Uncovering the Secrets of How WWI Planes Took Flight

[fugg]

Hello. I've just been curious as to the answer to this question. Modern aerofoils are fine due to the geometry that allows for a pressure difference between the upper/lower surface. But as I remember WWI planes, they all have 4-5 levels of straight wings. Does that serve the same purpose? How? I tried googling it but couldn't sort through the irrelevant topics. I'd appreciate anyone who can feed my curiosity!

 

[Razzor7]

Pilots were much stronger back then.

 

[Cyrus]

The airplanes had airfoils.

 

[derek e]

Hi, interesting question. I don't know the answer but I googled some pictures of WWI planes. A lot of them had two layers of wings that look like they have some curvature. This combined shape looks like a silhouette of sections of an airfoil, (from Cyrus) probably because each wing is an airfoil.
http://www.grahams.com.au/glennsgraphics/aircraftww1-1,1.gif

 

[Cyrus]

http://books.google.com/books?id=pW...gbHxCQ&sa=X&oi=book_result&resnum=1&ct=result

 

[russ_watters]

Just an fyi, even a flat plate will fly if it has a positive angle of attack...but I don't think anyone has ever tried to fly one. Even the Wright Flyer had a real airfoil.

 

[Vanadium 50]

A plane works by pushing air down. That's exactly what the WW1 vintage planes did - and as pointed out, they do have an airfoil.

 

[DaveC426913]

But as I remember WWI planes, they all have 4-5 levels of straight wings. Does that serve the same purpose? How?

4-5 levels? The most was 3 really (Fokker Triplane) the large majority had 2 wings. I think the reason they were bi-wings rather than the later mono-wings has more to do with the strength of materials and how much lift a wing of a given length could support.

 

[fugg]

mersi kurosh
Thanks, good to know!

 

[Cyrus]

mersi kurosh
Thanks, good to know!

 

[Phrak]

4-5 levels? The most was 3 really (Fokker Triplane) the large majority had 2 wings. I think the reason they were bi-wings rather than the later mono-wings has more to do with the strength of materials and how much lift a wing of a given length could support.

Adding vertically stacked layers improves lift, but with diminishing returns with each added layer This is due to interference. There's no improvement in aspect ratio by stacking wings; the drag increases with each layer, as the lift advantage slows.

You're right, the box construction was for strength. The Fokker triplane has an additional small foil between the wheel. Any structural members such as the carriage axle produce drag. Wrapping an aerodynamic shape around it reduced drag. So presumably, it's a source of free lift if you give it an angle of attack.

Even the cross wires where teardrop shaped, eventually. A teardrop shape half an inch across has about the same aerodynamic drag as a wire of about 100 mils diameter.

 

[DaveC426913]

The Fokker triplane has an additional small foil between the wheel. Any structural members such as the carriage axle produce drag. Wrapping an aerodynamic shape around it reduced drag. So presumably, it's a source of free lift if you give it an angle of attack.

OK so, 3 1/2 wings.

 

[Phrak]

I did find one example of a stack of 4 wings as pictured http://www.htmy.org/hattrick/stacked-wing-attacks/".

 

[Cantab Morgan]

A plane works by pushing air down. That's exactly what the WW1 vintage planes did - and as pointed out, they do have an airfoil.

Is that really so or are you speaking whimsically? I'm sure a helicopter works by pushing air down, but a plane?

I thought planes worked because the shape of the wing decreases the air pressure above the wing's surface, giving it a net lift.

 

[cragar]

A plane works because of Bernoulli's principle the air flows faster on top
because of the shape of the wing thus creating a low pressure on top
and the high pressure on the bottom of the wing pushes the plane up , I mean yes it can climb by moving the aileron's .

 

[Cyrus]

A plane works because of Bernoulli's principle the air flows faster on top
because of the shape of the wing thus creating a low pressure on top
and the high pressure on the bottom of the wing pushes the plane up , I mean yes it can climb by moving the aileron's .

<Raises my eyebrow> ...um, no.

 

[rcgldr]

A flat plate will fly if it has a positive angle of attack.

The old "dime store" type balsa gliders have flat wings and glide just fine. Rubber powered balsa planes with flat wings also fly well.

http://www.retroplanet.com/PROD/24887
http://www.retroplanet.com/PROD/24886

Is that really so or are you speaking whimsically? I'm sure a helicopter works by pushing air down, but a plane? I thought planes worked because the shape of the wing decreases the air pressure above the wing's surface, giving it a net lift.

The point is to accelerate the air downwards. The air is drawn downwards towards a low pressure zone above a wing, and/or pushed downwards away from a high pressure zone below. Technically the air accelerates away from higher pressure zones to lower pressure zones in all directions, except that air can't flow through a solid wing, so the net result of a wing moving forwards with an effective angle of attack is to accelerate the air downwards (corresponding to lift), and somewhat forwards (corresponding to drag).

 

[cragar]

ok then how does it work cyrus , learn me

 

[Cyrus]

ok then how does it work cyrus , learn me

I provided you a link to an online book. I would recommend reading it. Ailerons cause pure rolling moment (ideally). They do not make the aircraft climb, that would be the elevator.

