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
78 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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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
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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
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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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3answers
201 views

What is the 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
85 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
335 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
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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
339 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
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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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1answer
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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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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
527 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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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
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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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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
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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
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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 (...
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4answers
648 views

Spinning wing heat dispersion dynamics for Mach 24 and beyond?

Could a spinning disk dropped from orbit survive speeds faster than conventional aircraft in our atmosphere? Does the rate of spin matter when dispersing heat? Does a spinning disk create stability ...
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1answer
221 views

How do the linearised equations of motion work?

I am reading this book: "Flight Dynamic Principles" by Cook, second edition. You can read it here: https://aerocastle.files.wordpress.com/2012/04/flightdynamicsprinciples.pdf First, go to the page 76,...
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1answer
875 views

Why are yaw rate and pitch rate obtained by these equations?

I am reading "Introduction to Aircraft Aeroelasticity and Loads" by Jan R. Wright and Jonathan E. Cooper. The book said: In steady bank turn (as shown in picture below), The rate of turn is given by:...
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Why is it, with less airflow, you'll have less control effectiveness?

I understand the principle of less airflow, less control, but why is that the case?
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What is the best distance glider that can carry a 200 lb load?

Good morning, I'm an emigrant from Worldbuilding and I ask this first question in part to help me discover what I don't know I don't know. My definition of best: Longest recorded single flight time ...
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1answer
345 views

How to compute quaternions from raw IMU and magnetometer data?

I have raw accelerometer data (w_ib^b) and magnetometer data from a UAV test flight. I would like to reconstruct the quaternion dynamics of the UAV without accumulating error from integration. The ...
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How can an aircraft turn if the horizontal force component is zero?

Here is the simplest coordinated turn diagram Picture from https://physics.stackexchange.com/questions/100169/pendulum-in-a-turning-airplane Being: $L$ = aerodynamic lift $\tau$ = angle between ...
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3answers
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What's the meaning of “straight and level”?

Indeed a very strange question. My understanding of straight and level is: The aircraft is flying at a constant heading and constant altitude, and maybe at a constant speed, and this has nothing to ...
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2answers
635 views

How is the climb/descent performance affected by wind gradient?

I am exchanging opinions with other pilots concerning climbing and descending with a wind gradient, and I'm facing strong opposition... In my opinion, a plane trimmed for S&L flight, if it ...
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1answer
219 views

At which speed is a plane traveling at hypersonic? [duplicate]

What is the measurement used when a plane is said to travel at hypersonic? How does the air act at the nose of the plane? Would the nose and wing have to be razor sharp to cut the air? because the ...
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3answers
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Why do (some) aircraft shake at low speeds with flaps, slats extended?

I landed a couple of times as a passenger with the Embraer 190 (I like Embraer very much) on runways with a length below 2 km. I noticed that the plane started to shake or vibrate quite strongly ...
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1answer
732 views

Does slipping in turns allow higher climb rates?

Sailplanes, among others, use a cotton string to show the sideslip angle. I've often heard that while circling in thermals the cotton string should show a slight slip angle to climb faster. This ...
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2answers
913 views

How to calculate aileron deflection for achieving similar roll dynamics at thin and dense air?

my question is inspired by projects like Perlan etc when one is trying to fly in thin air with a glider. It is well known that at high altitude (say 10-20km) aircraft control becomes 'sluggish'. ...
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Is this explanation of adverse yaw correct?

It is explained here that adverse yaw is caused by the difference in induced drag due to the difference in lift being generated by each wing. I've also seen a couple of websites (including Wikipedia) ...
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2answers
657 views

Which of these is true for a glider flying with constant angle of attack?

I'm trying to answer the following question, but I'm not sure of which one is correct. A glider is gliding with constant angle of attack along its path. We can assume the hypothesis of small angles....
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2answers
2k views

What is the direction of the sideslip induced by roll on a conventional aircraft?

For the sake of this question let's assume that the considered aircraft is an A320. The question is what is the sign of the aerodynamic $C_{n_q}$ coefficient? In another word, when the aircraft starts ...
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2answers
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How to start deriving longitudinal equations of motion for an aircraft?

I hope this is a relevant place for me to ask a math question regarding aircraft design. I am trying to understand how one would implement a controller to control the pitch angle of an airplane for a ...