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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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What helicopter has the most rotor blades?

I have seen 2 rotor blades up to many and wonder when does having more rotor blades become less efficient? What helicopter has the most rotor blades? Related: Why don't helicopters prefer shorter ...
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2answers
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Why isn't the bell distribution used? [on hold]

Why has the bell distribution not become widely used? Is the bell distribution only ideal in inviscid flow scenarios or is there another reason for the lack of use?
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0answers
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Drag Coefficient of a rounded nose cylinders [on hold]

According to this pages: http://www.aerospaceweb.org/question/aerodynamics/q0231.shtml The drag coefficient of a rounded cylindrical bodies is given by this graph :http://www.aerospaceweb.org/...
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Are any commercial airliners other than the Boeing 737 MAX dynamically unstable? [duplicate]

There are many reports online that the 737 MAX is dynamically unstable. Is this unprecedented in modern commercial aviation? References: https://spectrum.ieee.org/aerospace/aviation/how-the-boeing-...
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3answers
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Why is airspeed different in climbs and descents although the AoA doesn't change?

Here are the background facts: This excercise has the objective to familiarise the student with the slow flight characteristics. The steps are: 1)Establish straight and level, 90% RPM, 15 units ...
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3answers
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Why in helicopter autorotation phase the opposing torque is eliminated?

As you many know, according to Newton's 3rd law for every action there is an equal and opposite reaction, as the main rotor of a helicopter turns in one direction, the fuselage tends to rotate in ...
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6answers
360 views

How does the engine produce aerodynamic lift at high angle of attack?

This answer asserts that "at high angle of attack the engine is producing aerodynamic lift". In the context of that answer, we are concerned about the increased torque that raises the nose of the ...
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0answers
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What is the difference between flutter and vortex induced vibration?

During flutter, the airfoil oscillates with a large amplitude, which generates vortices at the wake. In vortex induced vibration (VIV) the oscillations of the airfoil are caused by the shedding of ...
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2answers
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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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1answer
585 views

Is drag coefficient lowest at zero angle of attack?

The drag coefficient of a symmetric airfoil is lowest when its angle of attack is zero. I'm not sure if this is true in general.
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2answers
304 views

Why doesn't Stratolaunch have connected tailplanes like it has connected wings?

As a complete layman, the design of the Stratolaunch airplane, especially when reminding myself of its size, seems too flimsy, in that the only connection between the two fuselages is the center wing. ...
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2answers
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Does load factor affect roll rate?

To be clear I am referring to a given aircraft at a given weight, speed, attitude, etc everything else the same except one is at say 0.5g and the other at 2.5g will there be a difference in roll rate ...
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2answers
101 views

How does engine geometry affect flight stability?

News items around the recent aviation accidents involving Boing 737 MAX 8 aircraft suggest, that bigger engine diameter demanded for a different (longer) nacelle strut for proper ground clearance ...
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2answers
57 views

How does the advancing wing in a flat spin create nose thrust?

Peter's answer to this question leads me to another question. How does the advancing wing in a flat spin create nose thrust? I imagine this like some object spinning in a liquid. I would think ...
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1answer
74 views

Is there a way to calculate the perfect angle of incidence of a horizontal stab for a given airspeed?

I have a Grumman AA1. It’s been modified several times through stc’s to increase power and speed. The aircraft requires full nose down trim to fly level in cruise. Is there a way to calculate the ...
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4answers
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How do conventional missiles fly?

With the exception of cruise missiles, most missiles don't have any obvious lifting device. If you watch a missile being fired, prior to its rocket firing it does exactly what you'd expect: ...
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0answers
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Is there a relationship between 2D airfoil aerodynamic results and a revolution body from that airfoil?

