All Questions
6,620
questions
67
votes
12
answers
52k
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?
- 24.3k
25
votes
9
answers
28k
views
Does lift equal weight in a climb?
This subject keeps coming up in the discussions and questions such as this one, which asks if lift equals weight in level flight. Good answers there, pointing out that upwards force has many sources. ...
- 62.3k
36
votes
3
answers
13k
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 ...
- 24.3k
49
votes
3
answers
21k
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 ...
- 24.3k
70
votes
10
answers
95k
views
Why do jet engines get better fuel efficiency at high altitudes?
I'm told that this is true, but I can't imagine why. It seems like the fact that there is less air would make the engines less efficient... But that probably just shows how little I know about jet ...
- 24.3k
28
votes
1
answer
19k
views
Is there any equation to bind velocity, thrust and power?
I am designing a remote controlled airship. I will tune it so that the lift given by Archimedes' Principle will exactly balance the weight of all the structure. It will be propelled by brushless ...
- 383
58
votes
6
answers
17k
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 ...
- 236k
55
votes
9
answers
16k
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 ...
- 9,368
52
votes
4
answers
12k
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 ...
- 77.1k
35
votes
8
answers
22k
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’...
- 4,117
31
votes
3
answers
10k
views
What is the immediate cause of stall?
The direct cause of stall is unclear to me.
I heard about exceeding maximum angle of attack (around 40°) ;
I heard about reaching the stall speed in the current configuration (flaps, etc).
I heard ...
- 1,811
20
votes
3
answers
21k
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 ...
- 10.5k
62
votes
4
answers
39k
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, ...
- 1,125
40
votes
4
answers
19k
views
Why do gases in the combustion chamber only flow one direction to the gas turbine in a jet engine?
As far as I know from the working principle of jets engines, compressed air in the combustion chamber (or combustion canister) is mixed with fuel. The ignited mixture expands backwards to turn the ...
- 723
19
votes
2
answers
29k
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 ...
- 24.3k
18
votes
5
answers
11k
views
Why is there a difference between GPS Speed and Indicator speed?
I just played with flight simulator and noticed that the GPS shows different speed from the speed indicator in the cockpit. Also, GPS speed is higher than the Indicator. Any Idea why?
- 915
12
votes
2
answers
6k
views
How is the induced drag calculated for a wing with elliptical planform?
How is the induced drag calculated for a wing with elliptical planform ? Is this wing shape the most efficient ?
- 121
15
votes
4
answers
15k
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 ...
- 469
11
votes
2
answers
25k
views
How can I calculate the fuel consumption of an Airbus 320-200 at various loads?
I want to know:
What is the fuel consumption of an Airbus A320-200 - 180 Seats, at 100% load factor for a distance of 2000 km?
What is the fuel consumption of an Airbus A320-200 - 180 Seats, at 80% ...
- 119
203
votes
14
answers
268k
views
Can Microsoft Flight Simulator help me learn to fly (or make me a better pilot)?
Microsoft Flight Simulator has "flight lessons" with a virtual flight instructor, some of which teach concepts that are taught during actual flight training. These simulators are becoming very ...
- 59.1k
68
votes
5
answers
43k
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?
- 771
56
votes
12
answers
21k
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 ...
- 983
52
votes
6
answers
105k
views
How are runways numbered?
I'm not a professional pilot, just an enthusiast, so this might seem obvious to others; but I noticed that airports don't use sequential numbering for runways, starting from 1.
Liverpool (for example)...
- 16.7k
30
votes
4
answers
22k
views
How does wind affect the airspeed that I should fly for maximum range in an airplane?
I have heard that wind affects the actual airspeed that I should fly for maximum range in an aircraft.
I understand that wind will not affect the airspeed that I should fly if I am looking for ...
- 59.1k
27
votes
5
answers
12k
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?
- 1,220
19
votes
3
answers
30k
views
Why and when to use flaps?
On a commercial airliner, what is the purpose of the flaps? I understand that depending on which direction they move in, they can be used to decrease airspeed, but I don't know when flaps are used. ...
- 487
7
votes
3
answers
5k
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?
- 715
71
votes
3
answers
18k
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 ...
