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




At 14:24 12 April 2007, Toad wrote:

In reading those types of accident reports, it seems
that most of the
pilots didn't think about there takeoff performance
charts at all.
They did not do a take off calculation. They just
thought, 'I've
allways made it before.' Nor did they think, 'Hey,
I'm halfway down
the runway. I should be flying by now, better abort.'

For a glider takeoff. It would be interesting to have
good data on
expected takeoff rolls and climb rates. Each set of
data would be
specific to towplane-glider pairs. Takeoff surface
and winds would
have to be carefully recorded in addition to a GPS
log with location
and airspeeds.

Any calculations would be suspect until experimentally
verified. So
skip the calculations and start recording data. Get
a flight log of
every takeoff. Try and quantify surface types, towplane
ID and
winds. Then plot the data and make your conclusions.

And then use the data with a grain of salt.

Todd Smith
3S