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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1answer
22 views

What is effective airflow?

As I understood when relative airflow meets wing it changed and resulting flow is called effective airflow?
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1answer
102 views

Is the airspeed for the minimum the same for the theoretical power required curve as for the shaft power required curve?

I am aware that the efficiency of the propeller implies a difference in the values of the theoretical power required curve and the corresponding shaft power required, but does that efficiency ...
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82 views

In flat spin is rudder deflection used for recovery of the F16?

If the horizontal tails is used due MPO switch in recovery of the flat spin, is the rudder used for stopping the yaw of the F16 ? I know that for inverted flat spin is surely used, but I believe ...
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If an fighter jet that it have twin rudders, in use the angle of deployment it is not identical. Which is more deflected and why?

If an aircraft have two vertical tails then pilot push in the rudder pedal the rudders will not be deployed at the same angle.It is used throughout the all envelope of flight or is it possible only ...
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3answers
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How to calculate lift and drag coeffecients for VTOL aircraft in the takeoff stage?

How would I calculate CL and CD for a VTOL aircraft while it is in it's takeoff/landing stage? The particular aircraft is a fixed wing/quadcopter hybrid so I know that I can treat this as a thin ...
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1answer
77 views

What airfoils are used for the current generation of general aviation VTOL aircraft?

What airfoils are used for VTOL ultralights at 60-70 deg AOA without flaps or slats? An example of this would be the Blackfly with a takeoff distance of 3', about 25% of it's own length....!!!! I ...
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2answers
124 views

A Twin made from two Cub J3s [on hold]

I plan to merge two Piper Cub models by shortening the port wing on one of them, and the starboard wing on the other. How much would I need to cut off to still have a similar climb out (using the ...
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1answer
66 views

Why do oblique-wing aircraft suffer from significant aerodynamic cross-coupling?

Oblique-winged aircraft (which have one long wing that pivots around a central point, so that the wing is straight at low speeds but strongly-swept - one side forwards, the other side back - at high ...
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1answer
186 views

Would a triplane be way more efficient if the wings intersected at the tips to create one wing tip vortex instead of 3?

Would a triplane be way more efficient if the wing tips were joined at the tips to create one wing tip vortex instead of 3, at RE 200-600k? At that low of a speed, I assume interference and form drag ...
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Do contra-rotating props have worse tip vortices than single props?

As I understand it, blades from a propeller have their own tip vortices, because the blades produce lift via the same aerodynamic principles as wings. So they must have tip vortexes too. So with ...
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1answer
206 views

Do wings on a plane need to be in the same plane horizontally, or can one wing root be 6" lower than the other?

Do wings on a plane need to be in the same plane horizontally, or can one wing root be 6" lower than the other? The proposed application would be for a ultralight with high mount folding wings, where ...
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Does a windmilling propeller create more drag than a stopped propeller in an engine out scenario?

For this question lets assume that we are talking about a fixed pitch propeller and not a variable pitch propeller. I do understand that variable pitch props should be feathered during an engine ...
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58 views

Do most aircraft require a nose-up attitude for level flight? [duplicate]

I recently saw a picture of a HUD on a commercial plane, and I noticed the nose was level to the horizon but the flight path indicator is almost always under the horizon line no matter the speed, does ...
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3answers
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What is the direction of the sideslip induced by roll on a conventional aircraft?

For the sake of this question let's assume that the considered aircraft is an A320. The question is what is the sign of the aerodynamic $C_{n_q}$ coefficient? In another word, when the aircraft starts ...
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5answers
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Where is the 'zone of reversed commands…'?

There seems to be some confusion about where the 'zone of reversed commands' really is, i.e. where a decrease of airspeed results in an increase of drag. Some references place that zone to the left ...
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Can airflow reverse over the flight surfaces of a uav in high wind conditions

Can airflow reverse over the wing of a uav in high tail winds and low forward airspeed i.e 25knt fwd airspeed in a 35 knt tailwind? What would be the overall effect on the elevator and rudder? I ...
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Does slipping in turns allow higher climb rates?

