Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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How flapping rudder produce net thrust if one half stroke produce thrust and second half-stroke produce drag?

Idea is to produce thrust with flapping rudder at model plane.(dont ask why) Flapping rudders(even stiff), fins change pressures fields at their surface, they push fluid backward,but I strickly ...
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What are these points in the Propeller Schematic?

If it matters, this is taken from EASA PPL questions. The graphic appears to be taken from the side point of view, although I've never seen such a round Spinner, unless it's a variable pitch propeller ...
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2 answers
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What are these points in this drag curve ("Lilienthal'sches Polardiagramm")?

If it matters, this is taken from EASA PPL questions by AustroControl. So far I think the points correspond to the following situations: 1 Inverted Flight (confirmed) 2 ??? 3 Maybe Best Gliding Angle?...
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1 vote
2 answers
141 views

Why increase chord length for supersonic aircraft (swept vs delta wings)?

TL/DR For supersonic transport and a given sweep angle, why are delta wings used instead of swept wings? If you write the drag equations, a sweep of $55^{\circ}$ seems sufficient with no modification ...
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10 votes
4 answers
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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) ...
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15 votes
2 answers
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Do airliners reduce their angle of attack to maintain lift = weight as fuel burns off during cruise?

For an aircraft to remain in level flight, it must generate lift force that is exactly equivalent to its weight. However, modern airliners lose a lot of weight when they are in cruise flight in the ...
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2 votes
1 answer
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What are some features of a wing, which effects its lift coefficient other than its sectional view? [duplicate]

What geometrical features of a lifting surface apart from which airfoil it has, I mean the ones visible from the top and front view of a wing (for ex: its span, AR, sweep, dihedral etc.) effects its ...
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Progress in supercritical airfoils - an answer [duplicate]

I previously asked a question about progress in improving the characteristics of supercritical airfoils. The basic supercritical airfoil design was created in the early 1970s by Richard Whitcomb. I ...
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4 answers
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Hovering for free

I'm thinking about light solar drones, and started wondering if you could hover while not using any power by flying downwind. Something similar to how prey birds hover while tracking the ground. It ...
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8 votes
2 answers
695 views

Does Headwind on Landing affect Ground Effect?

I am currently training for my commercial Pilot check ride and I am trying to execute the short field spot landing. Under FAA ACS standards you have to hit your spot within -0 to + 100 feet. I live ...
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3 votes
4 answers
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What causes lift?

Now this seems to be the question of the ages, and various questions on this site regards it. The often told description of lift is that it is due to air traveling faster over the wing than under it, ...
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What is the aerodynamic impact of the curved/crescenteric wing of the Boeing 787? [duplicate]

From certain angles (see pictures below), the wing of the Boeing 787 seems almost curved/crescenteric in shape, particularly closer to the wing-tip. While the Boeing 787 makes use of "raked ...
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2 answers
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Does tip dihedral have lesser increase in lift over a full dihedral wing?

I have read some articles mentioning that a full dihedral reduces the lift produced by a wing. So what about a tip (or cranked) dihedral that has the angled part starting from the mid-wing rather than ...
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1 vote
2 answers
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Are shockwaves responsible for heating in very sparse atmospheres?

I recall learning about hypersonic flow in high atmosphere. I think one of the modelling assumptions used is that the relative air flow is so fast, and the average space between molecules is so great, ...
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4 votes
1 answer
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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_\...
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The evolution of commercial airliner wing twist distributions over time

As far as I understand, wing twist is used by commercial wing designers to make the span-wise distribution of lift as elliptical as possible for tapered wings, increasing the span-efficiency factor ...
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How have aerodynamicists improved transonic wing performance over time?

The following two graphs depict improvements in transonic wing technology that have occurred over the past 20-25 years. Both are sourced from Boeing Commercial Aircraft. In essence, both note that ...
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Is it always true that a laminar boundary layer will always have a smaller skin friction coefficient than a turbulent boundary layer?

