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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What does deploying landing flaps do to the (L/D)max and minimum drag speed of an airplane?

I thought that deploying flaps will increase both the drag and lift, thus increasing L/D ratio? But do they increase proportionately? And how exactly does that correlate with the increase/decrease of ...
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1 vote
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Change of absolute ceiling with weight

Let's say an aircraft has an abs ceiling of some value at the start of its cruise and then it consumes some percentage of its fuel during cruise. How will this change the new abs ceiling at the end of ...
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5 answers
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Aircraft pitch and AOA change during a coordinated turn maneuver

Let us say I am flying a constant airspeed turn while maintaining my altitude, when I enter into the turn, lift has to be increased and since airspeed remains constant, the AOA has to be increased to ...
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Can an encapsulated airfoil generate enough lift to lift the capsule?

Can an airfoil generate enough lift, if it is contained in an enclosed space, to lift the enclosed space? Assume that there would be sufficient airflow over the foil to generate lift if it was not in ...
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-1 votes
2 answers
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If i have equal lift and drag, do they cancel each other out?

I am working on a throw glider and was wondering, How much lift would be too much lift, as in it causes the glider to stall (maybe thrust that causes this, but still). also, if I create a body that ...
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Body angle rate and body angular velocity

Are these terms used interchangeably to mean the same things? I'm aware of the conversion between body rates (often, $[p, q, r])$ and Euler rates (commonly, [$\dot\phi, \dot\theta, \dot\psi])$. This ...
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Which one produces more lift?

I have come across this question on Twitter. I have found a similar question here. The aircraft isn't flying but just doing Cobra Maneuver. Since the direction of the lift is in the same direction and ...
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6 answers
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What is the name of the effect that causes a plane in a dive to go up?

What's the name of the effect that causes the aircraft to automatically pull out of a dive and buffet up due to aerodynamic lift produced at high speeds?
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How can ground speed be higher than airspeed? [duplicate]

I've heard that ground speed is higher than air speed when the plane is being pushed by wind wind. But how is this possible? Wouldn't your AirSpeed also increase since you're going faster?
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4 votes
3 answers
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Given roll angle and constant velocity, calculate new position

I'm simulating an aircraft in Simulink and then using a controller to make it follow a reference path. My control inputs are elevator, aileron and rudder angles and the outputs of the state space are ...
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8 votes
3 answers
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What "designs" the dihedral angle in modern airliners?

Is this an accurate description of the design process for modern jet airliners? If not, why not? What other factors come into play in determining the choice of dihedral angle? Designer starts by ...
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How to calculate lateral velocity of a turning aircraft

An aircraft in a 45 degree banked turn has a horizontal lift force vector equal to the weight of the aircraft. Although the Coefficient of Drag is much larger for the aircraft profile, it seems there ...
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5 votes
4 answers
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Viable to slip onto the center line?

One of the constant problems of aviation is drawing onto the center line on final. Either due to a bad rollout or due to crosswinds a pilot often finds that the aircraft is not on the center line for ...
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16 votes
3 answers
7k views

Why is this plane struggling to gain altitude?

Here in this video, you can see an airplane trying hard to gain altitude (happens at 1 min 17 secs, original video): Plane Gets Struck By Lightning I am skeptical. Does it actually happen, or is the ...
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Why does power go up with the cube of the airspeed?

If i have an airplane with over 100 kN of thrust, and i want to accelerate from a velocity at which drag force is 25kN to a velocity twice higher, is it possible that i wont be able to do this because ...
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Calculate Rudder Angle by Bank Angle [closed]

My question: Is rudder angle equal to bank angle? Or, does rudder angle has some relationship with ROT formula? Below is my steps trying to solve this question. Step 1: Found below graph from this ...
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3 answers
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Calculate speed by turn angle and distance [closed]

I'm trying to combine two rate of turn formulas, which I found it online this and this. The first is ROT = 1091 * tan(bank angle) / speed in knots The second is <...
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11 votes
2 answers
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Why is the ball no longer centred in a multi-engine airplane with inoperable engine?

I'm currently working on my PPL, and whilst trying to understand fully how the turn coordinator works, I got down a rabbit hole that makes me question my understanding, and that I can't dig myself out ...
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1 answer
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What means when center of pressure is out of physical dimension of wing?

