Questions tagged [flight-dynamics]

Flight dynamics is the study of the physics driving the performance, stability, and control of aircraft. It is concerned with how forces acting on the aircraft influence its speed, altitude and attitude with respect to time.

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2answers
46 views

Can we show through simple geometry rather than formulae or graphs that the best glide ratio occurs at the maximum ratio of Lift to Drag?

For an unpowered glider, can we show through simple geometry involving force vector diagrams, rather than mathematical formulae or graphs, that the best still-air glide ratio is achieved at the angle-...
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7answers
437 views

How can speed and power be made independent in an airplane? [closed]

I heard a piece of information many years ago, and the more I think about it, the less it makes sense. It was like: When airplanes what to raise altitude, they do not increase speed, but they ...
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1answer
106 views

What is the difference between a spin and an uncontrolled roll in an high speed dive?

A comment I had on another (now deleted) question states that Air china 006 didn't spin. For me it was a spin (unwanted roll due to asymmetrical stall). The comment states it was "it was a slow ...
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1answer
93 views

Is the mach number of an aircraft measured with respect to stagnation speed of sound?

I was reading chapter 8 of JD Anderson Aerodynamics when I came across something I find weird. I found out that there are different types of Mach number, based on what the speed of sound was taken as. ...
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4answers
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Can hang glider hover straight into wind and keep same position? [duplicate]

Isnt resultant force allways pointing slighlty backward at every wing,so why hang glider is not push downwind by the wind? From theory that cant be possible,so does wind somehow coming at him at ...
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0answers
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Coefficients outputs by DATCOM

I'm trying to understand the outputs given by the DATCOM method. For example I have this formula for pitching moment coefficient : DATCOM give me these coefficients related to the pitching moment : <...
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2answers
115 views

In a full-rudder sideslip in a Schweizer 2-22 or 2-33 glider, is the descent rate higher at 50 mph airspeed than at 60 mph airspeed?

Is it really true that in a full-rudder sideslip in a Schweizer 2-22 or 2-33 glider, the descent rate is higher at 50 mph airspeed than at 60 mph airspeed? Likewise, is it really true that in a full-...
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3answers
130 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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6answers
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Can gliding your plane save fuel?

Aimed towards lighter piston planes including a powered glider, if a pilot wants to extend a plane's range unconventionally, could flying like a glider by climbing and then gliding down or would ...
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1answer
85 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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7answers
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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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1answer
77 views

Why does a steady-state non-zero body yaw and/ or roll rate induce side force?

An answer on ASE states The presence of steady-state non-zero body yaw and roll rate induces side force ($C_{y_p}$ and $C_{y_r}$). What is a non-mathematical explanation of why this is so? Is it ...
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3answers
143 views

Why does a banked aircraft create sideslip?

Below is an excerpt from Raymer (Aircraft Design) where he explains the dihedral effect. He states that a banked aircraft (due to say a roll disturbance) will have a sideslip which leads to a ...
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2answers
229 views

What are the forces present in a coordinated turn?

During straight and level flight, coordinated flight is assumed when there is no net lateral force (no slip or no skid). But this concept totally breaks down when it comes to turning, in a co-...
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0answers
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How long can an aerobatic (or any) plane fly “on its side”? [duplicate]

This recent question Can a plane bank without turning? asked if a plane can sustain some amount of roll in straight flight, sure they can. Consider an aerobatic plane (perhaps a Pitts?). As far as I'm ...
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6answers
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Can a plane bank without turning?

Can planes bank without turning, and if so, how is it possible? A plane's wing is designed to naturally create lift; the explanation for that is that the greater speed of the air moving over the wing ...
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5answers
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How do handling characteristics depend on flying with a full vs. an empty tank?

Modern aircraft are capable of carrying a lot of fuel to achieve extra-long range; we're at a point where nearly every pair of destinations can be reached non-stop. Carrying so much fuel imposes ...
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2answers
389 views

What is Neil Armstrong teaching in this image?

It seems to me that in this image Neil Armstrong is teaching something related with aerodynamics forces (lift, drag...), but I don't know exactly what is that "Triangle" that He drew (It doesn't seem ...
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1answer
65 views

How are coefficients of equation of sideslip angle in the paper “A general Solution to the Aircraft Trim Problem” calculated?

