Zak
  • Member for 2 years, 5 months
  • Last seen more than a month ago
Why is the A380's fuselage designed with a flat bottom?
14 votes

Hobbes' reply has some of the main reasons, but there's some more: That flat bit is called the "belly fairing", and its functions are: Avoid some aerodynamically awkward corners that would ...

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What is the most 'environmentally friendly' way to learn to fly?
6 votes

The answers by Bianfable are pretty good. I'd add one more option: Use a powered glider. There are gliders with a small engine, electric or otherwise. Some look like propeller planes with glider ...

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Why do propellers have less theoretical range (i.e. range ignoring impatient passengers wanting to go fast) than jets, despite greater efficiency?
Accepted answer
5 votes

Update As @Zeus has pointed out correctly: Drag coefficient stay constant in my scenario, not drag -- I've updated the explanation accordingly. Sorry for that blunder. The conclusion does not change: ...

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How can wall to wall airfoil in wind tunnel produce downwash?
5 votes

There's no vacuum, there's just expanding and contracting streamtubes. At some point you have probably read (or worse: been told) something about wingtip vortices and lift which was at best misleading,...

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How to distinguish the induced drag of a lift-producing wing from its pressure drag?
Accepted answer
3 votes

There are multiple ways to decompose lift and drag forces, and they are unfortunately not compatible with each other. If you know the flow field (for example because you ran a CFD simulation), then to ...

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Would a coaxial propeller with the second prop slower and larger improve speed?
3 votes

I think what you'd ideally want to do is to have a fast-rotating "inner" propeller and a slower "outer" one, or actually a propeller whose RPM gradually decrease from the inside to the outside. ...

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Can wing-tip vortices be reduced/eliminated with a rear-facing propeller near the wing-tip?
3 votes

The wingtip vortices carry some energy, and not leaving it behind seems like a good idea. That's why winglets are a thing, after all. So, what if you put a propeller at the wingtip, aligning the axis ...

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Why don't short runways use (downhill) ramps for takeoff?
3 votes

it could always back-taxi on the runway before turning around and taking off. So ... that would limit the steepness of the slope significantly, and thus the potential benefit. Most other aspects are ...

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Can the divergence Mach be greater than 1?
3 votes

The general perspective I have so far seen multiple definitions for what "divergence Mach number" actually means (and worked with several of them), but it's usually tied to some empirical criterion ...

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How do I simplify explanations for the drag formula?
Accepted answer
2 votes

Trying a less mathematical way to make the equation plausible: $D = q \times A_{ref}\times c_D $ (with $q = \frac{\rho}{2}v^2$) $q$ is the so-called "dynamic pressure". That's the increase ...

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Why are true and indicated airspeed different?
2 votes

TL-DR: IAS is not about speed but about dynamic pressure. You can read it as "This is how fast I would need to fly at sea level standard conditions in order to get the same dynamic pressure" ...

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Why don't bypass ducts in jet engines narrow down the flow to accelerate it?
1 votes

You are of course correct in that higher exhaust velocity (for the same massflow) would produce more thrust. You may have overlooked that current turbofan engines do have a convergent bypass duct/...

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Does a biplane need wing twist?
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1 votes

Wing twist is not required for any wing, although it is often used (as you said) to make sure that not the entire wing stalls at the same time, but also to tune the spanwise lift distribution. Both ...

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Why are prop blades not shaped like household fan blades?
1 votes

Most of the other answers are already correct. Just one more aspect: Blade chord length. With something that spins as fast as an airplane propeller, the blades need to be as light as possible, to ...

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Could flaps be raised upward to serve as spoilers / lift dumpers?
1 votes

The concept you're sketching would reduce effective camber and increase pressure on upper wing surface (both of which is desired in a spoiler). It would however also produce a "nose up" moment while ...

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How to transform a NACA airfoil into a near-circle using the inverse Karman-Trefftz?
0 votes

As you say yourself, you know the radius of curvature on the leading edge. You also probably have the leading-edge coordinate itself. You appear to have the equations for the airfoil, too ($x(t), z(t)$...

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