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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21
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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 (...
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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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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 ...
17
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1answer
956 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 ...
16
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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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4answers
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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)?
16
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4answers
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Do any airplane designs exist that don't involve a flight surface that provides downforce?

Most aircraft maintain longitudinal stability by balancing three forces: The down force acting through the center of gravity (CG) The lifting force acting through the center of lift The down force ...
14
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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 ...
9
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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 ...
8
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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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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 ...
7
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4answers
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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
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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) ...
7
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2answers
680 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, ...
7
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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 ...
7
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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 ...
7
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2answers
590 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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5answers
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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 ...
6
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2answers
799 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?
6
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3answers
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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 ...
6
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1answer
1k 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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5answers
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How does the angle of attack vary in turns?

I read somewhere that when the aircraft banks to turn, its angle of attack increases.Since angle of attack is the angle between the relative wind and chord line, how does turning increase it? Is it ...
5
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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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4answers
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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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6answers
968 views

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?
5
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1answer
202 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 ...
5
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1answer
198 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 ...
4
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4answers
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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 ...
4
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4answers
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How can an airplane keep going forward if it has no thrust?

Every pilot is familiar with the basic model of aircraft forces: If lift is greater than weight, the plane climbs, if less, descends. If thrust is greater than drag, the plane accelerates, if less, ...
4
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2answers
719 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. ...
4
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3answers
970 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 ...
4
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2answers
765 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 ...
4
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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 ...
4
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1answer
162 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 ...
4
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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 : ...
4
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1answer
421 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 ...
4
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1answer
63 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 ...
4
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1answer
199 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 ...
4
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2answers
141 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 ...
4
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2answers
422 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 ...
4
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4answers
937 views

Descending on a given glide slope (e.g. ILS) at a given airspeed— is the size of the lift vector different in headwind versus tailwind?

We had a discussion with friend and we were talking about if the airplane is on approach and the one is landing with tailwind and the other one is landing with headwind, so both have the same value of ...
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6answers
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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. ...
3
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3answers
138 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 ...
3
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3answers
340 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 ...
3
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1answer
90 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. ...
3
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1answer
100 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 ...
3
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1answer
140 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 ...
3
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0answers
258 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 ...
2
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3answers
246 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 ...
2
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2answers
221 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-...