The airfoil would be symmetric and the axis of revolution would be its chord line. Edit1: To clarify the question, suppose we have a NACA 0010. Then, using for example XFoil, I'm able to get, for ...
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1answer
3k views

Airplane gently rocking its wings during whole flight

I was on a flight with a regional airline a while ago in a Bombardier airplane (if I recall correctly) where the airplane would slowly and gently rock its wings just a little bit on the whole flight. ...
2
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1answer
368 views

What’s this vortex generator like thing below the wing?

In Barcelona’s El Prat Airport I saw some ceiling fans and noticed that they have on the lower part of the wings something that looks like a wingtip device or vortex generator. As far as I understand ...
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4answers
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Aerodynamics of lift [duplicate]

How can lift on a canvas covered airplane wing in level cruising flight be explained without introducing Bernoulli ? Both upper and lower surfaces are bulged out,which indicates lower than ambient ...
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2answers
77 views

Can I use the load factor to estimate the lift?

If I have a fixed aircraft as the baseline, then I am not sure the specific flight condition, can I use the load factor to estimate the lift on the wing?
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1answer
45 views

Why are some dynamic derivatives not included in DATCOM file? [closed]

I am trying to understand Flight dynamics, particularly I am using Missile Datcom to get aerodynamic parameters of a missile, then use MATLAB, simulink to simulate its trajectory. It seems there are a ...
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2answers
153 views

What is the difference between static and dynamic stall?

What are the static and dynamic stalls on the aircrafts wing? When would we encounter static and when dynamic one? What is the difference between them?
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2answers
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Is the physical MAX8 design bad because software is required for the aircraft to stay airborne? [closed]

I'm not an aviator by any means, but one thing that has come up in recent conversations with friends is that the MAX8 is inherently unsafe because alone, unpowered, the craft is not 'aerodynamically ...
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2answers
953 views

Is there a conventional notation or name for the slip angle?

Angle of attack is usually designed by alpha (as in alpha_prot). Is there such a conventional notation or name for other axes? I'm particularly interested in the slip angle.
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1answer
2k views

How do ground effect vehicles perform turns?

Considering that Wing-In-Ground-Effect (WIGE) vehicles fly with a rather low ground clearance, there is not much room for banking. How do WIGE vehicles turn? Do they turn just very slow with a low ...
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0answers
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What's the theoretical background of the critical angle of attack?

The critical angle of attack seems to be at all (most?) airfoils around 15-20°. Why is that? Why is it in this range and not lower or higher? Is it just the result of optimizing airfoils? Or is it ...
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1answer
86 views

Are the holes inside the engine nacelle used for uniform intake of air? [duplicate]

I read the post here: What is the function of the holes in splitter plates? My question is, what are those hole looking things inside the engine nacelle? It seems reasonable to me that as air enters ...
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2answers
518 views

How does having a bigger engine placed slightly more forward and higher impact the plane in pitch?

I'm asking about general aerodynamics for under-wing twin-jets – I'm not after information/speculation on the Max 8 crashes/systems, but I mention the crash below because of what I see as an unclear (...
7
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1answer
126 views

What is scrub drag?

I've come across the term "scrub drag" in several papers recently, but can't find a detailed definition of this phenomenon. This is specifically in reference to aircraft and seems to apply to engine ...
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0answers
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Compute Thrust from RPM and Induced Velocity

I'm attempting to calculate the difference in thrust in a secondary propeller operating in the wake behind a primary propeller, in the context of a trailing quad-copter following a leading quad-copter ...
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2answers
68 views

Are flaps a good idea for airfoils with a lot of camber?

I have a wing with an airfoil s1223 which is an airfoil with a lot of camber. the take off distance is limited so I want to implement flaps for this issue but I have the doubt if this is a good idea.
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0answers
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What are the effective span and lifting properties of a circular wing?

Today I read an article on FlightGlobal about the Bell air taxi demonstrator. It includes some paraphrased quotes from the Bell VP of innovation, Scott Drennan, among which the following stood out: ...
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1answer
97 views

Why does transonic drag happen?

