poor lateral control on a slow tow?

At 15:05 31 December 2010, John Cochrane wrote:
Is poor handling at low speed on tow a common experience?

Well not for me, but only because I don't often get towed slow.
=A0For
my ballasted ASW-28, 65kts indicated in the glider is as slow as I'd
like to be. =A0On the few tows that the speed has dropped to 60kts
it's
barely possible to stay in control in any sort of turbulence. =A0Both
pitch and roll control are greatly reduced, I never noticed a problem
with yaw control.


This is precisely the aerodynamic puzzle. The same standard class
glider stalls in the low 40s and is perfectly happy thermaling at
45-50. So why does 60 feel so awful on tow?

This does seem a lot worse in standard class than 15 meter, another
hint for the puzzle.

If it were downwash, one would think that just flying higher would
solve it. But that's the best theory I've heard so far.

I have seen quite a few contests with tow pilots who had little
experience with fully ballasted gliders. It's really important to get
the word out to them 1) yes, we really want to tow that fast. 2) get
up to speed in ground effect, then start climbing.

I distinctly remember that helpless feeling sitting in a tanked up
discus, crossing the end of the runway, as the towplane departed what
looked like straight up at about 50 knots.

On another occasion, every single tow by one pilot was accompanied by
a chorus of demands for more speed on the radio. Eventually he piped
up "what do y'all want to fly so fast for anyway?'' I guess the 2-33
never wanted to go 70 on tow.

John Cochrane


In the normal tow position I don't think you can get high enough to get
away from the wing wake without tipping the tug on its nose. On the other
hand, my simple modelling suggests that a typical low tow position should
be a lot better.

15m vs standard class ... Forgive my ignorance (I've never flown a
flapped glider), but presumably a 15m glider is towed with the flaps
deflected, which would tend to unload the tips and hence maintain aileron
authority at high incidence. Would the ailerons typically be drooped at
this flap setting?

Doug