Auto-Towing - why is this not more popular?

On Tuesday, October 6, 2015 at 2:37:30 PM UTC-7, Waveguru wrote:
the tow car will have to hit nearly 100mph.

I guess you didn't bother to watch the videos, eh Bill? We launched many glass ships to thousands of feet.

Boggs

Gary, what were your typical truck speeds?

Thanks,
Craig

On Tue, 06 Oct 2015 13:38:01 -0700, WB wrote:

I would not classify a 1000m field as particularly short.

Agreed. With a remotely placed winch, all you need is a launch and
landing area that's about 350-400m square.

In a southwesterly, pretty much our usual wind direction, we operate off
the 'diamond' in front of our club house. This is 390m on the SW axis and
300m across. We set up the launch point halfway along the southerly edge.
The winch is 1200m away at the far end of 22, a grass run 175m wide that
extends out of the diamond.

With this arrangement almost everybody, including many ab-initios, can
land in the first half of the 'diamond' and stop more or less in line
with the launch point, so a landed glider doesn't block the next winch
launch. In this wind the remainder of 22 is only used for aero-tows,
cable breaks and cable break training, though its available as a huge
safety margin if an ab-initio overshoots his first few landings.

Our Robins can easily launch the Puchacz or an ASK-21 from the diamond,
though this is normally only done for the first aero-tow of the day.


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

WB, I 'm glad you like winch launching. However, I do have just one tiny nit to pick just for the benefit of those not familiar with winch launch. Pilots don't "drop" the rope, they release it (or more likely, it auto-releases). Then the parachute opens preventing the rope from dropping too fast. That gives the winch operator plenty of time to wind in the rope all the way to the winch before it can hit the ground. There's usually less than 100' of rope left out when the winch stops.

If a winch is capable of it, the transmission can be shifted to overdrive and the 'chute ripped out of the sky at more than 100mph to minimize drift. Of course, the operator has to be absolutely certain he can stop the drum before the 'chute is pulled through the fairlead.




On Tuesday, October 6, 2015 at 2:38:05 PM UTC-6, WB wrote:

All of these objections to winch launch have been put to rest. If you want to see small field winch operations, use Google Earth to look at European, particularly German, glider airports. Many are as short as 1000m and surrounded by trees. Just pick club names from OLC and enter them in the GE search field.

Winch launch will never drop the rope anywhere except right in front of the winch unless the rope breaks which is getting very rare with ultra-strong ropes.

If a pilot really thinks a distant tow is necessary, then use a sustainer from a winch launch.

SSA group insurance offers winch coverage for traveling to and operating at any airfield.


I would not classify a 1000m field as particularly short. I have operated winch and auto launch off of shorter fields, but it is not too good for anything but pattern practice. I would say that in some ways winching can do something that aerotow would not do as well: With a winch you only need 1000 feet (or less) of launching/landing area if the winch can be placed a sufficient distance beyond the "runway" end. That opens up a lot of possibilities for flying from non-airports. I agree that when everything works correctly the winch line will not end up in the trees. However, there's always the pilot who forgets to correct for crosswind and drops the rope too far downwind or the line breaks and falls into the trees. Even the synthetics break occasionally. Timely replacement when worn makes breaks unlikely. And with synthetics we no longer have the problem of a highly conductive steel cable on power lines.

Glad to hear that SSA group plan covers winch transport. That may not have always been the case. Or, it might have just been the case that our self mobile winch was not insured for over the road. That winch left us a long time ago. Wish we had it back.

Bill....at best, not accurate.

On Tuesday, October 6, 2015 at 3:37:30 PM UTC-6, Waveguru wrote:
the tow car will have to hit nearly 100mph.

I guess you didn't bother to watch the videos, eh Bill? We launched many glass ships to thousands of feet.

Boggs

Yeah, I watched your video.

Out in the prairies, trees and power lines
are less prevalent than center pivot
irrigators and barbed wire fences. The
neighboring farmers might let us put in
gates to run the winch line another 3000'
+, but I'm wondering if we could mount
high pulleys at the fence lines to avoid
rubbing against fence posts etc.

If we could get a drone with PowerFLARM
to pull the line back, life would be really
good except for the pipeline patrol guy.

We figured the truck speed as stall speed plus 10 or 15 minus the wind speed. At the Alvord we had to add five or 10 for density altitude. I don't think we ever went more than 75mph, usually 60-65 We never launched any ships with water. The slower you can go and still get the job done the better. It's really important for there to be good three way communication between pilot, driver, and winch operator. Having the cable pressure set so that in lift the glider just climbs faster and in sink it doesn't pay out at all takes out the wild fluctuations in airspeed we used to get with the solid wire auto tow. It's much safer and the cable rarely breaks. Only when you get a nick in it some how.

