# 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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### Formula for comparing drag on planes flying at different speeds at different altitudes. Ex: Mach .80 at 40,000 ft, vs Mach 5 at 100,000 ft

I am interested in getting a sense of how much extra energy is needed to overcome drag at different speeds and altitudes. For example, for me a baseline would the drag on an airplane flying something ...
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### Why are vortices produced at wingtips a source of drag, while vortices from the leading edge (harnessed by delta wings) good?

From my understanding, wingtip vortices produce a downward force on the aircraft, effectively increasing drag. Meanwhile, when considering leading-edge vortices on delta wings, we only consider the ...
1 vote
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### Model of aircraft banked turn

I'm trying to write a model of aircraft motion during a banked turn, so for say a 60Degree roll angle constant altitude turn will require 2g lift. However to achieve this lift the aircraft has to ...
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### Does a wing produce an appreciable amount of lift during the takeoff roll prior to rotation?

I was hoping for some insight on this, perhaps also from pilots who have used AOA indicators. This because I assume that an AOA indicator is the only means to get at least an idea of how much lift is ...
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### How can I design a slotted flap?

I have not been able to find satisfactory methods on design of slotted flaps, or flaps in general. Most of the answers are about eyeballing or experience. Can you guide me on what could be good ...
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### Is thrust larger than weight in a vertical climb?

Image source Very much related to the many questions and great answers to lift and weight in a climb - if an F-16 climbs vertically at a constant speed, is thrust greater than weight?
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### What's the difference between an accelerated stall and a dynamic stall?

I am a commercial pilot. I always like to understand everything in detail, so here's my question: What's the difference between an accelerated stall and a dynamic stall? For example, in a high-speed ...
1 vote
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### Servo-actuated aerofoil

I intend on calculating the the servo torque required to actuate a 75mmx38mm NACA0012 airfoil. The example at the end of the page in the link https://github.com/build-week/hover-jet/blob/feature/start-...
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### Is it possible for an airplane to enter another airplane? [duplicate]

I was making some cool fictional airplane designs and realized that most of my larger airplanes have a bay inside that stores a plane or two. But then I thought, is it even possible to make a plane ...
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### Does it make sense having a MiG 19 fuselage 'area ruled'? [closed]

If the MiG 19 fuselage diameters followed the Area Rule, instead of being a constant size cigar, perhaps transonic performance will be improved; someone answered to this question elsewhere indicating ...
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### Getting the cl vs aoa plot from Cp distribution

I am making a CFD simulation where my goal is to calculate the section lift coefficient vs angle of attack plot of an airfoil. From Fundamentals of Aerodynamics (Anderson, 2018), I get the following ...
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### Is there a limit to how large an airplane wing can be? [duplicate]

There are some agreeably large planes out there, like the C-5 Super Galaxy. But how big can these planes' wings really get? The heavier the plane, it is usually larger, and with size of the fuselage ...
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### Could the Mars helicopter Ingenuity have been test-flown outdoors at JPL just for the heck of it? (not that they would)

The Ingenuity helicopter that has flown on Mars is designed for roughly 0.01 bar pressure and a colder atmosphere made of mostly CO2. See links (including video) in this answer to What JPL laboratory ...
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### Definition of aircraft longitudinal axis?

I know that longitudinal axis connect nose and tail, but at what exactly point? What definition says? I have a glider and I want to draw with pen longitudinal axis to measure angle of incidence for ...
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### Would this mechanical apparatus be a new means of creating aerodynamic lift? [closed]

I recently came up with a conceptual idea for creating aerodynamic lift which would use an unconventional centrifugal impeller. I would like to know if this conceptual design of mine is something that ...
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### Can gliders and single-engine planes have vortices?

I read, A third physical explanation of the source of induced drag is that the wing tip vortices contain a certain amount of rotational kinetic energy. This energy has to come from somewhere; indeed, ...
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### In constant speed propeller, if i increase RPM lever from 2300 to 2500, will the Blade AOA decrease?

