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Questions tagged [theory]

Questions about the theoretical aspects of aviation.

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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 ...
22flower's user avatar
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3 votes
1 answer
238 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 ...
Shogunrv's user avatar
0 votes
0 answers
65 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 ...
Slartibartfast's user avatar
2 votes
2 answers
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,...
22flower's user avatar
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0 votes
1 answer
110 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 ...
22flower's user avatar
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2 votes
1 answer
204 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 ...
Faito Dayo's user avatar
0 votes
2 answers
82 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 ...
22flower's user avatar
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0 votes
0 answers
53 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 ...
Edvin Simic's user avatar
0 votes
1 answer
603 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 ...
AlexGenesis's user avatar
1 vote
1 answer
137 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 ...
Mateo's user avatar
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1 vote
3 answers
228 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 ...
Robust Bottlecap's user avatar
3 votes
1 answer
140 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 ...
MathFareswell's user avatar
0 votes
2 answers
199 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 ...
22flower's user avatar
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0 votes
3 answers
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 ...
22flower's user avatar
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-3 votes
2 answers
321 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 ...
22flower's user avatar
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2 votes
2 answers
215 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 ...
22flower's user avatar
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3 votes
2 answers
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 ...
Timothy Scherer's user avatar
1 vote
3 answers
182 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 ...
clueless.monkey's user avatar
3 votes
2 answers
247 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 ...
james_erikson's user avatar
3 votes
1 answer
414 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 ...
BryBuriya's user avatar
  • 307
4 votes
2 answers
328 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 ...
Uzair's user avatar
  • 185
-3 votes
1 answer
295 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?
22flower's user avatar
  • 1,958
1 vote
1 answer
259 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 ...
22flower's user avatar
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0 votes
1 answer
165 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. ...
user74815926's user avatar
-3 votes
1 answer
175 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–...
22flower's user avatar
  • 1,958
1 vote
4 answers
473 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 ...
22flower's user avatar
  • 1,958
1 vote
1 answer
189 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 ...
Naj Litarvan's user avatar
5 votes
3 answers
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 ...
Naj Litarvan's user avatar
10 votes
4 answers
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) ...
Naj Litarvan's user avatar
5 votes
2 answers
1k views

2D to 3D Non-Elliptical Lift Curve Slope Correction Factor Reference

I'm working on automating some aerodynamic calculations for a particular multidisciplinary design tool and in the course of setting it up I ran across this formula from the input theory manual $$ {CL_\...
spacegirl1923's user avatar
7 votes
1 answer
855 views

How to determine the base of stratus clouds? [closed]

For cumulus clouds this applies Calculate the 'spread,' where you're taking the current surface temperature and subtracting the dew point. Divide the spread by 4.4 (if temperatures are in °F) or 2.5 (...
Yosef Jabbour's user avatar
1 vote
2 answers
570 views

Takeoff-chart Interpolating Numbers from a range

I'm studying for my AIRAT (Instructor Written) in Canada using Nizus, but I've always had trouble answering the questions about takeoff distances at 27 ºC when given a chart with 20 ºC and 30 ºC, even ...
zeeb's user avatar
  • 11
1 vote
2 answers
193 views

What methods are used to calculate the geometry needed to obtain a bell-shaped lift distribution?

In aerodynamics, what methods do people use to calculate the geometry of a wing (and body) needed to obtain a bell shaped lift distribution? Please go into as much detail as possible for a stack ...
Justin H's user avatar
1 vote
2 answers
303 views

Is aerodynamics science still being discoverd? [closed]

Is aerodynamics science still being discovered(like mathematics for example) or everything has already done?
22flower's user avatar
  • 1,958
1 vote
2 answers
2k views

How calculate lift/drag using static pressure taps in wind tunnel test?

