New 29 Palms Winchfest Video

By the way Marc,

The DG 600 in question did have an AoA stall warning device.
Obviously, that didn't help.

"The stall warning system fitted to the glider consisted
of two orifices on either side of the fuselage, one close
to the wing leading edge and one at approximately
mid-chord. The pressure readings from these orifices
are fed into a cockpit mounted variometer. As the
angle of attack of the glider's wing approaches the
stalling angle, the airflow over the wing changes
giving a differential pressure between the forward and
mid-chord orifices. This produces a movement of the
variometer needle, and an audible signal to warn the
pilot of an impending stall."

Marc Ramsey wrote:
From a pure
dynamics point of view, if you have the stick back during the final
stage of the rotation to climb and the winch looses power, will the
airspeed necessarily decay to near "stall" speed before the glider
actually stalls? It's worth thinking about.

Fair comment, though some awareness of attitude should have helped too.
My instructors have always tended to discourage pole-bending. As a
result I tend to fly the launch after rotating into full climb with
little or no stick back pressure. I check attitude after rotation by
glancing at the tip to compare its angle to the horizon and correct if
needed.

If our CFI thinks a student is messing up the launch by thrashing the
stick and conditions are calm he demonstrates a complete launch post
rotation in the K-21 with his hands off the stick, slow clapping to show
he isn't cheating.

Absolutely, but if an effective and inexpensive AoA meter was available,
I'd want both...

It would be interesting to try one, but I do slightly wonder whether the
increased workload of monitoring it as well as the ASI might be
unhelpful. IMO its no substitute for the ASI during lift-off and
rotation: it can't show the acceleration that indicates its safe to
start rotation.

However, an audible AOA warning may be useful because it wouldn't add to
the normal workload: it would be just one more eventuality.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

This is only part of the report. The full report is available at the Air
Accident Investigation Branch website (no time to find reference at the
moment), and the possible causes were quite complex.

I knew the pilot involved, so won't enter this discussion other than to
suggest reading the full report.

Marc Ramsey wrote:
tommytoyz wrote:
Marc,
Let us assume the accident report is accurate,unless you can show why
is would not be.

With respect to the DG600 accident the shoulder straps
were found to be unfastened after the crash. Therefore
there was at least a possibility that the pilot had
slipped backwards along the very reclined seat on this
type, either due to the ground run acceleration or
entering the climb, as a result, and had pulled the
stick hard back in the process. Hence the unusually
steep climb. Or he could just have been pole bending.

One of our clubs DG1000s has a pneumatic stall warning
device, probably similar to the one in the 600. Problem
is that it goes off anyway during the ground run and
rotation, so people now ignore it. It also keeps going
off in gusty thermals at any speed below about 60 knots
- Not good for our tiny UK thermals!

I don't know what people want from an AoA device; a
stall warning or another dial to look at. If it's just
to warn you of impending instant death, it shouldn't
cry wolf like the one on our DG1000.

As for controlling speed on the winch, this depends
on the winch. I tried out one of the latest Skylaunch
winches yesterday and found that you could vary the
speed by about 5 knots either way by pulling harder
or easing forward. This is almost impossible with our
old Tost winches, despite having very similar engines
and gearboxes to the Skylaunch!

Del Copeland



At 13:06 13 December 2007, Martin Gregorie wrote:
Marc Ramsey wrote:
From a pure
dynamics point of view, if you have the stick back
during the final
stage of the rotation to climb and the winch looses
power, will the
airspeed necessarily decay to near 'stall' speed before
the glider
actually stalls? It's worth thinking about.

Fair comment, though some awareness of attitude should
have helped too.
My instructors have always tended to discourage pole-bending.
As a
result I tend to fly the launch after rotating into
full climb with
little or no stick back pressure. I check attitude
after rotation by
glancing at the tip to compare its angle to the horizon
and correct if
needed.

If our CFI thinks a student is messing up the launch
by thrashing the
stick and conditions are calm he demonstrates a complete
launch post
rotation in the K-21 with his hands off the stick,
slow clapping to show
he isn't cheating.

Absolutely, but if an effective and inexpensive AoA
meter was available,
I'd want both...

It would be interesting to try one, but I do slightly
wonder whether the
increased workload of monitoring it as well as the
ASI might be
unhelpful. IMO its no substitute for the ASI during
lift-off and
rotation: it can't show the acceleration that indicates
its safe to
start rotation.

However, an audible AOA warning may be useful because
it wouldn't add to
the normal workload: it would be just one more eventuality.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

tommytoyz wrote:
By the way Marc,

The DG 600 in question did have an AoA stall warning device.
Obviously, that didn't help.