Assume I am flying straight and level with power setting 21 inches of MAP and 2300 RPM with TAS=100 kts, now I change my Prop lever only (MAP = no change & TAS = no change) from 2300 to 2500, ...
1 vote
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### What is the correct definition of "spanwise" and "chordwise" with a swept wing?

What is the correct definition of "spanwise" and "chordwise" with a swept wing? For example, in the context of "spanwise airflow" and "chordwise airflow"? a) ...
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### In this MD-11 stall test video, are we seeing the tail stalling first?

Watching this short stall test video for the MD-11, one can notice obvious buffeting (starting at about 0:04) of the tail section, while at the same time – at least apparently – there doesn't seem to ...
1 vote
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### Does lift-to-drag ratio asymptote to 4 (or 6) at high Mach numbers?

The Kuchemann equations for L/D at high mach numbers, approximately verified by wind tunnel tests, were: $$\left(\frac{L}{D}\right)_{max} = \frac{4\cdot(M+3)}{M}$$ and, for wave riders \left(\frac{L}...
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### What is causing these "corners" on this F-104 V-n diagram?

In this V-n diagram for an F-104 (source: this Wikipedia link), on the left-hand edge of the flight envelope, what is causing the "corners" that we see at the following points? (Numbers are ...
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1 vote
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### How does the turbulent boundary layer thickness affect separation?

I read that for a turbulent boundary layer, a thicker (turbulent) boundary layer separates earlier than a thinner (turbulent) boundary layer? Why is that? Or is it the other way around?
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### Why do X-wing configurations missile/guide bombs use symmetric airfoils?

From all the missiles/guide bombs I have come across, I've always observed that a symmetric airfoil is used for both the wing and tail. Why not have a cambered airfoil for the wing and a symmetric ...
1 vote
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### How are foam cores shaped for tapered and swept back wings?

How are foam cores shaped for tapered and swept back wings? I understand that many constant chord, constant thickness rectangular wings use the same sized airfoil shape from root to tip. Let's assume ...
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### Why does Vx have a relationship with thrust but Vy has a relationship with power?

https://www.boldmethod.com/learn-to-fly/performance/vx-vy-altitude-and-where-they-meet/ After I watch this article, now I understand the relationship between altitude and the rate of climbs. But I ...
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### How does airfoil affect the coefficient of lift vs. AOA slope?

I'm trying to understand whether the airfoil shape can affect the slope of Cl vs. AOA (coefficient of lift vs. angle of attack) in the "linear" portion, e.g., from a few degrees negative to ...
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### Does altitude affect glide ratio?

Lower altitude means higher air density, which means more liff, which means a glider can maintain a given glide slope at lower airspeed. As a rule, aircraft tend to have higher peak L/Ds at low ...
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### Do manufactures list the maximum speed of an aircraft based on its theoretical maximum speed or dive speed?

I know that the absolute maximum velocity of an aircraft is based on the thrust available. However the aircraft is usually limited beforehand by other speed limits such as dive speed and Mach Never ...
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### What is the Mach Never Exceed number for a C-130J Hercules under ISA conditions (approximations are welcomed!)

I am looking for the Mach Never Exceed number for a C-130J Hercules so that I can create an approximate 1g envelope. Does anyone have any idea what this can be? I am trying to find the value for ...
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### What is the CLmax of the CF-100 Canuck?

I've been struggling to find specifications for the CF-100 Canuck. What is the CLmax of the CF-100 Canuck and how can I find it?
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### What differentiates the entry procedures for spins and snap rolls?

Both a spin and a snap roll are aerobatic manoeuvres involving stalling one of an airplane's wings earlier and more deeply than the other. Both are entered by pitching up sharply to stall the ...
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### What is the approximate thrust at sea level for a C-130J Hercules?

