Originally Posted by
Gadget freak
Jonkster,
I'm not trying to argue for or against any myths or theories, just trying to get the basic physics straight.
An aircraft going downwind at 120kts airspeed, into a 60 kt headwind with 180 kts groundspeed tailwind has a lot more kinetic energy and inertia than one going at 120 kts airspeed into a 60 kt headwind with only 60 kts groundspeed. Compare the braking distances if you try and land off those conditions. The question is so what? When turning downwind that extra kinetic energy has to come from somewhere and over the course of a downwind turn the aerodynamic forces provide that acceleration without drama.
However, someone above suggested trying a loop in a glider into a strong headwind starting with zero knots groundspeed. Try that and let us know how you get on?
kinetic energy is not an absolute thing - it is relative to a reference frame. As the aerodynamic forces on the aircraft come from the airflow the energy that matters to me in a turn is the KE relative to the air. If it is a car we look at the forces impacting the cars motion come from the ground so the earth would be what mattered. If I was driving on a huge conveyer belt doing circles my speedometer would read constant and I would use the belt as my reference frame.
As for the loop in a glider I would happily do a loop in a glider with 0 knots groundspeed providing my entry airspeed was correct and it was a steady flow airstream.