the airflow, the bigger the drag, the slower you go. The propellor was the next thing, that had to go; it limited the monoplane, because of its drag.

Edgar

[MikeC]

Biplanes will always have a romantic mystique about them. The best place to go watcth them, at least in great numbers, is Rhinebeck, NY. Cole Palin knew exactly what he was doing.

I have yet to fly one, but I sense a Stearman ride coming someday soon.

I'm sure when that happens, it'll be impossible to get the stupid grin off my face for at least a manth.

RS

Rusty,

I'll see your Rhinebeck, NY, and raise you the Shuttleworth collection at Old Warden. Nothing like watching a Gladiator land whilst the Hind is warming up literally in front of you. I only lived 10 miles away until I moved here!

[RipVW]

I've flown a bunch of different trainers in my Very limited flying experience (PT-17, PT-19, AT-6, T-28, T-37 and T-41) But doing loops and rolls over Lake Mathews, CA and barnstorming Art Scholl's air strip in the Stearman was the most fun I had.

And Rusty - I was back at Rheinbeck three years ago, and the place (and the machines) is just as beautiful as ever. It's wonderful to see some of the oldest original flying machines in the world trundle up and down the Rheinbeck grass strip!

ATB -

- Rip -

[mchuray]

In addition to the other items listed another is co$t. Even being made of moderen materials the cost of building an extra set of wings, & keeping them prorerly riiged was much higher than a monoplane. While many wax nostalgic about biplanes and steam engines the facts are thay were built in at a time when labor was cheep and materials were expensive.

Mark

[ikar]

Years ago when I was asigned to Loring AFB in Maine I went south towards the coast to a airshow at Camden (I think.) It was at the Owlshead Museum. They had quite a collection of old items that included a hanger of WWI aircraft. They said that if it didn't work, it wasn't there. A few of the aircraft that flew that day included a Curtis pusher, Neuport, Fokker triplane, and a couple staggerwings.

[agboak]

Some manufacturers did try building cantilever biplanes, i.e. without all the struts and wires etc. However, having two wings, on above the other, is inherently more draggy than having one bigger wing. Biplanes will inevitably be slower than contemporary monoplanes, once the constructional problems of the cantilever wing were solved.

[ross blackford]

:mellow: A couple of people who have posted in this discussion mention the airflow from each wing interfearing with that of the other wing. When I was learning to fly our instructors told us that at a Tiger Moth's cruising speed (about 80 - 85knots) the boundary layer was only about 1/16 " thick and became thinner as airspeed increased until at 360 knots it is measured in thousandths of an inch. If this is true then would not the airflow from one wing of a biplane be nowhere near that of the other wing? Certainly the extra wing and all the associated wiring and struttery will have an effect on the performance of the biplane but I'm not too sure about the interfearence one wing will cause to the other. If we have any aircraft designers or homebuilders among us perhaps they could fill us in on this subject.

BTW there are quite a few homebuilt modern biplanes around. To see some of them go explore the homebuilt pages.

Cheers,

Ross.

Edited July 16, 2006 by ross blackford

[agboak]

I'm not sure I recognise those values of boundary layer thickness - but it does depend upon the distance downstream - thousands of an inch is about right for the nose of (say) a BAE Hawk, but it is OK to use round-head rivets on the rear fuselage.

However, the boundary layer is only where the viscous effects occur. The airflow is disturbed up to a considerably greater distance from the surface. I realise that "take my word for it" may not have a lot of credence, but I was a professional performance aerodynamicist for the British aircraft industry. I have done drag calculations for aircraft such as the Hawk and Jaguar, and although none of them were biplanes I do believe that biplanes are intrinsically draggier than monoplanes because of interference between the two surfaces. The interference is dependent upon the span ratio and the distance between them. You'd have to consult the textbooks for a fuller explanation, and I've sold mine. Maybe a google search....

[Grey Ghost 531]

Years ago when I was asigned to Loring AFB in Maine I went south towards the coast to a airshow at Camden (I think.) It was at the Owlshead Museum. They had quite a collection of old items that included a hanger of WWI aircraft. They said that if it didn't work, it wasn't there. A few of the aircraft that flew that day included a Curtis pusher, Neuport, Fokker triplane, and a couple staggerwings.

It's just outside of Rockport. I've been there a couple of times, they have a great antique motorcycle event every Labor Day weekend. It's almost as much fun to see a guy putting around on an ought-something Harley single as it is to see a round engined bipe fly!

