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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1answer
33 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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4answers
206 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, but that ...
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3answers
315 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
121 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
185 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
136 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 ...
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1answer
128 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
155 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
383 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
270 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
83 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
220 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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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
77 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
205 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
62 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
193 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
189 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
98 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
142 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
48 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
149 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 ...
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1answer
165 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
319 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
143 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?
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1answer
188 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 ...
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1answer
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What is MCAS trying to fix on B737 MAX?

New sources such as Seattle Times and Aviation Week provide a pretty good overlay of the MCAS function on B737 MAX. However, I'm unclear as to the issue that MCAS is attempting to fix. From what I can ...
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3answers
331 views

How Helicopters Change Attitude (Gyroscopic Precession or Thrust Vector Tilt)

I am trying to determine how helicopters pitch and roll (i.e. change attitude). I have heard two explanations. 1) Pitch/roll change is achieved by tilting the tip path plane and therefor tilting the ...
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3answers
279 views

Does propwash increase pitch stability?

Here is a polar for a piston single-engine aircraft: (This is lifted from a Russian manual for Yak-52, so $C_x$ is drag, $C_D$, and $C_y$ is lift, $C_L$). 1 is the 'normal' case without propwash. 2 ...
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2answers
121 views

How to calculate the variation of Z force with elevator deflection (Zδe) in Nelson for pitching dynamics?

I have been trying to model the pitching dynamics of a General Aircraft (Nelson, "Flight Stability and Control"). I need to use the Zδe which uses ...
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4answers
424 views

What is the time derivative of the angle of attack?

Suppose a flying missile's velocity vector has components $u, v, w$, as illustrated below. From my knowledge of flight dynamics, the angle of attack is $$\alpha = \arctan \left(\frac{w}{u}\right)$$ ...
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1answer
129 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
674 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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1answer
217 views

How does a G1000 equipped with a GDC 74 calculate IAS from dynamic pressure?

How exactly does a G1000 system equipped with a GDC 74 air data computer calculate the indicated airspeed that is displayed on the PFD from difference between the total and static pressure (i.e. ...
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2answers
421 views

How can I switch off the yaw damper in an Airbus A350?

How can I switch off the yaw damper in an Airbus A350? In the A320, this can be done by switching off the FAC, but the A350 doesn't have a FAC switch; it has prim and sec instead of FAC and ELAC.
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2answers
394 views

What is a “natural flight loop”?

I'm roughly (edit: very well) familiar with flight simulation, but recently I came across a new term. In this brochure (scroll to the second page) by Airbus about flight simulators, they talk about ...
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6answers
953 views

What produces thrust along the line of flight in a glider?

After reviewing discussions and vector diagrams of gliders in flight, the vertical lift component and the vertical drag components seem to produce a steady state, 0 acceleration balance with gravity. ...
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1answer
252 views

Does the rate of turn increase or decrease by turning at a higher speed? [duplicate]

It is easy to derive a formula for rate of turn in a steady banked turn as: $$\dot\psi=\frac{g \cdot tan\phi}{v}$$ which indicates that as speed increases rate of turn decreases. This feels ...
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1answer
208 views

Why does an elevator deflection (step) result in a nonzero short-term-steady-state response in pitch rate?

I know from the simplified Short Period linearized equations (state space with Angle of Attack ($\alpha$) and Pitch Rate ($q$) as states) that the steady-state value of the pitch rate response to ...
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3answers
849 views

What is the pivot point of pitch change on an aircraft?

I was wondering if there is a way to determine the pivot point when an aircraft changes pitch, assuming a standard slightly nose heavy and back elevator trimmed Cessna 172. Will it pivot around the ...
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5answers
935 views

In which direction will an aircraft drift after taking off in a crosswind?

Assuming the pilot applies the appropriate crosswind flight controls (see below) during takeoff and rotation, and releases those flight controls after the aircraft leaves the ground, in what direction ...
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1answer
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What is the difference between Body Pitch Rate and Inertial Pitch Rate?

ARINC 429 specifies two series of attitude rate labels for ADIRS/AHRS/IRS systems: Body 326 : Body Pitch Rate 327 : Body Roll Rate 330 : Body Yaw Rate Inertial 336 : Inertial Pitch Rate 337 : ...
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1answer
2k views

What are Altitude, Attitude and Heading Hold?

Can someone give a good and simple explanation about these three dynamics? Altitude Hold Attitude Hold Heading Hold
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2answers
635 views

Can the fly-by-wire system of a modern airliner handle an unstable condition?

According to this answer airliners/large passenger aircraft such as an A320 are designed such that they are longitudinally, statically stable under normal flying conditions. What if, for some reason, ...
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3answers
4k views

How do elevons work to roll a flying wing?

I have an RC Flying Wing that uses elevons for control. To go up both elevons move upwards and the wing pitches up. Both go down and the wing pitches down. I’m OK with this. However, if I want to ...
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4answers
4k views

Can a barrel roll really be executed at a constant 1G?

I see this stated from time to time, for example in an answer to Can large airliners do aerobatics such as loops? A barrel roll is one thing; they can be performed at constant load factor of 1 G (...