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
84 views

Would plain and slotted flaps increase lift substantially in a distributed propulsion application?

Would plain and slotted flaps increase lift substantially in a distributed propulsion application for a slow moving aircraft (15mph)? I understand that: A classic NACA foil without flaps such as the ...
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3answers
96 views

How do I simplify explanations for the drag formula?

With reference to aircraft aerodynamics: As the aircraft speed increases the aerodynamic load increases in a mathematical relationship proportional to the air density and the square of velocity. ...
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5answers
441 views

Why is fuel quantity expressed in flight hours [duplicate]

Going through a few aircraft documentaries online, I've noticed the thing that they usually express the fuel quantity in flight hours. Ex - A 747 burns 4 litres of fuel every second. So with a ton of ...
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1answer
57 views

On an aerofoil or circular cylinder why does the airflow stay attached after passing the point of maximum thickness?

Why does it follow the curvature rather than separating? Its not due to the coanda effect as the accelerated flow near the surface of the aerofoil can't be considered a jet. It's not due to surface ...
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3answers
91 views

Autorotation: Positive Pitch during descent phase possible?

I was wondering if a rotorcraft, that descends very slowly compared to its nominal rotor rotation rate (for example an RC Helicopter vertically autorotating with 3m/s descent rate and 2200RPM on the ...
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1answer
107 views

Can a wind tunnel simulate airflow when a vehicle goes around a curve?

In real life, airflow in a turn is curved, how does a wind tunnel simulate this condition? If we just yaw the test object at some angle in wind tunnel, do we simulate the airflow in correct way?
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1answer
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Resultant force vs AoA, pictures?

Interesting to see how resultant force point backward from 0-10 AoA and point forward from 10-40 AoA in respect to vertical of chord line. I find picture(below) very rare in aero-books,if someone ...
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7answers
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Why is there a a nose-up pitching tendency during a forward slip in a Cessna 172?

Why is there a tendency for the nose to pitch-up during a forward slip in a Cessna 172 (According to the TC Flight training manual)? Quote: "If full rudder is used, considerable aileron pressure ...
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3answers
116 views

What is airflow direction in turn?

Let imagine that we put wind indicator on rotating merry-go-around. Will wind indicator stay prepedicular to the radius of circle,showing tangetinal airflow velocity? (Wind indicator has equal mass ...
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2answers
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Does the Fairchild Metroliner have any unusual handling characteristics?

I have been told by several people that the Fairchild Metroliner is a quite difficult to handle aircraft. Aside from that, I have seen that it has suffered several accidents throughout its history. ...
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1answer
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Why not always take off with 10 degree flaps in a Cessna 172?

10 degree flaps increase our lift, reduce stall speed, reduce ground roll. Seems like all advantages with no disadvantages. So why does the Cessna 172 POH say normal take off is 0-10 degree flaps? Why ...
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2answers
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Why can airliners not fly as fast as fighter jets? [duplicate]

Why do passenger aircraft not fly at the speed of fighter jets? What factors stop them from achieving such speed?
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81 views

Different reference area change value of Cl and Cd [duplicate]

example: wind tunnel meassure wing lift=5000N frontal area is 2m2 planform area is 15m2 air 1,2kg/m3 airspeed 50m/sec Find Cl? if we use frontal area Cl = 1.66 if we use planform area Cl=0.22 So ...
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1answer
109 views

What is the angle of Incidence of wing of Airbus A320?

What is the Angle of Incidence/ Mounting Angle of the wing of AIRBUS A320?
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1answer
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What are some specific benefits of cryogenic wind tunnels?

