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41 votes

Could propeller wash provide sufficient lift to take off - even in theory?

Yes. The wing doesn't care what is causing air to flow past it. Headwind, propwash, 747 wake, gopher sneezes. If the airplane is restrained from forward motion, and the propwash over most of the ...
Camille Goudeseune's user avatar
20 votes
Accepted

How does the bypass air provide thrust?

The bypass air is accelerated by the fan at the front of the turbofan engine. This changes its velocity and therefore its momentum, which is the definition of a force (in this case: thrust): $$ F = \...
Bianfable's user avatar
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17 votes

Why does an aircraft pitch up when the speed increases?

What you ask is: If a model glider is thrown at a higher speed than its trim speed, why does it pitch up? Short answer: Because the rear horizontal surface produces less lift per area than the ...
Peter Kämpf's user avatar
17 votes
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Is it possible for an airplane to enter another airplane?

Clearly the plane must enter and exit through the belly of the larger plane Why so? If you drop this condition, things become much easier, because you could attach the smaller planes externally and ...
Zeus's user avatar
  • 9,083
17 votes

Vertically moving wings

If you ever wonder what different types of wing motions are good for, look at birds. They use all of them. In this case it reduces lift while keeping drag the same. Birds use this when landing. It ...
DKNguyen's user avatar
  • 644
14 votes

Why does this curved wind tunnel rotate?

While superficially similar, this curved windtunnel solves a very different problem from a straight windtunnel. A straight windtunnel is used to study steady flight without needing a very long ...
Sanchises's user avatar
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13 votes

Could propeller wash provide sufficient lift to take off - even in theory?

In principle yes, but why would you do it? For vertical take-off this would be grossly inefficient. Lift is produced by deflecting air downwards. This becomes easier as more air is available for ...
Peter Kämpf's user avatar
13 votes

Could gliders be a clean, practical alternative to other forms of transport?

There's one thing that will forever prevent an unpowered aircraft from entering commercial passenger service: the inability to make a second attempt at a landing. Airliners, with all their ...
Zeiss Ikon's user avatar
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12 votes

Is there any engine that doesn't use a propellant to produce thrust?

Yes there are. Although they are not for commercial aviation. One example are solar powered engines: Source Wikipedia Alternatively, there are other means of storing energy - rubber bands, but this ...
Alexus's user avatar
  • 746
12 votes

Vertically moving wings

The XB-70 had wingtips that folded down in flight so it could use the shock wave to create additional lift. However this particular approach (compression lift) only applies to supersonic airplanes. (...
Eugene Styer's user avatar
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11 votes
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What flying sources does Richard Feynman consider incorrect?

He's talking about "Flying Saucers" not flying sources. This is even clearer when you listen at 2:00 where he refers "known irrational characteristics of terrestrial intelligence" ...
Federico's user avatar
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10 votes
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What is the physical meaning of circulation found in Kutta condition?

Circulation of a fluid around an object by itself will produce no lift. The classic example of this is the spinning cylinder with no other airflow. Viscosity will cause the fluid near a cylinder ...
Gerry's user avatar
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10 votes

How does the bypass air provide thrust?

A bypass fan provides thrust in the same way a propeller provides thrust: by increasing the energy content of the gas mass passing through the disk. The added energy is most effectively converted ...
Koyovis's user avatar
  • 61.8k
9 votes

Could propeller wash provide sufficient lift to take off - even in theory?

Restricting the question to approximately horizontal airflow ... it's been tried. The Custer Channel Wing was one that tried ... it didn't quite make it, but was claimed to be able to fly at 8 to 11 ...
user_1818839's user avatar
  • 1,378
9 votes

Why does this curved wind tunnel rotate?

Here you'll find his paper about the wind tunnel. Apparently the rotation has been introduced in order to compensate for the Coriolis effect.
sophit's user avatar
  • 13.8k
8 votes

How does the bypass air provide thrust?

It doesn't bypass everything, just the combustion chamber. Notably, the air still goes through a fan. High-bypass turbofan engines make most of their thrust from the ducted fan. Very much like a ...
Peter Cordes's user avatar
8 votes
Accepted

How to determine the base of stratus clouds?

There is no formula for determining the height of the base of stratus clouds based on the ground-level temperature and dewpoint (or relative humidity). Unlike convective cumulus clouds, stratus ...
quiet flyer's user avatar
  • 22.8k
8 votes

Immobile pressure-sensitive stick

This is an actual design, used in the early iterations of the F-16 fighter jet. The ideology behind the design was much the same you described, with the additions on the "solid" stick ...
Jpe61's user avatar
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7 votes
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Is there any engine that doesn't use a propellant to produce thrust?

No matter which kind of engine, you need some way to supply the engine with energy and you need some way to store that energy until you need it in flight. Short of going nuclear (and there are some ...
hmakholm left over Monica's user avatar
7 votes

Is there an aerofoil that gives reasonably good lift for both air flow directions: forward and backward?

Walter Morrison answered this question in the 30s, and found a practical use for it also. We know it as a flying saucer, or Frisbee.
Greg Taylor's user avatar
  • 3,791
7 votes

What is the physical meaning of circulation found in Kutta condition?

There is no molecule in the air which actually revolves around the airfoil in the way you would normally think of it. Circulation is a mathematical concept used to explain the motion of air from a ...
Pilothead's user avatar
  • 20.7k
7 votes

Why does an aircraft pitch up when the speed increases?

The horizontal stabilizer always provides a downward force to balance the forces of lift and weight with the centre of gravity. This also provides stability because if the aircraft pitches down and ...
Mike Sowsun's user avatar
  • 37.8k
7 votes

What's a typical first lesson of glider flying like?

I'm a glider instructor. The first lesson would have been introductory and if there weren't any soaring conditions, I'm guessing the flight was pretty short, less than 15 minutes, so you probably did/...
John K's user avatar
  • 132k
7 votes
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Could gliders be a clean, practical alternative to other forms of transport?

Theoretically, yes. Practically, no. Day to day weather is a huge factor in powered aviation. It is an even larger factor for non-powered aviation. You would not be able to satisfy the predictability ...
Dean F.'s user avatar
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6 votes
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Why is the aerodynamic center for most airfoils located at the quarter chord location?

It has to do with the Birnbaum distribution. The center of its area is at one quarter. In potential flow theory, lift can be calculated as the linear superposition of a contribution from camber and ...
Peter Kämpf's user avatar
6 votes

Which source(s) provides the most authorative and correct flight dynamics theory?

There is unanimous agreement (at least among people who actually understand physics) that the Navier-Stokes equations are the best we've got and you can't get simpler than that! By the second point ...
Jan Hudec's user avatar
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6 votes
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Is aerodynamics science still being discoverd?

Aerodynamics science is not a standalone discipline and involves many other aspects that are peculiar to it. In particular, only to cite some: Fluid mechanics : fluid mechanics research is very ...
albiremo's user avatar
  • 491
6 votes
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How does deploying full flaps affect Takeoff run and distance?

Is there any scenario or plausible logic that might make EASA answer [meaning answer A] correct for even a single corner case? Yes-- consider a Cessna 152 with 30 degrees maximum flaps available, on ...
quiet flyer's user avatar
  • 22.8k
6 votes

Why does this curved wind tunnel rotate?

Key point from another related answer: A stationary curved windtunnel would not be the same, because now the air mass needs to curve. This introduces very different phenomena. Perhaps easiest to ...
quiet flyer's user avatar
  • 22.8k

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