I have heard of transonic speed and it is between supersonic and not supersonic. What is it and why does it happen to aircraft and how does it produce a lot of drag. How do you prevent it from ...
3
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2answers
241 views

Does altitude influence the flight range of an engine driven aircraft?

I'm reading a chapter about flight performance during the cruise phase and the influence of altitude. My book (Aerodynamica, prestatieleer en vliegtuigtechniek by Bas Vrijhof on page 155, written in ...
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4answers
220 views

Could flaps replace spoilers by deflecting more than 90°?

Could flaps replace spoilers by deflecting more than 90° after touchdown?
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0answers
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What is the relationship between the Center of Pressure and flap deployment?

I have been reading regarding the Center of Pressure of an airfoil (Cp) and the relationship with angle of attack. What is a good way to explain in layman's terms why the pressure changes in such a ...
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1answer
158 views

Why does the A320’s maximum allowable aileron deflection decrease, rather than increase, when the flaps are extended?

According to this answer to why the A320 uses mainly spoilerons for roll control during landing, rather than conventional ailerons, the ailerons can’t extend as far when the flaps are extended, for ...
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5answers
250 views

Was the adoption of conventional tailplanes as 'everyday aircraft' inevitable, or are there other designs that can be just as good?

I originally asked a variant of this on Worldbuilding.SE, but they didn't seem to like it. So I apologize if it's out of place even here. I ask, because I've been forming in my head an alternate ...
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1answer
242 views

Could Falcon 9 fairing become glidable / flyable?

Reading and thinking about this and this questions on space exploration stackexchange, I was wondering if the fairing could shape itself, so that it becomes one stable and steerable gliding element ...
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2answers
182 views

Are there any airplanes with the Centre of Gravity behind the Centre of Pressure? [duplicate]

We are used to seeing a forward CG in all airplanes, from a small Cessna to a large Boeing. I wonder whether any airplane with CG behind wing CP exists in production? Is it even possible? If so, what ...
3
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1answer
121 views

Air flow over an airfoil

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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1answer
109 views

How to calculate the power required during transition from VTOL to fixed wing?

In a VTOL, I have calculated the power required for take off and cruise which was not difficult at all. Between take off and cruise, there is a phase where the VTOL has to transition by tilting the ...
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0answers
48 views

What is subcritical and supercritical boundary layer?

What is subcritical and supercritical boundary layer? What is the difference between them?
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1answer
94 views

Can the ball on a turn coordinator be to the full right/left while the wings are level?

Can it ever happen in a wings level flight that the Turn and Slip indicator ball is to the full right/left? If so then when and what will be the flight path of such an aircraft? Thanks in advance.
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4answers
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Would a propeller extracting air from a cylinder with holes in it be an ideal lift apparatus for a VTOL aircraft?

I am wondering if enough lift can be created for a VTOL aircraft using a propeller that is extracting air from a cylinder which is closed at one end and has holes in the top half of the cylinder. ...
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3answers
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Was the Space Shuttle aerodynamically neutral while piggybacking, or did the combination act like a giant biplane?

Trying to investigate this question, I see that 'Ask the Captain' says: The weight of the shuttle is calculated like any payload. The 747 produces enough lift to fly and to carry the weight of ...
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1answer
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How can I calculate the velocity of air drawn by a pusher configured propeller?

I am attempting to construct a model plane using Custer channel wings. In order to calculate (or at least approximate) the lift generated I need to find the speed of the air through the channel due to ...
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2answers
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How are these parameters derived from readings of sensors in an aircraft: angle of attack, slip angle, and airspeed?

From what I've learned, the reading comes from an angle of attack sensor and a slip angle sensor. Let's call the readings $\hat\alpha$ and $\hat\beta$ respectively. These are of either the ...
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3answers
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Why does an aircraft's nose tend to pitch downward at higher bank angles?

In the usual aircraft configuration, the center of lift is located behind the CG producing negative pitch moment (the horizontal stabilizer counteracts it by producing downforce - positive pitching ...