Decision making in ground roll

I attended a winch training a few years ago. I had aero-tow only prior. Of course, it was stressed to release if the wing dropped. This particular winch was pretty strong and we were airborne rapidly. I remember thinking that, by the time I realized the wing was dropping and reacted to it, we would be tumbling down the runway. It was only 10 launches over couple of days and I still wasn't over the sensory overload on #10. Hand near but not on the release, BTW. I wonder how many flights it would take me or the average pilot to get comfortable but there are limited opportunities in my neck of the woods.

On Friday, 26 March 2021 at 16:25:39 UTC, ProfJ wrote:

It's kind of fun to have all the experts invalidate my actual lived experience, and also physics. Let's go watch some videos of winch launches, shall we?

Here's Bruno Vassel launching https://www.youtube.com/watch?v=VrUT...el=BrunoVassel . Due to the wonders of actual video evidence, we see the glider taking seven seconds from first roll to airborne.
Here's one from Oxford Gliding - https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer - nine seconds from first movement to airborne.
Here's one from Mount Beauty - https://www.youtube.com/watch?v=SE5J...=GeorgeSkarbek - five seconds to airborne.
Here's one - called "Rather fast winch launch" ! - https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer - five seconds to airborne.

I didn't cherry-pick these, they were the first four I found where you could see the glider roll. If anyone can find one showing a two-second roll, go ahead and show us.

Yes, it seems like it's two seconds. That's the problem of sensory overload. Apparently even the experience of 1500 launches on a variety of airfields doesn't overcome it.

This one at my club shows the glider in the air after about 2 seconds:

https://www.youtube.com/watch?v=f_ASzIsviAE

On 3/26/2021 5:13 PM, waremark wrote:
On Friday, 26 March 2021 at 16:25:39 UTC, ProfJ wrote:

It's kind of fun to have all the experts invalidate my actual lived
experience, and also physics. Let's go watch some videos of winch
launches, shall we?

Here's Bruno Vassel launching
https://www.youtube.com/watch?v=VrUT...el=BrunoVassel . Due
to the wonders of actual video evidence, we see the glider taking seven
seconds from first roll to airborne. Here's one from Oxford Gliding -
https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer - nine
seconds from first movement to airborne. Here's one from Mount Beauty -
https://www.youtube.com/watch?v=SE5J...=GeorgeSkarbek -
five seconds to airborne. Here's one - called "Rather fast winch launch"
! - https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer -
five seconds to airborne.

I didn't cherry-pick these, they were the first four I found where you
could see the glider roll. If anyone can find one showing a two-second
roll, go ahead and show us.

Yes, it seems like it's two seconds. That's the problem of sensory
overload. Apparently even the experience of 1500 launches on a variety of
airfields doesn't overcome it.

This one at my club shows the glider in the air after about 2 seconds:

https://www.youtube.com/watch?v=f_ASzIsviAE


Reality is what a person experiences; camera views aren't 100% representative
(cf: Hollywood).

A beady-eyed look at several of the Mt. Beauty launch views-from-afar show
multiple launches with ~2-sec ground rolls *after* the line slack is removed
and the ship is beyond wing-runner assistance...which by my reckoning is "when
the winch launch begins". Everything prior to that is preparation.

YMMV.

Bob W.

On Saturday, March 27, 2021 at 8:34:29 AM UTC-4, Bob Whelan wrote:
On 3/26/2021 5:13 PM, waremark wrote:
On Friday, 26 March 2021 at 16:25:39 UTC, ProfJ wrote:

It's kind of fun to have all the experts invalidate my actual lived
experience, and also physics. Let's go watch some videos of winch
launches, shall we?

Here's Bruno Vassel launching
https://www.youtube.com/watch?v=VrUT...el=BrunoVassel . Due
to the wonders of actual video evidence, we see the glider taking seven
seconds from first roll to airborne. Here's one from Oxford Gliding -
https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer - nine
seconds from first movement to airborne. Here's one from Mount Beauty -
https://www.youtube.com/watch?v=SE5J...=GeorgeSkarbek -
five seconds to airborne. Here's one - called "Rather fast winch launch"
! - https://www.youtube.com/watch?v=-eTU...nel=GreatFlyer -
five seconds to airborne.

