Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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7 votes
3 answers
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Can a steady flow have stagnation points?

I am confused by this idea. If a flow is steady, its streamlines are unchanging. Taking the typical example of an airfoil, there is (at least) one streamline which will hit the leading edge of the ...
0 votes
0 answers
84 views

Thought experiment: can an aircraft that is dropped from the sky get into gliding? [duplicate]

Here's a totally hypothetical question that came up in a discussion with friends: If a commercial aircraft (say, an Airbus A320) was "dropped" from a typical cruising altitude (say, 35,000ft) with a ...
6 votes
3 answers
7k views

What is the function of the tail section on a fixed-wing aircraft? [duplicate]

In a generic fixed-wing aircraft like a Cessna, what is the function of the tail section, i.e. the rudder and elevators?
13 votes
1 answer
529 views

How do aerodynamic loads explain the Spaceship2 accident?

From the NTSB's preliminary report, we read in the "Findings" section: Although the copilot made the required 0.8 Mach callout at the correct point in the flight, he incorrectly unlocked the ...
4 votes
2 answers
2k views

Stalls: which flight control surface is effective last?

In an aerodynamic stall, which flight control surface (limited to ailerons, elevators and rudder) remains effective for the longest period of time during the stalling condition? In other words, which ...
22 votes
5 answers
38k views

Should full flaps be deployed on takeoff?

Are full flaps ever used on takeoff? One flying book I read strongly discouraged anything more than quarter flaps on most planes due to the amount of drag produced. I was just wondering if there are ...
2 votes
2 answers
2k views

What is the typical fatigue life of a helicopter airframe? [duplicate]

For military helicopters such as the Sikorsky UH-60 Black Hawk, what is the typical fatigue life of a helicopter airframe (in cycles and hours) ?
2 votes
0 answers
129 views

How does a 'Highly Swept leading-edge' delta wing reduces fuel burn and increases range? [duplicate]

Spike Aerospace claims to have designed an aircraft called S-512, with maximum speed of 1.8 mach and cruise speed of 1.6 mach, speaking about the notable changes in the aircraft, Spike Aerospace says:...
2 votes
1 answer
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What is the difference between types of propeller? [closed]

I have been noticing almost every Multirotor vehicle uses a single thin double-bladed propellor on each axis. And yet clearly, there are some that do not fit the norm. Can someone explain what the ...
26 votes
2 answers
6k views

Why does a missile have small wings but better agility than a plane?

An anti air missile has often very small wings but out performs a fighter aircraft, e.g. much higher g-load, since g-load comes from lift which is the area of wing. Why not designing an aircraft like ...
4 votes
1 answer
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Why most of the supersonic or fighter aircraft use all-moving control surfaces?

What are the advantages of using all-moving control surfaces? can someone give explanations based on aerodynamics?
4 votes
1 answer
968 views

Would solar panels on the wing of an aircraft increase drag?

If a small scale UAV (wingspan <2 metres) was to be fitted with solar panels on its wings to have more power available, would the addition of these panels cause an increase in the drag coefficient, ...
3 votes
1 answer
556 views

How does a wing mounted jet engine on a supersonic airplane prevent the interference in the flow due to Shock? [duplicate]

Wing mounted jet engines face the free stream at Mach number 1 or above, and they work perfectly for Mach numbers below 1 as well, even though the free stream characteristics change a lot after Mach 1....
35 votes
7 answers
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Is it possible for an airliner to safely fly with doors open?

From another question asks about the possibility of dropping bombs from converted airliners. My question: is it possible to safely fly aircraft with a door open for the whole flight envelope? Would ...
1 vote
2 answers
3k views

What is P-Factor in Propeller Aerodynamics? [duplicate]

What is the P-Factor when we're talking about a Propeller Aerodynamics ? Thanks
8 votes
1 answer
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What is the working principle of trim tabs on the elevators?

Trim tabs are used on the tail's horizontal elevators to adjust its neutral position. What is the working principle behind this? How does this affect the sensitivity (the feel) of the pitch to the ...
7 votes
2 answers
918 views

Why don't all wind tunnels use magnets to suspend models?

