19 votes

Can we add treadmill-like structures over the airplane surfaces to reduce friction, decrease drag and producing energy?

You can't reduce friction with machines. The nature of machines is that everything you do adds inefficiency. A moveable wing surface adds weight, complexity, and additional losses. Even if you did it ...
Tiger Guy's user avatar
  • 6,783
15 votes
Accepted

How does a helicopter hover

Most helicopters of modern manufacture are dynamically unstable while hovering- they require constant, "hands-on" control inputs from the pilot to keep things in balance. This task is very ...
niels nielsen's user avatar
14 votes
Accepted

In case a plane stalls, what should stall first, the tip or the root of the Wing? Why?

It is preferable for the wing root to stall first. If the wingtip stalls before the root, the disrupted airflow near the wingtip can reduce aileron effectiveness to such a extent that it may be ...
Satya's user avatar
  • 412
9 votes

Can we add treadmill-like structures over the airplane surfaces to reduce friction, decrease drag and producing energy?

Can you reduce friction by making a surface frictionless? Yes. Will that reduce drag? Most of the drag comes from lift. Without lift, the airplane falls out of the sky. Most of the rest of the drag ...
david's user avatar
  • 733
6 votes
Accepted

What technologies prevent drones from being as efficient as birds?

Somebody needs to design a chocolate-powered drone. Yes, seriously. The total energy stored in a 40AH 12V battery is about the same as the calorific value of five 100g chocolate bars from your ...
alephzero's user avatar
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6 votes
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Do all airfoils have a lift curve slope of $2\pi$?

In general, most airfoils only approximately display the $2\pi$ lift slope as predicted by thin airfoil theory. That is because airfoils are not actually infinitely thin in practice, and will deviate ...
TRF's user avatar
  • 251
6 votes

Are rocket engines practical for commercial aircraft?

At a fundamental level, it should be clear that throwing stuff out the back is going to be less economical than sucking in stuff in the front and throwing it out the back faster. For one thing, the ...
Olin Lathrop's user avatar
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6 votes

In case a plane stalls, what should stall first, the tip or the root of the Wing? Why?

It depends on wing geometry. You need to look at the aerodynamic center of the wing, which is the center of effort for perturbation forces. The center of lift (unstalled) will usually be well forward ...
Phil Sweet's user avatar
  • 4,696
6 votes

Can we add treadmill-like structures over the airplane surfaces to reduce friction, decrease drag and producing energy?

Let's be honest here... From an engineering point of view, this is totally impractical and could never work with anything like current technology. Consider that the surface of an aircraft is not a ...
rghome's user avatar
  • 161
5 votes

Can a blimp enter Mar's atmosphere as a glider?

I assume that the person you are referring to is Felix Baumgartner, who achieved a maximum speed of Mach 1.25. While this speed is very fast, this is nowhere near the speeds achieved by meteorites, ...
MountainClimberi's user avatar
5 votes

Can we add treadmill-like structures over the airplane surfaces to reduce friction, decrease drag and producing energy?

Air on a wing or aileron or any airfoil does not slide on the surface of these, a very thin layer of air (boundary layer's contact surface) sticks to the surface and moves at the same speed as the ...
kamran's user avatar
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4 votes
Accepted

For how long could a plane handle turbulences?

You may want to look for aircraft fatigue loads, which are the typical loads that an airplane may experience during a fly (some sets include data for harsh conditions). They look like this (depending ...
user190081's user avatar
4 votes

Are rocket engines practical for commercial aircraft?

Economically a rocket engine will always lose out to a jet engine. We'll ignore solid fuel rockets, they are impractical for commercial air travel due to their fixed thrust and inability to turn on ...
Andrew's user avatar
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4 votes
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Will a lift force be created by the Coanda effect if high velocity air flows under a half-toroid shaped saucer?

