# Questions tagged [theory]

Questions about the theoretical aspects of aviation.

96 questions
Filter by
Sorted by
Tagged with
52 views

### Coordinate system for describing 3D target position relative to plane FRD

I'm trying to understand what is the most popular convention for describing the position of a point in 3D space relative to a plane's body frame, with axis "front", "right" and &...
3k views

### Why does this curved wind tunnel rotate?

Why does this curved wind tunnel rotate, why is it not just curved? A curved wind tunnel has a radial pressure gradient, but this pressure gradient doesn't exist in a real turn, so how do you get ...
• 1,958
277 views

### What does the C* (Cstar) parameter demand ?(A320)

I have been reading a LOT of research papers and many articles, but none of them tell how the C* parameter in Airbus is used for the vertical augmentation of the aircraft. I am aware that with a ...
• 33
73 views

### Gyroscopic Precession in Coaxial Helicopters

I'm trying to understand gyroscopic Precession in the case of coaxial helicopters. Obviously the effect still exists. But if gyroscopic Precession is a result of counter torque. Shouldn't the effect ...
229 views

### In general, how much is V/V∞ ratio at upper wing surface?

Airflow on upper surface is always faster then freestream, in general, how much is airflow speed to freestream speed ratio(V/V∞, max values) at upper wing surface, are we talking about 1.1 to 2 or 2,3,...
• 1,958
114 views

### Why induced drag shows up as reduced pressure downstream of the wing?

Quote from book (Understanding Aerodynamics: Arguing from the Real Physics, Doug Mclean): "When we look at the force/momentum balance, the induced drag shows up in the flowfield primarily as ...
• 1,958
207 views

### A transfer function relating jet engine thrust to pitch angle during a phugoid motion

Crossposted on Mathematics SE I am doing a school project that requires me to find a transfer function that relates the thrust of a jet engine (which could change with time in one way or another) and ...
• 603
85 views

### "Pure" Aerospace engineering vs mechanical engineering/pathway aerospace?

Does "pure" aerospace engineering give better aero-knowledge then mechanical engineering/pathway aerospace? What is point of specialization aerospace at mechanical engineering, isn't ...
• 1,958
69 views

### ATPL theoretical course hours per subject

do someone know what is the hours per subject mandatory for ATPL (A) EASA program. In the Easy Access Rules for Aircrew (PART FCL) it said: The 750 hours of instruction should be divided in such a way ...
678 views

### Difference between velocity potential and stream function?

I am currenty reading Fundamentals of aerodynamics(sixth edition) Jhon Anderson and in sections 2.14, 2.15 was introduced stream function and velocity potential concepts. I understand that both of ...
1 vote
150 views

### How would the shock-ramjet engine work?

I discovered a new theoretical engine called the shock-ramjet (schramjet) and I was wondering, how would it work exactly? I've read that its a high-speed engine that could be used around Mach 10, but ...
• 746
1 vote
238 views

### What is a wing theory?

I have an assignment to summarize the topic "wing theory", with the preferred reference used is the book Fundamentals of Aerodynamics by John D. Anderson. But there's no dedicated chapter ...
149 views

### Energy Maneuverability Theory Applied to WW1 Fighters

I am trying to test the Fokker D.VII, Spad S.XIII, Sopwith Camel, Nieuport 28, and the Se5a using the model in this paper: https://apps.dtic.mil/sti/pdfs/ADA066034.pdf It's called Combat Performance ...
222 views

### Is Biot–Savart law physical in aerodynamics?

Biot–Savart law comes from electromagnetics theory. Vorticity behind the wing(in the wake) induce downward vertical velocity upstream of the wing, so effective AoA of the wing is reduced. Is this ...
• 1,958
142 views

### Has resultant pressure vector backward component at 2D airfoil in viscid flow?

When we integrate static pressure around 2D airfoil that produce lift(viscid flow), has resultant pressure vector backward component? I think pressure vector will point slighlty back, so it has some ...
• 1,958
338 views

### Why total drag formula include drag at zero lift?

Total drag = Do + DL Why total drag include drag at zero lift if we are interested at drag when wing produce lift? We cant assume that friciton and particularly pressure drag at zero lift AoA dont ...
• 1,958
230 views

