High tow vs. low tow for rough tows (long)

On 5 Dec 2003 10:53:17 -0700, (Mark James Boyd)
wrote:

A lot of different techniques - little consensus

Bruce - Hi to slow and get slack out, then match speeds by diving
Brian - Yaw to reduce snappiness when line comes taut
Janusz - Shorter rope so tug and glider are in the same air
Michel - Low tow and avoid slack line

Let me add the standard procedure that I was told and that all pilots
I know of are using:
Extend the airbrakes (carefully - only about one inch) to get the
slack out. Don't let the speed difference between glider and tow plane
get too big.

Not mentioned is the use of spoilers. I've noticed
one ranked pilot who flies a slick glider sometimes with
ballast uses slight spoiler adjustment to regulate slack line.

Ooops... seems like others are using that method too..

There's one important part when trying to get the slack out: Do not
let the glider get too slow (compared to the tow plane) - otherwise
the acceleration when the tow rope tautens might break the weak link.

The method of how to slow the glider down is a question of taste -
I've used sideslips for that part which also work well (but I teach my
students to use tha airbrake).


Bye
Andreas

In article ,
Andreas Maurer wrote:

On 5 Dec 2003 10:53:17 -0700, (Mark James Boyd)
wrote:

A lot of different techniques - little consensus

Bruce - Hi to slow and get slack out, then match speeds by diving
Brian - Yaw to reduce snappiness when line comes taut
Janusz - Shorter rope so tug and glider are in the same air
Michel - Low tow and avoid slack line

Let me add the standard procedure that I was told and that all pilots
I know of are using:
Extend the airbrakes (carefully - only about one inch) to get the
slack out. Don't let the speed difference between glider and tow plane
get too big.

And if it does, what do you do then?

That's why if I'm going faster than the towplane I prefer to store the
energy by climing a little, rather than by simply throwing it away using
the brakes, or a slip, or a yaw.

The slack isn't going to come out until you're going slower than the
towplane, and you need a way to get back to about the same speed again.

-- Bruce

U¿ytkownik Bruce Hoult w wiadomo¶ci do grup
dyskusyjnych ...
In article ,

That's why if I'm going faster than the towplane I prefer to store the
energy by climing a little, rather than by simply throwing it away
using
the brakes, or a slip, or a yaw.

But there's a risk that the towplane gets "out of the screen" because You
got higher than it, and then You have a problem...

JK

On Sat, 06 Dec 2003 16:59:44 +1300, Bruce Hoult
wrote:


Extend the airbrakes (carefully - only about one inch) to get the
slack out. Don't let the speed difference between glider and tow plane
get too big.

And if it does, what do you do then?

Pray that I don't break the cable.


That's why if I'm going faster than the towplane I prefer to store the
energy by climing a little, rather than by simply throwing it away using
the brakes, or a slip, or a yaw.

The slack isn't going to come out until you're going slower than the
towplane, and you need a way to get back to about the same speed again.

Basically a good idea - but higher than the tow plane, especially in
gusty conditions, is a place where I try not to be.

Bye
Andreas

Let me add the standard procedure that I was told and that all pilots
I know of are using:
Extend the airbrakes (carefully - only about one inch) to get the

Try this in a Janus. Extending isn't a problem, but I wish you luck
closing them again during the tow. Chances are that after successfully
closing them, slack is much bigger than before.

Stefan

On Sat, 06 Dec 2003 11:35:46 +0100, Stefan
wrote:


Try this in a Janus. Extending isn't a problem, but I wish you luck
closing them again during the tow. Chances are that after successfully
closing them, slack is much bigger than before.

Why?
I haven't flown the Janus that often, but to me its airbrakes didn't
feel extraordinary to me?

Bye
Andreas

In article ,
Stefan wrote:

Let me add the standard procedure that I was told and that all pilots
I know of are using:
Extend the airbrakes (carefully - only about one inch) to get the

Try this in a Janus. Extending isn't a problem, but I wish you luck
closing them again during the tow. Chances are that after successfully
closing them, slack is much bigger than before.