NASA and the French aerospace agency have conducted research into magnetic suspension and balancing systems (MSBS) to suspend models during wind tunnel tests, like this system in South Korea. Where ...
5 votes
2 answers
964 views

Will wind tunnel modelling ever be completely replaced by computer models? [closed]

With computer-based fluid simulation already being extremely realistic (and likely faster and cheaper than physical wind tunnels), are they, anywhere, completely replacing physical wind tunnels? If ...
13 votes
1 answer
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Where does ice collect first on a wing in flight and why?

I've seen some reports that say ice forms on the back half of the wing and on the outside edge of the wing (the part furthest from the body) before it will form anywhere else. I'm wondering if this ...
0 votes
1 answer
873 views

What are the opimum values of Cl during descent?

Statistical Analysis of A320 aircraft shows the Cl values to be as under: cl_value. L is assumed to be 0.5*MaximumLandingWeight of A320 as the Aircraft is about to land. The Units used are: Flight ...
3 votes
4 answers
698 views

Why is a control surface that allows two sides of airflow better than those that allow one?

For example, ailerons allow air to flow past both the top and bottom surfaces, which makes it more aerodynamic than speedbrakes. Also, plane rudders have air flowing on both sides, which is apparently ...
18 votes
2 answers
9k views

What causes aileron and elevator flutter?

This video shows a Hawker jet with the wing fluttering up and down like it's about to break. What can cause flutter like that? Can it actually cause a wing or stabilizer failure? How can flutter be ...
18 votes
2 answers
8k views

Why do some airplanes have vertical strakes?

A lot of different aircraft have vertical or near-vertical fins below the empennage, or above the empennage and attached to the front of the vertical stabilizer. What purpose do these devices serve?
15 votes
1 answer
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How much thrust was provided by a typical Meredith Effect radiator?

The Meredith Effect was used on some aircraft to provide more thrust by channeling air through the radiator such that the air is expanded, heated and then compressed through a constriction, generating ...
12 votes
1 answer
3k views

In a slip or skid, how does one wing have a higher angle of attack and more lift?

I've discussed this with my instructor numerous times, and I have the concept memorized, but from an aerodynamic point of view, I can't see how the angle of relative wind to chord line is different ...
5 votes
1 answer
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Why can not two modes coincide perfectly for some cases in Flutter phenomena?

I have a question about flutter phenomena. As you know, flutter occurs when two modes (for example, first mode and second mode) coincide (that is, after a specific velocity, the frequencies of two ...
13 votes
2 answers
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How are the glide polar and L/D ratio charts related?

We know from other questions and answers that airplanes and gliders in particular can have their performance described in terms of glide polar and Lift-to-Drag ratio. As it appears from the images in ...
9 votes
1 answer
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Minix wingtip vortices mitigation - How does it work?

I stumbled upon this article: Minix wing tip device promises 6% gain in fuel efficiency for airliners. Such an economy is appealing and I must confess the design is "sexy". Could someone expand a ...
10 votes
1 answer
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How did flight 2574 break up?

My understanding of Continental Express flight 2574 is that a de-icing boot on the horizontal stabilizer of the EMB120 was missing screws and therefore detached, leading to the tail separating. I ...
8 votes
1 answer
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Do the effects of turbulence change when banking/turning compared to level flight?

Are the effects created by turbulence on the aircraft different when the aircraft is banking or in level flight? By logic I'd say yes but I would like some technical and practical explanation. When ...
1 vote
0 answers
76 views

Flying sideways, how is it done? [duplicate]

I assume that the fuselage and tail fin can generate lift when flying sideways with a constant heading and a little pitch up (er, yaw right assuming left wing down) will introduce a vertical component ...
7 votes
2 answers
2k views

What is the advantage of increasing an aircraft's horizontal tail surface area?

Most aircraft have horizontal tails. What is the advantage of increasing the horizontal tail surface area?
14 votes
1 answer
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What operational differences were there in WWII for constant speed vs. fixed pitch propeller warbirds?