Sailplanes, among others, use a cotton string to show the sideslip angle. I've often heard that while circling in thermals the cotton string should show a slight slip angle to climb faster. This ...
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4answers
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How is a sideslip maintained (aerodynamically)?

(Public domain image that I've modified.) The initial rudder deflection to the left creates a side force that points right and yaws the plane to the left. NASA puts it this way: For the vertical ...
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Does the F-16 Alt. Flap switch lock the leading edge flaps in place in an emergency?

The Alt. Flap switch is useful for the interception of slower aircraft (Cessnas, Diamonds, etc) at speeds around 145 knots but at the same time you'd have only half of the F16 roll and sluggish gains.
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1answer
252 views

What is the effect of airflow speed on separation?

We know that in real viscous flow, boundary layer exists around the airfoil and there will be a separation point which flow starts to separate from the back of the airfoil( velocity gradient equal ...
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2answers
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At what angle-of-attack (sideslip angle) would a symmetric vertical fin plus a deflected rudder have a lift coefficient of exactly zero?

For rudder deflection angles of 5, 10, 20, 30, and 45 degrees, at what (negative) angle-of-attack does a fin-rudder combination (including dorsal fin if present) have a lift coefficient of exactly ...
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Why does a T-tail produce a pitch-down moment in sideslip?

Here is something which I did not find in any book, but confirmed in several wind tunnel and flight tests: A T-tail causes a strong nose-down moment in sideslip. This can even be observed in a ...
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3answers
135 views

Is a high alpha sideslip possible and safe?

Is a high alpha sideslip possible and safe? We use a sideslip to increase drag when trying to reduce altitude before landing on a short runway, etc., which is crossing your rudder and ailerons, to ...
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1answer
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Downwash distribution on basis of Lift distribution

I am new here so I might make some elementary mistakes. Correct me if I am wrong. I just stumbled upon the downwash distribution for a given lift per unit span distribution along the wingspan. I have ...
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What are the relative contributions of the body and wings to missile lift?

Slender bodies like arrow shafts, airliner fuselages, and submarine hulls are all capable of generating lift, albeit much less efficiently than a high aspect ratio wing. They also generate little drag,...
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105 views

In fighter jets, is the minimum speed calculated with the flaps in the down position or up? [closed]

I asked that question because F16 flying straight and level at minimum speed does not have flaps down. So how is the minimum speed calculated by aircraft designers?
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1answer
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Types of canards (active and free in slipstream). Why? [closed]

There's ones that's moving free in slipstream , and another's is actively working by the aircraft actuators. Why?
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107 views

What are the speeds for absolute ceiling and coffin corner?

This picture is taken from Safety First (Airbus magazine). Could you please clarify some things: 1). Is "Absolute aerodynamic ceiling" = "Coffin corner"? 2). Have I correctly understood that there is ...
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1answer
66 views

How to calculate aerodynamic efficiency at minimum power conditions?

The drag polar of a propeller driven aircraft is $C_{D}=0.039+0.071 C_L^2$. The lift curve slope of the wing ($C_{L_\alpha}$) is 0.09/deg and zero lift angle ($\alpha_{L=0})= -1.5^o$. Stall angle of ...
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137 views

Does a left spin differ from a right spin for a single-engine propeller aircraft, in terms of spin characteristics & ease of recovery?

Given a single-engine propeller aircraft with its nose-mounted propeller rotating on the right-hand side when viewed from the cockpit, and given the typical effects like P-factor, prop-wash and ...
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2answers
4k views

Why is the wrong explanation of “air travels a longer distance and creates a lift” so popular?

When I was learning for my license, one of the first diagrams I remember was about the wing profile. The air going around the wing and on the upper side it has to travel a longer way, thus generating ...
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How do wings generate lift?

Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?
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Why are some Tomahawk missiles' nose duck-nose shaped?

Why there is a duck-like shape in this Tomahawk missile's nose? I see this shape in most Tomahawk images; however, not every Tomahawk's nose is shaped like this. If it is an aerodynamic feature, ...
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How to calculate the moment/torque at the center axis of a blade?

