# Tag Info

Accepted

### How to build a 2 mile long runway on a 1 mile square island?

Anyone who has ever flown at Zar (EPZR) in Poland knows how much a runway slope can reduce the needed field length. For aircraft which need a 2 miles long level runway, a 1 mile long one with a 15% ...
• 217k
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• 44.5k

### Why can gliders fly for so long?

The primary difference between a glider and a paper airplane is that most folded paper airplanes have very bad aerodynamics. Most folded paper airplanes have short stubby wings. This in itself makes ...
• 2,376
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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 ...
• 8,605
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### Why are the power and drag curves called polars?

It is an historical name. The first polars were drawn by Otto Lilienthal in polar coordinates. Here (sorry, German link) we find an example:
• 31.5k

### 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 ...
• 217k

### Can planes take off from a treadmill?

Yes. Airplanes get their thrust by using the air. The wheels are not powered. The drag from the wheels will limit how fast the treadmill can go before the plane won't be able to take off anymore. ...
• 26.9k
Accepted

### How long would a cruising aircraft take to crash if everyone spontaneously vanished?

There is a far more important question (and the real deciding factor) How much fuel is on board? If left unattended a plane will fly until it runs out of gas quite literally, the more gas in the ...
• 96k

### Are aircraft capable of sustained inverted flight at constant altitude?

Yes they are! Aerobatic aircraft can have symmetrical wing to improve inverted performance. So with these aircraft there is no any problem at all. Other agile aircraft, gliders can fly inverted as ...
• 3,684

### 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 ...
• 217k

### Would a 90 kg object jettisoned from an aircraft create a detectable movement?

Yes It's not just weight, it's also aerodynamics. First let's assume that the aircraft was trimmed slightly nose-heavy (no passengers), therefore it's trimmed slightly "tail down" anyway When the ...
• 10.3k

### 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 ...
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### Principle of aerodynamic lift: are misconceptions also taught in flight schools?

I can only speak on behalf of the Australian Syllabus as put out by CASA (Civil Aviation Safety Authority - Australia), but we are expected to teach both Bernoulli's Theorem, and the Theorem of Air ...
• 2,011
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### Is the maximum lift-drag ratio found at minimum drag?

Well, for all L/D curves and D curves, the assumption is that the weight of the aircraft is constant and that there is no acceleration. Therefore the lift equals the weight (neglecting the small ...
• 74.8k

### How to build a 2 mile long runway on a 1 mile square island?

A seaplane would be a suitable solution. Then the only infrastructure required on the island is a jetty and fuel/servicing. This also enables a much larger aircraft and so easier cargo resupply and a ...
• 301

### Why can gliders fly for so long?

The glider and a paper aircraft are designed and operated in different ways which affects their stalling characteristics. Both aircraft trade one form of energy (potential energy or altitude) in ...
• 98.5k
Accepted

### Where does upward momentum come from in leading edge vortex?

Does this vortex draw in air from above, pulling it downward and as a result lifting the plane up? Yes, the bound vortex in combination with translational flow accelerates air downwards. Or is ...
• 217k