An airfoil section in a wind tunnel has many static taps on its upper and lower surface. These static ports can only read static pressure which acts perpendicularly to the local airfoil surface. In ...
22flower's user avatar
  • 1,958
0 votes
2 answers
782 views

Help with calculate forces from pressure distribution

V=50m/s deltaPg= -981 Pa deltaPd=490,5 Pa c=1m r.com/PCshZ.png Above is calculate Fz with integrals and with average pressure. Why F3 is calculate from 0 to C/2 if pressure distribution is drawn at ...
22flower's user avatar
  • 1,958
1 vote
0 answers
53 views

How long is a BAK exam valid for? (CASA Australia))

I am looking to get back into flying, and I passed my BAK theory in 2016. Is that still valid? I want to go straight to PPL so I will be doing PPL theory anyway, just would save me a step, unless I ...
mgrande465's user avatar
0 votes
0 answers
37 views

EASA PPL theory instrumental approaches rules

I am learning for EASA PPL in Czech. I noticed that in some of the books there is chapters about Instrumental Approaches Air Law rules. For example - ILS approaches Parallel approaches Simple ...
Meir Tolpin's user avatar
1 vote
0 answers
207 views

How to choose the right map projections for flight plan?

There are 2 projection of maps that I saw online. UK CAA is a transverse projection map, while ICAO maps are conical. It seems that transverse map is easier for flight planing as straight lines are ...
Meir Tolpin's user avatar
-1 votes
1 answer
192 views

If aircraft specific energy is a combination of kinetic and potential energy, why is altitude not a variable in the energy-maneuverability theory? [closed]

The Energy-Manueverability formula is $$ P_S = V \left( \frac{T - D}{W} \right) $$ with velocity $V$, thrust $T$, drag $D$ and weight $W$. $P_s$ represents specific energy, which is a combination of ...
MD88Fan's user avatar
  • 2,484
2 votes
3 answers
188 views

Which source(s) provides the most authorative and correct flight dynamics theory? [closed]

Just like many curious people, the question: " How airplanes actually work?" occupied my mind for a long time. Different sources gave different answers where most claimed the Bernoulli ...
Lost's user avatar
  • 137
5 votes
5 answers
3k views

Is it possible for an airplane to enter another airplane? [duplicate]

I was making some cool fictional airplane designs and realized that most of my larger airplanes have a bay inside that stores a plane or two. But then I thought, is it even possible to make a plane ...
Ginger's user avatar
  • 1,167
3 votes
2 answers
2k views

Relation between lift force and torque produced in propeller used for vertical take-off and landing aircrafts

There are many answers for this question but none of them are specific. I need to find the exact relation between the lift force of a propeller of specific pitch, attack angle , dimensions and ...
Mohammed Siddique's user avatar
1 vote
1 answer
187 views

Is it incorrect to say that "passenger jets like to cruise at higher altitudes because there's less drag"?

I hear it stated quite often that aircraft like to fly high because there's less drag at higher altitudes. $$ \text{Range} = \frac{V}{g} \frac{1}{\text{SFC}} \frac{L}{D} \ln \left( \frac{W_\text{...
Rory McDonald's user avatar
3 votes
2 answers
288 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}\...
MichaelW's user avatar
  • 251
4 votes
2 answers
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 ...
ROIMaison's user avatar
  • 7,447
4 votes
4 answers
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 ...
Dakkaron's user avatar
  • 445
12 votes
5 answers
6k views

Could propeller wash provide sufficient lift to take off - even in theory?

I know this seems a crazy thing to ask but it is not the same as lifting oneself by the bootstraps. If you try to lift yourself that way, there are two equal and opposite forces, yet there are ...
chasly - supports Monica's user avatar
2 votes
2 answers
767 views

Is the Batjet Design Physically Feasible?

I realize the plane is fictional. However, in the Batman Animated Series by Warner Bros, we see this Batjet. So this got me thinking (and I'm not a physicist): is this air frame configuration even ...
Jon's user avatar
  • 1,411
0 votes
1 answer
773 views

How to determine the number of compression stages given a compression ratio?

I have a personal project to design a gas turbine engine, the main problem that puzzles me is how do I determine the pressure rise in each stage of an axial compressor? Say, I'm planning on a 38:1 ...
Salmonbeing00's user avatar