For a particular Reynolds number, I was wondering whether a laminar boundary layer is always preferable in terms of skin friction. So I looked towards the equations: Blasius, laminar: $$ C_{fl} = \...
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How high could modern transonic commercial transport designers reasonably push L/D ratios?

One facet of the evolution of commercial transonic transport design since 1970 years is that L/D ratios (alternatively, the M * L/D) have increased only mildly over time. For example, see the ...
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1 answer
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Interpreting a graph depicting airfoil technology improvement

I found this image in a paper titled, "Design and validation of advanced transonic wings using CFD and very high Reynolds number wind tunnel testing" that was published in part by Mark I. ...
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3 votes
1 answer
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UH1 fin under chin bubble

What is the purpose of the fin under the nose. It’s close to the co pilot side and starts at the bottom of the battery compartment and ends Near the bottom of the chin bubble. Wikipedia Photo
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3 votes
1 answer
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What aerodynamic improvements were introduced on the Boeing 787?

When discussing the Boeing 787, three topics are brought up most often: 1) The new, extremely high-bypass GEnx engines 2) The shift to carbon composite construction and 3) The significant troubles ...
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3 votes
2 answers
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How a power assurance check works?

In a Bell 407 the power assurance check takes into account torque, pressure altitude and MGT (measured gas temperature aka TOT). The flight manual states that if MGT when tested is less than or equal ...
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Temperature profile for a boundary layer

So I was reading the textbook today, and I see this picture for the temperature profile through the boundary layer. And I was confused on why the shape looks like this? Should it not look more like ...
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0 votes
1 answer
118 views

How to calculate lift and drag of commerical aircraft in different phases of flight?

What is the best way to mathematically calculate values of lift and drag forces, in different phases of flight: takeoff, climb, cruise, descent, and approach? Edit: I have the idea of calculating the ...
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Why can't supersonic flow work its way upstream?

I am reading this textbook today. And it described supersonic flow as follows: In a supersonic flow, because the local flow velocity is greater than the speed of sound, disturbances created at some ...
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2 answers
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Why does the leading edge vortex accelerate the flow downward?

I know leading edge vortices over delta wings make more lift. I understood that the core of the vortex sheet is low, so there is suction flow that makes lift. But, I can't understand how a leading ...
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What is the purpose of the small vertical dorsal fin about halfway along the fuselage of the Boeing 737? [duplicate]

I've searched for an answer to this question on this site and others: What is the purpose of the small vertical dorsal fin about halfway along the fuselage of the Boeing 737? See the attached image ...
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1 vote
2 answers
210 views

What does deploying landing flaps do to the (L/D)max and minimum drag speed of an airplane?

I thought that deploying flaps will increase both the drag and lift, thus increasing L/D ratio? But do they increase proportionately? And how exactly does that correlate with the increase/decrease of ...
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1 vote
0 answers
81 views

Change of absolute ceiling with weight

Let's say an aircraft has an abs ceiling of some value at the start of its cruise and then it consumes some percentage of its fuel during cruise. How will this change the new abs ceiling at the end of ...
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7 votes
6 answers
514 views

Aircraft pitch and AOA change during a coordinated turn maneuver

Let us say I am flying a constant airspeed turn while maintaining my altitude, when I enter into the turn, lift has to be increased and since airspeed remains constant, the AOA has to be increased to ...
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6 votes
8 answers
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Can an encapsulated airfoil generate enough lift to lift the capsule?

Can an airfoil generate enough lift, if it is contained in an enclosed space, to lift the enclosed space? Assume that there would be sufficient airflow over the foil to generate lift if it was not in ...
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3 votes
2 answers
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how is ITT peak temperature affected by altitude during an airstart?

another T-6 Texan II (turboprop aircraft) question. When reading the airstart prodedure in the engine failure during flight section of the manual, I found something that Id appreciate the ...
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-1 votes
2 answers
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Has there ever been a VTOL aircraft thruster that generated lift through the use of a drag force?

