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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116 votes
9 answers
29k views

Is there a maximum possible size for an airplane?

Is there any theoretical or practical limit to the maximum number of passengers - and therefore size - one can build an airplane for?
77 votes
7 answers
21k views

Do helicopters use more fuel when hovering?

This answer says A helicopter uses a LOT more fuel hovering than it does in forward flight. Is this correct? Why?
73 votes
10 answers
140k views

What happens when an airplane stalls and why do pilots practice it?

When a non-pilot hears the word stall, it brings to mind what happens when a car stalls - the engine quits. It seems like that would be a dangerous scenario in an airplane. From a non-pilot ...
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68 votes
3 answers
15k views

Are we at peak speed efficiency for jet airliners at Mach 0.85?

The cruising speed of large jet airliners has not increased in the past four decades. The 747 cruised at Mach 0.85 and the new Dreamliner 787 also cruises at Mach 0.85 even though it was designed 40 ...
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62 votes
11 answers
45k views

How do wings generate lift?

Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?
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58 votes
4 answers
24k views

Why are the F/A-18 rudders deflected in opposing directions during takeoff?

Looking at some videos and photos of F/A-18 Hornets and Super Hornets taking off from carriers and from airfields, I recognised that the left rudder is pointing right, and the right rudder pointing ...
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57 votes
6 answers
15k views

Is a winglet better than an equal span extension?

Is there indisputable evidence that a winglet improves performance over an equal span extension? Please note: I am only interested in L/D improvements. Winglets do improve roll performance, that is ...
55 votes
3 answers
53k views

What's the advantage of the F4U Corsair's gull wing design?

What is the advantage of the F4U Corsair's gull wing design? Is there also a disadvantage to this? The wing design just seems odd, and as far as I know it is one of the only planes to use this design....
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54 votes
11 answers
20k views

Why do airplanes lift up their nose to climb?

Is it right that basically an airplane just needs to accelerate to climb? Greater velocity of an airplane leads to greater lift - and since its weight remains constant (or even decreases) - a greater ...
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54 votes
2 answers
21k views

Is it possible to install a bike rack on a Cessna 172?

I stumbled upon a nice photo manipulation on aviationhumor.net. Source My question is short and concise: Is it practically possible to do that? Is it okay in terms of aerodynamics, weight, CG? ...
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50 votes
8 answers
14k views

How complete is our understanding of lift?

I'm currently studying for my PPL and one of the accepted textbooks contains the following disclaimer at the end of the Principles of Flight section on lift: It is important to note that the forgoing ...
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49 votes
2 answers
28k views

Why/when is the blunt nose better?

Most large aircraft and some fighters have blunt, rounded nose cone. OTOH many fighters (that don't use the nose for air intake) and notably the two supersonic airliners (Concorde, TU-144) have the ...
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44 votes
5 answers
37k views

What is a 'deep stall' and how can pilots recover from it?

West Caribbean Airways Flight 708 which crashed in 2005, fell victim when their plane encountered a deep-stall. From my understanding, only certain planes can 'deep-stall' How can pilots recover ...
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44 votes
3 answers
8k views

Was the Space Shuttle aerodynamically neutral while piggybacking, or did the combination act like a giant biplane?

Trying to investigate this question, I see that 'Ask the Captain' says: The weight of the shuttle is calculated like any payload. The 747 produces enough lift to fly and to carry the weight of ...
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43 votes
3 answers
33k views

Why do many fighter jets have double vertical stabilizers?

Many fighter jets have double vertical stabilizers, e.g. F-14, F-15, F/A-18, F-22: On the contrary, most general aviation planes and commercial airliners do not. While there are certainly exceptions ...
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41 votes
4 answers
14k views

How do conventional missiles fly?

With the exception of cruise missiles, most missiles don't have any obvious lifting device. If you watch a missile being fired, prior to its rocket firing it does exactly what you'd expect: ...
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41 votes
8 answers
27k views

Why would a glider have water ballast? If it is trying to stay aloft without an engine, wouldn't it be better to be as light as possible?