I am looking for the approximate thrust of a C-130J Hercules under ISA sea level conditions. Also the efficiency of its propeller would be of help. An answer to this question would really help my ...
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### Swept back wing theory

I'm a beginner in airfoil design. I just came across swept-back wings. There is a point that I couldn't understand that theory. Why is the only perpendicular component of the airflow to the wing(...
1 vote
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### Why don't we simulate similarity parameters simultaneously in the same wind tunnel?

As 'Fundamentals of Aerodynamics' by JD Anderson suggest Today, for the most part, we do not attempt to simulate all the parameters simultaneously; rather, Mach number simulation is achieved in one ...
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### What exactly causes pitch moment in the Phugoid mode?

I am trying to figure out exactly what causes the pitching moment for the Phugoid mode? We know that alpha remains mostly constant, so what is causing the pitching moment? I thought maybe it is the ...
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### Is the Bede BD5 actually a tandem wing airplane, and not a mono wing?

Is the Bede BD5 a tandem wing airplane, and not a mono wing? The following picture (Source: Wikipedia.org) shows a Bede BD5 with a high angle of incidence on the horizontal tail, estimated at about 5 ...
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### Why am I getting a low L/D of 4.3 for this supercritical airfoil in Autodesk CFD?

I am a high school student learning to analyze aircraft models in Autodesk CFD for the first time. My current project is analyzing a supercritical airfoil on Autodesk CFD (that was designed in ...
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### Relation between lift force and torque produced in propeller used for vertical take-off and landing aircrafts

There are many answers for this question but none of them are specific. I need to find the exact relation between the lift force of a propeller of specific pitch, attack angle , dimensions and ...
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### Could leading-edge dynamic stall occur for a tripped airfoil?

As far as I know leading-edge dynamic stall is characterized by the formation of a Leading edge vortex. This leading edge vortex forms due to the 'bursting' of the LSB (Laminar separation bubble). ...
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### Would it be beneficial to have rotors AND propellers instead of a tiltrotor?

Would it be beneficial for tiltrotor aircraft if they had BOTH rotors and propellers, instead of the hybrid proprotors that are neither good propellers nor good rotors? Like imagine the V-22 Osprey ...
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### Why do the ailerons of this flying wing work oppositely compared to those of an airplane?

I made this simple wing glider and put some ailerons on it. I thought that the ailerons in this glider would work the same way it works on airplanes, wherein the roll will be in the direction of the ...
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### Are 0g pushovers in a C172 safe/legal?

I see YouTube pilots do it all the time, but I’m wondering how safe this maneuver really is given the fuel is a gravity fed system. Also, is it legal?
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### Relation between weight of the aircraft and mach number [closed]

Is there any formula that relates weight of the aircraft with mach number?
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### Why aren't isentropic noses and tails used in supersonic aircraft?

An inside out paraboloid would theoretically produce isentropic compression for an inlet cone. But this question is about nose and tail cones on fuselages, and leading and trailing edges of wings. An ...
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### What are the pros and cons of putting a propeller immediately before a slipstream pylon vs. immediately after

In the following situation with a slipstream pylon for a self-launching glider, what are the tradeoffs in sticking the propeller before vs. after the pylon? The wind turbine industry has the same ...
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### For jetliners, how is a swept wing justified over a thin wing?

For a given speed, a swept wing is a fatter alternative to a straight, thin wing. But why? Does not the sweep lengthen the wing and make it heavier? Is the swept wing chosen for the extra fuel tank ...
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### Induced drag reduction from tandem wing

Induced drag is proportional to the square of span loading. The normal method to decrease it would be to increase span. This, however, leads to an exponential weight increase. So, my question is, if ...
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### How does gross weight affect helicopter autorotation?

The factors which affect helicopter autorotational aerodynamics include airspeed, gross weight, rotor RPM, and density altitude. The effects of these factors can be examined during a few phases of the ...
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### Is possible to stick two '2-blade' propellers to get multi-blade propeller?

Does propeller blades' airflow interfere with each other blades and decrease overall thrust? Should I consider high pitch propeller for this purpose? My purpose: I'm looking for a 20-inch four-blade ...
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