Aerodynamics

[granard]

Hi

I'm doing self study in Aerodynamics, could you help me ?

Static Stability and Dynamic Stability.

Question.

Is sometimes Static stability called Passive stability and Dynamic Stability called Active stability


I'm not looking for someone to explain stability ,just have you come across the words Passive and Active when describing the above stabilities.

Help greatly appreciated if not to basic a question.

[Volume]

Static stability basically means, if your flight condition is disturbed (e.g. by a gust) the aircraft returns to the initial state. This happens very quickly, and only extremely exceptionally skilled pilots (or clever computers, like on the Eurofighter) could do this manually. Normally you expect the aircraft to do this entirely by itself.
Dynamic stability means after returning to the initial state, the overcorrection is small, resulting again in a deviation in the other direction, which returns to the initial state and then swings back to the first disturbed condition. If those oscilations around the initial state fade, the aircraft is dynamically stable. If those oscilations do increase, the aircraft is dynamically instable. Typically a pilot (or a conventional autopilot) can dampen this out, so light dynamic instability is not unusual.
You may google Phygoid to learn more about it.

[AerocatS2A]

I'm not looking for someone to explain stability ,just have you come across the words Passive and Active when describing the above stabilities.

No I haven't.

[keith williams]

I have not heard these terms used in the manner which you describe, but I think you will find that:

The term "Passive Stability" refers to a situation in which the vehicle is naturally (inherently) stable and does not require any artificial stabilization systems. This would require positive static stability and positive dynamic stability.

The term "Active Stability" refers to the use of artificial stabilizing systems, to improve the handling of vehicles which do not exhibit sufficient passive stability. An example of such a system would be an aircraft Automatic Stabilization system (Basic Autopilot)

[DaveReidUK]

Originally Posted by AerocatS2A

No I haven't.

Me neither.

Hard to see why there would be a need to invent new synonyms for longstanding and widely understood terms.

[PAX_Britannica]

Dunno if this is immediately helpful, but if you can do differential equations, Doug McLean's book is good. Entertaining and informative YouTube lecture: https://www.youtube.com/watch?v=QKCK4lJLQHU

P.s. Or are you looking for help with control theory ?

[Peter H]

Originally Posted by keith williams

I have not heard these terms used in the manner which you describe, but I think you will find that:

The term "Passive Stability" refers to a situation in which the vehicle is naturally (inherently) stable and does not require any artificial stabilization systems. This would require positive static stability and positive dynamic stability.

The term "Active Stability" refers to the use of artificial stabilizing systems, to improve the handling of vehicles which do not exhibit sufficient passive stability. An example of such a system would be an aircraft Automatic Stabilization system (Basic Autopilot)

I think Keith is right, and his view is certainly consistent with the usage in:

this examination of two flying wings:
It’s a Bird; It’s a Plane; It’s a…Cucumber? An Examination of the Stabilizing Characteristics of Alsomitra Macrocarpa
It?s a Bird; It?s a Plane; It?s a?Cucumber? An Examination of the Stabilizing Characteristics of Alsomitra Macrocarpa | Bio-Aerial Locomotion

... and this
Active and passive stabilization of body pitch in insect flight
Active and passive stabilization of body pitch in insect flight | Journal of The Royal Society Interface

[granard]

Thanks

Hi all.
Thanks for all the replys.

Keith , your answer says it all for me. Peter I watched a video on youtube showing the seed in flight, we only repeat what nature teaches us.

Kind regards
J