Safety of winch launch vrs. aero tow?

Bob Johnson wrote:

I would like to learn how they do this. Our Blanik has perhaps the best
located CG hook on any sailplane I'm aware of, although some would say
the bridle is somewhat awkward to use.
On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
winch engine throttle is advanced to the forward stop in 3 seconds and
at this time the engine is already rapidly approaching redline 5000 RPM.
At this point the Blanik is already beginning its climb and the throttle
is eased.

As a winch driver, I allways try to leave the throttle in the position it
has when the plane leaves the ground, for about the first 1/3 of the climb.
Then I slightly slow down, depending on the wind and the climb angle of the
plane. This can mean full throttle for a double seater and almost idle for
a Ka8 with strong headwind. This method works in all wind conditions.

With an ASK21 or Grob G103, the ground roll is not longer than 2 or 3
seconds. The first ca. 100 feet we keep a flat attitude, than we go
slightly into a climb angle of about 40 degrees.

We limit our climb airspeed to 55-60 kt, which I believe is the POH
recommendation.

This seems a bit slow for me, but may be correct for the Blanik. The ASK21
has a recommended speed of about 60 kt, and 65 is no problem. More speed
means more lift too.

Very little if any back stick is necessary, and the
Blanik attains the 55 kt climb pretty much on its own until the last
part of the 45 second tow, when some back stick is applied to counter
the downward (with respect to the ground) pull of the rope.

In the last part of the climb it is even important to give the stick a
little forward, so the angle between cable and plane does not exceed the
point where the backrelease is triggered. That way you can stay longer on
the rope, getting higher. Also the release is much softer.

Just my 2 cents...
Eggert

Eggert -

You are exactly right with those finer points of flying the launch.
Thanks for adding those to the thread.

Also we will want to try maybe 60-65 kt in the climb next time we go
out.

Cheers,

BJ

Eggert Ehmke wrote:

Bob Johnson wrote:

I would like to learn how they do this. Our Blanik has perhaps the best
located CG hook on any sailplane I'm aware of, although some would say
the bridle is somewhat awkward to use.
On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
winch engine throttle is advanced to the forward stop in 3 seconds and
at this time the engine is already rapidly approaching redline 5000 RPM.
At this point the Blanik is already beginning its climb and the throttle
is eased.

As a winch driver, I allways try to leave the throttle in the position it
has when the plane leaves the ground, for about the first 1/3 of the climb.
Then I slightly slow down, depending on the wind and the climb angle of the
plane. This can mean full throttle for a double seater and almost idle for
a Ka8 with strong headwind. This method works in all wind conditions.

With an ASK21 or Grob G103, the ground roll is not longer than 2 or 3
seconds. The first ca. 100 feet we keep a flat attitude, than we go
slightly into a climb angle of about 40 degrees.

We limit our climb airspeed to 55-60 kt, which I believe is the POH
recommendation.

This seems a bit slow for me, but may be correct for the Blanik. The ASK21
has a recommended speed of about 60 kt, and 65 is no problem. More speed
means more lift too.

Very little if any back stick is necessary, and the
Blanik attains the 55 kt climb pretty much on its own until the last
part of the 45 second tow, when some back stick is applied to counter
the downward (with respect to the ground) pull of the rope.

In the last part of the climb it is even important to give the stick a
little forward, so the angle between cable and plane does not exceed the
point where the backrelease is triggered. That way you can stay longer on
the rope, getting higher. Also the release is much softer.

Just my 2 cents...
Eggert