Decision making in ground roll

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...

On Wednesday, March 24, 2021 at 10:56:06 PM UTC-4, 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...


Four seconds of ground roll in a winch launch?? What kind of a winch is/was that? Mule-powered? Must have been an older design you often see in use in clubs in the UK!
A modern winch will get you airborne in about 2 seconds - way faster than it takes for the wings to drop. The ground roll on our winch is typically two to three lengths of the fuselage and you have full rudder authority almost immediately.

Uli
'AS'

I have done maybe 1500 winch launches on quite a variety of airfields, most of them as an instructor, and I've never heared such a nonsense.
You hold your hand close to the release, maybe on the cable behind the knob, but you never grab it.
The tail is not bobbing around. On two-seaters like the ASK21, it will come down during the initial acceleration, and it will stay down unless your winch is a piece of junk.
You don't raise the tail.
You don't think about controls authorities. The nose veers 10 degrees off - you release. A wing threatens to hit the ground - you release. No thinking involved.
And you will have full authorities of controls 10 m into the ground roll.

Bert
Ventus cM "TW"

Le jeudi 25 mars 2021 Ã* 03:56:06 UTC+1, ProfJ a écritÂ*:
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...

On Thu, 25 Mar 2021 00:13:44 -0700 (PDT), Tango Whisky
wrote:

I have done maybe 1500 winch launches on quite a variety of airfields, most of them as an instructor, and I've never heared such a nonsense.
You hold your hand close to the release, maybe on the cable behind the knob, but you never grab it.
The tail is not bobbing around. On two-seaters like the ASK21, it will come down during the initial acceleration, and it will stay down unless your winch is a piece of junk.
You don't raise the tail.
You don't think about controls authorities. The nose veers 10 degrees off - you release. A wing threatens to hit the ground - you release. No thinking involved.
And you will have full authorities of controls 10 m into the ground roll.

Bert
Ventus cM "TW"


Bert is right, as usual.


Cheers
Andreas, 5.000+ winch launches as instructor.

On 3/24/21 8:56 PM, 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...


I see others have provided feedback related to the "weak point" in your
logical - and IMO fundamentally sensible - reasoning. My knee-jerk
mental response to your logic was along the lines of: It's sensible in
basic theory, but likely "only minimally applicable" to most of the real
(winching) world.

It would take some combo of a weak
winch,"leisurely-winch-operator"/lacking-headwind to yield a
4-second-to-liftoff winch launch in my direct/observational
experience...writing as one whose first experience with a winch was a
1948, Buick straight-8-powered, old/tired when our paths crossed
baby...and *IT* easily, consistently, bettered 4-seconds-to-liftoff
launches of loaded 2-33s.

In any event, if your logical/linear reasoning worked for you - awesome!
Mebbe the problem lies in translating reality to words, I dunno. But
sensory-input overload is an inescapable hurdle teaching/experiencing
winch launching contains to be sure. There's no substitute for
experience...assuming a person survives it.

YMMV.

Bob W.

On Thursday, 25 March 2021 at 08:33:54 UTC-6, Bob W. wrote:
On 3/24/21 8:56 PM, 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...

I see others have provided feedback related to the "weak point" in your
logical - and IMO fundamentally sensible - reasoning. My knee-jerk
mental response to your logic was along the lines of: It's sensible in
basic theory, but likely "only minimally applicable" to most of the real
(winching) world.

It would take some combo of a weak
winch,"leisurely-winch-operator"/lacking-headwind to yield a
4-second-to-liftoff winch launch in my direct/observational
experience...writing as one whose first experience with a winch was a
1948, Buick straight-8-powered, old/tired when our paths crossed
baby...and *IT* easily, consistently, bettered 4-seconds-to-liftoff
launches of loaded 2-33s.

In any event, if your logical/linear reasoning worked for you - awesome!
Mebbe the problem lies in translating reality to words, I dunno. But
sensory-input overload is an inescapable hurdle teaching/experiencing
winch launching contains to be sure. There's no substitute for
experience...assuming a person survives it.

YMMV.

Bob W.

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.

On Friday, 26 March 2021 at 10:25:39 UTC-6, ProfJ wrote:
On Thursday, 25 March 2021 at 08:33:54 UTC-6, Bob W. wrote:
On 3/24/21 8:56 PM, 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...

I see others have provided feedback related to the "weak point" in your
logical - and IMO fundamentally sensible - reasoning. My knee-jerk
mental response to your logic was along the lines of: It's sensible in
basic theory, but likely "only minimally applicable" to most of the real
(winching) world.

It would take some combo of a weak
winch,"leisurely-winch-operator"/lacking-headwind to yield a
4-second-to-liftoff winch launch in my direct/observational
experience...writing as one whose first experience with a winch was a
1948, Buick straight-8-powered, old/tired when our paths crossed
baby...and *IT* easily, consistently, bettered 4-seconds-to-liftoff
launches of loaded 2-33s.

