poor lateral control on a slow tow?

At 02:13 05 January 2011, AGL wrote:

In very slow flight without flaps my 1-35 drops into a stall long
before it gets as bad as a tow does at 60 statute mph. You would
think that I would have stalled out of the tow too. Perhaps the
wallowing around on tow is just the turbulent air on the ailerons and
not an imminent stall at all. (Think rotor in wave or turbulence
behind a hill on a smaller scale)

Are there any reports of incidents where a glider drops into a stall
on a slow tow or are there just complaints of glider pilot annoyance?
(I agree it's not fun)

For example, if the air turbulence was going "down" on the right side
just when you try to bank "left" that would make the controls feel
sluggish. At some angle of bank, assuming that everything else was
symmetrical, the two ailerons would be in different parts of the
turbulence, confusing the situation.

Has anyone tried some flaps in an integrated flap machine (which
reduces stall speed) to see if the wallowing goes away?

Unfortunately, my trailer is in a snowbank.



That's a useful comment: the aerodynamic modelling I did suggests that
the lateral control problems on tow should be different (worse) than those
in a typical stall, because the wing is stalling at the tips rather than
the root.

No-one has yet admitted to actually stalling or dropping a wing on tow -
so the effect seems to be annoying rather than dangerous.

Flaps should (theoretically) improve matters by (a) reducing stall speed
and (b) shifting the spanwise lift distribution inboard and unloading the
tips. However, if the flaps are integrated with the ailerons then the
associated aileron droop would counteract (b).

On 1/5/2011 12:53 AM, Doug Greenwell wrote:
At 02:13 05 January 2011, AGL wrote:

Has anyone tried some flaps in an integrated flap machine (which
reduces stall speed) to see if the wallowing goes away?

Unfortunately, my trailer is in a snowbank.

That's a useful comment: the aerodynamic modelling I did suggests that
the lateral control problems on tow should be different (worse) than those
in a typical stall, because the wing is stalling at the tips rather than
the root.

No-one has yet admitted to actually stalling or dropping a wing on tow -
so the effect seems to be annoying rather than dangerous.

Flaps should (theoretically) improve matters by (a) reducing stall speed
and (b) shifting the spanwise lift distribution inboard and unloading the
tips. However, if the flaps are integrated with the ailerons then the
associated aileron droop would counteract (b).

My ASH 26E has the flaps and ailerons moving in unison in the 1,2, and 3
"cruise" positions; flap 4 (thermal) moves the flaps down a bit more
than the ailerons, so there is some washout in the wing. That might make
it handle better during a slow tow than it otherwise would. I've never
had a slow tow, so I can't say. If I ever take another tow, I'll compare
flap 3 and 4 with the tow plane going "slow".

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "