Aviation Stack Exchange
Aviation Stack Exchange

Questions tagged [stability]

The physics of maintaining a specific state in the dynamic system of aircraft flight.

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Why do some fighter jets have movable horizontal stabilizer instead of elevators installed on the stabilizers?

I have noticed that the horizontal stabilizers on some fighter jets move up and down to increase and decrease the angle of attack, but on some airliners they use elevators to adjust the angle of attack. Why isn't this kind of system used on…
Ethan
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Can a pendulum stabilizer for airplanes really work?

Can a pendulum really stabilize a plane for both roll and pitch? I have read about various experiments (the one in the picture being just a simple case) but I still do not find an example of plane that was stabilised beyond any doubt with the help…
Robert Werner
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What is aerodynamic damping?

Could someone explain what aerodynamic damping exactly is? I'm not able to understand the whole concept. Pls try to keep the explanation simple. I tried to understand the concept from the link below. Is aerodynamic damping the same as the dihedral…
Johnson
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Can an automatic vane-based stabilizer really work?

Can the pitch stabilizer in the picture really work for a plane or glider? The image shows an automatic pitch stabilizer (the mechanism in the black rectangle) that is based on the vane 50 whose movements up and down would drive, with the help of a…
Simplex11
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Is a horizontal stabilizer necessary on an aircraft with a tandem wing?

Let's say that there is an aircraft with more than one main wing and each of these wings have elevators. Would it be necessary to have a horizontal stabilizer? The figure below shows an example of what I'm thinking.
Ethan
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Are there any relationship between lateral and directional stability?

Directional stability is affected by the side areas such as the vertical stabilizers and lateral stability is affected by dihedrals. Is there any relationship between lateral and directional stability as a roll result in a pitch and most aircraft…
Alexong123
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Under what circumstances is the Aircraft 'Stability-Axis' system used in either design or analysis of aircraft?

I understand the definition of aircraft 'Stability-Axis', but I am unsure as to the circumstances in which forces or moments would be expressed in this axis system. Is there a convention? What I do know: It is useful for wind tunnel analysis,…
William
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Contribution of wing vertical location to roll stability

Recently, I was reading about the factors that contribute to roll stability of an aircraft and came across a point stating that the wing's vertical location (Distance of wing from CG) contributes to the roll stability of the aircraft. I cannot…
CuthillMckee
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What causes 'wing rock' and how does it work?

Currently studying for a course on fighter aircraft. I came across the phenomenon of 'wing rock', which occurs at very high angles of attack, but I couldn't find any good sources that explain how this phenomenon works in detail. Could anyone give me…
Wouterr G
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What is the location of AC for typical modern airplanes?

Some sources state that AC must be located behind CG, so that AC is stable. There is a source, which throughout the study of stability and control consider AC located ahead of CG and positive cambered tailplane, stating that such airplane will be…
Nikita
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Stability and Control of an aircraft

Why is the pitching moment coefficient of an airplane said to be constant about the aerodynamic centre of an aerofoil
caleb olojo
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How to calculate Cm0 and Cmac,wb for an RC plane?

I am currently going through all of my stability and control calculations and am a bit confused on how to find $C_{m_{ac,wb}}$. The only things I'm finding online is that they are given through airfoil data? Not sure how to acquire this information…
Andrew
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Wing moment - providing stability or not

It is said that wing alone is unstable, because it provides a nose up moment, so tailplane is needed to damp it. But normally wing provides a pitch down moment (as far as I know, apart from very high aoa situation) because centre of pressure is…
Konrad
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Explaining development of sideslip due to bank

In lateral static stability: "Once an airplane banked due to a disturbance, the airplane develops a sideslip in the direction of the bank because of a spanwise component of the weight w*sin($\phi$)" I need to understand that in terms of forces and…
hadi floka
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What is the main source of yaw stability?

I am creating a flight simulator and I need to implement lateral and longitudinal stability. Roll stability is now working because I am computing the lift of each wing independently. But yaw stability is confusing to me. What is the main source of…
Anselme
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