Almost perfect payout winch launch.

On Friday, May 10, 2013 7:19:27 AM UTC-6, son_of_flubber wrote:

Okay. I do have a few observations/opinions:

1)That the payout winch payouts more line and keeps line tension constant when the glider hits lift seems an inherent advantage of this approach when compared to a traditional winch launch.

If a glider can hit at thermal, it can also hit sink. A conventional winch can call on huge reserves of power to pull the glider through sink but the payout winch is more limited in this ability.


2)Don's suggestion that traditional winch launching is proven and that there is therefore no reason to experiment with payout winching misses the point. In a country where beefy pickup trucks are common, the start-up costs for payout winching are much lower than traditional winching. Secondly, far fewer humans need to be deployed and coordinated to run a payout winch. The relevant question is "Which is better to use on a dry lake bed, 1)autotow with payout winch or 2)traditional autotow? What are the tradeoffs?

If space is essentially unlimited, as is sometimes the case on dry lakes, a traditional auto-tow is both simpler and safer. When space is limited, as on a runway, conventional winches will prove more efficient and, I think, safer. I've run the numbers several times and a conventional winch will always get you higher than a payout winch given a limited runway length. Don's point that a conventional winch is simpler is valid. In the extreme it only requires as many people as aero tow.

The conventional winch is a very mature technology with an enormous body of safety data. In the 7 or 8 decades of its history, the potentially dangerous aspects have been found and procedures developed to minimize them. Germans manage 180,000 winch launches or so between accidents where we have an aero tow accident roughly every 26,000 tows. Unfortunately, the Brits suffer a winch accident every 16,000 launches which calls their methods into question. No one knows what the accident rate with payout winches would be, but until everyone climbs the learning curve, I suspect it won't be stellar.

On Fri, 10 May 2013 06:19:27 -0700, son_of_flubber wrote:

Okay. I do have a few observations/opinions:

1)That the payout winch payouts more line and keeps line tension
constant when the glider hits lift seems an inherent advantage of this
approach when compared to a traditional winch launch.

As Bill says, a payout winch can't easily compensate for sink or a rear
gust at the start of a launch in calm conditions.

2)Don's suggestion that traditional winch launching is proven and that
there is therefore no reason to experiment with payout winching misses
the point. In a country where beefy pickup trucks are common, the
start-up costs for payout winching are much lower than traditional
winching. Secondly, far fewer humans need to be deployed and
coordinated to run a payout winch. The relevant question is "Which is
better to use on a dry lake bed, 1)autotow with payout winch or
2)traditional autotow? What are the tradeoffs?

As Don mentioned, we've been shown videos of payout winches with *no
gillotine fitted*. Its relatively rare, but cases of failures to release
have happened and are highly liable to be fatal without prompt use of the
guillotine. Even with a guillotine, what are the chances of a solo payout
winch driver noticing the problem in time? Even if he does notice, how
fast can he get to the guillotine's release and operate it?

I wouldn't accept a winch or auto-tow launch if there wasn't a functional
guillotine installed so that its release was instantly accessible to the
driver and/or the person monitoring the launch.


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

Guillotine? How about simply mounting a release mechanism to the back of
the tow vehicle with the release cable within reach of the driver or
observer? That's the way they do it on the dry lake in Nevada and I was not
the least concerned about accepting ground launches. And, of course,
there's always the weak link at the glider end...


"Martin Gregorie" wrote in message
...
On Fri, 10 May 2013 06:19:27 -0700, son_of_flubber wrote:

Okay. I do have a few observations/opinions:

1)That the payout winch payouts more line and keeps line tension
constant when the glider hits lift seems an inherent advantage of this
approach when compared to a traditional winch launch.

As Bill says, a payout winch can't easily compensate for sink or a rear
gust at the start of a launch in calm conditions.

2)Don's suggestion that traditional winch launching is proven and that
there is therefore no reason to experiment with payout winching misses
the point. In a country where beefy pickup trucks are common, the
start-up costs for payout winching are much lower than traditional
winching. Secondly, far fewer humans need to be deployed and
coordinated to run a payout winch. The relevant question is "Which is
better to use on a dry lake bed, 1)autotow with payout winch or
2)traditional autotow? What are the tradeoffs?

As Don mentioned, we've been shown videos of payout winches with *no
gillotine fitted*. Its relatively rare, but cases of failures to release
have happened and are highly liable to be fatal without prompt use of the
guillotine. Even with a guillotine, what are the chances of a solo payout
winch driver noticing the problem in time? Even if he does notice, how
fast can he get to the guillotine's release and operate it?

I wouldn't accept a winch or auto-tow launch if there wasn't a functional
guillotine installed so that its release was instantly accessible to the
driver and/or the person monitoring the launch.


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

In article ,
Martin Gregorie wrote:



I wouldn't accept a winch or auto-tow launch if there wasn't a functional
guillotine installed so that its release was instantly accessible to the
driver and/or the person monitoring the launch.



We used to do a lot of ground launching via the "pulley method". We
always had an observer in the tow car watching the launch. Our
"guillotine" was a sharp machete in the hands of the observer. Of course
we were also taught to immediately bank into a tight turn and circle the
tow vehicle if we could not release. I always had my doubts about
recognizing the release failure in time to cut the line or to turn and
get tension off the line before things got out of hand.

All the pulley launch rigs I have seen are just a bare pulley, usually a
truck rim mounted an a trailer hitch. No fairleads or other structure. I
guess a guillotine could be mounted to such a rig. Would be a good Idea,
I think.