I'm not sure I understand what you're talking about. We've got:

1) a Janus
2) 1000 ft high ridges
3) frequent strong winds onto the ridges
4) airspace limitations restricting us to, say, 2500 ft in some
of the places the ridges take us.

So I've spent a fair amount of time flying the Janus at 90 - 100 knots
and needing some brake to stop from busting the altitude limit. It's
not a problem.

See, for example:

http://www.hoult.org/bruce/gliding/sasha/p17.html

Someone previously asked if I always fly around with the brakes half
open. Yes, on days like that, in that area.

-- Bruce

small correction, I wasn't suggesting yawing the airplane to slow it
down and take out the slack. What I was saying is if you move off to
the side when the slack comes out it will automatically yaw the
towplane and a nose hook equipped glider. No timing required just stay
out to the side.

Brian


(Mark James Boyd) wrote in message news:3fd0d41d$1@darkstar...
A lot of different techniques - little consensus

Bruce - Hi to slow and get slack out, then match speeds by diving
Brian - Yaw to reduce snappiness when line comes taut
Janusz - Shorter rope so tug and glider are in the same air
Michel - Low tow and avoid slack line

Although Bruce's approach is most elegant, I think it
also requires the most skill and best timing. Matching
airspeeds is challenging.

Brian's approach is pretty standard, but also requires a
little bit of timing. I'd also be surprised if he
isn't subtly using a little bit of dive at the end
to help match airspeeds.

Janusz and his 20 meter rope leaves me speechless.
I'd have to try it to have any real opinion.

Michel's low tow seems like a low-skill winner.
As long as you don't get too low and scare the towpilot
into releasing it seems you'll do ok.

Not mentioned is the use of spoilers. I've noticed
one ranked pilot who flies a slick glider sometimes with
ballast uses slight spoiler adjustment to regulate slack line.

Any rotor towpilots have any further opinions?

In article ,
Brian Case wrote:
small correction, I wasn't suggesting yawing the airplane to slow it
down and take out the slack. What I was saying is if you move off to
the side when the slack comes out it will automatically yaw the
towplane and a nose hook equipped glider. No timing required just stay
out to the side.

Brian


Thank you, Brian. A subtle but important distinction...being out
to the side clearly means the slack is taken out with quite a bit
less "snappiness." And this is a different dampening than the
yaw of the glider and tug when the line comes taut. Excellent!

small correction, I wasn't suggesting yawing the airplane to slow it
down and take out the slack. What I was saying is if you move off to
the side when the slack comes out it will automatically yaw the
towplane and a nose hook equipped glider. No timing required just stay
out to the side.

Brian

If we can base the idea on two premises, first that we have a lot of
slack and second that breaking the rope is undesirable.

The reality is that large amounts of slack tend to result in big speed
differentials between the tow plane and the glider, particularly with
glass gliders and powerful tugs.

While the rope is slack, no thrust is transmitted to the glider.
Even with no pitch change, the glider begins decelerating. Due to
the loss of the glider's drag, the tug either accelerates or increases
rate of climb (depending on the tow pilot's actions). Presuming a
beginning generous gust or slap, and big slack, this allows a long
enough time period for a noticeable speed differential to be created.
Now, with differential speed, the slack is coming out rapidly.

One pilot sits level with or slightly below the tow plane and offset
to one side believing that the imminent yawing between the tow plane
and glider will dampen the loads sufficiently to prevent the rope
from breaking.

A second pilot has positioned himself slightly above the tow plane
and offset enough that he can easily watch the towline and it's
rate of tightening. As the line starts to come tight, this pilot
points his nose toward the tow plane and lowers the nose,
believing that he is in a good position and attitude for at least
some of the tow line loads to be absorbed in accelerating the glider.
The speed differential is diminished, as is the AOA of the glider.

Which of these two pilots is least likely to break the rope? And do
you have sound physics (rather than emotion) to support your position?

M Eiler