I am sure many of you guys must have read the paper, "A General solution to the Aircraft Trim Problem" by Marco, Duke and Bernt. I am working with the turning of the Aircraft and I am not able to ...
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2answers
121 views

Do horizontal stabiliser force direction change with CG variation for a given aircraft? [duplicate]

I am wondering about the direction in which horizontal stabilizer provide force. I know that it can provide either upforce or downforce. But I am wondering whether is it determined for a particular ...
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1answer
112 views

Helicopter Basics: How does lead-lag of blades actually help in compensating for increase/decrease in speed due to flapping?

I understand the following - Due to dissymmetry of lift, flapping up and down occurs. Since angular momentum has to be conserved, the speed of blade increases/decreases during flapping up/down ...
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5answers
428 views

How does retracting flaps help extend the glide of an aircraft?

As per the video from Smithsonian channel BA flight 38's captain retracted the flaps of the Boeing 777 by 5 degrees to extend glide, to travel further. Why?
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3answers
431 views

Do adding high thrust in plane prevents it from stalling?

I am convinced that fighter jets (every flying object) do stall. So from quora, Why don't fighter jets stall? But most of the fighters have thrust:Weight ratio > 1 which means that they are not ...
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3answers
128 views

How does vertical stabilisation work?

I know that similar questions are available all over the internet, including this website. However, none of the answers make full sense to me. I'm looking for simple answer (explain-like-I-am-5 type ...
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2answers
202 views

Why did the Wright brothers take steps to increase the amount of vertical surface area forward of the CG on some of their aircraft?

Why did the Wright brothers take steps to increase the amount of vertical surface area in front of the CG on some of their aircraft? Could this have actually improved the flight characteristics in ...
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1answer
209 views

When a paraglider pilot applies brake on one side and maintains the brake pressure, why does the roll rate eventually come to zero?

I recently started to study paragliding and I am confused about the rolling movement created when a brake is maintained. I was reading this answer How do paraglider controls work? and I am not clear ...
3
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1answer
141 views

How are pitching and rolling moments transferred from rotor to the body?

When a rotorcraft pilot moves pushes on the cyclic control stick, the swashplate tilts so that angle of attack of the retreating blades increase and of the advancing blades decrease, which creates ...
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2answers
201 views

Forces in a slipping turn [duplicate]

I have trouble understanding why the ball (on the turn & slip indicator) falls into the turn e.g. drop to the left when aircraft is rolled left, when in an uncoordinated turn (slipping turn). What ...
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3answers
494 views

What is missing from these diagrams of the forces in slips and skids?

See these images that are widely reproduced in many different on-line ground school materials. A) Is the magnitude of the wing's lift vector illustrated correctly in each of the three cases? Should ...
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6answers
304 views

Forces “felt” by pilot, G-meter, inclinometer--are they the aerodynamic forces generated by the aircraft, or the sum of weight+centrifugal force?

Consider a pilot sitting at the CG of an aircraft, with instruments also located at the CG of the aircraft. (Feel free to consider other cases as a bonus, but the core of the question is aimed at ...
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4answers
1k views

What exactly happens when power is reduced in trimmed, straight and level flight?

I understand that trimming an aircraft at a particular airspeed e.g. 100kts will keep the aircraft flying at that airspeed (100kts) even if you were to e.g. Lower power. This is apparently ...
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1answer
102 views

Are there any helicopters with tail rotors where slip-skid ball may be centered even when fuselage is streamlined to the airflow in cruising flight?

In a related answer, I stated "The tail rotor of a helicopter also generates an aerodynamic sideforce. Again, just as with the twin-engine airplane with one failed engine, when the fuselage is ...
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4answers
237 views

When do the lift and drag vectors contribute a force component along a glider's path of travel as seen from the ground?

It is often said that the lift vector helps to propel a glider forwards. The lift vector has no component acting parallel to the glider's trajectory through the airmass, but in many cases the lift ...
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4answers
5k views

How do “tip jet” helicopters cancel the torque effect of the main rotor?

