Keep your hand off the release handle during aero tows!

Time for pogo sticks.

The idea of launching a glider by having someone run the wing originated with wooden gliders and quite low speeds for stall and aileron effectiveness. Those speeds have gradually crept up through the years, to the point that really nobody can run the wing of a modern glider, with waterballast, and anything less than 10 mph straight down the runway, to the point of aileron effectiveness. Mostly we hope that the wing runner lets go, with the aircraft in balanced position, and it picks up speed faster than one wing drops. That often isn't true.

For airtows the results are usually just some scraped gel coat; sometimes a collision with a runway light, and occasionally a ground loop. There have been accidents where wing down gliders hurt bystanders, the Tonopah 15 m nationals being the one I remember best.

Clearly, for winching, wing-down events are much more serious.

The answer: either retractable or disposable pogo sticks on the wingtips, or mid-wing. Something that keeps the wings level to 25 mph and then either drops off or retracts into the wing.

Reading the UK Nimbus 3 report, it would seem that a video link between winch driver and launch point would be a good idea, and quite cheap with current technology. It would cut a crucial second or so out of the abort-the-launch loop

John Cochrane

JC wrote:
The answer: either retractable or disposable pogo sticks on the wingtips, or mid-wing. Something that keeps the wings level to 25 mph and then either drops off or retracts into the wing.

Along this line, many self-launchers have small in-line skate wheels on the wingtips so they can start with the wing already touching the runway. Perhaps a simple retrofit could save your gel-coat (or your life).
As for dropable pogo sticks, hang gliders that aerotow often use a 3 wheeled launch cart(with a wide stance)to keep the wing level until it flies away from the cart. No one wants to lift their sailplane into a cart so this won't work for us. :-)

On Wednesday, October 9, 2013 12:53:26 PM UTC-4, Soartech wrote:
Along this line, many self-launchers have small in-line
skate wheels on the wingtips so they can start with the
wing already touching the runway. Perhaps a simple retrofit
could save your gel-coat (or your life).

Without a steerable tail-wheel and enough tail weight to make
it actually steer, tip wheels merely avoid scraping the wingtip
finish as you ground-loop.

As some who have observed interesting Whale take-offs can attest ;-)

OTH, as it has a proper steerable tail-wheel, I normally
take off without a wing-tip runner in Antares...

Wingtip wheels would help airtow wing drops -- and encourage a lot more toughing it out and waiting for the wing to come up. Especially with water, and double especially with half water, they're not ideal. I'm not a winch expert, but I assume wingtip wheels would be of little help in those accidents..


John Cochrane

My LAK-17a has wheels like the first picture in this link:
http://www.williamssoaring.com/catal...ane-parts.html

They work great on pavement, but are useless on grass.


"Soartech" wrote in message
...
JC wrote:
The answer: either retractable or disposable pogo sticks on the wingtips,
or mid-wing. Something that keeps the wings level to 25 mph and then
either drops off or retracts into the wing.

Along this line, many self-launchers have small in-line skate wheels on
the wingtips so they can start with the wing already touching the runway.
Perhaps a simple retrofit could save your gel-coat (or your life).
As for dropable pogo sticks, hang gliders that aerotow often use a 3
wheeled launch cart(with a wide stance)to keep the wing level until it
flies away from the cart. No one wants to lift their sailplane into a cart
so this won't work for us. :-)

Long grass or other vegetatation, and rough surfaces of any
kind can make ground loop or cartwheel type winching accidents
more likely. Small wingtip wheels are probably more likely to
snag in grass than skids.

BTW, UK winch launches using modern high powered winches
give the much the same acceleration as German or anybody
else's winch launches. 0-50 knots in about 3 seconds to give
almost immediate aileron control. Any faster than this produces
additional problems, particularly tail-banging, dangerous over-
rotation with the risk of a stall/spin, and pilots sliding back in
sailplane types with very reclining seats. N.B. always do your
straps up as tightly as possible for winch launching.