"The stall warning system fitted to the glider consisted
of two orifices on either side of the fuselage, one close
to the wing leading edge and one at approximately
mid-chord. The pressure readings from these orifices
are fed into a cockpit mounted variometer. As the
angle of attack of the glider's wing approaches the
stalling angle, the airflow over the wing changes
giving a differential pressure between the forward and
mid-chord orifices. This produces a movement of the
variometer needle, and an audible signal to warn the
pilot of an impending stall."

My DG-600 had the AoA device installed, too, it was an annoyance since I
could never get it calibrated to any useful degree. I took it out
eventually...

Marc

I suppose it is OK to highjack a thread that I started?....HU

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inventory, I doubt it will be repeated for 2009. To help the team,
please order a few for your buddies as gifts!

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HoUdino


PS- Our glider field helped arrange the photo shoot, but none of us
have a financial interest (but it did make for an interesting day at
Hemet-Ryan).
PSS- Better than Winchfest... ;-)








On Dec 13, 7:54 am, Del C
wrote:
With respect to the DG600 accident the shoulder straps
were found to be unfastened after the crash. Therefore
there was at least a possibility that the pilot had
slipped backwards along the very reclined seat on this
type, either due to the ground run acceleration or
entering the climb, as a result, and had pulled the
stick hard back in the process. Hence the unusually
steep climb. Or he could just have been pole bending.

One of our clubs DG1000s has a pneumatic stall warning
device, probably similar to the one in the 600. Problem
is that it goes off anyway during the ground run and
rotation, so people now ignore it. It also keeps going
off in gusty thermals at any speed below about 60 knots
- Not good for our tiny UK thermals!

I don't know what people want from an AoA device; a
stall warning or another dial to look at. If it's just
to warn you of impending instant death, it shouldn't
cry wolf like the one on our DG1000.

As for controlling speed on the winch, this depends
on the winch. I tried out one of the latest Skylaunch
winches yesterday and found that you could vary the
speed by about 5 knots either way by pulling harder
or easing forward. This is almost impossible with our
old Tost winches, despite having very similar engines
and gearboxes to the Skylaunch!

Del Copeland

At 13:06 13 December 2007, Martin Gregorie wrote:



Marc Ramsey wrote:
From a pure
dynamics point of view, if you have the stick back
during the final
stage of the rotation to climb and the winch looses
power, will the
airspeed necessarily decay to near 'stall' speed before
the glider
actually stalls? It's worth thinking about.

Fair comment, though some awareness of attitude should
have helped too.
My instructors have always tended to discourage pole-bending.
As a
result I tend to fly the launch after rotating into
full climb with
little or no stick back pressure. I check attitude
after rotation by
glancing at the tip to compare its angle to the horizon
and correct if
needed.

If our CFI thinks a student is messing up the launch
by thrashing the
stick and conditions are calm he demonstrates a complete
launch post
rotation in the K-21 with his hands off the stick,
slow clapping to show
he isn't cheating.

Absolutely, but if an effective and inexpensive AoA
meter was available,
I'd want both...

It would be interesting to try one, but I do slightly
wonder whether the
increased workload of monitoring it as well as the
ASI might be
unhelpful. IMO its no substitute for the ASI during
lift-off and
rotation: it can't show the acceleration that indicates
its safe to
start rotation.

However, an audible AOA warning may be useful because
it wouldn't add to
the normal workload: it would be just one more eventuality.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |- Hide quoted text -

- Show quoted text -

On Wed, 12 Dec 2007 22:33:24 +0000, Martin Gregorie
wrote:

Speaking for myself, I watched the video and saw a succession of
launches with right wing low. As wing low launching is something that,
on my field, would earn you a talk with the duty instructor, I was
unhappy with the description of this being a "best practices" event and
said so.

I agree, Martin.
I've never seen such a series of really critical winch launches
before. With all due respect - a very serious ground-loop accident is
going to happen rather sooner than later.


Comment on launch speed. The rules we use a
- after lift off, maintain a shallow climb until the ASI passes 50 kts
with steady acceleration.
- then and only then rotate slowly. The ideal is to complete rotation
not less than 5 seconds after lift off.
- we have a high torque, high inertia, fluid clutch winch. The pilot
cannot and should not attempt to control its speed except by
signalling the winch driver.
- if you're above Vwinch when the launch starts to flatten toward the
top (i.e. when the angle is below 35 degrees or so), release.
- if the speed drops toward 50 kts, lower the nose to maintain at least
50 kts and monitor the speed.
- if the speed picks up, resume the climb.
- if the nose approaches level and the speed doesn't rise, release.

The same rules apply for us. Works like a charm.



Bye
Andreas

Actually guys, you CAN and SHOULD control airspeed on some winches. There
are few winches that have enough power to prevent a large, heavy glider from
pulling down the drum RPM. Maybe you guys have one - maybe not.