I have been recently thinking about a conceptual VTOL aircraft thruster that should generate lift through the use of a drag force and I am very curious to know if such a thruster has ever been built ...
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12 votes
2 answers
1k views

How does the weight affect the altitude that can be reached by trading speed after a total engine failure?

I recently read in the manual for The Beechcraft T-6 Texan II (a turboprop aircraft) about engine failure during flight at different altitudes and the gains from pitching up after the engine failure ...
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2 votes
1 answer
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Airfoil Sections orientation on a Swept Wing

The swept wing on a typical airliner consists of multiple airfoil sections. Are these sections oriented perpendicular to the wing leading edge, or parallel to the longitudinal axis of the fuselage? ...
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8 votes
1 answer
223 views

Improvements in supercritical airfoil design from 1980 - 2000

I originally asked a question (Comparisons between the A340 and 747-200 wing: sweep angle and span) about the technological developments which allowed the Airbus A340 to have a wing with greater ...
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1 vote
2 answers
162 views

Is flow attached in the center of delta wing?

Is flow attached in center of delta wing or only on the edge where two vortices operate? Any video of delta wing vs AoA with smoke?
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Can big vertical strakes produce "vortex-lift" at high aspect wing?

Delta wings use a strong vortex flow to keep flow attached even at high AoA (30°). My goal is make high aspect wing with highest CL and stall angle, and I don't care about drag. Can we use big angled ...
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1 vote
3 answers
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What is the maths behind Loitering of Aircraft?

I am making a controller for loitering using PIDs. The equation which is used to find the radius of circle given bank angle and speed is in following link: How to calculate angular velocity and radius ...
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3 votes
1 answer
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Could the Wright Flyer II takeoff without wind?

The Wright Flyer II could reach about 20 mph of airspeed on the track alone. The aircraft needed an airspeed of about 30 mph to make a proper takeoff (without hanging in ground effect). Before the ...
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2 votes
1 answer
136 views

What is the modern approach to extract vehicle system responses to control input? [closed]

What is the modern approach to extract vehicle system responses to control input? Is everything thrown into a CFD simulation and the responses recorded or is something else done? Are wind tunnels ...
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2 votes
1 answer
263 views

Converting 2d Cl to 3d [closed]

I am trying to convert 2d Cl data obtained from javafoil for a NACA 4412 into 3d data to be used for analysis of the airfoil, but cant find any equations online
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1 vote
1 answer
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Extrapolating Oswald Efficiency Factor from CL^2 vs CD Graph

I have plotted this CL^2 vs CD graph for a glide test performed in a flight simulator. I want to find the Oswald Efficiency Factor, e from it and I assume I can do that from its gradient. With a wing ...
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5 votes
3 answers
1k views

Are the aerodynamic benefits of winglets similar for both powered airplanes and gliders?

Are the aerodynamic benefits of winglets similar for both powered airplanes and (unpowered) gliders? (without considering fuel consumption of course)
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2 votes
0 answers
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Is there a difference from alignment with the fuselage between J79 and Spey engine versions used in the F4?

Is there a difference between the J79 and Spey engine versions used in the F4 Phantom in terms of alignment with the fuselage? It looks to me like the Spey nozzles are pointing downward.
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7 votes
6 answers
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What is the name of the effect that causes a plane in a dive to go up?

What's the name of the effect that causes the aircraft to automatically pull out of a dive and buffet up due to aerodynamic lift produced at high speeds?
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1 vote
2 answers
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How can I derive lift coefficients of wing area and horizontal stabilizers seperately from available data?

I am fairly new to aerodynamics and I am trying to create a flight simulation based on data available for F-4E Phantom. I found various flight test data for this particular aircraft and trying to ...
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1 answer
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How can I estimate the coefficient of lift for take off?

For the CLto (take off lift coefficient), is there some way to estimate this? I was thinking of using CLmax but wouldn’t this be too big? I was thinking maybe CL cruise?
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0 votes
1 answer
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Where should vortex generators be positioned on the chord line?

Where is the best place for vortex generators? Maybe at the place where airflow speed is highest to induce strongest vortices?
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