[majortomski]

:lol: A couple of people who have posted in this discussion mention the airflow from each wing interfearing with that of the other wing. When I was learning to fly our instructors told us that at a Tiger Moth's cruising speed (about 80 - 85knots) the boundary layer was only about 1/16 " thick and became thinner as airspeed increased until at 360 knots it is measured in thousandths of an inch. If this is true then would not the airflow from one wing of a biplane be nowhere near that of the other wing?

Nothing to do with the boundary layer. Has to do with the compression effect of the air trapped between the two surfaces.

360KNOTs in a TIGER MOTH! Wow, that's some engine! :D

[ross blackford]

Thank you to those who have clarified the situation for me, especially Graham. And no majortomski, I wasn't referring to a Tiger Moth capable of 360 knots, that would be a miraculous biplane, just any aircraft that would go that fast or faster. The Polikarpov I-153 was probably the fastest biplane produced and it had a top speed somewhere around 280 - 290 mph on 1100 hp. And yes Graham I have observed the rivet farm on the empenage of a Herc many times during my before flight inspections.

Cheers,

Ross.

[majortomski]

From the book of world records

Fastest biplane:

"Fastest Biplane

The fastest biplane was the Italian Fiat CR42B. The plane had a 1,100-hp (753-kw) Daimler-Benz DB601A engine, which propelled the craft to speeds of 520 km/h (323 mph) in 1941. Although only a single CR42B prototype was built, 1,780 of the CR42B Falco were produced. It proved invaluable to the Italian Air Force in World War II."

[joncarrfarrelly]

Partly right. The principle driver behind a biplane is strength The two wings, and the associated wirirng and struts form a warren truss beam. The same type of beam used to support railroad trains. It gives lots of bending strenght for very little weight. The power factor comes in if you try to make a monoplane with the same area to fly as well on the same amount of power. The early monoplane wing gets too big and heavey to be effective. Drawback to biplane is the associated drag of all those parts. Starting with Fokker and Dornier's work with thick canteliver wings the designers learned to get nearly the same strenght out of a monoplane and picked up speed with the loss of all those draggy parts.

Actually only the Ansaldo SVA series of biplane aircraft used a Warren truss design, the rest are a relatively simple tensioned box. The SPAD aircraft used an extremely thin airfoil for reduced drag which required increased external stiffening, for this reason they are, unlike the majority of their contemporaries, generally a two-bay wing design. Your comments on strength versus drag apply to the cantilever wing monoplanes but not the wire-braced variety which predate the war and were used throughout and after in various guises. The much later Boeing P-26 used external bracing wires for reasons of drag and weight reduction...Boeing found that a wing of that design allowed a higher top speed than the fully cantilevered wings allowed by the technology of the period. The thick Fokker and Dornier cantilever wings were not less draggy than a braced design of similar dimensions with similar power of the same period...the later fairly major improvements in engine power and engine placement brought the unbraced cantilever wing to the fore.

The major advantage of the biplane is reduced wingloading, and thus enhanced manouverability, for a given engine rating within a fairly compact and relatively light weight package.

[The Loggie]

Further top my post of 07 Jul 06, there is a 3rd 'modern' biplane - the Antanov An.12 Colt.

George, out..............

[ross blackford]

Yes, of course George. How could I forget the most produced post WW2 biplane. It's interesting to read in Gunston's Osprey Encyclopedia of Russian Aircraft 1875 - 1995 that it did not even occur to Antonov that a biplane would be considered an enigma in the modern age. The biplane layout provided the best solution to the problem at hand so he went down that road. Majortomski, when I mentioned the I-153 I meant mass produced and combat blooded biplanes although I forgot to mention that. The DB powered Fiat CR42 was probably the fastest bipalne ever built but as you said it was a one off.

It would be interesting to see a flying CR42 in mock combat with an I-153 and see just what advantages each aircraft had over the other and just how close they are in performance, manouverability and handling qualities and what the pilots thought of them overall. I know I would certainly like to get my hands on examples of both for a few hours each and compare them. There is nothing wrong with dreaming I guess.

Cheers,

Ross

[Julien (UK)]

Further top my post of 07 Jul 06, there is a 3rd 'modern' biplane - the Antanov An.12 Colt.

George, out..............

You do mean the AN-2 Colt I hope :huh:

Apparently they estimate over 2000 still flying and they are re-manufacturing them all the time!

Julien