# 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 attitude, speed, and altitude vary when increasing pitch?

I have been struggling with the following question for a while, would greatly appreciate some help and explanation why. Scenario: I'm cruising in my Cessna- cruise attitude 2300 RPM trimmed for 95. ...
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### How is Vx speed and Vy affected when climbing?

If my speed for best angle of climb is 60 and rate is 79, if I kept a 500 fpm climb to my cruise altitude of let’s say 4500, would those speed change? The flights are being done on separate occasions.
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### Why the heavier the aircraft is, the higher the airspeed must be to obtain the same glide ratio?

I know weight does not affect glide ratio. But why does higher weight need higher gliding speed?
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### 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 ...
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### FAA's Airplane Flying Handbook says more lift is necessary during a climb. Isn't it the opposite? [duplicate]

"If a climb is started from cruise flight, the airspeed gradually decreases is the airplane enters a stabilized climb attitude. The thrust required to maintain straight-and-leve flight at a given ...
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### Can I climb with no excess thrust [duplicate]

I've been searching on the internet about this question and all say you are not able to climb with no excess thrust. But I am wondering that if I have no excess thrust, can I still climb in exchange ...
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### Is more lift needed for a stabilized climb [duplicate]

First, the photo depicts a vector diagram during a climb. L means Lift. Lv means the vertical component of lift. Lh means the horizontal component of lift. T means Thrust. D means drag. W means weight....
1 vote
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### Why will all air slow down by the same amount in an adverse pressure gradient?

Boundary layer separation is caused by air slowing down to zero and reversing before reaching the end of the body. This is due to friction (viscous effects) + adverse pressure gradient. The formation ...
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### Why does a turbulent boundary layer cause more friction drag than a laminar boundary layer?

From what I understand, friction is caused by viscosity and a bigger Reynolds number signifies lower viscosity. Thus, a higher Reynolds number(i.e. turbulent flow) results in lower friction. But, ...
1 vote
250 views

### Circulation around an airfoil at negative α

I was recently reading this very helpful string What is the physical meaning of circulation found in Kutta condition? and it explained very nicely potential flow around an airfoil. My question then is ...
1 vote
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### What are some of the advantages of inverse-tapered wings?

Inverse tapered wings are rarely used in aviation. The only legitimate plane I know about with inverse-tapered wings is the XF-91 Thunderceptor. So why aren't they used. What are the disadvantages of ...
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### Does the X-59 comply with the "area rule"?

The Lockheed Martin X-59 was rolled out yesterday :-) Brett Tingley, Watch NASA's sci-fi-looking X-59 'quiet' supersonic jet roll out of the hangar, August 2023. I am no expert here (and no English ...
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### In a plane with airbrakes, such as a glider, how do slips and airbrakes interact?

While adding a slip to enhance my descent rate, I got to thinking that the airbrakes might be losing effectiveness as the slip twists them out of the relative wind. This thought arose because I did ...
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### Did the dog-tooth notches in the wing of the F-8 Crusader really have anything to do with "yaw stability"?

What was the real function of the "dog-tooth" notches in the leading edge of the wing of the Vought F8U crusader? Wikipedia says:1 Vought's design team... produced... a relatively ...
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### Why would a lower trailing edge angle allow for more rear-loading?

In reading a paper on transonic aerodynamics by Jeff Jupp (Chief Wing Designer for the A310), he states, "the trailing edge angle in modern airfoils is reducing significantly, almost to zero in ...
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### How to Define Aerodynamic Center for Real-World Airforil?

When using thin airfoil theory, there exist a point that the moment about this point does not vary with Cl, which is the aerodynamic center. However for most of the real-world airfoils, Cm does vary ...
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### How do I plot Cd vs Re graphs for an airfoil?

I am looking for a platform where I can plot the value of the drag coefficient of an airfoil for a range of Reynolds numbers (Cd vs Re plots). I wish to analyze the trend of Cd with changing Re and ...
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### Helicopter induced velocity

I found this on one book I am now reading, and I dont uderstand how induced velocity is decreasing whyle climbing? And what is the difference between induced velocity and inflow velocity ?
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### What is the formula used to display energy markers on HUD?

I would like to know what is the formula used to display energy markers on the head-up display (HUD) of fighter aircraft. Does it consist of Mach number or TAS or CAS?
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### In the gyroscopic precession left turning tendency, why does a pitch down cause a forward force at the top of the propeller?

I'm a student pilot, and all the textbooks and online resources I'm reading show a pitch down as a forward force acting on the top of the propeller (causing the resulting forward force on the right ...
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### How to calculate and understand glide distance?

How would I calculate my glide distance? If I am at 8000 feet would I multiply 1.5 by 8 because the ratio is 1.5 NM per thousand ft? Which would be 12 NM Also where did a ratio of 9:5 come from? I may ...
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### How can dynamic and static pressure be explained?

How exactly do you explain dynamic pressure? If someone asked me what the ASI reads, I would say it reads the dynamic pressure, which is the ram air pressure (total pressure) - static pressure = ...
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### Textured Spray Paint for Promoting Turbulent Flow

I'm looking for textured spray paint to apply on my RC model to ensure turbulent flow on a few of the smaller aero surfaces. Does anyone have any experience doing this and have any recommendations on ...
1 vote
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### Why does bank angle have no effect on pivotal altitude?

Pivotal altitude is the height for a given ground speed at which the line of sight from the cockpit directly parallel to the lateral axis of the aircraft will remain stationary on an object on the ...
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### What determines the direction of rotation for counter-rotating propellers?