I have read about the operational differences between constant speed and fixed pitch propellers. Being a World War II buff, I was reminded of reading once about both principles being used in period ...
7 votes
3 answers
4k views

Is there always a stall if you exceed a specific angle of attack?

So lets consider that the stall angle (=Cl max) of a B747 is at 16° (in clean configuration). Does this mean, that, at whatever speed you are flying (i.e. 500 knots), you would stall if you go on a ...
4 votes
2 answers
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How much lift do planes produce before rotation?

In the takeoff roll, I'm pretty sure planes produce some lift before rotation, but how much? Is it insignificant compared to post-rotation, or is it large compared to the post-rotation lift?
3 votes
1 answer
725 views

How can I calculate polar curve?

I recently got the polar curve of an aircraft with the method of Anderson. But this method is too old. Does someone know a recent method for the polar curve without using CFD?
5 votes
5 answers
7k views

Is head-on or trailing wind better?

Does a powered aircraft fly faster when in a head wind or with a trailing wind? The question revolves around the head wind should provide 'better' lift, and trailing winds have very little to 'push' ...
6 votes
1 answer
878 views

What makes an airplane fly?

How does conventional flight work? Explain what factors are in play in order to get a plane airborne and stay there.
3 votes
1 answer
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How can you calculate the gliding distance for a remote controlled jet?

Is there a way to calculate the gliding distance for a remote controlled (RD) jet aircraft, in case of engine failure? We have some telemetry data on the model, giving us speed and altitude so as to ...
4 votes
2 answers
2k views

What is the relationship between blade inertia and rotor kinetic energy?

As far as I know: High blade inertia provides good pilot intervention time (the time between recognizing engine fail and pushing the collective down). High kinetic energy allows for a soft touch down ...
7 votes
2 answers
765 views

Why is an outward spinning propeller better in theory on the North American F-82 Twin Mustang?

In this question the Wikipedia article of the F-82 Twin Mustang is quoted. In the third paragraph of the article it says: In this arrangement both propellers would turn upward as they approached ...
8 votes
2 answers
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How will flying through mountains cause altimeter problems?

There is an old warning on mountain flying that wind flowing through a narrow valley will cause Venturi effect, thus causing a drop in static pressure and making our little Cessna fly lower than ...
14 votes
4 answers
2k views

How does wake turbulence affect parachutists?

If one were to parachute out of a jumbo jetliner, would wake turbulence from the plane be an issue? A 747 for instance produces much more wake turbulence than the smaller planes usually used to drop ...
2 votes
1 answer
900 views

What is the total pressure of an air stream in motion?

This question is from a French aeronautics exam so I translated as best I can but I suck at these terms in English. Anyways, can someone please explain this question to me because I'm just really ...
15 votes
3 answers
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Why are aircraft external lights round, not tear-drop shaped?

I saw this image of a Cessna 172's tail posted on another question and it made me wonder why the beacon light is basically a cylinder, and not a more aerodynamic, teardrop shape? Image source
10 votes
2 answers
336 views

Could landing gear weighing scales be used to detect lack of lift?

There have been several crashes due to ice on wings destroying lift. One of the issues with this is that you can't detect that you don't have sufficient lift until you're already in the air, way too ...
4 votes
1 answer
1k views

How turbercle wings could generate aerodynamic advantage?

Recently it has been discovered that turbercles present in fins from whales are actually providing hydrodynamic benefit for them. As well, it has been proposed that this effect will provide benefit ...
14 votes
2 answers
6k views

Why do only some aircraft require tail anti-icing?

Why do some aircraft require anti-icing on the tail while others (Dassault Falcon Jets, Boeing 737, 747, etc.) don't?
2 votes
2 answers
676 views

How is the Angle of Attack influenced in the slipstream of a propeller?

My question is how can the angle of attack be changed when the wing is in the slipstream of a propeller, giving "enough air flow" to the wing. The propeller sends the flow of air in the same direction ...
9 votes
1 answer
3k views

How are condensation cones created by supersonic airplanes?

There are many awesome pictures of this phenomenon such as this one: What is the physical explanation of how this occurs? Does it occur only when the airplane crosses the sound barrier or does it ...