Boggs

On Tuesday, October 6, 2015 at 8:45:05 PM UTC-6, George Haeh wrote:
Out in the prairies, trees and power lines
are less prevalent than center pivot
irrigators and barbed wire fences. The
neighboring farmers might let us put in
gates to run the winch line another 3000'
+, but I'm wondering if we could mount
high pulleys at the fence lines to avoid
rubbing against fence posts etc.

If we could get a drone with PowerFLARM
to pull the line back, life would be really
good except for the pipeline patrol guy.

Would take a bit more time to retrieve the rope, but an wheel rim on a shaft on top of a fence topping frame would probably work if done properly, though a gate would be better and much more desireable. Retrieve drivers would have to be able to drive in a straight line. Not too hard on a flat surface.

There was a club that reportedly used a wheel rim of some sort on a post to guide the rope around a runway dogleg during the start of the launch. It may have been in the UK.

Frank Whiteley

On Tuesday, October 6, 2015 at 8:25:43 PM UTC-5, wrote:
WB, I 'm glad you like winch launching. However, I do have just one tiny nit to pick just for the benefit of those not familiar with winch launch. Pilots don't "drop" the rope, they release it (or more likely, it auto-releases). Then the parachute opens preventing the rope from dropping too fast. That gives the winch operator plenty of time to wind in the rope all the way to the winch before it can hit the ground. There's usually less than 100' of rope left out when the winch stops.

If a winch is capable of it, the transmission can be shifted to overdrive and the 'chute ripped out of the sky at more than 100mph to minimize drift.. Of course, the operator has to be absolutely certain he can stop the drum before the 'chute is pulled through

Yes, most of the time we did just let it back release. I would often shift our winch (the Eagle Winch, now at Philadelphia) into second gear to recover the line. Usually could lay it down right in front of the winch. Worked even better after the steel cable was replaced with Spectra.

As promised, the following clip was copied from raw film shot for an
ESPN show, Secrets of Speed. The ground launch begins around 30 seconds
into the clip but I left the low pass just for fun. This shows what
happens to the tow car when the glider (me in my LS-6a) pull too
aggressively at the top.

https://www.dropbox.com/s/k9a4v2wbg9...aunch.mp4?dl=0

On 10/6/2015 9:35 AM, Dan Marotta wrote:
...
I have the raw footage on DVD. Perhaps I can find a "free" video
editor program and pull out the car pulley sequence and upload to
google drive. We'll see...

Dan

On 10/6/2015 9:21 AM, Dan Marotta wrote:
Thanks, Bill.

I only did a couple of pulley tows for the filming of the ESPN
thing. Some of the raw footage (not shown on TV) shows the rear end
of the car being lifted sufficiently that the driver lost control of
the car. Fortunately the passenger/observer was Emerson Fittipaldi
and he reached across, took the wheel, and straightened out the car.
When I released, it was quite a sight seeing the rope literally
slamming down on the runway. I can easily imagine the tangles this
caused in the pulley system. =-O

Dan

On 10/5/2015 6:18 PM, wrote:


Dan, a pulley tow launches a glider just fine - but then you need to reset for the next launch. Often, this means untangling the rope. Straight auto tow or winch launch rarely tangles the rope.

There are very few pulley tow operations in the world and cycle time is the usual reason why they gave up on pulleys and moved on to winch launch.


On Monday, October 5, 2015 at 9:16:28 AM UTC-6, Dan Marotta wrote:
I once flew for an ESPN video on flying (Secrets of Speed). One of
the launch methods used was an auto pulley tow wherein the pulley
was mounted to the receiver on the back of the car and the cable was
staked to the ground near mid field. The car drove in the takeoff
direction during the launch and, with the 2:1 advantage of the
pulley, it was every bit as exciting as a winch. The car drove at
about 1/2 the speed of the glider. We were using a 3,400' runway
and I don't recall the release height, though it was not as high as
a winch with a full runway length of cable.




On 10/5/2015 5:01 AM, GB wrote:



Good question. Seems to me reverse car tows(fixed pulley windward car drives toward the glider) would be the way to go. Has there been any sailplane work with car mounted pay out winches? Pay out winches are what the hangglider and paraglider community have mostly settled on using. Both of these solutions somewhat mitigate the space needed to auto tow.






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Dan, 5J

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Dan, 5J

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Dan, 5J

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Dan, 5J