So I was looking at the description of a ASW 27 B glider and ran across this statement: Two water tanks in the wing plus a further 35 liter tank in the fuselage enable the ASW 27 B to carry more ...
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41 votes
9 answers
8k views

Why was the boat mounted this way on the underside of the wing on the "Landseaire" flying yacht?

After seeing the below image of the "Landseaire" flying yacht here I was curious to know why the small boat mounted to the underside of the plane was mounted the way it was. At least to me (and @Dave ...
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40 votes
9 answers
14k views

Why do model aircraft fly and maneuver so differently from real aircraft?

I recently viewed on Youtube many videos of small and giant models of airplanes. In some cases they are small (for example an A330, 1 meter long) and in others they are huge (for example an A380, 5 ...
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40 votes
9 answers
89k views

What are the pros and cons of high-wing compared to low-wing design?

What are the advantages and disadvantages of a high-wing vs. low-wing aircraft design? When might one prefer one to the other? Is the answer the same for large and small aircraft?
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40 votes
5 answers
10k views

Why do most biplanes have their top wing slightly forward of the lower wing?

In most of the biplanes, the top wing is located a little forward of the lower wing. What is the use of this? Also, how does this affect stability of the aircraft.
39 votes
4 answers
7k views

What does the behaviour of water on the skin of an aircraft in flight tell us?

Sometimes in damp conditions I notice some surprising (surprising to me, anyway) behaviour of water. I'll see moisture glistening in the heads of rivets or bolts on the top of the engine pylons - ...
39 votes
4 answers
4k views

Is a rotary wing craft capable of supersonic flight?

Just what the title states. Since the Wright brothers, aviation technology for fixed-wing craft has advanced by an order or more. Rotary wing craft on the other hand (I know little about aviation; ...
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37 votes
5 answers
22k views

Why did the Junkers Ju-52 have corrugated external surfaces?

Every time I pass by Munich I have to pay a visit to the Deutsches museum, in particular to the aviation wing. Among the other aircraft on display, there is a Junkers Ju-52. A different photo taken ...
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36 votes
9 answers
38k views

Why does An-225 have anhedral wings though it is a cargo aircraft?

What are the rationale behind this anhedral high mounted wing configuration? Is that usual for very large carge aircraft?
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36 votes
8 answers
20k views

How does stall depend on angle of attack but not speed?

Everyone says that the angle of attack is what determines a stall, not the speed. I understand the theory and understand that it is separation of the airflow that matters for stalling. However, I don’...
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36 votes
8 answers
12k views

Why are prop blades not shaped like household fan blades?

My two projects right now are learning to fly and 3D modeling a replacement blade for antique fan, and a question occurred to me: Why are airplane propeller blades not shaped like household fan ...
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36 votes
2 answers
5k views

Why do helicopters not roll over when flying forwards?

Related to this answer: with velocities so different at forward going and rearward going blade, why does the helicopter not roll over? The higher airspeed at the forward going blade should cause more ...
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36 votes
2 answers
8k views

Why do aircraft need a vertical tailfin, but birds don't? (and lots of fish do?)

I don't know of any bird that has a vertical tailfin, but apparently aircraft need them for lateral stability. Why is this? I did realize, however, that most fish have a vertical tailfin, or a ...
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35 votes
7 answers
13k views

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 ...
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35 votes
3 answers
51k views

What are the effects of the Boeing 787's very flexible wings?

I recently came across this picture of the Boeing 787 series aircraft's incredible wingflex: I suppose this is a consequence of using very light CFRP wings, but how does the wingflex itself improve ...
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35 votes
6 answers
11k views

Why do propeller blades not have winglets?

On the first look this question might sound ridiculous and maybe it is. But as propeller blades act by the same physical laws as wings, and winglets reduce the induced drag by quite a bit, then why ...
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34 votes
1 answer
4k views

How does a towed banner maintain a steady tilt?

Today a small airplane is towing an advertising banner, about 20 by 30 feet, in a circular path around my town's university campus. The banner stays tilted about 45 degrees to make it easier to read ...
33 votes
6 answers
89k views

If a typical passenger plane had total failure of all engines mid-flight, is it possible for passengers to survive?

