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Questions tagged [aircraft-design]

Questions about the different choices that aircraft designers (typically aerospace engineers) make in order to create an aircraft.

36
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3answers
8k views

How does an aircraft form wake turbulence?

This question discusses how wake turbulence can affect planes flying in formation. It got me wondering, how do aircraft (the wings in particular) form wake turbulence to begin with? It can't be as ...
40
votes
3answers
14k views

Why does supersonic flight detach airflow from a wing?

I've read in several answers to questions that when a wing passes the speed of sound the airflow will become detached from the craft towards the rear quarter of the wing (thus making things like ...
42
votes
4answers
8k views

Why are many jet aircraft designed to cruise around FL350-370?

If the flight distance permits, the B737-800 will cruise at FL350, the A320 a little bit higher... Flying at FL370. Photo: Live from the Flight Deck by GolfCharlie232 (reframed) Elements such as: ...
56
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4answers
26k views

Why can't jet engines operate with supersonic air and how do they slow it down?

Typically jets cannot operate when intake airflow is supersonic relative to the engine. Why is this so? Also, why are scramjets able to use supersonic air? To slow down the air to subsonic speeds, ...
18
votes
2answers
17k views

How does chord length affect wing design?

In comments on the answer to a question about transonic speeds and control surfaces I came across this comment and I'm having a hard time understanding it. If you increase the chord, lift goes up ...
65
votes
5answers
29k views

What determines the maximum altitude a plane can reach?

What factors determine the maximum altitude for a plane? Is it limited by wing design, engine thrust, and so on? Is there a formula by which one can calculate the maximum altitude a plane can reach?
15
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4answers
8k views

What is the propeller efficiency, $μ_p$, of modern propellers for light sport aircraft?

Roskam's book on preliminary design gives a value of 0.7 for "homebuilt" aircraft and 0.8 for general aviation. What explains this difference in propeller efficiency? The content of Roskam's book is ...
34
votes
4answers
23k views

How does the mounting location of a jet engine affect aircraft performance?

Different jet airplanes mount the engines in different ways. For example: Under the wing To the fuselage How does the engine location affect aircraft performance? Is one better than the other?
23
votes
3answers
3k views

Is wingtip design mature?

There are many wingtip design, all made to reduce vortex related drag, and neither boeing nor airbus seems to prefer one over another. They move from one design to another at each new aircraft, always ...
25
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5answers
7k views

How does an aircraft tailplane work?

How does an aircraft tailplane keep the aircraft stable, and prevent it from tipping over? Also, how does the lift generated by a tailplane compare to that generated by the wing?
19
votes
3answers
16k views

What dictates the aspect ratio of an aircraft's wing?

When designing an aircraft, there has to be a decision as to the aspect ratio of a wing. It's been said that having a higher aspect wing will reduce drag for the same wing area, however most of the ...
63
votes
2answers
24k views

Why are aircraft tires not pre-spun prior to landing to preserve them?

Why has someone not designed a landing wheel with a fin or fins on it so that the air will start the wheels turning before the wheels touch the ground? Wouldn't that preserve the tires longer from ...
45
votes
11answers
76k views

Why are push-propellers so rare, yet they are still around?

Jet engines are by their very nature push-engines, however, most propeller airplanes use pull-engines. Is there an inherent advantage to using pull-propellers except for the increased airflow over the ...
62
votes
3answers
50k views

What is the purpose of the sharp pods under airliner wings?

What are the pods with the sharp trailing edges underneath the wings of large airliners, as shown in the image below? My best guess would be fuel tanks
12
votes
3answers
35k views

How does wing sweep increase aircraft stability?

I was told at one point that the sweep of a wing can help with the straight line stability of the craft, in fact I think it's one of the main systems that keeps flying wings flying straight (like the ...
31
votes
3answers
27k views

Are fighter jets designed to be so inherently unstable that a human can't fly one unassisted?

I'm told that in order to be more maneuverable fighter jets are designed in a way that makes them impossible for a human to control without the help of a flight computer. Is this actually true? ...
25
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2answers
16k views

How much force does a 747 land with?

I've been told before that the runways for large commercial aircraft have to be built to withstand a large amount of force. But I'm wondering exactly how much it is? When a 747 touches down, how ...
14
votes
2answers
9k views

What is the reason for the poor low-speed characteristics of sweptback wings?

I know there are advantages of swept-back wings delaying shock-wave allowing a aircraft to fly faster. However, what are the disadvantages. I know one of them is that they have very poor low speed ...
41
votes
9answers
66k 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?
34
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4answers
29k views

What do winglets do to increase aircraft performance?

It seems like a lot of the newer airliners have winglets or wing fences. How do they improve aircraft performance?
33
votes
9answers
22k 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?
22
votes
2answers
21k views

What are the advantages of more than 4 propeller blades?

I have heard that propellers with more than four blades are not as efficient as 4 or less blades because of lower thrust which may result from interfering prop-streams. But I see the ATR-42/72 and ...
19
votes
2answers
50k views

What are the different wing planforms? What are each's advantages? Where are they commonly used?

I remember reading that there are four common wing planforms: Rectangular Eliptical Tapered Sweptback I'm sure there are more. What are the different types of planform out there? Each must have its ...
20
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3answers
4k views

Why is the use of tail-down force so common?

Why is the use of tail-down force so prevalent in aircraft design? Why not use canards to avoid induced drag?
14
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2answers
8k views

What is the “area rule”?

The "area rule" states that the supersonic drag on an aircraft is related to the total area on part of the aircraft. What is the exact definition of the rule? Why does this happen?
79
votes
18answers
157k views

Why haven't quadcopters been scaled up yet?