I didn't cherry-pick these, they were the first four I found where you
could see the glider roll. If anyone can find one showing a two-second
roll, go ahead and show us.

Yes, it seems like it's two seconds. That's the problem of sensory
overload. Apparently even the experience of 1500 launches on a variety of
airfields doesn't overcome it.

This one at my club shows the glider in the air after about 2 seconds:

https://www.youtube.com/watch?v=f_ASzIsviAE

Reality is what a person experiences; camera views aren't 100% representative
(cf: Hollywood).

A beady-eyed look at several of the Mt. Beauty launch views-from-afar show
multiple launches with ~2-sec ground rolls *after* the line slack is removed
and the ship is beyond wing-runner assistance...which by my reckoning is "when
the winch launch begins". Everything prior to that is preparation.

YMMV.

Bob W.

Bob - couldn't agree more with your separation between 'preparation' and 'winch launch begins'.
I wanted to point out the Design Guidelines for the design and approval of a glider winch issued by the DAeC in Germany, of which I made a full translation which got 'lost' by the old Yahoo winchdesign group administration when they shut them down:

https://www.daec.de/fileadmin/user_u...2010_Rev02.pdf

Original Text:
Paragraph 2115: Beschleunigungsnachweis
Bei Windstille muss das zu startende Luftfahrzeug nach einer
Beschleunigungsstrecke von 15 m um die Längsachse steuerbar sein und
nach höchstens weiteren 45 m Beschleunigungsstrecke die
Abhebegeschwindigkeit erreicht haben.
Der Roll- und Luftwiderstand, sowie die Seilreibung am Boden müssen
beim rechnerischen Nachweis durch einen Zuschlag von 30%
berücksichtigt werden. Der Zuschlag kann bei der Verwendung von
Kunststoffseilen auf 10% vermindert werden.

Translation:
Acceleration requirements
In clam air, the glider to be launched must have control around the longitudinal axis [i.e. aileron control] after a distance of 15m and must have reached lift-off speed after a further 45m.
Rolling- and air resistance as well as the cable friction against the ground have to be considered in the calculations by a factor of 1.3. This additional friction factor can be reduced to 1.1 when plastic lines are being used.

There are more paragraphs governing the speed and power requirements.
What that means is that any winch designed and built either commercially or by clubs in Germany must comply with these guidelines or else they will not get approved and therefore their operation would be illegal and not covered by by the club's insurance. (The DAeC guidelines are de facto the law, similar to BGA regulations in the UK)
When we (a few winch enthusiasts and I ) started the discussion group winchdesign almost 20 years ago and I provided a full translation of these guidelines (with the written permission of the DAeC), it was the general consensus that having guidelines like this makes perfect sense and avoids most hazardous conditions during the winch launch.

So, if ProfJ sees winches accelerating the gliders in a very anemic way it could mean that either the operator is not doing his/her job correctly or the winch is not designed in accordance with these guidelines, which is very possible since many winches around the world were designed in accordance with the rule 'Hold my beer - watch this!'
But of course issuing strict and heavy-handed guidelines based on sound engineering and physics in the interest of operational safety like these must be just another example of a socialist government stifling individualism and free expression, right? ;-)

Uli
'AS'

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

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 .

On Mon, 19 Apr 2021 11:50:38 -0700 (PDT), Jon May
wrote:


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.

Indeed - my club has been using a using a strong winch for three
decades now and I'm always surprised how easy a winch launch is with
such a strong winch.

Pitch control, keeping nose/tail in a certain position is not even a
question - any glider will rotate onto its tail and the only thing to
think about is having the correct trim setting and not let the
acceleration push back your hand (and the stick). Very hard to drop a
wing during a 50m ground run, either.

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 .

Good thought!

The idea how it's being taught in Germany is to touch the release
with your fingertips (so you can find it immediately without looking
at it), but not have the fingers around it - in case of a sudden
acceleration (and subsequent backward move of the hand) it's
otherwise far too easy to pull the release inadvertently.


Cheers
Andreas