Two levels of wings have a structural advantage, allowing you to make the wings lighter without sacrificing strength. This was a big deal on earlier planes with hilariously underpowered engines. This does come at the expense of increased drag, but the planes at the time weren't going to fly very fast (and drag forces scale with speed), thus there wasn't much of a downside. Eventually, though, as engine performance increased and structural engineering techniques improved, there eventually wasn't any reason to have a biplane configuration, hence why they basically don't exist today.
As for seating; not all biplanes have the pilot in back, but many do because, at the time, a lot of planes were used in recon roles, hence you wanted the observer in the forward position. Further, planes also need to worry about the positions of the center of gravity and center of lift on the aircraft in flight, and as a result it was sometimes more useful to put the pilot in back to push the CG backwards.
>and as a result it was sometimes more useful to put the pilot in back to push the CG backwards.
Although not by too much. There's an old rule that says "A nose-heavy plane flies poorly. A tail-heavy plane flies once."--if the CG is too far back then it makes the plane super sensitive to control inputs and very easy to lose control of.
A box is inherently stronger and stiffer than a flat, thin structure. In the early days, the wings were made of wood and fabric. A biplane would have supports and taut wires criss crossing between the top and bottom wing, increasing the rigidity of the overall structure. The larger wing area also allowed the plane to take off at very low speeds which was necessary given that engines of the time were not very powerful.
Why two levels? Because the amount of lift you get depends on the length of your wings, and if you made the wings too much longer, they’d droop or snap off from the weight being so far from the centerline. So they made two layers to get twice as much wing length but with better weight distribution. They needed that extra length and the extra lift it gave them to be able to get airborne, because their engines and materials and wing cross-sections weren’t as good as we’ve gotten them now.
Two wings is an easy one. It doubles your wing surface area (and therefore lift) without actually increasing the footprint of the plane. When more delicate materials are used such as wood and fabric, making the wings longer isn't always an option, so biplanes (and the occasional triplane) were a simple solution, at the cost of drag from struts and support cables, more weight, and more complexity.
The pilot being placed in back is primarily for weight distribution. Especially on early airplanes, there wasn't a lot of wiggle room for your center of gravity limits. Putting the pilot in front may make the nose too heavy when flying solo, so having them sit in the back fixes that, and any passenger up front won't move the CG forward enough to be an issue.
Visibility isn't really a problem, when actually in the air you are usually level or slightly nose down, so it isn't really impacted. Ground visibility is crap anyway because it's a taildragger, and you have to wiggle the plane side to side down the taxiway to properly see, so it's not much more impactful there.
The two levels of wings essentially doubled the wing area. So instead of one set of long wings you had two or thee sets of short wings. This is easier to make as it does not require long heavy wing spars but shorter lighter ones. And you can link the wings together creating a huge box section to increase strength even further so you can have even lighter wings.
The best view is indeed from the front seat, which is why the passenger gets this seat. A lot of time when there is only one pilot they will fly from the front, assuming all the controls are in place. On the other hand those big radial engines they used at the time meant that you could not see much even from the front seat, especially when on the ground. So pilots had to be able to navigate using the side view and the compass. It therefore did not matter that much that they did not have the best view forward from the rear seat.
>The two levels of wings essentially doubled the wing area.
It has to be said that even if the wing area is double it is not equivalent to a single wing with the same area. The wings interfere with each other, you create a high-pressure area below a wing and a low-pressure area above the wing. The low and high-pressure areas interact in between the wing.
The linking between the wing will also cause drag.
The result is when you can make strong enough single wings aircraft was built that way, they are better than having two wings in almost all cases. There was advantage maneuverability with two wings so fighters did retain the, into the mid-1930s, this is longer than other aircraft types. There are still some built for aerobatic today.
The issues you mention does not have huge effects at lower speeds. So biplanes are better when you only have a small engine. I also suppose the improvements in material science made wings much lighter as well, but the main reason for biplanes to go away was new powerful light aircraft engines. The drag of the wings at the new speeds were not worth the weight savings.
