"Kilo Charlie" wrote in message
...

"Gary Nuttall" wrote in message
...
And keep a note of how much fuel the tug has on board.
How heavy the glider pilot is. How clean the glider
wings are. What time of day it was. Outside Air Temperature,
pressure and moisture content. Local CAPE and Lifted
Index. Length of rope (and its elasticity). Power
setting of tug. What mood each of the pilots were
in. Stick position on ground run. Local thermal and
wave activity. All can have an effect on take-off
distance and climb rate.

There's so many variables that I'd be dubious of any
metrics developed beyond the fact that high altitude,
high temperature and heavy gliders do not make a good
combination.

Anybody who comes up with a set of explicit numbers
and sticks to them is likely to discover how often
theory doesn't work in practice!

Happy soaring
Gary Nuttall


Continues to amaze me at how much disdain glider pilots have for
quantitation. I suppose that may be what draws some of them into the
soaring in the first place. I also enjoy that aspect but think that
attitude has gotten many powered pilots into bad situations. To think
that we are immune to it because we don't have engines is naive.

Casey

I agree, Casy

It would be a big safety factor if we had takeoff performance charts
available. I've been involved in some extremely hazardous high density
altitude takeoffs where the tug was unable to provide adequate climb
performance.

Having enough information to decline the tow might save a few lives. It
seems like a major safety oversight that we don't have hard information on
this. If the STC for a tow hook doesn't require new performance charts, it
should. The glider tow chart should add glider gross weight and L/D to the
tugs TO performance chart and make 300FPM the minimum acceptable climb rate.

I have flown light airplanes in the high and hot western US all my life and
ALWAYS looked at the performance chart before takeoff. Many who didn't left
crumpled aluminum on mountainsides. I think charts would have to be
developed empirically from tests on a specific tug but once there were a few
data points, interpolation should be possible.

I also agree with the poster who selects a go-no-go point on the runway for
release if not airborne. Keep in mind that gliders have a high L/D in
ground effect and usually poor wheel brakes so leave a generous safety
margin for getting stopped after an aborted TO.

Bill Daniels