If you are a little too fast, pitch up, load the winch a little and wait to
see what the airspeed does. In most cases, it will ease back down to the
desired airspeed. If you are a bit slow, lower the nose which unloads the
winch a bit and wait for the effect. Once you get the hang of it, it works
sweet.

Many pilots think this won't work becasue they haven't tried it. Give it a
try and get back to us.

Bill Daniels


"Andreas Maurer" wrote in message
...
On Wed, 12 Dec 2007 22:33:24 +0000, Martin Gregorie
wrote:

Speaking for myself, I watched the video and saw a succession of
launches with right wing low. As wing low launching is something that,
on my field, would earn you a talk with the duty instructor, I was
unhappy with the description of this being a "best practices" event and
said so.

I agree, Martin.
I've never seen such a series of really critical winch launches
before. With all due respect - a very serious ground-loop accident is
going to happen rather sooner than later.


Comment on launch speed. The rules we use a
- after lift off, maintain a shallow climb until the ASI passes 50 kts
with steady acceleration.
- then and only then rotate slowly. The ideal is to complete rotation
not less than 5 seconds after lift off.
- we have a high torque, high inertia, fluid clutch winch. The pilot
cannot and should not attempt to control its speed except by
signalling the winch driver.
- if you're above Vwinch when the launch starts to flatten toward the
top (i.e. when the angle is below 35 degrees or so), release.
- if the speed drops toward 50 kts, lower the nose to maintain at least
50 kts and monitor the speed.
- if the speed picks up, resume the climb.
- if the nose approaches level and the speed doesn't rise, release.

The same rules apply for us. Works like a charm.



Bye
Andreas

Bill Daniels wrote:
Actually guys, you CAN and SHOULD control airspeed on some winches. There
are few winches that have enough power to prevent a large, heavy glider from
pulling down the drum RPM. Maybe you guys have one - maybe not.

If you are a little too fast, pitch up, load the winch a little and wait to
see what the airspeed does. In most cases, it will ease back down to the
desired airspeed. If you are a bit slow, lower the nose which unloads the
winch a bit and wait for the effect. Once you get the hang of it, it works
sweet.

Many pilots think this won't work becasue they haven't tried it. Give it a
try and get back to us.

I tried it enough times when I was pre-solo, thanks, in both ASK-21 and
Puchacz. Didn't work with them. The only effect I remember it having was
breaking a weak link with the Puchacz in a gust.

I did experience a small speed drop today, also in the Puchacz as it
happens, but from the rate and amount of the decrease that was the
driver adjusting the power by making a small reduction at around 500 ft.
After that the remainder of the launch was smack on Vwinch (59 kts)
until he chopped power at the top and we floated off at 55 kts.

We have two Supacats. One has a 240 hp Deutz aircooled diesel V8
industrial engine and the second a big diesel straight six, probably
around 180 hp: I think we were using the straight six winch today. Both
winches drive the drums with a custom gearbox, in turn driven through a
fluid clutch. There are no gear changes during a launch. AFAIK the
gearbox does the following:
- reduction gear. Drum speed is less than engine RPM (of course)
- drum selection (its a two drum winch)
- oscillating drive for the pay-on system


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

"Martin Gregorie" wrote in message
...
Bill Daniels wrote:
Actually guys, you CAN and SHOULD control airspeed on some winches.
There are few winches that have enough power to prevent a large, heavy
glider from pulling down the drum RPM. Maybe you guys have one - maybe
not.

If you are a little too fast, pitch up, load the winch a little and wait
to see what the airspeed does. In most cases, it will ease back down to
the desired airspeed. If you are a bit slow, lower the nose which
unloads the winch a bit and wait for the effect. Once you get the hang
of it, it works sweet.

Many pilots think this won't work becasue they haven't tried it. Give it
a try and get back to us.

I tried it enough times when I was pre-solo, thanks, in both ASK-21 and
Puchacz. Didn't work with them. The only effect I remember it having was
breaking a weak link with the Puchacz in a gust.

I did experience a small speed drop today, also in the Puchacz as it
happens, but from the rate and amount of the decrease that was the driver
adjusting the power by making a small reduction at around 500 ft. After
that the remainder of the launch was smack on Vwinch (59 kts) until he
chopped power at the top and we floated off at 55 kts.

We have two Supacats. One has a 240 hp Deutz aircooled diesel V8
industrial engine and the second a big diesel straight six, probably
around 180 hp: I think we were using the straight six winch today. Both
winches drive the drums with a custom gearbox, in turn driven through a
fluid clutch. There are no gear changes during a launch. AFAIK the gearbox
does the following:
- reduction gear. Drum speed is less than engine RPM (of course)
- drum selection (its a two drum winch)
- oscillating drive for the pay-on system


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Keep trying it. I think you will find you have control over airspeed.
180 - 240 HP isn't nearly enough power to prevent a big 2-seat glider from
slowing the winch.

Bill Daniels