Center of pressure(CoP) is point where total force vector acting at. If you hold wing at this point, wing will not rotate(moment=0). Example hanging point at hanglider. I see at some diagrams for very ...
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2 votes
3 answers
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How the AOA, Pitch and FPA are changing during a flight maneuver

For a steady state flight, there is a equation that FPA + AOA = Pitch, but how these three variables are correlated during a flight maneuver like currently I am in a leveling flight and then I want to ...
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7 votes
2 answers
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G Load during payload drop

Some days ago I saw the accident of the airtractor that, just after a drop, suffered a spar failure in both the wings. Luckily the pilot survived. If load factor in his simplest formula is: n=lift/...
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3 votes
0 answers
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Can I just differentiate my Euler rates to get the angular rates?

There is this matrix: $${W_{\eta}}=\begin{bmatrix} -\sin(\theta) & 0 & 1 \\ \cos(\theta) \sin(\phi) & \cos(\phi) & 0 \\ \cos(\theta) \cos(\phi) & -\sin(\phi) & 0 \end{bmatrix}$...
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7 votes
4 answers
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In a banked turn, why does the center of gravity, rather than the center of lift, follow the path of a circular arc?

I'm a post-solo student pilot who sometimes gets hung up on fundamental points of aerodynamics. "As long as the aircraft is banked, the side force is a constant, unopposed force on the aircraft. ...
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4 votes
4 answers
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When pitching, how do planes establish a pitch rate which corresponds to the centripetal acceleration?

Coordinated flight requires that the yaw rate and the centripetal acceleration correspond. In other words, for a given $a_{centripetal} = v^2/r = \omega ^2 r$ this means that the yaw rate must equal $\...
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2 votes
1 answer
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Are the gyroscopic precession and P-factor of a pusher propeller in opposite directions?

according to this picture the P factor cuases airplane to yaw to the right but if pilot wants to pitch up , then p factor and gyroscopic precession acts on airplane at the same time but in opposite ...
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1 vote
1 answer
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How do you quantify rudder effectiveness as a function of bank angle?

I'm currently reviewing just for fun aircraft dynamics based on OEI (one engine inoperative) scenarios. After reading that "lower pedal forces at higher bank angles" are required, it got me ...
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0 answers
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How should I understand aircraft rotation conventions (euler angles)? [duplicate]

I'm reading the manual for an IMU and it claims it reports out the vehicle's (aircraft's) heading, pitch, and roll, and I'm trying to get a feel for what these things mean. It seems to me that the ...
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1 vote
1 answer
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Equations for Computing Temperature and Air Density Ratios at Different Altitudes

When computing aircraft performance at different altitudes, two useful variables are the air density ratio (dr) and temperature (T). Using a ratio is helpful because you can recompute values, such as ...
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1 vote
2 answers
250 views

Can yaw develop a spiral dive?

I'm wondering if the 'prolonged' effect of using yaw causes a spiral dive. I understand that a spiral dive is caused by an excessive angle of bank, but can it also be created by an excessive amount of ...
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2 votes
4 answers
212 views

Which way to turn to return to runway for downwind landing-- into crosswind or with crosswind?

The scenario-- you are taking off with a significant headwind component but also a significant crosswind component. You experience a power loss (or perhaps a tow rope break in a glider). You judge ...
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2 votes
1 answer
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What is the difference between equilibrium and steady flight?

If I'm flying a regular Cessna 172 and its perfectly trimmed and flying in circles holding the same altitude, is the aircraft in equilibrium? Or steady flight? (The definition of equilibrium flight ...
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0 answers
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How to calculate Longitudinal dynamic stability derivative for a wing? Mq and Mα

How to calculate Moment due to rate of change in pitch(Mq) and Moment due to rate of change in AOA(Mα) manually and How to extract from CFD software? Consider a fighter aircraft is in Case 1- Cruise ...
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5 votes
4 answers
438 views

Is the total upwards vertical force (lift included) greater than the weight in a steady climb?

Related to questions on forces in a climb: if any aircraft is climbing with a constant velocity, is the total upwards vertical force (lift included) greater than the weight?
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1 vote
3 answers
247 views

Calculating angle of attack during bank

I'm programming a flight dynamics simulation and am running into issues with calculating the angle of attack during banked flight. I know what I'm doing wrong, but I'm not sure what I should be doing ...
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3 votes
1 answer
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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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In large transport aircraft, is the amount of elevator travel that is physically possible ever a limiting factor in turning performance?

