Aerodynamics of aero towing

On Mar 7, 7:43*am, Karen wrote:
On Mar 7, 2:15*am, Martin Gregorie
wrote: This is a quick observation report. Its really a follow up to a sub-topic
on the "Poor lateral control on a slow tow" thread.

AIRSPEED! AIRSPEED!

It is way more disconcerting when you see the tops of the wings of a
Pawnee from the grounf just before the DG300 behind him stalls,
releases and and spins in from 100 ft.







Last Friday I was sitting outside the CGC clubhouse, which was at the
upwind end of the active runway, when our Pawnee went past at about 200
ft with a Ventus on the line. As it went away I had a clear rear quarter
view which made the attitudes if the two aircraft really easy to see. The
Ventus looked to be at the same height as the Pawnee, but was clearly
flying much more nose-up. I'd estimate that it was at around 4 degrees
nose-up relative to the Pawnee.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

We have discussed this many times before. The nose-up attitude of the
glider results in extra forces that have to be overcome by the wings
and tail surfaces. In particular, modern standard-class ships with a
low angle of incidence of the wing have a pronounced nose-up attitude
that results in loss of control at speeds well above free-flight stall
speed.

I find my Discus 2 won't high-tow very well below 60 knots, even
though its stall speed is nearer 40 or 45. One strategy I use if the
tow plane won't or can't speed up is to descend into low tow, which
buys an extra 5 knots or so.

Extra speed is great, but not under control of the glider pilot!

Mike