- 8,081
42
votes
11
answers
56k
views
Could an electric engine provide the same performance as jet engines on current aircraft?
I have looked at various questions on this SE site regarding this topic but I have not really found a satisfactory answer. Some comments here regarding torque and power in electric motors vs gasoline ...
- 531
31
votes
2
answers
22k
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 ...
- 9,369
9
votes
1
answer
5k
views
What is the aerodynamic centre and how does it relate to the pitching moment?
Okay so I have been trying to get my head around the Aerodynamic centre and the Pitching moment. Wikipedia really isn't helping much but from what I can gather the Pitching moment is a force caused by ...
- 91
20
votes
3
answers
10k
views
Why do some military aircraft use variable-sweep wings?
There are a couple of American military aircraft (the retired F-14 and the B-1 come to mind immediately), that have variable swept wings. I know that they keep the wings full out (roughly ...
- 24.3k
13
votes
3
answers
4k
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.
- 236k
31
votes
3
answers
16k
views
Why are propeller engines uncommon on airliners?
My experience in aviation is essentially zero, but looking at Wikipedia it seems like the Tu-95 Bear offers high subsonic speed and extreme range.
I assume that turboprop engines are more fuel ...
- 583
13
votes
2
answers
44k
views
What is the method to calculate a finite wing's lift from its sectional airfoil shape?
I am struggling to get my head around a concept that I believe should be fairly simple to understand.
Lift versus drag and AoA data of many airfoils are freely available, for instance the NACA 4-...
- 2,038
89
votes
6
answers
26k
views
Why do we still use pilots to fly airplanes?
With the recent advances in drone and remote control technology, why are there still commercial and military pilots?
I understand that there can be some serious tactical advantages to human pilots in ...
- 6,907
41
votes
5
answers
99k
views
How much is the minimum safe distance between two planes in-flight?
According to FAA regulations, how far should a commercial jet be away from another plane in-flight?
How about military planes? They get really close when in formations... Is there a minimum distance?
- 7,072
33
votes
3
answers
3k
views
Could the CVR and FDR record to the cloud?
Another enthusiast question. I watch a lot of the National Geographic Channel's "Air Crash Investigation", for better or worse, and it seems accident investigators make tremendous use of the Cockpit ...
- 1,207
31
votes
4
answers
13k
views
Why do aircraft on FlightRadar24 jump around randomly sometimes?
I use FlightRadar24 on my iPad to track friends'/family's flights when they are traveling (not paranoia, just curious). I've noticed that, quite often, their plane will jump from one location to ...
- 24.3k
27
votes
2
answers
7k
views
How do insects decrease aircraft performance?
Is it true that insects hitting the fuselage could decrease aircraft performance and increase fuel consumption? Insects are small in mass. I think even a large amount of them accumulate on the ...
- 1,862
54
votes
12
answers
124k
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 ...
- 11.8k
45
votes
5
answers
42k
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 ...
- 782
15
votes
1
answer
19k
views
What is the relation between an airplane's altitude and the drag it is experiencing?
The Reynolds-Number $Re$ is defined as $Re = \frac{c \cdot L \cdot \rho}{\mu} = \frac{c \cdot L}{\nu}$, with
the velocity $c~\left[ \frac{m}{s} \right]$,
the reference length $L~\left[ m \right]$,
...
user12485
12
votes
4
answers
4k
views
11
votes
3
answers
12k
views
Does the downwash created by induced drag increase or decrease lift?
According to the theory I know, lift is produced by accelerating air downwards at the trailing edge (downwash). Hence, as downwash increases so does lift. Induced drag is due to vortices at the wing ...
- 751
79
votes
3
answers
36k
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 ...
- 791
33
votes
4
answers
34k
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?
- 59.1k
32
votes
2
answers
44k
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 ...
- 12k
27
votes
3
answers
4k
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 ...
- 16.5k
27
votes
1
answer
10k
views
I have a European EASA license - what do I need to do to be allowed to fly in the US?
I own a PPL(A) license following JAR-FCL. Recently, this license has been exchanged for a European EASA license.
My training was on a motor glider (TMG), I do not have ratings for SEP, but TMG and ...
- 1,331