Originally Posted by
Dutch M
@sensor_validation
Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.
You need to keep your reference axes the same, moving at the same constant initial velocity then there is no change in Kinetic energy - but OK "v" is no longer airspeed, if windspeed changes.
The energy exchange Ekin vs Epot, is in general only valid for speeds in the direction of the change of Epot (ie Height) and not when trading speed between perpendicular axis.
WRONG. Of course you have to make assumptions about constant windspeed, thrust=drag, g constant etc but correctly applied the maths/physics works, in 3-d vector co-ordinates - until you get close to speed of light!
And back to the point, the reference points quoted for AF447 are consistent with a zoom-climb trading speed for altitude. AF447 did not get caught up in 7000ft/min updraught where an external force supplied the work done to increase the gravitational potential energy.
Note - a zoom climb was discussed on these forums as soon as the wreckage position reported, way before the BEA confirmed it - it was the most obvious way AF447 could shed horizontal speed so quickly and end up so close to its last transmitted position.