Questions tagged [aircraft-design]

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

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39
votes
3answers
11k 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 ...
44
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3answers
17k 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 ...
60
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4answers
32k 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, ...
50
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4answers
10k 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 ...
19
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2answers
22k 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 ...
22
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3answers
18k 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 ...
67
votes
5answers
36k 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
11k 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 ...
26
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5answers
9k 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?
49
votes
12answers
103k 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 ...
27
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2answers
31k 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 ...
34
votes
4answers
29k 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?
15
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2answers
14k 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 ...
26
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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 ...
68
votes
2answers
29k 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 ...
14
votes
3answers
43k 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 ...
37
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4answers
35k 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?
8
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3answers
2k views

What is compressibility drag?

I don't mean wave drag here. What is compressibility drag, which is understood to be a form of miscellaneous drag?
11
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3answers
3k 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.
64
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2answers
62k 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
36
votes
3answers
35k 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? ...
83
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18answers
171k 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?
41
votes
9answers
85k 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?
35
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9answers
33k 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?
14
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2answers
10k 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?
59
votes
10answers
21k 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 ...
26
votes
2answers
18k 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 ...
22
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3answers
5k 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?
47
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2answers
24k 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 ...
19
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2answers
67k 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 ...
18
votes
3answers
16k 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-...
50
votes
3answers
40k 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 ...
11
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2answers
7k 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/...
8
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3answers
2k views

Does “pendulum effect” apply to hang gliders or any aircraft?

In discussion of aircraft roll stability in FAA paragraph on dihedral effect and in keel effect and in Why are high wing aircraft more stable the question of pendulum effect arises. This is usually ...
23
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3answers
13k 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 ...
39
votes
7answers
63k 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 ...
30
votes
5answers
49k 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?
25
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4answers
15k views

What is the purpose of eyebrow windows?

Nowadays they are no longer needed but why do they cover them up like in this photo? What is their purpose and why aren't they used anymore? Source
15
votes
10answers
30k views

Can an ultralight aircraft fly with a 18hp engine?

I have some questions - I'm planning on building single seat UL aircraft with this plan sketch (I have more), I drew this based on real plain and some research. Empty weight is between 50-70kg with ...
14
votes
6answers
4k views

Can biplane or triplane designs be revived with modern materials?

With the new-age technologies and cutting-edge composite materials etc available currently, is it possible that biplane and triplane designs will make a comeback in the near future?
59
votes
8answers
15k 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 ...
46
votes
3answers
20k views

Why is the Tu-95 so efficient despite having propellers that spin faster than the speed of sound?

I've ready many, many times that propellers are not efficient near the speed of sound because it's so hard to get a tip-speed above Mach 1. Then I came across this: It's the Tu-95 "Bear", a ...
107
votes
9answers
23k 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?
32
votes
5answers
52k 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
21
votes
8answers
16k views

Why are there no blended-wing passenger airplanes in operation?

Blended wings are more beneficial when it comes to fuel efficiency increase and noise reduction. However, no manufacturer has decided to produce these airplanes for major airline operation so far. ...
20
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3answers
23k views

What is a high speed stall?

I'm told that planes can actually stall when the airflow over the wing goes past Mach 1? Why does this happen and how do you design an aircraft to avoid it?
17
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2answers
4k 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 ...
16
votes
4answers
3k views

Do any airplane designs exist that don't involve a flight surface that provides downforce?

Most aircraft maintain longitudinal stability by balancing three forces: The down force acting through the center of gravity (CG) The lifting force acting through the center of lift The down force ...
24
votes
4answers
4k 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 ...
12
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1answer
1k 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 ...

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