Is there an aerodynamic reason why the concept of biplane or triplane has been completely abandoned? Practically all planes were biplanes in WW1, and in WW2 practically none were developed.
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2$\begingroup$ Whilst not strictly a duplicate the top answer to this question covers it pretty well. Essentially in the early years of flight the advantages of biplanes outweighed the disadvantages; as material science and engine power improved this reversed and monoplanes became dominant. $\endgroup$– Nigel HarperCommented Jan 29, 2015 at 11:41
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$\begingroup$ Viking Dragonfly, Pitts Special, Rutan had at least one with canard large enough to count as a wing. $\endgroup$– copper.hatCommented Feb 2, 2015 at 4:52
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$\begingroup$ You'd think a bi-plane design would be really good for drones, and should be lighter in weight since you don't need as much structural support as really long wings need. And I'd think the drag problem could be overcome by how you choose to position the 2 wings. MIT and the Japanese have looked at a 1935 design that would use 2 wings to cancel out a sonic boom for supersonic passenger planes. $\endgroup$– WillieNAzCommented Nov 7, 2016 at 7:22
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2 Answers
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Firstly, there are:
For example this company currently makes a biplane
But the main reason is that they're inefficient, and don't really do much that a monoplane can't.
They produce a lot of drag compared to the amount of lift they produce, meaning they use a lot of fuel to travel the same distance. They have fairly poor visibility, which is usually considered a bad thing!
They do have a few advantages - they have a good roll rate, making them quite maneuverable, and they have a very low stall speed and can fly on little power, meaning they can fly slowly very well (where their increased drag doesn't make much difference: drag increases with the square of airspeed)
Overall, though, the above makes them suited only to aerobatics, which can also be performed by monoplanes. Advances in wing design and composite materials take away most of the advantages of a biplane for any other use: ie actually travelling (the main purpose of an aeroplane) and carrying a load.
Overall, then, they're more complex than a monoplane, less efficient, and aren't much more manoeuverable. They have more disadvantages than advantages.
Biplanes were popular in WWI not because of any inherent advantage, but simply because technology hadn't advanced far enough to allow any other options. Once the monoplane was properly developed, it allowed much higher speeds (450mph for a late WWII fighter, 300mph for an Early WWII fighter, compared to around 120 mph for a late WWI fighter). High speed fighters beat low speed fighters (at least before stealth technology and guided missiles)
There were a few leftover biplanes in WWII - The Fairey Swordfish torpedo bomber was one of the most widely used, as the low speed and good lift from the biplane design allowed it to carry a heavy torpedo, while the drag issues didn't matter at the slow speeds they needed to fly to be able to release the torpedo properly and on target. Others were the Gloster Gladiator (UK), Fiat CR.42 (Italy) and Polikarpov I-15 (Soviet Union) which achieved varying levels of success in the early stages, but were well and truly outclassed when facing even early-war monoplanes.
This answer on a similar question gives some useful context about the direct advantages and disadvantages. It doesn't directly explain why biplanes fell out of favour, but it may help understand my own answer here.
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5$\begingroup$ @ROIMaison - they (biplanes) have LESS mass far away from the centre of gravity because the wings are shorter (up to half the length of a comparable monoplane wing) and can also be lighter in some cases. It also affects how much wing is "resisting" the roll through the air, similar to how clipped wings work - see the Spitfire L.F (clipped wings for roll rate at low altitude) vs the Spitfire F (Regular) variants. Ailerons make some difference, but for a comparable aileron size and wing area, a biplane will roll better than a monoplane $\endgroup$ Commented Jan 29, 2015 at 13:42
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1$\begingroup$ @JonStory I will suggest to include in your answer that biplane wings produce more drag as longer wings (biggest aspect ratio) produce less drag. On top all the strings connecting both wings produce not needed drag. $\endgroup$ Commented Jan 29, 2015 at 20:13
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2$\begingroup$ Don't forget the Antonov An-2 utility biplane, still flying! It is an old design (1947) but is still in production. It's even being constantly updated with new variants being developed as recently as 2013. $\endgroup$– UrquiolaCommented Feb 22, 2015 at 22:45
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1$\begingroup$ Another advantage of biplanes is that they are very good in a bush plane role, where the slow take-off and landing speeds and the short wings help operation in the wilderness where the terrain is rugged and full of obstacles. This is a niche role where biplanes are often used even today. The famous An-2 can land almost anywhere, as it has a stall speed so low it can basically land like a parachute, an impressive feat for an aircraft of that size. $\endgroup$– vszCommented Jul 5, 2015 at 10:00
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1$\begingroup$ @supercat: Don't forget crop dusters, which also have to "fly around an area at moderate altitude for as long as possible on a given amount of fuel, without having to go anywhere". Okay, not strictly as long as possible, but if you're spraying a lot of field... $\endgroup$– VikkiCommented May 4, 2018 at 22:03
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Well there ARE still biplanes produced today, either for nostalgic, or recreational reasons; they're just cool and harken back to classic age in aviation. Biplanes are still popular with aerobatic pilots today for their agility as well.
The chief reasons the biplane largely went the way of the dinosaur have to do primarily with aerodynamics and structural mechanics. When the cantilevered wing was perfected as well as construction from lightweight, high strength aluminum alloys which facilitated the monoplane, aircraft designers could take advantage of the superior characteristics of a monoplane, specifically much lower drag, allowing for higher speed flight. World War II accelerated this transition, as the need for higher performance military fighters made the monoplane extremely attractive to designers on both sides.
But a Stearman or a Pitts are still a hell of a lot of fun to fly.
answered Jun 30, 2016 at 6:55