As Wikipedia and other sources make clear, most twins with counter-rotating props are configured with the left (#1) prop turning clockwise (as viewed from behind the plane) and the right (#2) prop ...
1 vote
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### Forces acting on ram air parachute (for pulling ships)

I recently stumpled across this question about the ram-air parachutes for use in pulling ships. In this answer it is stated that the parachute needs to travel perpendicularly to the ship's motion in ...
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### Why a kite flying at 1000 feet in "figure-of-eight loops" serves to "multiply the pulling effect of the airflow" on the ship to which it is attached?

In CNN's June 30, 2023 Giant kites could pull cargo ships across the ocean – and slash their carbon emissions “What differentiates it from other wind solutions,” says Bernatets1, “is that the wing is ...
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### Does Oswald Efficiency make a significant difference on RC-aircraft?

As we know, Oswald Efficiency ($\epsilon$) is caused by change in downwash over the span of the wing, thus causing a change in effective angle of attack over the wing and therefore induced drag ...
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### Why phase lag on helicopter blade is sometimes 90°, and sometimes less?

On semi rigid rotor head, phase lag is 90°, and also the advance angle between pitch link and coresponding blade. But of fully articulated rotor the phase lag is less then 90°, and also the advance ...
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### Does the cross-sectional shape of a fuselage affect drag?

Comparing two bodies with the same streamlined longitudinal shape, and the same cross-sectional area, one with a circular cross-sectional shape, the other with a quadratic cross-sectional shape, ...
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### Can engines with a fixed nozzle in the angle of attack have the same effect as the thrust vectoring?

If the figure above represents a missile at the angle of attack and we vector resolution the thrust output from the nozzle, we can see that the thrust is divided into sine and cosine parts. Does the ...
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### Why arrow wings are more efficient than delta wings?

From page 29 of this slide (https://archive.aoe.vt.edu/mason/Mason_f/SupersonicPres.pdf), an arrow wing has higher lift slope and lower induced drag slope than a delta wing with a straight trailing ...
1 vote
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### How to calculate lift force of a revolved NACA 0009 airfoil?

How would I calculate the lift force as a function of angle of attack for a revolved NACA 0009 3D body (incompressible flow)? I have data for CL vs. AoA for the 2D airfoil, but how would I use this to ...
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### Is an airfoil's critical angle of attack measured using "geometric angle of attack" or "effective angle of attack?"

One of the first things we learn about stalls is that they occur when a wing exceeds a certain critical angle of attack, which depends on the specific design of the wing. But if a given wing has a ...
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### Forward Slip - Which speed to maintain?

Which is the proper speed to be maintained during a Forward Slip? Near Vfe or Vref? Which one will let you lower with the shorter ground distance and why?
1 vote
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### What are the flight formulas for aircraft

I am making a 2D flight "simulator" (trying to be as realistic as you can for 2d) and I need flight formulas for lift, speed and pitch. I have tried a few sites but I do not understand what ...
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### Helicopter blades flapping with the cyclic – can you help with the explanation?

I am now reading books about helicopter aerodynamics. And I have one question about blades flapping. If you push forward on the cyclic, the swashplate will tilt forward and will set the maximum pitch ...
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### What would the effect be of flap deployment on a UAV such as the Reaper or Predator?

I've read answers that said that the climb performance is usually worse with flaps extended, and the pilots would, if they could, just retract them and get into a clean config as soon as possible. ...
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### Why is the cross-sectional shape of some airliners' nose not perfectly a circle?

I found that the cross-sectional shape of some jet airliners' nose is not perfectly a circle. For example the Boeing 737 aircraft: (source: aeroprints.com via Wikimedia Commons, CC BY-SA 3.0) Look at ...
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### 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 ...
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### How to export cp vector plot obtained in xfoil?

How can I export an image of the plot showing the distribution of pressure coefficient vectors on the surface of an airfoil generated in Xfoil?
1 vote
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### Does the obstruction in a propeller duct increase exhaust pressure or decrease pressure/increase speed?

I came up with this question when looking through the answer for this question, which states that a convergent duct(obstruction) compresses the exhaust so that its pressure matches the ambient ...
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### effect of wing chord length on lift coefficient

In the bertin's Aerodynamics book It is written that reducing the wing chord increases the lift coefficient( decreases stall angle) and as a result, the wingtip stalls earlier than the wing root how ?
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### Why does thrust differ in different reference frames?

If a jet engine flies with 4 m/s in the air and we want to calculate thrust for two different reference frames, can we prove that the calculated thrust for both reference frames are equal to each ...
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### What causes the "dead band" phenomenon during takeoff on the Boeing 737?

During takeoff, the Boeing 737 encounters a distinctive "dead band" phenomenon after the initial pitch reaches approximately 10 degrees. Essentially, a slight increase in back pressure is ...
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### what is the effect of cone back pressure on shock wave angle?

this is a part of anderson's book : "Note that, for a given cone angle θc and given M∞, there are two possible oblique shock waves—the strong- and weak-shock solutions. This is directly analogous ...
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### What are the vertical pieces of metal on the Slingsby Swallow wing for?

I was watching James May's Toy Stories, particularly the one where they try to fly a glider across the English Channel. In the middle of the episode they mention a glider that was used for training ...
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### Is it possible to determine a maximum L/D possible

Over the last couple of decades L/D ratio has increased significantly. Is it possible to determine an "upper limit" on how much more potential there is for common tube-wing aircraft to ...