How do I calculate the moment/torque at the center axis (same plane with lift and drag force) of a blade with NACA airfoil standard when it is placed inside a wind tunnel or exposed to airflow?
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2answers
185 views

Why the Mig21 don't use the ailerons like control surfaces on delta wings at landings or take off?

Mig21 is a delta wing , so why do not use the ailerons like any other delta's ? For lowering the approach and touch down speed. It is not possible that?
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When a B-2 takes off, does it use some device to ionise the airflow in front it?

At takeoff, does the B-2 use some sort of ionization device in the leading edges of its wings?
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1answer
345 views

In F-16, is rudder used to arrest the adverse yaw effects (by FBW) in direction of roll during an aileron roll? or opposite way?

Is the rudder moving by FBW in direction of roll or in the opposite direction? I understand that the rudder is used due to the ARI system (ailerons - rudder interconnect), but don't have any idea ...
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3answers
193 views

Does a biplane need wing twist?

Does a biplane need wing twist? I understand wing twist is used to: creat a soft/partial stall ( hopefully create a partial stall before a full stall) balance the wing so a smaller horizontal tail ...
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3answers
7k views

What are the advantages and disadvantages of an oblique wing over a swing wing?

This question asks about the benefits of an oblique wing over a delta wing, but I am more interested in the benefits of an oblique wing compared to a swing wing. Wikipedia states: This is a ...
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3answers
1k views

What are the benefits of a pivot wing?

The answer to another question mentions the rather unusual pivot wing. From an aerodynamical standpoint, what are the benefits of an oblique wing compared to a delta, a trapezoid or a forward swept ...
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What are the benefits of a non-orthogonal (scissor) tail-rotor?

Why is the tail-rotor of some helicopters (e.g., Boeing AH-64 Apache) made of non-orthogonal (scissor) blades? What are the aerodynamic benefits (or any other benefits) compared to the orthogonal ...
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1answer
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What is the validity of doing 2D airfoil simulation for axisymmetric bodies?

I am currently working on axisymmetric bodies like fuselages/droplets etc. For this, I am interested in the point of flow separation (if there is) and velocity components at a certain point in space. ...
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2answers
2k views

Would a 737 pilot use flaps in nose dive?

Since flaps help lift the plane, would they deploy flaps if the plane was nosediving? And what would they do if the back pressure was too much? I know speed increases lift, but can full throttle make ...
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Why are the wings of some modern gliders tadpole shaped?

Why are the wings of some modern gliders tadpole shaped, rather than teardrop shaped? An example is the Schleicher ASG 29. Or did they just add a flat plate at the trailing edge for the flaps and ...
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Why the lift and drag coefficients for the simulations differ from the experimental value?

I am doing CFD simulations for NACA Airfoil 2415 using K-Omega SST model on ANSYS fluent. I am using an tetrahedral unstructured mesh with 20 Inflation layers on the wall. I have been comparing my ...
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1answer
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Does a high pitching moment symetrical airfoil exist?

Looking for high pitching moment symetrical airfoil. I understand the Zenith 701 uses a reverse NACA4412 as it has a high pitching moment. This allows for a smaller horizontal tail. What about a ...
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Are monoplane struts under tension, doubling the stress limit of the spar? [closed]

Are monoplane struts under tension, doubling the stress limit of the spar? If monoplane struts are under tension, they would be pulling the wing down, which would put the bottom of the spar under ...
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Why is the center of pressure of a rocket at its centroid?

From thin airfoil theory, at subsonic speeds, the center of pressure of any uncambered airfoil is at quarter chord. For sounding rockets, however, the center of pressure is generally assumed to be ...
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Will a self balancing wing using an Eppler 186 airfoil still generate a Clmax of about 3+ with slats and slotted flaps?

Will a self balancing wing using an Eppler 186 airfoil still generate a cl of about 3+ with slats and slotted flaps? Although the NACA2415 used in the pegasus wing for the Zenith 701 has a low Cm, ...
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1answer
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How do I obtain the max endurance altitude?

There are excellent explanations of the physics that determine maximum endurance speed here, here, and here. I was thinking of aircraft that have to be "on station" without an indicated altitude and ...