In any event, if your logical/linear reasoning worked for you - awesome!
Mebbe the problem lies in translating reality to words, I dunno. But
sensory-input overload is an inescapable hurdle teaching/experiencing
winch launching contains to be sure. There's no substitute for
experience...assuming a person survives it.

YMMV.

Bob W.
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.

Oh yeah, and those videos which have cockpit view - note the hand on the release. Tango Whiskey, you better let Bruno know he's doing it all wrong...

On Fri, 26 Mar 2021 09:27:45 -0700 (PDT), ProfJ
wrote:

Oh yeah, and those videos which have cockpit view - note the hand on the release. Tango Whiskey, you better let Bruno know he's doing it all wrong...

Keeping the hand on the release is doing it all wrong, sorry to say
that. Seen a couple of incidents caused by inadvertent release.

Before you ask - I see about 3.000 winch launches per year on my home
airfield alone. This is probably more than all the winch launches in
the US combined, hence I reckon us Germans have a little bit of
experience with that launch method...


Cheers from Germany
Andreas

On 3/26/2021 12:25 PM, ProfJ wrote:
On Thursday, 25 March 2021 at 08:33:54 UTC-6, Bob W. wrote:
On 3/24/21 8:56 PM, 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...

I see others have provided feedback related to the "weak point" in your
logical - and IMO fundamentally sensible - reasoning. My knee-jerk
mental response to your logic was along the lines of: It's sensible in
basic theory, but likely "only minimally applicable" to most of the real
(winching) world.

It would take some combo of a weak
winch,"leisurely-winch-operator"/lacking-headwind to yield a
4-second-to-liftoff winch launch in my direct/observational
experience...writing as one whose first experience with a winch was a
1948, Buick straight-8-powered, old/tired when our paths crossed
baby...and *IT* easily, consistently, bettered 4-seconds-to-liftoff
launches of loaded 2-33s.

In any event, if your logical/linear reasoning worked for you - awesome!
Mebbe the problem lies in translating reality to words, I dunno. But
sensory-input overload is an inescapable hurdle teaching/experiencing
winch launching contains to be sure. There's no substitute for
experience...assuming a person survives it.

YMMV.

Bob W.

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.

Never let mere facts get in the way of a good theory!

On Fri, 26 Mar 2021 13:37:25 -0400, Moshe Braner wrote:

On 3/26/2021 12:25 PM, ProfJ wrote:
On Thursday, 25 March 2021 at 08:33:54 UTC-6, Bob W. wrote:
On 3/24/21 8:56 PM, 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...

I see others have provided feedback related to the "weak point" in
your logical - and IMO fundamentally sensible - reasoning. My
knee-jerk mental response to your logic was along the lines of: It's
sensible in basic theory, but likely "only minimally applicable" to
most of the real (winching) world.

It would take some combo of a weak
winch,"leisurely-winch-operator"/lacking-headwind to yield a
4-second-to-liftoff winch launch in my direct/observational
experience...writing as one whose first experience with a winch was a
1948, Buick straight-8-powered, old/tired when our paths crossed
baby...and *IT* easily, consistently, bettered 4-seconds-to-liftoff
launches of loaded 2-33s.

In any event, if your logical/linear reasoning worked for you -
awesome!
Mebbe the problem lies in translating reality to words, I dunno. But
sensory-input overload is an inescapable hurdle teaching/experiencing
winch launching contains to be sure. There's no substitute for
experience...assuming a person survives it.

YMMV.

Bob W.

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.

Never let mere facts get in the way of a good theory!

....but all the same, all those launches look like those we had back in
2000 when I was learning to fly. That was a Supacat with steel cables,
which take much more power to pull in when the cable is still on the
ground than the plastic cable we use now. That winch had a 250hp aircooled
diesel V8 engine that I'm told was designed for pumping water to keep
mines dry.

Now we have a 400 hp Skylaunch (V8 truck engine running on LPG and fitted
with plastic cables, and initial acceleration is a LOT faster.

We use a 1km cable: when we were using steel cable even six men pulling
it couldn't pull the cable back after an aborted launch: we just told the
winch driver the wind it in and put the glider on the next cable.
However, with the plastic cable we use now, in the same situation two
blokes can pull the cable back the the launch point without difficulty.
That large difference in the effort needed to pull the cable along the
ground makes a huge difference to the initial launch acceleration.

I think the UK and Australian videos all showed winches using steel
cable. I can't see what winch or type of cable Bruno was using, but he
did mention 8000 feet of cable while the others all looked to be quite a
lot shorter.



--
Martin | martin at
Gregorie | gregorie dot org