Derek Copeland

At 23:44 09 October 2013, Dan Marotta wrote:
My LAK-17a has wheels like the first picture in this link:
http://www.williamssoaring.com/catal...ane-parts.html

They work great on pavement, but are useless on grass.


"Soartech" wrote in message
news:facbc642-bebd-4794-a53b-
...
JC wrote:
The answer: either retractable or disposable pogo sticks on
the
wingtips,
or mid-wing. Something that keeps the wings level to 25
mph and then
either drops off or retracts into the wing.

Along this line, many self-launchers have small in-line skate
wheels on
the wingtips so they can start with the wing already touching
the runway.

Perhaps a simple retrofit could save your gel-coat (or your
life).
As for dropable pogo sticks, hang gliders that aerotow often
use a 3
wheeled launch cart(with a wide stance)to keep the wing
level until it
flies away from the cart. No one wants to lift their sailplane
into a
cart
so this won't work for us. :-)

On Wednesday, October 9, 2013 8:44:52 AM UTC-6, wrote:
Time for pogo sticks.



The idea of launching a glider by having someone run the wing originated with wooden gliders and quite low speeds for stall and aileron effectiveness. Those speeds have gradually crept up through the years, to the point that really nobody can run the wing of a modern glider, with waterballast, and anything less than 10 mph straight down the runway, to the point of aileron effectiveness. Mostly we hope that the wing runner lets go, with the aircraft in balanced position, and it picks up speed faster than one wing drops.. That often isn't true.



For airtows the results are usually just some scraped gel coat; sometimes a collision with a runway light, and occasionally a ground loop. There have been accidents where wing down gliders hurt bystanders, the Tonopah 15 m nationals being the one I remember best.



Clearly, for winching, wing-down events are much more serious.



The answer: either retractable or disposable pogo sticks on the wingtips, or mid-wing. Something that keeps the wings level to 25 mph and then either drops off or retracts into the wing.



Reading the UK Nimbus 3 report, it would seem that a video link between winch driver and launch point would be a good idea, and quite cheap with current technology. It would cut a crucial second or so out of the abort-the-launch loop



John Cochrane

John, wing-down events are indeed more serious for winch launch simply because of the CG hook and the large amount of energy being delivered to the glider by the winch. The best solution is one where wing drops don't happen at all - or are least extremely unlikely.

It's true that modern, heavy gliders have minimum aileron control speeds much higher than a wing runner can reach. Just as with aero tow, slow acceleration leaves a glider vulnerable to a wing drop. As with aero tow, reaching minimum control speed quickly is a very good thing.

The time for a glider on winch launch to reach aileron control speed from a standstill (Anywhere except the UK) is a second or less so how can a wing drop in that interval? Even in a crosswind, a glider can be balanced laterally so if the wing tip is simply released it will take two or three seconds for it to drop. Something has to cause it to drop or it won't happen.

A rare problem is a pilot unintentionally holding aileron input at the start of the roll. Control authority comes on fast that a wing may go down before a pilot realizes his error and backs off the aileron input. The solution is being careful to neutralize the ailerons before the roll starts.

Also rare (Again, outside the UK) is mis-aligned staging which results in the rope pulling the glider slightly sideways. This can start a wing down before aileron control speed is reached. The solution is to be careful to stage the glider so it points at the winch.

Strong gusts can be problem but the longer a glider wobbles along with minimal control authority, the greater the vulnerability to them.

Wing runners should be re-trained from what they learned with aero tow. Any attempt to hold on will be disastrous so they need to do a very "clean" release. They must also learn the art of balancing the wing rather than just holding it sort of level. They won't so much "run" the wing as take a very quick step or two.

Video is under serious consideration. As you say, a CCTV link is very cheap as are all sorts of data-links. I think one of the best uses is a simple data-link to send a "STOP" message to the winch operator. That message could be displayed in .2 seconds from when an observer at the launch point first sees a launch starting to go wrong and the rope cut with the guillotine in another .2 seconds stopping the launch.