In large transport aircraft, do we ever encounter the situation where we are unable to maintain a given, low airspeed while banked and turning, because we "run out of elevator travel" (...
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-2 votes
3 answers
252 views

Is lift less in a steeper descent than in a shallower descent, and if so, by how much?

Is lift less in a steeper descent than in a shallower descent, and if so, by how much? For example, if we change our ratio of horizontal distance travelled to vertical distance travelled (through the ...
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1 vote
1 answer
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Can a normally poorly handling airframe with high moments of inertia actually have superior flight dynamics under autonomous control? [closed]

I’m not a pilot but know a thing or two about flight dynamics. As you know there are currently quite a few aircraft under development designed for low-and-slow and (eventually) autonomous flight. ...
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7 votes
6 answers
2k views

Is a trimmed flight not always an unstable system?

As soon as I am flying in trimmed flight condition, my pitching moment around the center of gravity becomes zero. So my center of pressure has to be located in the center of gravity, so that there is ...
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1 vote
2 answers
261 views

What happens if an aircraft is only stable at higher angles of attack?

Does anybody know what will happen to an aircraft, if it is stable (in longitude) for let's say: -8° > angle of attack > 8° ? So for angle of attack 4° the aircraft is not stable (centre of ...
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4 votes
2 answers
333 views

In this F-104 V-n diagram, why does the stall speed (in terms of IAS) decrease with altitude in some parts of the flight envelope?

(This question has been edited to reflect a change in perspective: based on answers to the related question What is causing these "corners" on this F-104 V-n diagram?, I now believe that the ...
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1 vote
1 answer
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With flight dynamic equations, how do I return to positive alpha if alpha is always negative with negative w?

I'm coding a flight dynamics simulation, but my simulation runs into a problem with negative angles of attack. Once alpha is negative, it is impossible to get back to a state where the plane is ...
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1 vote
5 answers
489 views

What causes the ball to not be centered in a slip/skid?

I've reviewed quite a few questions on this forum including Forces in a slipping turn is-this-vector-diagram-of-the-forces-at-play-in-turning-flight-correct what-does-the-balance-ball-actually-...
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1 vote
2 answers
280 views

Can a slow small plane, flying at a few meters above the ground, drop to the ground if the headwind abruptly stops? [duplicate]

Why do I ask this question? Because Wilbur Wright sent a letter to Georges Spratt (an aviation enthusiast he personally knew) saying that his plane, Flyer II, once in flight, accelerated easily to 45 ...
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1 vote
2 answers
302 views

Can a plane with a thrust-to-weight ratio less than one fly vertically and perform loops?

In the game Battlefield 1 you can fly a Sopwith Camel vertically and perform different kinds of aerobatic maneuvers like loops. According to its specifications, its thrust-to-weight ratio should be ...
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-1 votes
1 answer
119 views

Relationship between Load-Factor AND Gliding Ratio

I am wondering about the g-load and its relation to the so called gliding ratio. I read this really good contribution here on this forum: Does lift equal weight in a climb? So the g load factor is ...
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5 votes
2 answers
1k views

What is the effect of thrust vectoring effect on the rate of turn?

I just got a question after reading my old Principles of Flight book. The equation for the rate of turn is $\textrm{ROT} = 1,091 \cdot \frac{\tan(\phi)}{V}$, with $\phi$ denoting bank angle and $V$ ...
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0 votes
1 answer
78 views

Is there any formula that directly relate density to altitude for a wide range of altitude?

I am working on a code to simulate a vehicle trajectory based on forces act on it in different altitudes, I need a formula that gives density in an altitude range between 0 and 40 km to obtain lift ...
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2 votes
1 answer
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The relation between Euler-angle rate and body-axis rates?

A paper about quadcopter dynamics and control shows the relation between Euler-angle rate and body-axis rates as: Q1: why are there $R_{v2}^{b}(\dot{\phi})$, $R_{v1}^{v2}(\dot{\theta})$, and $R_{v}^{...
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5 votes
2 answers
534 views

Why do most aircraft with variable incidence tailplane have the possibility to trim much more degrees for nose up than for nose down?

Probably the question will be a little bit confusing but I'll try my best to make it clear. Due the position of the CP with respect of the AC, symmetrical airfoils don't produce pitching moments, but ...
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