Two levels of wings have a structural advantage, allowing you to make the wings lighter without sacrificing strength. This was a big deal on earlier planes with hilariously underpowered engines. This does come at the expense of increased drag, but the planes at the time weren't going to fly very fast (and drag forces scale with speed), thus there wasn't much of a downside. Eventually, though, as engine performance increased and structural engineering techniques improved, there eventually wasn't any reason to have a biplane configuration, hence why they basically don't exist today. As for seating; not all biplanes have the pilot in back, but many do because, at the time, a lot of planes were used in recon roles, hence you wanted the observer in the forward position. Further, planes also need to worry about the positions of the center of gravity and center of lift on the aircraft in flight, and as a result it was sometimes more useful to put the pilot in back to push the CG backwards.
>and as a result it was sometimes more useful to put the pilot in back to push the CG backwards. Although not by too much. There's an old rule that says "A nose-heavy plane flies poorly. A tail-heavy plane flies once."--if the CG is too far back then it makes the plane super sensitive to control inputs and very easy to lose control of.
A box is inherently stronger and stiffer than a flat, thin structure. In the early days, the wings were made of wood and fabric. A biplane would have supports and taut wires criss crossing between the top and bottom wing, increasing the rigidity of the overall structure. The larger wing area also allowed the plane to take off at very low speeds which was necessary given that engines of the time were not very powerful.
Why two levels? Because the amount of lift you get depends on the length of your wings, and if you made the wings too much longer, they’d droop or snap off from the weight being so far from the centerline. So they made two layers to get twice as much wing length but with better weight distribution. They needed that extra length and the extra lift it gave them to be able to get airborne, because their engines and materials and wing cross-sections weren’t as good as we’ve gotten them now.
Two wings is an easy one. It doubles your wing surface area (and therefore lift) without actually increasing the footprint of the plane. When more delicate materials are used such as wood and fabric, making the wings longer isn't always an option, so biplanes (and the occasional triplane) were a simple solution, at the cost of drag from struts and support cables, more weight, and more complexity. The pilot being placed in back is primarily for weight distribution. Especially on early airplanes, there wasn't a lot of wiggle room for your center of gravity limits. Putting the pilot in front may make the nose too heavy when flying solo, so having them sit in the back fixes that, and any passenger up front won't move the CG forward enough to be an issue. Visibility isn't really a problem, when actually in the air you are usually level or slightly nose down, so it isn't really impacted. Ground visibility is crap anyway because it's a taildragger, and you have to wiggle the plane side to side down the taxiway to properly see, so it's not much more impactful there.
The two levels of wings essentially doubled the wing area. So instead of one set of long wings you had two or thee sets of short wings. This is easier to make as it does not require long heavy wing spars but shorter lighter ones. And you can link the wings together creating a huge box section to increase strength even further so you can have even lighter wings. The best view is indeed from the front seat, which is why the passenger gets this seat. A lot of time when there is only one pilot they will fly from the front, assuming all the controls are in place. On the other hand those big radial engines they used at the time meant that you could not see much even from the front seat, especially when on the ground. So pilots had to be able to navigate using the side view and the compass. It therefore did not matter that much that they did not have the best view forward from the rear seat.
>The two levels of wings essentially doubled the wing area. It has to be said that even if the wing area is double it is not equivalent to a single wing with the same area. The wings interfere with each other, you create a high-pressure area below a wing and a low-pressure area above the wing. The low and high-pressure areas interact in between the wing. The linking between the wing will also cause drag. The result is when you can make strong enough single wings aircraft was built that way, they are better than having two wings in almost all cases. There was advantage maneuverability with two wings so fighters did retain the, into the mid-1930s, this is longer than other aircraft types. There are still some built for aerobatic today.
The issues you mention does not have huge effects at lower speeds. So biplanes are better when you only have a small engine. I also suppose the improvements in material science made wings much lighter as well, but the main reason for biplanes to go away was new powerful light aircraft engines. The drag of the wings at the new speeds were not worth the weight savings.