Greetings all.
Haven't looked in for a few days as Mrs Pit Bull and I have been scouring the countryside looking for a new Kennel.
JF. With you. Once you start looking at how the aeroplane rotates (as opposed to where it goes), then I can see how the aeroplanes axes would be a better reference rather then its flight path. Presumably you now need to track its angular inertia (i forget the correct term) about each axis, and since the mass is distributed with reference to the a/c not the flight path, the a/c becomes a better reference?
Bookworm. Agreed. I think it is most important to distinguish between short and long term tendancies. With reference to the case in point, I recall being taught Effects of Controls on the old JP. Open the taps up, and the a/c pitchs down every so slightly for a few seconds before the increased airspeed overwhelms the effect and pitchs you back up again.
For All. With reference to a handy explanation for induced drag. When teaching P of F, I found most of the 'tilting vector' type arguements quite tricky to put across, so I preferred to track energy instead. Basic arguement goes like this:
- The generation of a vortex is reasonably easy to visualise, even if how it causes drag is less so.
- Although we often visualise the airflow around the wing, it is sometimes handy to remember that in reality the air is sitting there minding its own business when along comes a wing and churns it up. (Model: stationary aerofoil. Reality: stationary air)
- A formless aircraft with a perfectly frictionless skin would still form the vortices, due lift production.
- So, before the aircraft, the air was still. After the aircraft, it is rotating. Therefore it has gained energy.
- The energy the air has gained must have come from the aircraft. Anything that removes energy from the aircraft is drag.
Regards, everyone.
CPB