Some helicopters use "tip jet" on the rotor blades tips such as the McDonnell XH-20 Little Henry and Hiller YH-32 Hornet. How do they cancel the rotor torque (often canceled by the tail rotor)?
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0answers
264 views

First Boeing 757-200 N757A 'Catfish' was modified with a Canard foreplane. How did it behave?

The aircraft had these changes made around 2006 to act as an F-22 Avionics test bed. One would expect that the fore plane changed many performances of machine, including take off and landing attitude ...
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1answer
78 views

Can having too small of a roll or yaw stiffness destabilize the dutch roll mode?

For a dutch roll mode, can having too small of a roll or yaw stiffness destabilize it? I would think not because you want a lower value to maintain it?
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2answers
211 views

How many significant digits should I use for simulating aircraft equations of motion?

I have coded the equations of motion in Matlab, and I am using the ode45 function to simulate the nonlinear dynamics of F/A-18 Hornet without any controller (just the airframe). I have given initial ...
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1answer
65 views

Procedure for simulating nonlinear flight dynamics

I am trying to simulate F/A-18 Hornet on Simulink. So, here is how I have made the model: Firstly, the initial flight parameters(Alpha, beta, V(magnitude), rho) are being calculated based on the ...
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1answer
200 views

What frame of reference should I use for my Simulink simulation of the F/A-18 Hornet?

I want to simulate the Equations of Motions for F/A-18 Hornet (12 states & 6 DOF) on MATLAB using Simulink. I have the Aerodynamic model, from which I will get CL, CD, CY, Cl, Cn, Cm that are ...
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3answers
260 views

What is physics explanation for minimum sink rate airspeed?

I did some research on Minimum Sink Rate, and saw much information defining it, (such as it is the speed at which the aircraft will remain in the air for the longest time, etc.) and how it is ...
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1answer
121 views

For an aircraft, what are the differences between nonlinear and linear equations of motion?

So, as far as I understand, linearized equations of motion are just nonlinear equations of motion converted to linear EoM's using approximations and assumptions to simplify/remove elements from the ...
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1answer
167 views

Finding Angle of Attack/Angle of Sideslip using East/North/Up Coordinates

I've got a set of data that includes: x rate, y rate, z rate (all ENU) which I'll call xd, yd, zd. roll, pitch, yaw (which I'll call ϕ, θ, ψ) roll rates, pitch rates, yaw rates I'm looking at some ...
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2answers
73 views

What is the Dimension of Equilibrium Space in Longitudinal Space?

Full untrimmed Flight Dynamics model of an Airplane is separated into two separate systems: Longitudinal and Lateral. When the untrimmed model in Longitudinal direction, which is six dimensional, is ...
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0answers
52 views

Hinge Moment Coefficient Prediction

Is there any tool for Hinge Moment coefficient calculation that takes input of aircraft specification that includes general data such as wing, aileron, horizontal tail plane and elevator data. The ...
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2answers
178 views

What 's the difference between Angle of Attack and Pitch? [duplicate]

I am interested in knowing the theoretical and practical differences between the Angle of Attack (AoA) and Pitch: Graphical definitions How are they related? In what circumstances these angles are ...
2
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1answer
202 views

Why A320/330 use C* FBW control without speed stability?

The A320 and A330 family are FBW aircraft that use C* longitudinal control laws for longitudinal sidestick command tracking. In essence, stick neutral commands 1G flight. When stick is deflected ...
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4answers
478 views

What is the difference between turn rate and yaw rate in aircraft?

Attitude heading computers generate both a turn rate and a yaw rate. How are these different from each other? Is Euler yaw rate the same as turn rate?
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1answer
154 views

Why are the Phugoid and Short period approximated instead of calculated exactly?

We can calculate the period and half-amplitude time for phugoid and short period using equations of motion. We will get an exact answer. Then why is there a need for doing approximations to ...
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3answers
155 views

What kind of motion will an airplane enter into when disturbed?

When an airplane is disturbed from a longitudinal equilibrium position, what sort of motion will the aircraft experience? Will it be a phugoid or a short period motion? Or will it be both?
5
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1answer
201 views

Is a retreating blade stall a problem that can be overcome on dual-rotor helicopters?

I know that regular main+tail rotor helicopters stall at higher speeds as the relative airspeed of the retreating blade approaches zero. I'm curious if coaxial or intermeshing dual-rotor helicopters ...