# Questions tagged [stability]

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

18 questions with no upvoted or accepted answers
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### Does/Can combustion instabilities occur in SCRAM jet?

I was told that combustion occurs at Supersonic speeds in SCRAM jet. So acoustic disturbances/ pressure fluctuations can't travel into incoming jet stream. Does this avoids combustion instabilities in ...
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### Was the Wright Brothers' 1902 machine a working glider or just a kite?

Was the Wright Brothers' 1902 machine a working glider or just a kite? I spent the last days reading the letters and articles of Amos I. Root, the man who claimed he had seen Wilbur Wright flying his ...
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### Lateral Stability- Why aircraft will not return of its own accord to the original heading after a sideway gust?

I am reading the Stability section of FAA it says: If an aircraft is flying in a straight line, and a sideward gust of air gives the aircraft a slight rotation about its vertical axis (i.e., the ...
902 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 ...
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### Is center of gravity (C.G.) of wing itself in line with hang point (hang glider)?

Where is center of gravity (C.G.) of hang glider wing? Is it the hang point, in front of it, or behind it? Is the control bar "neutral" when the glider is at rest and there is no wind or ...
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### Doubt in the Coriolis component of the net force acting on the aircraft

I dig a little and got to know that the force equation in 6DOF are nothing but a mathematical depiction of the fact that for a translating & Rotating body in 3D,The net force is the Translational ...
91 views

### Is there an ideal value for the difference between the stick fixed and stick free static margin?

I'm calculating the static stability for a fictional aircraft and have to determine the elevator size. I have all the calculations but don't know how to choose the correct size and position. Is it ...
195 views

### Does the 737 MAX's engine nacelle camber affect the pitching moment?

A side view of the B737 MAX's engine nacelle shows a positive camber at the top. As nose camber of any lifting shape (wing or nacelle) generally allows more lift at higher AoA, do you think this ...
380 views

### Does the angular momentum of a jet engine affect aircraft performance?

I am interested, do jet engines have angular momentum? And how does such momentum affect airplane stability?
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### What Inertial effects should be considered to achieve blade stability on a Variable Pitch Propeller tailoredby aerodynamic loads?

I am developing a self adjusting variable pitch propeller tailored by its pitching moments due to aerodynamic loads setting the blade rotation axis in an offset from the aerodynamic center as shown ...
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1 vote
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### What can cause an unstable phugoid mode?

For clarity, I am wondering about how aircraft design can lead to the phugoid poles becoming complex with a positive real part, so an oscillation with increasing amplitudes. My understanding of the ...
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1 vote
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### How do boxwing and tandem airplanes balance moment

I want to build a hydrofoil like this picture: I discovered that you can pump it with a leg motion and moving the center of mass. Like this: I discovered xflr5 and ...
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### After designing an autopilot, how does it affect aircraft modes?

Let's say an autopilot will be designed for the longitudinal axis. A pitch attitude hold will be made with a sas in the inner loop and a pid in the outer loop. How does this system change the phugoid ...
201 views

### Why might a canard aircraft suddenly pitch down from a level flight?

I have a canard aircraft which has pitch stability issues that I'm trying to troubleshoot. The aircraft has a characteristic tendency to depart level flight in sudden dive/ or generate a massive nose-...
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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 ...
94 views

### Should the planform area inside the fuselage be considered for a stability calculation?

I am using lower order tools (xflr) for calculation of neutral point and CG location.I can think of modelling the wing in three ways wing with section inside the fuse missing wing with section ...
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