aircraft longitudinal static stability

[@senorPFox]

lovely explanation. I have a degree in aerospace engineering and came back here to remind myself of the principles behind static stability

[@venkateshbaskaran9162]

How to create a video like this. We write in the notepad, but it doesn't show the pen. ?

[@Thechad201]

Thank you Mr Evans. Great lecture.

[@chafaon]

Would be great if you could do us some more lectures on related subject matter

[@vikramswamykannu2872]

Aerodynamic centre behind the aircraft center of gravity is?????

[@mithunmahato309]

I can't understand the CoP and the AC ! As of my reading through the defination aerodynamic centre(AC) is the point in the aircraft where the pitching moment never changes with the change in angle of attack(AoA). My understanding of the Centre of pressure(CoP) is that it is the resultant pressure point in the aerofoil and it slides rearward when AoA decreases and vice-versa. So it changes its position wrt the AoA. Now the point is how the pitching moment(force arm i.e dist between CoP and that particular point called AC multiplied by the force) remains constant when the CoP itself moves with the change in AoA ?

[@petraschack-beckschulte4072]

As far as I know, as the cup moves away from the cg the Lift will decrease so the piching moment will be almost constant (f•l=m) sry for my bad english.

[@AmanSingh-we4yw]

Hi, I just wanted to know in breifly that 1). How to know that our (airfoil/wing) is having negative moment which makes aircraft stable?

[@petraschack-beckschulte4072]

If you using „airfoil tools“ for your airfoil selection you can se an alpha v cm chart (Sry for my bad english)

[@chafaon]

Great explanation Mr Evans. Distinctly British accent! In which university do you teach?

[@chafaon]

Sorry for being an idiot; I finally read that very obvious line about Swansea University!

[@superchuy520]

Could someone please explain me better the last part on where the wing is providing less down force because of the wing and the tail tends to provide a force on the upward direction. I just couldn't understand this scenario, if someone could help it would mean a lot to me. Thank you. Min: 14:00

[@petraschack-beckschulte4072]

When the cp is behind the cg the wing will pich down, to counteract that movement you need a second lifting area that is trying to push the nose of the plane up. (Sry for my bad English)

[@burkee3086]

i dont understand because Do neutral point and the a.c. have to be in the same point.

[@jimmypestos7736]

+burkee No not at all, the a.c. is a point on the wing, usually around 25% chord where the moment doesnt change with respects to the angle of attack. The neutral point is the very last point that is juuustt stable, if the cg would move aft more the plane would be unstable. If your np is in the same place as your ac you should probably design a new plane xD Because then you have a very small static margin, if you can even put your cg in front of the ac. (static margin is the distance between the cg and the np.) Very informative video btw :) I have an exam which also regards static staility tomorrow. Cool to see that people from other universities are learning exactly the same as I am learning :P -a TU Delft student :D