On Monday, 19 April 2021 at 18:30:14 UTC+1, Andreas Maurer wrote:
On Wed, 24 Mar 2021 19:56:04 -0700 (PDT), ProfJ
wrote:
Hi Folks,

There's a lot of focus at the moment on wing dropping during the ground roll phase. I did my primary training on winch launches. For those who have never winch launched, it's quite an experience being in a 900 lb. vehicle which is accelerated by a 300hp motor which is fixed to the ground and connected by a cable, i.e. no slip anywhere. One of my co-trainees was a large and apparently fearless professional rugby player; some time later he admitted to me that he had kept his eyes tightly closed for his first half dozen launches.

As a way of dealing with the sensory overload of the first few seconds of a winch launch, I used a protocol which was based on what I could control.. It went like this:

In the first second of roll, there is only one control which has any authority, and that is the cable release. You have to release if the glider jerks forward and overruns the cable. So, have a good grip on the release and the only thing you have to think about in the first second is, should I release? None of the other controls have any effect at this speed, so don't think about them.

In the second second of roll, the rudder starts to have authority. The initial jerk probably pulled the glider offline. So get back on line. Given the yaw/roll coupling, this will probably help raise any falling wingtip.

In the third second of roll, the elevator has authority. So raise the tail (or nose, depending) and get balanced on the main wheel.

You might question, why control yaw then roll? Even with two wheels on the ground, there is some yaw control, and the initial launch jerk probably has the tail bobbing up and down anyway, so don't worry about pitch yet. Get in line.

In the fourth second of roll, the ailerons finally have some authority and you can level the wings. By that time, with a winch, you're probably airborne anyway.

This was helpful to me because it gave a structure for dealing with a very fluid and rapidly evolving situation.

The main reason for describing this, is that it requires you to have a grip on the release and understand that it's a primary control during ground roll; certainly the only one that works in the initial roll.

Just my two cents...
Just a question: How many winch launches do you have and in which
glider types?

Just asking because most of your assumptions are, let me put it like
this, not completely correct and seem to refer to an incredibly
underpowered winch.


Cheers
Andreas

Just an aside.
I have just changed gliding clubs and very sensibly the CFI asked me to do some winch checks, knowing lockdown had kept me grounded and my previous club was mainly an aerotow site.
We launched using a sky launch winch with Dylene ? rope not wire.
WOW the acceleration was phenomenal airborne in less than 20M.
Of course there was a bang and the cable came off first time low second time about 600ft so I never got a proper launch.
But the speed was really an eye opener after the kit I was using before.
Just to add the glider was a K21 and its very easy to put the heal of your hand against the airbrakes and your fingers lightly round the release.
That makes sure the brakes stay shut and stops you pulling the release by accident .