Questions tagged [theory]
Questions about the theoretical aspects of aviation.
87
questions
1
vote
1
answer
92
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
3
answers
175
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 ...
3
votes
1
answer
113
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 ...
0
votes
2
answers
153
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 ...
- 1,630
0
votes
3
answers
140
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 ...
- 1,630
-3
votes
2
answers
250
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 ...
- 1,630
1
vote
2
answers
200
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 ...
- 1,630
3
votes
2
answers
421
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 ...
- 295
1
vote
3
answers
89
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 ...
3
votes
2
answers
203
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 ...
3
votes
1
answer
377
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
4
votes
2
answers
244
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
-3
votes
1
answer
287
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?
- 1,630
1
vote
1
answer
226
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 ...
- 1,630
0
votes
1
answer
137
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.
...
-3
votes
1
answer
156
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–...
- 1,630
0
votes
0
answers
59
views
How to interpret “list of modifications” and “summary of highlights” in FCOM?
Under preliminary pages, there are 4 sub-chapters, 1.list of effective sections/subsections 2.aircraft allocation table 3.list of modifications 4.summary of highlights
What does 3 & 4 mean to ...
- 949
1
vote
4
answers
423
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 ...
- 1,630
1
vote
1
answer
154
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
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 ...
- 165
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) ...
- 165
5
votes
2
answers
483
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_\...
- 435
7
votes
1
answer
754
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 (...
- 307
1
vote
2
answers
323
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 ...
- 11
1
vote
2
answers
171
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 ...
- 23
1
vote
2
answers
291
views
Is aerodynamics science still being discoverd? [closed]
Is aerodynamics science still being discovered(like mathematics for example) or everything has already done?
- 1,630
1
vote
2
answers
1k
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 ...
- 1,630
0
votes
2
answers
487
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 ...
- 1,630
1
vote
0
answers
47
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 ...
- 111
0
votes
0
answers
35
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 ...
- 305
1
vote
0
answers
132
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 ...
- 305
-1
votes
1
answer
155
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) $$
with velocity $V$, thrust $T$, drag $D$ and weight $W$.
$P_s$ represents specific energy, which is a combination of ...
- 2,474
2
votes
3
answers
170
views
Which source(s) provides the most authorative and correct flight dynamics theory? [closed]
Just like many curious people, the question: " How airplanes actually work?" occupied my mind for a long time.
Different sources gave different answers where most claimed the Bernoulli ...
- 137
5
votes
5
answers
3k
views
Is it possible for an airplane to enter another airplane? [duplicate]
I was making some cool fictional airplane designs and realized that most of my larger airplanes have a bay inside that stores a plane or two. But then I thought, is it even possible to make a plane ...
- 1,137
3
votes
2
answers
1k
views
Relation between lift force and torque produced in propeller used for vertical take-off and landing aircrafts
There are many answers for this question but none of them are specific.
I need to find the exact relation between the lift force of a propeller of specific pitch, attack angle , dimensions and ...
1
vote
1
answer
175
views
Is it incorrect to say that "passenger jets like to cruise at higher altitudes because there's less drag"?
I hear it stated quite often that aircraft like to fly high because there's less drag at higher altitudes.
$$ \text{Range} = \frac{V}{g} \frac{1}{\text{SFC}} \frac{L}{D} \ln \left( \frac{W_\text{...
- 611
3
votes
2
answers
233
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}\...
- 241
4
votes
2
answers
2k
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 ...
- 6,567
4
votes
4
answers
1k
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 ...
- 445
12
votes
5
answers
5k
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 ...
- 1,925
2
votes
2
answers
522
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 ...
- 1,413
0
votes
1
answer
478
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 ...
- 601
0
votes
1
answer
1k
views
Why does Vmca decrease with increasing altitude?
A question from a mock MEP class rating test:
Many thanks for your help.
- 1,761
1
vote
0
answers
93
views
Is there any bibliography for triplane aircraft design?
I've been tasked with designing an RC aircraft that has the greatest lift force for a specified wingspan, total length and takeoff velocity, and thus have been studying the different wing ...
9
votes
3
answers
5k
views
How does the bypass air provide thrust?
To my knowledge, bypass air produces 80% of total thrust. But I don't understand to how it does that. By accelerating the air, by increasing the speed or increasing the pressure of the air? Is it ...
- 93
2
votes
1
answer
712
views
Would adding a slat and a slotted flap increase the max CL of a multi element airfoil to 6.5?
Would adding a slat and a slotted flap increase the of a multi element foil to 6.5?
I understand, as a general rule, the max $C_L$ for a classic NACA airfoil is as follows:
Base: 1.5
Slat: + 0.7
...
- 1,507
0
votes
1
answer
394
views
Pitching moment as a pure moment and its measurement with a homemade force balance
In mechanics, we learn that a force $F$ acting at a certain application point $P$ can exert a torque (also called moment of the force) about another arbitrary point $Q$ in the plane, i.e. $\tau= F \...
- 173
0
votes
1
answer
97
views
Would turbine blade twist change if all conditions except the density of the fluid remained the same?
While designing a turbine, the blade twist is apparent from the velocity triangles, and this analysis only depends on the velocity.
However, would there be any difference for different media? When ...
- 111
1
vote
0
answers
91
views
What is the relation between solidity and lift coefficients?
I've seen this graph in a couple of places. I'm not sure what it's supposed to mean, as the formulae I've seen in the papers cannot be found in any standard book or reference.
Please let me know if ...
- 111
0
votes
1
answer
413
views
How to refute this geometrical method to find MH370? [closed]
A geometrical method to find MH370 has been published on the Net (see images below).
I am sure it is wrong (because if it were that easy, thousands of people would have had this idea back in 2014). ...
- 3,344