 

[cragar]

ailerons can do both roll and elevate , when you pull back
on the stick the elevators and the ailerons move down so I wasn't completely wrong but you wouldn't have known based on your comment and the B-2 bomber doesn't even have elevators

 

[Cyrus]

ailerons can do both roll and elevate , when you pull back
on the stick the elevators and the ailerons move down so I wasn't completely wrong but you wouldn't have known based on your comment and the B-2 bomber doesn't even have elevators

No, they cannot. When you pull back on the stick the ailerons don't do anything. That's not how they work. What you just wrote is fundamentally wrong.

Again, please read the book I linked earlier.

(The B-2 is a flying wing. It has what are called elevons).

 

[Phrak]

This is actually a good question. Why did the WWI era biplanes have thin foil sections?

The Write brothers' wind tunnel tests lead them to believe that a very thin, section with a concave bottom was best--at least as far as their initial applications went. This may have been their conclusion because the Reynold number, within the tunnel where the tests were conducted, was comparatively low. Then again, there were so many possible shapes to test.

Which leads us to biplanes. With a thin wing section, using the materials of the time, there no chance of containing the structual members internal to the wing.

 

[cragar]

ok sorry , you are right , i stand corrected

 

[Cyrus]

ok sorry , you are right , i stand corrected

What you wrote about the wing though, is correct .

 

[rcgldr]

ailerons can do both roll and elevate

When you pull back on the stick the ailerons don't do anything.

Depends on the aircraft. Most aircraft don't use the ailerons as spoilerons or flaps, but some fighter aircraft adjust wing camber with respect to elevator inputs, rotating both leading edge "flaps" and the entire trailing edge of the wing (flaps and alilerons) downwards in addition to moving the elevator upwards when pulling back on the stick. It's also very common to adjust camber on radio control gliders by moving the entire trailing edge of the wing (flaps and ailerons) upwards (reflex), or downwards (more camber), either via a separate control and/or tied into elevator inputs.

In the first part of this video, the ailerons are raised and the flaps lowered ("crow" mode) to allow for slow flight. (It's better to raise the ailerons to reduce adverse yaw, and it also reduces lift):

http://www.youtube.com/watch?v=LUVRUMc7DP8&fmt=22

B-2 bomber doesn't even have elevators

Or ailerons. Fying wings use "elevons", which act as both ailerons and elevators.

On an aircraft where the entire stabilizer acts as an elevator, it's called a "stabilator". Terms for radio control models: "wingeron" - the entire wing acts as an aileron, these models have conventional elevators. "pitcheron" - the entire wing act as both aileron and has an adjustable AOA, the elevator is fixed.

 

[Phrak]

Then there are hang gliders where the entire wing does everything in relation to the pilot's center of mass.

 

[Cantab Morgan]

The point is to accelerate the air downwards. The air is drawn downwards towards a low pressure zone above a wing, and/or pushed downwards away from a high pressure zone below. Technically the air accelerates away from higher pressure zones to lower pressure zones in all directions, except that air can't flow through a solid wing, so the net result of a wing moving forwards with an effective angle of attack is to accelerate the air downwards (corresponding to lift), and somewhat forwards (corresponding to drag).

Ahhh. Then, could it be said that a well-designed wing shape accelerates the most air downwards but the least forwards?

It should have been obvious to me that airplanes have to accelerate air downwards to stay aloft. TANSTAAFL.

 

[Cyrus]

Ahhh. Then, could it be said that a well-designed wing shape accelerates the most air downwards but the least forwards?

It should have been obvious to me that airplanes have to accelerate air downwards to stay aloft. TANSTAAFL.

This doesn't even make any sense. A well designed wing has a high L/D ratio.

As for your second sentence, not really. A wing pushes the air down to a certain degree. But look at the streamlines of an airfoil and you will find the air pretty much leaves at the same angle it came in for laminar flow. The wing isn't shooting air downwards as it trails behind the airfoil section.

 

[rcgldr]

A wing pushes the air down to a certain degree. But look at the streamlines of an airfoil and you will find the air pretty much leaves at the same angle it came in for laminar flow. The wing isn't shooting air downwards as it trails behind the airfoil section.

an observer on the ground would see the air going almost straight down behind the plane.
From this website (similar text at other web sites):
http://home.comcast.net/~clipper-108/lift.htm

Not that I or others agree with everything on that website or anyone website about aerodynamics, but downwash of air in order to produce lift (the Newton part) is a common aspect of aerodynamic related web sites.

For a plane in level flight, or at least not accelerating vertically, gravity exerts a downforce on the plane, which exerts a downforce on the air, and the air ultimately exerts a downforce onto the surface of the earth.

 

[Lok]

Back then airplanes were made out of wood strings and canvas. Not too strong materials for holding 2 big wings on either side. Stacking the wings was stronger and used less material necessary for a good power to weight ratio. The wingspan had to be big as they didn't have enough power to fly on the small wings we see today. Less power means less speed so less lift, so the solution was bigger wings that generate enough lift at small speeds.

As i heard there was a time when nobody believed a normal wing plane would ever fly.