# 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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### Helicopter total power required: zero wind speed while climbing --vs-- down wind speed while hovering

I've been stumped on this for a while. Let's say you have a helicopter in climb mode (i.e., 100 ft/min) with zero wind speed present. Would the total power requirement be the same as if the helicopter ...
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### The F104 tail pipe is not parallel to the runaway when the aircraft taxi.What is the reason?

The tail section is upward for clearance or to vector up the engine exhaust that will help to rise the nose when the aircraft take-off?
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### Streamwise Pressure Gradient on Curved Walls

Could someone help me to understand how can a wall generate differents streamwise pressure gradients just by its curvature? I can understand how it works in cross-flow (perpendicular to the streamline)...
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### Other than looking cool, what is the reason behind the TSR-2's anhedral wingtips?

Pretty much what the title says. What is the purpose of the TSR-2's anhedral wingtips? I've heard someone say that they use it to counter yawing I think but is this the true reason or is it something ...
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### Can an aircraft use ram air to generate power while flying?

I am a student carrying out a project focused on efficiency on aircraft. I have arrived at an idea I believe to be feasible. I am looking for suggestions, specification of what I would need, and any ...
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1 vote
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### Lift direction at non-zero angle of attack for a swept wing, or for a straight wing in sideslip

When the direction of forces is popularly explained, they say "the lifting force is directed perpendicularly, and the drag force is parallel to the oncoming flow". But what if it's a swept ...
2k views

### Why are the trailing edges of wings not always made as 'sharp' as possible?

I noticed that wing trailing edges of new airliners like A220 (CSeries) are not completely sharp. Instead, they are blunt. I always thought that the sharper the better in subsonic flow. What is the ...
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### Thrust = Drag. What about Power?

Understanding all this has been a work in progress, but now from start to finish we have: Fuel/second ---> shaft Horsepower---> RPM ---> Thrust ---> Drag Drag Force = $\rho$ × Area × ...
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### Subsonic Bump Inlet?

Contemporary high-performance supersonic aircraft such as the F-35 use bump inlet (alternatively known as DSI). These have a sophisticated 3-D bump that causes a 3-D weak shockwave in supersonic ...
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### Why use indicated airspeed instead of dynamic pressure [closed]

It uses the difference between total pressure and static pressure, provided by the system, to either mechanically or electronically measure dynamic pressure. The dynamic pressure includes terms for ...
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### Making sailplane go faster

Sailplanes have much higher L/D than jetliners. But they are three times slower. Is it practical to make a vanilla sailplane glide at 600mph by lifting it to a ridiculous altitude? If so, what would ...
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### A Confusion about Digital DATCOM Calculations of a Tail Pitching Moment Coefficient

I'm using D DATCOM to estimate cm-alpha curve for a small tail planform with NACA-0012 airfoil using the namelist (\$HTPLNF). When taking the Tail planform aerodynamic center, ac (about 25% of MAC), as ...
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### Why do the wings in these pictures go from swept back to parallel with the airflow? [duplicate]

To better understand my question, look at this A320 below As you can see, the wing becomes parallel with the airflow at the wing root. Same thing on this 737 But this is not found on bigger planes ...
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### Will two counter rotating vortices cancel each other?

Suppose that an aircraft flies with its wing through a tip vortex of another aircraft which flew in the opposite direction. Suppose that the shed wing tip vortex of both aircraft are exactly the same ...
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### Lifting-Line Theory - Numerical solution for a wing with dihedral angle

I'm trying to calculate lift for a wing with a dihedral angle using the Lifting-Line Theory. While using the thesis "Non-Planar Lifting-Line Theory for Fixed and Deformable Geometries" as a ...
1 vote
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### What happens to aerofoil downwash with Flaps extended vs retracted and how does it affect the Tail down force?

In my logic: Flaps extended will cause a greater Angle of Attack, to maintain Straight and Level Flight, AoA will be reduced, due to the increased "Surface", this allows to fly at lower ...
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### Why does an aircraft fly a looping when pulling the stick?

let's assume an aircraft flies in straight level flight in the direction of an x-axis with an angle of attack of 3°. When the pilot pulls the flight stick, an additional lift is produced which acts ...
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### aerodynamic forces on an engine cowling

In Mendenhall's book about the Gee Bee racers, he describes that on the Models Z, R-1, and R-2, there was a strong tendency for the engine cowl to get pulled forward and into the prop during races, ...
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### Why cut off the tips of a delta wing to form a cropped delta?

According to wikipedia, the reason to cut off the tips of a standard delta wing is maintain lift outboard and reduce wingtip flow separation (stalling) at high angles of attack This type of delta ...
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### P Factor vs Spiral Slipstream

Does anyone know of any real aeroplane or wind-tunnel tests that quantifies the effects of asymmetric propeller blade loading (P factor) versus the Spiralling Slipstream effect in creating yaw. Which ...
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### What are the aerodynamic characteristics of the flying saucer?

It seems that Canadian VZ-9 Avrocar was aerodynamically unstable. Particularly at high altitudes, and so the project was cancelled. IIRC there was considerable interest in flying saucers in the 1950s ...
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### Does the 787 vertical stabilizer have a connection fairing?

In general, a vertical stabilizer connected with the fuselage will form junctions. The junctions trigger a mix of airstreams, and causes interference drag. A fairing is used the ease the sharp ...
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### Between hover and moving straight forward, which one is this Sikorsky uses more power?

Source: Consider this Sikorsky–Boeing SB-1 Defiant is being flying forward level and straight and being hover, which state is consumes more power? For both states, we assume that air is very still and ...
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### How the placement of the pitot and static ports decided?