On Friday, May 10, 2013 7:11:07 AM UTC-5, Don Johnstone wrote:
At 02:45 10 May 2013, Bob Kuykendall wrote:

Don, I can respect that you have reservations about the method in

question. But it would be a lot more constructive if you'd provide

specific examples of why the method in question is inadvisable, and

are prepared to tell us how it can go wrong. Otherwise, when you call

people "foolhardy" and tell them flat out to "stop it," you mostly

just come across as a disagreeable curmudgeon.



Furthermore, I think that anybody who has used a winch but decries the

"complexity" of other ground launch methods does not really understand

how complex a good winch is, and how many points of failure there

really are.



Thanks, Bob K.



Fair point Bob



If we consider the simplest winch where the engine is connected to a

transmission via a gearbox of some kind. In this type of winch the driver

is seated and controls the throttle to control the speed of cable

retrieval.



What can go wrong? Three basic things as regards the operation of the

winch.



1. A break in the cable

2. A mechanical failure of the winch

3. Winch driver error or incapitation.



All of these eventualities are dealt with by practising launch failures or

launch abandonment. As far as mechanical failure of the winch is concerned

there are only two main components to fail, the engine (Uncommon but not

unknown) and the transmission. In all cases the winch driver is seated with

a good view of what is going on and can react to problems as they arise, in

particular using the guillotine if required in a timely manner.

The first winch I drove was of this time, a 3 litre petrol engine driving a

winch drum through a conventional 4 speed gearbox.

The most complex winch I have driven was a Munster Van Gelder winch with a

ginormous turbo diesel engine providing power for 6 seperate drums through

a torque converter. The engine control, transmission and drum select

functions were complex but once the transmission was connected to the power

module the principle was the same as for the simple Eagle winch described

above. Failure of either winch by mechanical failure of the

engine/transmission during launching was very rare. The MVG winch was

however less reliable in that faults within the more complex system meant

that it was U/s far more often than the simple winch, and took longer to

fix. Having said that the components making up the MVG winch were of top

quality and specifcally designed or adapted to provide the proper function,

it was just that there were more components to go wrong. In both cases the

winch was fixed, the driver had control and could see the glider at all

times and take the appropriate action.



The payout winch provides an additional level of complexity and reduces the

ability of the operator to control the launch. Some aspects of the launch

rely totally on unsupervised mechanical/electrical operations, the payout

part of the operation. The system is really a combination of two launch

methods, an auto tow and a winch launch and is just one level of complexity

too much when the proven technology already exists to provide a good

launch without introducing more complex procedures, especially ones which

rely totally on a mechanical/electrical function with no human input or

control.

During an auto tow the driver is facing the wrong way or is peering over

his shoulder so his ability to offer proper control or reaction to an

emergency is compromised, add to that the fact that cable payout is taking

place while the vehicle is moving in the opposite direction and while the

glider is on the cable and the things that can go wrong increases

exponentially.

Winch launching has hazards, no denying that, some of them completely

outside the control of the winch operator. A fixed winch with the operator

in a good position to observe the launch provides the best and safest

solution.

I have of course assumed that the launch is contolled by one person, the

implications of having two people controlling a launch (or not) are too

horrible to consider. I cannot see that anyone would be daft enough to do

that.

I can see that the payout winch launch is dangerous, I have said so. I may

or may not be believed. Like all human activity it will continue until

something goes wrong. If god forbid someone is killed then many people will

pipe up saying they knew it was dangerous, I am just saying it in the vain

hope that people will look at what they are doing and see that however

attractive it might seem it is not woth the risks, before it ends in

tears.

Bottom line, a vehicle driving down a runway with a glider on tow and a

winch paying out cable while the launch is taking place is not something

that I would ever be involved in. Been gliding and winching for 50 years

and would like to continue for a few more years.

Interesting dichotomy between the European and American viewpoint. Being trained on the winch learning to soar and having 3,000 winch launches done from the winch driver seat I tend to agree with Don. To add to his points: A winch launch (1 km cable length) gets you to 1,300 - 1,600' altitude safely and cheaply. You learn to climb away from that altitude even in poor weather, or you land and do it again. I just don't see the need for winching to 2-3k feet in a glider and if you disagree you probably have some thermaling to learn. I witnessed a hang glider accident with a payout winch on a pick-up truck and it was not pretty. We asked the hang glider group to not fly from our site any more...
Herb

On Friday, May 10, 2013 7:21:55 AM UTC-6, wrote:
I just don't see the need for winching to 2-3k feet in a glider and if you disagree you probably have some thermaling to learn.

Herb

Depends on the purpose of the flight. Early morning or late evening student training flights can benefit from higher launches.

Don is right in thinking that there should be one person in charge of the
launch.

Unfortunately the person he thinks should be in charge is at the wrong end
of the cable.

With high powered winches driving through auto transmission (Skylaunch) the
pilot has little control over the speed of launch, he just has to accept
what the winch driver gives him.

With a launch system that provides cable tension, by whatever control
system
is used, the speed is under control of the pilot. Ease off on the stick
speed increases, ease back speed reduces, just like in normal flight.

I've launched on both in the UK & I know which I prefer

PF

At 13:52 10 May 2013, Bill D wrote:
On Friday, May 10, 2013 7:21:55 AM UTC-6, wrote:
I just don't see the need for winching to 2-3k feet in a glider and if
you disagree you probably have some thermaling to learn.

Herb

Depends on the purpose of the flight. Early morning or late evening
student training flights can benefit from higher launches.