### Does induced drag drop when wing is stalled?

From formula, induced drag is function of lift. When wing stalls, lift is reduced so induced drag must also be reduced? Stall decrease static pressure at suction side of wing, so I know pressure drag ...
• 1,958
1k views

### Why are aircraft piston engines are so low rpm lazy engines?

I understand that the propeller speed should not be too much otherwise it will stall at the tip and be useless so higher rpm engine would be useless when we first think about it. However, we can put a ...
1 vote
191 views

### Why does a wing's pitching moment distribution tend towards zero at the tip instead of towards cm0?

I am currently playing around with XFLR5 and am trying to wrap my head around the following: For airfoils, my understanding that the pitching moment has a component that is independent of lift, which ...
255 views

### How to compute the direction of the vector perpendicular to the wing?

I'm trying to compute the direction of the vector that extends perpendicularly up from the top of the aircraft's surface. Is there a way to compute the vector's 3-dimensional parameters in Cartesian ...
427 views

### Immobile pressure-sensitive stick [duplicate]

I was reading the Japanese sci-fi novel Yukikaze (greatly recommended btw) again and I came across a detail that describes that the stick of the fighter plane the main character is flying is fixed in ...
• 307
355 views

### How does deploying full flaps affect Takeoff run and distance?

There is a question in EASA Question Bank (AviationExam) that asks: How will the takeoff distance change if the flaps are increased from 0 to full? (a) Reduce (this is marked as correct since many ...
• 185
299 views

### What flying sources does Richard Feynman consider incorrect? [closed]

In this VIDEO from 1:09-2:15 Richard Feynman talk about some flying sources that he considers incorrect. What is the theory that he refers to?
• 1,958
1 vote
267 views

### If induced drag is caused by the downward deflection of the air streaming around the wing,why airfoil(that also deflect air down) has induced drag=0? [duplicate]

In this site induced drag is often explain as downward deflection of the air streaming around the wing. Airfoil (2D) also deflect air downward(otherwise it would not produce lift), why then airfoil ...
• 1,958
167 views

### Is induced drag zero for finite wing with constant lift distribution (dΓ/dy=0)?

Part 1 Observing how induced drag is derived, induced drag is loss of kinetic energy due to total vorticity that is produced by wing. I want to find induced drag of finite wing with L=const over span. ...
177 views

### Does Navier-Stokes "recognize" existence of induced drag, can we get induced drag from them?

"Early aerodynamic mathematical methods rely on potential flow concepts that formally isolate aerodynamic drag into a profile and an induced drag component. The more recent evolution of Navier–...
• 1,958
1 vote
480 views

### Does wing really "feels" effective airflow or it is just theory to fits numbers with experimental results?

Theory predict downwash that will cause reduction in airflow angle,this we call effective airflow. Does wing of aircraft during flight really "feels" this effective airflow or this is just ...
• 1,958
1 vote
196 views

### how are the properties of canards affected when they are angled compared to normal canards?

So i recently saw an image of the natf-23 a modified(more like completely redesigned) yf-23 and one of the interesting things it had were canards that were angled. What would the benefits and drawback ...
• 165
2k views

### Vertically moving wings

Would there be a benefit to vertically adjustable main wings? I recently watched this anime series and got curious if the wing moving mechanism could have any plus points, or if it was likely just ...
• 165
1k views

### Would aft stabilisers, that can move up and down, have any benefits?

I was looking at some aircraft as an inspiration for a project and found the X-02 Wyvern from the Ace Combat series and one feature that seemed interesting (let's ignore its Swiss Army knife wings) ...
• 165
1k views

301 views

### Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust: https://en.wikipedia.org/wiki/Turbojet#Net_thrust \$F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\...
• 251
3k views

### Why is the aerodynamic center for most airfoils located at the quarter chord location?

I've been reading several sources on the location of the aerodynamic center https://web.mit.edu/16.unified/www/FALL/fluids/Lectures/f03.pdf https://en.wikipedia.org/wiki/Aerodynamic_center John ...
• 8,032
2k views

### Could gliders be a clean, practical alternative to other forms of transport?

Would it be possible to use pure gliders as an eco-friendly mode of transport? From what I have read so far, gliders can travel at a speed of 100-170 km/h. That would not be able to compete with a jet ...
• 444