Why are quadcopters not flown by human pilots yet? Wouldn't they be more stable and easier to control than helicopters?
47
votes
3answers
34k views

Why are the Boeing 737 nacelles odd shaped?

Why is a Boeing 737 NG engine not completely round in shape? It seems to be flat at the bottom and round at the top and sides. Earlier Boeing 737 versions (100 and 200) seem to have a more rounded ...
56
votes
8answers
14k views

Even after years of research, why are planes unable to keep passengers alive in case of a fiery crash?

Aviation dates back to the 18th century, and since then tremendous research has been put into making aircraft safer and more efficient. Though these efforts have resulted in better aircraft, why are ...
35
votes
7answers
49k views

How far can airplanes glide?

On an another question, an answer said: You don't need an engine to fly as airplanes are designed to glide without it. I suspect this heavily depends on the type of the aircraft, so lets assume we ...
13
votes
2answers
3k views

What control issues did the X-1 have to overcome to achieve supersonic flight?

In Chuck Yeager's autobiography, he went into a little bit of detail as to why the X-1 was able to break the sound barrier safely where as the P-51D he flew during WWII could not have safely broken ...
12
votes
1answer
909 views

Why is the combustor volume of a jet engine decided by altitude?

I have read that the combustor volume of a jet engine is decided by the maximum altitude up to which that aircraft will fly. I'm getting confused by that, because the maximum mass flow rate will occur ...
7
votes
2answers
2k views

Would a vertical stabilizer that extends both above and below the centerline be benefit or hindrance?

Ignoring for a moment potential schematic difficulties in creating an aircraft that can land and take-off without threatening a downward vertical stabilizer, would a vertical stabilizer that extends ...
94
votes
14answers
38k views

Why are the cockpit controls of airplanes so complicated?

For a layman like myself, the cockpit of every single modern airplane that I've laid my eyes on seems like a complex, intimidating mess with knobs, buttons, screens and levers literally covering every ...
57
votes
10answers
17k views

Why is there really only one basic design for passenger airplanes?

So when I look around on the airport, I don't really see many differently shaped airplanes. They all look pretty much the same, only subtle differences. Image: Aircraft Recognition Why is this ...
17
votes
3answers
11k views

Why are high-wing aircraft more stable?

A high-wing aircraft is considered to be more stable in a side-slip because of the pendulum effect. How does the pendulum effect increase stability in high wing aircraft? This question is about high-...
27
votes
2answers
27k views

How can a helicopter be designed without a tail rotor?

How will the main rotor torque be balanced if a helicopter doesn't have a tail rotor?
28
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5answers
39k views

What are the advantages of a forward-swept wing over a rearward-swept wing?

What are the advantages of a forward-swept wing vs. a rearward swept one? Image credit: NASA Image credit: Paul Maritz / Wikimedia
26
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3answers
42k views

Why does the 747 have 4 engines instead of 2?

If the 747 can fly with two engines, why does it have four engines? What is gained by adding another 2 engines? Flights over the ocean? Fuel savings? Safety?
7
votes
2answers
3k views

Are the functions of ailerons and rudder similar?

The ailerons help the plane to bank left/right by increasing lift to one wing and decreasing in another. Likewise, the rudder also helps in turning the plane by yawing and deflecting the nose right/...
24
votes
4answers
3k views

Do similar angles on a plane make it more stealthy?

I learned in my intro to engineering class at my college that 5th gen fighters (which are stealth aircraft) are designed with similar angles to evade radar. Why is this true? Also, does the angle ...
6
votes
2answers
4k views

What are the properties of the wing (airfoil symmetry, angle of incidence) of an aerobatic aircraft?

On an aerobatic aircraft, such as an Sbach342, what type of airfoil does it have and what angle of incidence does it have in relation to the fuselage?
23
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3answers
10k views

What is the difference between the V-shape tail and the straight tail on the Beechcraft Bonanza?

In one of the answers to the question which aircraft is the oldest in production, the Beechcraft Bonanza is mentioned. While reading the Wikipedia entry on this interesting plane, I noticed that ...
97
votes
9answers
16k 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?
57
votes
2answers
15k views

Why do airplanes have curved windows?

Why are the windows of an airplane usually curved, or rather rounded at the edges?
8
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3answers
2k views

Does static longitudinal stability require download on the tail?

After having encountered this meme too often for comfort, I ask myself today in order to have the possibility to explain the issue in detail.
37
votes
5answers
56k views

Why do large aircraft have their engines mostly on the wings, while smaller ones tend to have them in the tail or the tip?

Large passenger planes almost always have their engines hanging from the wings, Fighters usually have them in the rear, and small Cessnas have them on the nose. What is the reason for these ...
35
votes
14answers
11k views

Why do passenger jets accept input that will cause the aircraft to perform dangerous maneuvers it was not designed for?

Examples: A bank angle > 45 degrees is considered an “upset,” putting the plane in a position that can lead to a loss of control. A pitch > 20 degrees can possibly be dangerous and cause the ...
15
votes
3answers
22k views

Why are delta wings not commonly used in commercial airliners?

Delta wings are most commonly seen on military aircraft. I understand that delta wings are ideal for supersonic flight, and provide high maneuverability. Having high maneuverability and speed are ...
33
votes
3answers
4k views

What happens when an airplane gets struck by lightning?

I know that they certify airplanes for lightning strikes (at least some of them anyway), but does it cause any damage to the airplane or to the electronics? Are there any required inspections if an ...
16
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4answers
3k views

Why are swept wings better for breaking the sound barrier?

I'm told that swept wings perform better when an aircraft is trying to break the sound barrier. I was wondering why that would be?