mstram
5th Apr 2003, 11:34
Ive been doing some reading about soaring.
Given a sailplane that is crusing at 100 knots, and descending at ~ 200 f.p.m. (or 2 knots on the variometer). (Just numbers made up to be easy).
You hit a thermal that gives +400 fpm ( + 4knot).
So you can immediately use 200 fpm (2 knots) to fly straight/level at 100 knots. That leaves you an "extra" 200 fpm (2 knots)
Instead of maintaining 100 knot / 200 fpm climb, you push the nose down to maintain altitude, and get the increased airpseed.
The question :
What does the arspeed increase to ? (Assume an "infinite thermal" :)
"Roller Coaster" answer
I was lookng at Denker's web site, and his "law of the roller coaster". He says that conversion factor = 9 feet per knot, per hundred knots.
A 200 fpm (2 not) gain would ~ 3 ft sec, so using the "roller coaster" logic, the speed gain would be ~ 1knot / 3 sec, i.e. ~ 20 knot speed increase. Does that make sense ?
Would the final speed by 120 knots? If so why would it stop at 120 ?
3 Angle of Attack - Lift Formual
I thought that somehow the Lift formula could be used to calculate the new speed.
How does a VSI rate relate to the L in the lift formual though?
Mike
Given a sailplane that is crusing at 100 knots, and descending at ~ 200 f.p.m. (or 2 knots on the variometer). (Just numbers made up to be easy).
You hit a thermal that gives +400 fpm ( + 4knot).
So you can immediately use 200 fpm (2 knots) to fly straight/level at 100 knots. That leaves you an "extra" 200 fpm (2 knots)
Instead of maintaining 100 knot / 200 fpm climb, you push the nose down to maintain altitude, and get the increased airpseed.
The question :
What does the arspeed increase to ? (Assume an "infinite thermal" :)
"Roller Coaster" answer
I was lookng at Denker's web site, and his "law of the roller coaster". He says that conversion factor = 9 feet per knot, per hundred knots.
A 200 fpm (2 not) gain would ~ 3 ft sec, so using the "roller coaster" logic, the speed gain would be ~ 1knot / 3 sec, i.e. ~ 20 knot speed increase. Does that make sense ?
Would the final speed by 120 knots? If so why would it stop at 120 ?
3 Angle of Attack - Lift Formual
I thought that somehow the Lift formula could be used to calculate the new speed.
How does a VSI rate relate to the L in the lift formual though?
Mike