Forgive the this topic placement as it might be similar to other older ones (Although I a bit sure that the main contents might be different than other older ones). In the upcoming days I will have a ...
1 vote
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### Does the reduced aerodynamic damping at higher altitudes affect the Vno (maneuvering speed) of an airplane?

Since reduced aerodynamic damping at higher altitudes reduces the needed control input for maneuvers, is this just about the required force to move the controls or also about the speed of the ...
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### Lateral Aerodynamic Derivatives from Digital DATCOM

As far as I know the Digital DATCOM can be used to estimate longitudinal aerodynamics by varying the angle of attack. Does it have the capability to vary sideslip angle for lateral analysis? and How? ...
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### What is the most efficient way to reduce interference drag when surface imperfections are unavoidable?

Interference drag can start to appear when there’s imperfections or excrescences on an aircraft outer surface. For example the following image shows some of these typical imperfections: Source of ...
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### If a hot air source was added to the wingtips, would it help control the formation of wingtip vortexes?

Let's say that somehow, an engineer made an exhaust pipe that constantly sprayed hot air at the wingtips in order to help control the formation of less turbulent wingtip vortexes. Would that have any ...
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### Are Foward Swept Wings for a Rear Propeller Airplane Feasible?

Would going with a forward swept wing design, with the same cord and length of the "A Wing", bring more air the the propeller and tail to increase range, power, or stability? Consider the ...
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### Do tufts show boundary layer flow or outer flow?

Outer flow and boundary flow are often different. Do tufts at the wing surface show boundary layer flow or outer flow? Picture source. Paint shows boundary layer flow. Picture source
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### Landing gear drag and weight calculations

I have read numerous books and researches, but I couldn’t find any formulae that actually work for how to calculate the following (for commercial aircrafts): 1- Drag coefficient for a retractable ...
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### Why do helicopter performance charts for hover out of ground effect (HOGE) have a "knee"?

Have a look at the following performance charts from Section 5 of Robinson R-22 Pilots Operating Handbook for hover out of ground effect (HOGE). If the temperature and gross weight are known, the ...
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### What is this phenomenon and why does it happen? [duplicate]

I captured this phenomenon occurring on a recent flight trip during the landing. I'm not sure why it happens or what it's called, but I thought it could be some form of condensation. I came across the ...
536 views

### Why do modern turbofans have swept blades?

(Picture sources: CF6 and GE90) Aircraft have swept wings for two reasons: It reduces the thickness-to-chord ratio of the effective chord, which is ideal for flight at higher Mach numbers. At ...
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### Why do helicopters experience a brief dip in altitude during IGE marginal power takeoffs?

The scenario is this: A helicopter is hovering IGE, and executes a marginal power takeoff. What causes the dip in altitude that occurs around 10 knots during the takeoff? Most pilots seem to describe ...
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### The Aim 9 missile mounted on the left side spin in the same direction as right side mounted after launching?

When the AIM 9 sidewinder missile is fired the spin is in the same direction?
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### How to calculate wing upwash angle?

How can I calculate upwash angle(alpha u) at the wing? I notice at every position upwash angle is different, which angle is chosen as the reference upwash angle?
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### What limits maximum Cl of wing with active jet blowing ("Blowing BLC")?

Maximum lift coefficient of wing (single-element or multiple-element) without suction or jet blowing are limited by boundary-layer separation(flow separation). Wings that use jet blowing for boundary-...
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### Does climbing or descending affect the rate of turn?

In the past, I used to have this idea that if all other factors remain constant, then climbing increases the rate of turn while descending decreases it. This idea was most likely planted into my mind ...
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### How is blended winglet better?

*Make sure to read the following as I cannot explain my question in one sentence Winglets are a kind of wingtip device that is installed on an aircraft to reduce drag and improve fuel efficiency. ...
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### Under what conditions do airplanes stall? [duplicate]

I've seen somewhat conflicting information on when planes stall. I've seen references to "stall speed," apparently a speed below which the airplane will stall, but stalling also seems to be ...
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### Can wingtip vortices formed around an unswept wing produce vortex lift?

Vortex lift is a kind of aerodynamic lift force due to vortices formed along the leading edge of highly-swept (usually 60 degrees of swept angle or higher) wings at high angles of attack. The "...
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### Would the dle 55ra engine be enough to power my paramotor(ducted fan)?

I plan on using the dle 55ra engine to produce 5hp at 8,500 rpm. I am using it in a paramotor, and to save space I am considering using a ducted propeller similar to the Fulcrum power pod. The duct ...
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### What is the glide ratio of the Ozone Mojo Power 2?

The ozone mojo power 2 is a paramotor wing aimed towards beginners. I am interested in purchasing it, however I have not found any data on the lift to glide ratio. Does anybody know this info?
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### What was the Vbg and glide ratio of the Rutan VariEze and the Beechcraft Starship?

These pusher designs were marketed featuring high cruise efficiency. No doubt the pusher configurations offered advantages in propulsion efficiency and cabin comfort, but how did this compare to ...
1 vote
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### 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 ...
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### 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. ...
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### In a CFD simulation the wingtip vortexes gets reduced/cancelled by means of Wingtip End Plates- if this is true is it then useful?

I am just working on a special kind of wing and I do named it a Transformer Wing. The transformation is about the wing camber. The main requirement of the project is that the wing is to be not ...
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### Does the rotation direction of intermeshing rotors have any noticeable effect?

Consider the Kaman K-Max, which has intermeshing (side-by-side) rotors that rotate as indicated below (when viewed from above, the rotor on the right (green) rotates clockwise, the left one (red) ...
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