What are some benefits to using a cryogenic wind tunnel over a more traditional one? Are there certain aerodynamic properties or principles that are better studied at low temperatures?
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1answer
60 views

Does the stability of a mass change if the center of gravity is above or below the point of thrust? [duplicate]

I was wondering if it makes any difference if the mass is balanced above or below the point of thrust. See image below for clarification: In the image you can see two configurations. The red arrow / ...
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0answers
53 views

What slows down industry for switch to aeroelastic design? [closed]

Aviation goes step by step toward birds! When we cut tail rudder,use bell lift distribution and make aeroelastic wings we will become birds!:) What stop industry for switch to aeroelastic desing,...
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1answer
36 views

Can an airfoil have multiple aerodynamic centers?

Aerodynamic center is a point where the moment is independent of angle of attack. Can we have 2 or more such points? Does it necessarily lie inside the airfoil?
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2answers
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What are the correct names for the two faces of an airfoil?

When representing a wing airfoil, often the low pressure is on the top side and the lift is positive: In this case upper and lower sides are enough to understand the role of the surfaces, But this is ...
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2answers
100 views

Which industry started to develop CFD software?

Which industry first started to develop CFD? (aviation,car-industry,meterology or maybe someone else)
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1answer
55 views

Navier-Stoke vs Prandtl lift calculation

Why Prandtl had need to calculte lift with his lifting line theory (1933) if Navier-Stoke published equation long time ago 1822? Also Navier-Stokes option is far more "accurate" then lifting ...
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4answers
150 views

Will it be more efficient if airplanes flap like birds? [duplicate]

Many airplanes have parts that are designed to mimic some features of animals. I have also read that birds are incredibly more efficient than most of the airplanes we see today. I wonder, will the ...
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1answer
39 views

If the VVI, FPM, airspeed indicator somehow failed you can use fuel flow to help you with your attitude (climbing or descending)?

If the VVI/attitude indicators , FPM, airspeed indicator somehow failed same time and now you could not get cross control check, can use fuel flow counter(because of the decrease consumption rate) to ...
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1answer
68 views

Which among the two contributes most of the lift, the upper or lower surface of the airfoil? [duplicate]

I see some explanations that lift is due to the suction of low pressure on the top surface of the wing and deflecting down of airflow on the bottom which results to upward force lift. I wonder, which ...
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2answers
99 views

How far away should the vertical stabilizer be from the leading edge of the main wings?

I am wondering what the advantages and disadvantages are of placing the vertical tail nearer to, or farther from, the main wing. For instance, when the vertical tail is just behind the wing, do the ...
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How accurate is CFD software compared to wind tunnel tests? [duplicate]

How accurate is computational fluid dynamics (CFD) software compared to wind tunnel tests? (I mean CFD computed with super-computers like the aircraft industry has.)
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1answer
137 views

Which CFD software is used in Boeing and Airbus? [closed]

Which Computational Fluid Dynamics (CFD) software is used in Boeing and Airbus, and in the aircraft industry generally?
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2answers
164 views

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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3answers
1k views

What is compressibility drag?

I don't mean wave drag here. What is compressibility drag, which is understood to be a form of miscellaneous drag?
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0answers
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Why does drag coefficient decrease with Mach number in the supersonic regime?

I'm trying to understand why the drag coefficient decreases in the supersonic regime with Mach number. While it is easy show this using supersonic, potential flow theory, I'm looking for a more ...
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How to correct dynamic stability of UAV fuselages?

I was trying to design a fuselage model of UAV with considering lift coefficient (CL), after this I analyzed stability of both wing on fuselage. First I did the individual analysis for wing and ...
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1answer
83 views

what is the actual force causes this issue according to IAS that shows normal descend speed?

When we have tail wind during approach , with respect of Aerodynamic forces that effect on airplane , the whole part of fuselage move forward due to tailwind, also we have about 70kts IAS (in general ...
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Why doesn't DATCOM calulate variation of pitching moment due to elevator deflection above certain altitude?

I'm trying to get the "Cmδm" (variation of pitching moment due to elevator deflection) thanks to DATCOM. I do get these coefficients at low altitudes but above around 10 000 meters all ...
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1answer
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When using the Source Panel method and dealing only with sources and sinks, why do lift and drag equal zero?