I have pretty bad flying phobia and often wonder what would happen if all the engines on the craft went out at the same time. I initially had the anxiety-ridden thought that the hundreds of thousands ...
33 votes
2 answers
25k views

What is this on top of the Air Force One?

Clarification: It wasn't Air Force One that visited Switzerland, it was the 747-200 E4 carrying Ashton Carter. Source What is this thing on top of the plane (In red circle): On other "Air Force One" ...
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32 votes
6 answers
11k views

Why is it rare for small aircraft to have winglets?

I've noticed that winglets are very rare on small aircraft. I wonder why this is the case. Wouldn't they have the same advantages, especially because they travel at low speed? Or is it just a wrong ...
32 votes
1 answer
6k views

Why did the DC-3 have wing sweep?

When looking at the silhouette of a DC-3, one can clearly see that the wings are swept. This design is from 1935, before the high-speed research work on wing sweep was ever implemented, and the DC-3 ...
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32 votes
9 answers
8k views

Is excess lift or excess power needed for a climb?

As answered in this question, aircraft need excess power - not excess lift - to climb. This is plausible when the aircraft's thrust vector has a vertical component (its nose and engine points upwards),...
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31 votes
11 answers
35k views

If a helicopter's tail rotor fails, is it possible to perform an emergency landing?

In the event of a total failure of the tail rotor, is it possible to maneuver a helicopter to an emergency landing spot that is within, say, 30 minutes flying time? What are the maneuvers required ...
31 votes
5 answers
7k views

How do aircraft refueling in-air deal with wake turbulence?

Many fighter planes have the capability to refuel in air. When a plane moves in air, turbulence is generated at its back. To refuel, the fighter plane must come near to the parent plane (which has ...
31 votes
7 answers
18k views

Can you fly an airplane at a 90° roll angle without losing altitude?

I've seen this answer to the question about flying upside-down, but tilted by 90°, there should be no surface creating lift (except maybe the vertical stabilizer).
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31 votes
2 answers
19k views

What is vortex lift?

In a recent question I asked, I was given an answer by Peter Kämpf and he described something about lift being created by a vortex used on delta wings and the Bird of Prey wing. How exactly does ...
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31 votes
4 answers
36k views

How do conventional and T-tails differ?

What design considerations go into the decision between conventional tails and T-tails? Functionally the horizontal stabilizer/stabilator are the same in both cases, providing negative lift, the ...
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31 votes
2 answers
166k views

What is the difference between centre of pressure, aerodynamic centre and neutral point?

I have just started learning some aerospace concepts, and I am not able to understand the difference between the three terms centre of pressure, aerodynamic centre and neutral point. What are their ...
31 votes
4 answers
7k views

Why does the B-2 have a smaller payload than other bombers of comparable size?

B-2 Spirit1 Payload 40,000 pounds (18,144 kilograms) Wingspan 172 feet (52.12 meters) Weight 160,000 pounds (72,575 kilograms) Maximum takeoff weight 336,500 pounds (152,634 kilograms) Range ...
31 votes
4 answers
7k views

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

Describing lift as the result of "equal transit time" on both sides of an airfoil is a fallacious theory widely found in technical books and articles for general public (see below for details about ...
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31 votes
2 answers
9k views

What is the cause of unusually strong wake turbulence from the 757?

The Boeing 757 (at least in the US) is in a special class of its own with respect to air traffic control wake turbulence advisories and separation. This is apparently due to it producing stronger wake ...
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31 votes
3 answers
1k views

Is it possible to build a paper airplane that will enter a fully developed spin?

Some students learn best when they can see aerodynamic principles in action. I'd really like to be able to show a student how a spin occurs. Is there a way to make a paper airplane that will enter a ...
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30 votes
6 answers
4k views

Would an 8% reduction in drag outweigh the weight addition from this custom CFD-tested winglet?

I'm writing an essay at school about why there is so much variation in winglet design. I am analysing all the primary types of winglets used today in the aviation industry. I'm constructing them in ...
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29 votes
4 answers
4k views

How do I explain what makes an airplane fly to a non-technical person?

As an engineer I can explain in very technical terms exactly what makes an airplane fly, however, it isn't easily understood by non-technical people. How can I explain it to a non-technical person, ...
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