It is important to realize any airborne device will go in the direction of the sum of all force vectors (including gravity). We have our centrifugal impeller drawing air in from the bottom. The device ...
Robert DiGiovanni's user avatar
3 votes

Lift Requirements for Hybrid Airship

As with any aircraft an airship need to be able to generate lift equal to its weight to remain airborne and also some additional lift to be able to gain height. Equally important is the ability to ...
Chris Johns's user avatar
  • 15.2k
3 votes

Why does the air in a jet engine not flow out of the front?

Well, it can, and sometimes it does. That is called a compressor stall. https://www.youtube.com/watch?v=7MYh2KtEUQk So if you waded through the video, let me explain a little bit more if I can. The ...
Phil Sweet's user avatar
  • 4,696
3 votes
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Infinite life of a material, Fatigue Strength

Studies on fatigue life estimations was first done on steel axis in trains and continued on for other steel constructions. The majority of the fatigue publications have been based on fatigue ...
loStraniero's user avatar
2 votes
Accepted

Will helium gas lift more weight in air when it is spread over large volume compared to equal weight heavily compressed small volume?

As a reality check lets consider industrial gas tanks as the specifications are easily available. A BOC size D hydrogen tank has a gross weight of 57kg and contains 23kg of hydrogen at 230bar. At ...
Chris Johns's user avatar
  • 15.2k
2 votes

How can we prove that Thrust-to-weight ratio depends by max speed?

First I'm going to use Wikipedia to disprove the statement: ...
hazzey's user avatar
  • 10.7k
2 votes

Wingspan formula for an Ornithopter

Wing loading: The graph below provides areas for living and man made flying machines - and this can be seen to be a quite good log-log fit of mass and wing loading. See his text for comment on the ...
Russell McMahon's user avatar
2 votes

Multiple Varying cross section beam deflection

Let's give the name "section 1" to the section with length $\ell_1$, similarly for sections 2 and 3. Section 1 can be treated as a cantilever with shear force $A+B+C$ applied at its end, and a moment ...
AndyT's user avatar
  • 3,143
2 votes

Propeller design

Just think of the propeller as a mean to thrust air in one direction. The higher the angle of incidence, the more the propeller is pushing the air (up to about 45°, then the force perpendicular to the ...
JE_Muc's user avatar
  • 223
2 votes
Accepted

Name of a keel between the bilge keel and the main keel

Sister keelson definitely does not translate to conventional marine usage. There are a couple of terms that apply to similar structural elements. Strake. A longitudinal hull element that may be ...
pHred's user avatar
  • 176
2 votes
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Compressing the air thrusted by an aircraft's propeller through a cone like tube

It would be slower. Compressing the air takes energy - that will slow the propeller, and the plane as a whole. Imagine a water pump, which is pumping water out of a pipe. Now, if you put your finger ...
Jonathan R Swift's user avatar
2 votes
Accepted

Heating the air inside a turbojet instead of combusting it

As a reference, consider the Meredith effect, which applies (applied) in the construction of the P-51 Mustang radiator. From the linked Wiki site: The Meredith effect occurs when air flowing ...
fred_dot_u's user avatar
  • 6,995
2 votes

Using RC scale-down model to pre-test aircraft design

You need to decide between geometric similarity, kinematic similarity and dynamic similarity. You need to decide which have to be met, while allowing others to vary so you can get meaningful results. ...
Solar Mike's user avatar
  • 15.6k
2 votes

What engineering obstacles would need to be overcometo make a hot air balloon bigger than the largest made?

As the volume of a hot air balloon is increased, so increases its surface area- through which the burner heat is lost. Since the volume increases faster than the area for a spherical balloon, more ...
niels nielsen's user avatar
2 votes

What engineering obstacles would need to be overcometo make a hot air balloon bigger than the largest made?

You need to figure out how to land a large balloon in conditions with no wind, without the passengers ending up underneath the collapsed balloon. In windy conditions, you also need a larger landing ...
alephzero's user avatar
  • 12.5k

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