I am trying to deal with the airfoil with the "Source Panel method", and when I try to calculate the lift and drag, they always equal to zero. And I have found an explanation in some ...
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1answer
94 views

Is there any specific location on airframe for gaining higher drag?

I have a model rocket and I want my rocket to reach specific height above the ground level. As soon as desired height is reached, an air brake (umbrella type) is allowed to deploy. In order to have ...
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4answers
3k views

Why do airfoil's trailing edges point downward?

The trailing edge of and airfoil is mostly pointing downward. Is there any reason for that? Down wash increases drag and down wash is due to the direction of air pointing down. If the trailing edge is ...
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0answers
57 views

How calculated the drag coefficient lift coefficient with pressure coefficient?

I have got the Cp Plot on a wing, now I am trying to calculate Cl and Cd. And the angle of attack is 0 degrees, the wing has been split into N Panels, and the normal vector ni for every Panel is ...
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1answer
168 views

How does a diffuser (in ground effect) accelerate the air in front of it?

A diffuser reduces speed and increases pressure, so how does a diffuser accelerate air in front of it if we have an adverse pressure gradient situation? Wouldn't be better that we put the lower ...
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1answer
134 views

How is true airspeed measured?

Now, indicated airspeed is pretty much the dynamic pressure that air is creating. What about true airspeed? How do the calculations go about factoring out all the wind patterns and finding the speed? ...
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4answers
4k views

How do I choose the correct airfoil?

I am currently working on a personal single seat, piston aircraft that I would fly myself and I am currently in a bit of conundrum when it comes to my wing design. In this project, I assigned us in 2 ...
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1answer
153 views

What methods are used for calculating maximum takeoff windspeed of a helicopter?

I would like to calculate the maximum windspeed in which a helicopter may safely take off and safely land, assuming a theoretical wind environment with constant wind direction and no gusts. I ...
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2answers
74 views

Why doesn't a wing in supersonic flow produce a shock that results in flow parallel to the leading edge?

When we look at a wedge in supersonic flow, a shock emanates from the leading edge such that the flow after the shock is turned and is parallel to the airfoil surface. The shock angle is based on the ...
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1answer
160 views

How do I calculate the total cruise power from the propellers accounting for the losses?

Let's say I have an aircraft with four propellers (see diagram below) and I am supposed to calculate the cruise power required to drive the aircraft forward. The wing creates the lift and propellers ...
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2answers
2k views

What is the pressure distribution around a supersonic wing?

In subsonic flight the lift manifests itself at 25% of chord, but shifts to 50% of chord when the airplane goes supersonic. Wondering about that made me think that the reason might be that there is ...
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3answers
335 views

Is a jet engine's shaft neutral in the direction of thrust?

I think I read somewhere that the forces on a jet engine shaft is neutral because the forces at the turbine and compressor cancel out. This means that the axial bearings don't have force on it in ...
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3answers
4k views

Do aircraft at cruise bob and/or skip?

Recently I started flying a model aircraft, admittedly a kindness for a motor stuck onto a piece of foam, and have noticed that it either bobs, for lack of a better term, like something afloat on ...
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7answers
4k views

Plane that always flies into the wind?

Suppose that you dropped an uncontrolled, dummy glider into the air. You want it to always face into the wind by design. Would it be possible? If so, what would such a plane look like?
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Stability Analysis of Aircraft

How can we do the complete lateral, longitudinal, and directional stability analysis of an aircraft by drawing appropriate geometry? I tried DATCOM+ but it has certain limitations. Is there any other ...
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1answer
102 views

Does the strength of a wingtip vortex generated by an airfoil peak at the critical angle of attack?

I know that generally, wingtip vortices increase in strength as the angle of attack increases. Is the critical angle of attack/Cl Max the peak strength, or do the vortices generally continue to ...

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