Safety of winch launch vrs. aero tow?

In article ,
(Chris OCallaghan) wrote:

Point of interest: did you let the spin fully develop after the
coordinated turning stall? There is an aerodynamic tipping point --
that is the self-righting tendency of the tail that would typically
favor a spiral over a spin assuming that the only deflected control
surface was the elevator. Of course a wing drops when in a turning
stall, but without aileron deflection generating drag my guess would
be that designed yaw stability would prevent spin development.

Even with the string in the middle, the elevator will *not* be the only
deflected control surface.

The Blanik makes this very obvious. As you slow down in a shallow turn
(10 degrees, say) you need more and more out of turn aileron in order to
prevent the turn from steepening, and you need more and more into turn
rudder to keep the string in the middle. Both controls can get a
significant way towards their limits in what seems like a perfectly
normal turn. When the inner wing eventually stalls everything is
perfectly set up for a rapid departure and spin.

-- Bruce

You've just described a cross-control stall. I think Eric's point was
that the additional drag at the wingtip wasn't necessary to initiate
auto rotation. The control inputs you've described are counter
intuitive. Is this a peculiarity of the Blanik? I only have a couple
of flights in them.

Typically, shallow banked turns like to roll level, especially if
there is any tendency to slip (dihedral). In most of the models I've
flown, overbanking doesn't become noticeable until you reach 30+
degrees.

Bruce Hoult wrote in message ...
In article ,
(Chris OCallaghan) wrote:

Point of interest: did you let the spin fully develop after the
coordinated turning stall? There is an aerodynamic tipping point --
that is the self-righting tendency of the tail that would typically
favor a spiral over a spin assuming that the only deflected control
surface was the elevator. Of course a wing drops when in a turning
stall, but without aileron deflection generating drag my guess would
be that designed yaw stability would prevent spin development.

Even with the string in the middle, the elevator will *not* be the only
deflected control surface.

The Blanik makes this very obvious. As you slow down in a shallow turn
(10 degrees, say) you need more and more out of turn aileron in order to
prevent the turn from steepening, and you need more and more into turn
rudder to keep the string in the middle. Both controls can get a
significant way towards their limits in what seems like a perfectly
normal turn. When the inner wing eventually stalls everything is
perfectly set up for a rapid departure and spin.

-- Bruce

Chris OCallaghan wrote:
You've just described a cross-control stall. I think Eric's point was
that the additional drag at the wingtip wasn't necessary to initiate
auto rotation. The control inputs you've described are counter
intuitive. Is this a peculiarity of the Blanik? I only have a couple
of flights in them.

Bruce's point, and mine, is that the controls ARE crossed in a
coordinated turn, and the crossing becomes greater as you slow down.
This is not a peculiarity of the Blanik, but is true for all the 20+
gliders I've flown.


Typically, shallow banked turns like to roll level, especially if
there is any tendency to slip (dihedral).

Yes, a slip will tend to roll level, but then you are not flying a
coordinated turn. A slipping turn will allow you to use less "top
aileron" (stick opposite the turn).

In most of the models I've
flown, overbanking doesn't become noticeable until you reach 30+
degrees.

Try it again at 15 to 20 degrees, and notice the control position as you
slow down. Top aileron becomes more pronounced as you near stall, but
it's there even at the usual thermalling speeds.


Bruce Hoult wrote in message ...

snip


Even with the string in the middle, the elevator will *not* be the only
deflected control surface.

The Blanik makes this very obvious. As you slow down in a shallow turn
(10 degrees, say) you need more and more out of turn aileron in order to
prevent the turn from steepening, and you need more and more into turn
rudder to keep the string in the middle. Both controls can get a
significant way towards their limits in what seems like a perfectly
normal turn. When the inner wing eventually stalls everything is
perfectly set up for a rapid departure and spin.

-- Bruce