All Questions

33
votes
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 ...
37
votes
3answers
13k 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 ...
46
votes
10answers
18k 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?
48
votes
5answers
7k 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 ...
59
votes
10answers
68k 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 ...
38
votes
4answers
7k 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... Why such cruise altitudes? What are the important criteria taken into consideration by engineers? ...
26
votes
3answers
6k 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 ...
52
votes
4answers
23k 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, ...
20
votes
1answer
7k 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 ...
25
votes
4answers
15k 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 ...
39
votes
9answers
8k 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 ...
154
votes
14answers
107k 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 ...
14
votes
2answers
15k 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 ...
27
votes
7answers
12k 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’...
31
votes
3answers
11k 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 ...
45
votes
9answers
14k 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 ...
40
votes
6answers
80k 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)...
7
votes
1answer
14k 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% ...
9
votes
2answers
3k 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 ?
78
votes
6answers
21k 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 ...
62
votes
4answers
27k 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?
20
votes
3answers
10k 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 ...
31
votes
3answers
2k 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 ...
14
votes
4answers
6k 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 ...
7
votes
1answer
2k 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 ...
21
votes
3answers
2k 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 ...
10
votes
2answers
15k 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-...
41
votes
4answers
17k views

Who has the higher authority, the pilot in command or ATC?

I'm sure many people have heard about the communication between a Delta flight 2244 and Atlanta tower being on news today. When the Controller informs the Pilot he is on a wrong taxi-way, things get ...
31
votes
4answers
21k 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?
31
votes
10answers
34k 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 ...
61
votes
2answers
22k 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 ...
55
votes
3answers
10k 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 ...
24
votes
1answer
13k views

How does a commercial airliner measure its weight/mass?

Other questions currently being answered cover situations regarding planes near, at or even above their MTOW. It raises a more basic question: how is the exact "ramp weight" of an airliner measured or ...
25
votes
1answer
6k 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 ...
17
votes
3answers
6k 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 ...
36
votes
5answers
70k 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?
21
votes
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?
25
votes
2answers
5k 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 ...
102
votes
4answers
27k views

Why is the maximum speed of current fighter aircraft lower than those from the 1960's and 1970's?

While reading about the characteristics of the newest fighter aircraft, I observed that their maximum speed is lower than of the aircraft in the same roles half a century ago. For example, the iconic ...
39
votes
4answers
23k 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 ...
39
votes
5answers
109k views

When to use Beacon, Anti Collision, Strobe, Logo and Navigation lights?

During taxi, the taxi-light are used, and I think the landing lights are required to be used up to 10.000 feet for all commercial flights. However, my question is regarding the above mentioned lights:...
44
votes
11answers
69k 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 ...
24
votes
3answers
59k views

What material is used to make the hot sections of jet engines?

What metal alloy is used for the hot section of a jet engine? Specifically the exhaust nozzle? I have found mention of a titanium alloy and nickel alloy but nothing with that much detail. What sort of ...
27
votes
8answers
12k views

Why aren't cell phones allowed to be used in aircraft?

What problems do cell phones cause? How is using a cell phone in the air different than using it from the ground?
18
votes
4answers
4k views

What does it mean for a plane to be aerodynamically stable?

I've heard that most planes (excepting fighter jets) are "aerodynamically stable." What does that mean? Let's say you're cursing around in a Cessna 172 without autopilot, and you take your hands off ...
25
votes
3answers
9k views

Why do aircraft on Flight Radar 24 jump around randomly sometimes?

I use Flight Radar 24 on my iPad to track friends/families flights when they are traveling (not paranoia, just curious). I've noticed that, quite often, their plane will jump from one location to ...
8
votes
3answers
7k 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 ...
17
votes
4answers
8k views

Why is air mixed with bypass air on the A/C of an aircraft?

Air is taken from the compressors, then it is cooled by the air that comes from the ram air inlet. After that, it is compressed and cooled again by an expansion turbine. When finally air is condensed, ...
16
votes
3answers
15k 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
14answers
48k views

Why are commercial flights not equipped with parachutes for the passengers?

I understand that commercial flights are equipped with life vests. I also understand that most military jets are equipped with ejection seats. It may be costly and technically challenging to equip ...

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