This should make most power pilots have kittens...

Finally, we got a break in the weather this weekend (it's been lousy
here for a while, no flying...)

At our glider club, we can either use the tow plane or the winch to get
the gliders in the air. Not many power pilots have come across the idea
of flinging an aircraft airborne on the best part of a mile of steel
piano wire, but we do this crazy thing. [Power pilots - whenever you see
the glider port symbol on your chart, remember that there may be a winch
there. They are less common in the US than over here, but they are used
in the US, and the 1/8th inch steel cable will not be kind to you if you
run into it. Never directly overfly gliderports below 3000' without
talking to their radio operator].

Anyway, I made a short video of a winch launch at our club. The winch
itself is powered by an inline 6 double overhead cam engine taken from a
4.2 litre Jaguar XJ6. The engine and running gear is mounted on the back
of a truck. It powers a drum of steel cable, and the glider is attached
on the other end. The 4.2L Jag engine has lots of power which results in
spectacular acceleration of the glider.

The video clip is at:
http://www.alioth.net/Video/Winch-launch.mp4 (MPEG-4 format)

(If you don't have the right codec etc. either use QuickTime or download
the excellent free/open source VLC from http://www.videolan.org)

Our next winch will use synthetic rope which is a fraction of the weight
of steel cable (I think the entire run of synthetic rope will only weigh
around 20kg). It will also be powered by an electronic fuel injected Jaguar
V12 engine which came courtesy of last year's hurricane force storm
which collapsed a garage on top of the donor car, completely flattening
the roof and cabin area of the car, but leaving all the running gear
completely intact :-)

--
Dylan Smith, Port St Mary, Isle of Man
Flying: http://www.dylansmith.net
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de
Frontier Elite Universe: http://www.alioth.net

[Power pilots - whenever you see
the glider port symbol on your chart, remember that there may be a winch
there. They are less common in the US than over here, but they are used
in the US, and the 1/8th inch steel cable will not be kind to you if you
run into it. Never directly overfly gliderports below 3000' without
talking to their radio operator]

How is this cable used, and why would it extend up three thousand feet?

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

This cable is attached to the nose of the glider and will remain attached
until the glider pilot pulls the cable release lever. The cable will be
towed aloft with the glider and if the pilot gets off in a thousand feet,
you've still got 4000 feet of cable between glider and ground.

Jim


"Jose" wrote in message
...
[Power pilots - whenever you see
the glider port symbol on your chart, remember that there may be a winch
there. They are less common in the US than over here, but they are used
in the US, and the 1/8th inch steel cable will not be kind to you if you
run into it. Never directly overfly gliderports below 3000' without
talking to their radio operator]

How is this cable used, and why would it extend up three thousand feet?

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

This cable is attached to the nose of the glider and will remain attached
until the glider pilot pulls the cable release lever. The cable will be
towed aloft with the glider and if the pilot gets off in a thousand feet,
you've still got 4000 feet of cable between glider and ground.

1: Does the other end remain attached to the ground?
2: When does the pilot normally pull the release lever?

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

"Jose" wrote in message
...
[Power pilots - whenever you see
the glider port symbol on your chart, remember that there may be a winch
there. They are less common in the US than over here, but they are used
in the US, and the 1/8th inch steel cable will not be kind to you if you
run into it. Never directly overfly gliderports below 3000' without
talking to their radio operator]

How is this cable used, and why would it extend up three thousand feet?

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

Think of running with a kite to get it up. One of the cable is hooked to
the glider, the other end is at the winch (4 or 5 thousand feet away) which
winds it in at 30 - 60 mph. 20-30 seconds later, the glider is at 2000 feet
or so over the winch and drops the end of the cable.

--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

On Mon, 14 Nov 2005 12:06:28 -0500, "Capt. Geoffry Thorpe" The Sea
Hawk at wow way d0t com wrote:

"Jose" wrote in message
m...
[Power pilots - whenever you see
the glider port symbol on your chart, remember that there may be a winch
there. They are less common in the US than over here, but they are used
in the US, and the 1/8th inch steel cable will not be kind to you if you
run into it. Never directly overfly gliderports below 3000' without
talking to their radio operator]

How is this cable used, and why would it extend up three thousand feet?

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

Think of running with a kite to get it up. One of the cable is hooked to
the glider, the other end is at the winch (4 or 5 thousand feet away) which
winds it in at 30 - 60 mph. 20-30 seconds later, the glider is at 2000 feet
or so over the winch and drops the end of the cable.

Ok I'm trying to visualize a winch sucking up cable at 88 feet/second
(60 mph) and 2000 feet of cable accelerating toward the ground at 32
ft/sec^2. And I'm thinking of my experience fishing with cheap
bait-casting reels. Does it ever get interesting? Anybody on the
ground ever lose significant body parts? How is the behavior of
synthetic rope going to differ from metal cable?

Don (Not asking snidely, but more in awe.)

Don Tuite wrote:
Ok I'm trying to visualize a winch sucking up cable at 88 feet/second
(60 mph) and 2000 feet of cable accelerating toward the ground at 32
ft/sec^2. And I'm thinking of my experience fishing with cheap
bait-casting reels. Does it ever get interesting?

you bet. Cable breaks are something quite interesting to start
with (especially if you were tempted to pull to a steep climb
too early -- 45 degrees nose up, no engine, and low, is
what I'd called interesting); that's why it is a part of the
training which is emphasized; I have known of accidents that
involved bad ground handling as well: in a place with a multiple
drums winch: only one cable winched at a time, but multiple
cables can be made ready to increase the rate of launches; the
guy I knew got into trouble when the cable he used got
entangled with another cable laying on the ground...

--Sylvain

On 2005-11-14, Don Tuite wrote:
Ok I'm trying to visualize a winch sucking up cable at 88 feet/second
(60 mph) and 2000 feet of cable accelerating toward the ground at 32
ft/sec^2. And I'm thinking of my experience fishing with cheap
bait-casting reels. Does it ever get interesting? Anybody on the
ground ever lose significant body parts?

Well, there is a small parachute that retards its descent. The cable
doesn't really accelerate much at all when the glider releases - the
speedo on the winch shows about 30mph when we reel it in (but I don't
know what that translates to on cable speed, 30mph would be what the
engine/transmission would be propelling the donor Jaguar XJ6 at!)

It *does* get interesting especially when the cable breaks. Being
pitched up at 45 degrees nose up and perhaps 55 knots indicated and
maybe only 200ft AGL is not a naturally tenable location for a glider
when the power abruptly ceases. It involves a zero-g pushover, then a
dive towards the very terror firma to regain flying speed,
psychologically difficult when all of a sudden you can see every blade
of grass rushing up to smite you.

But generally, so long as you don't 'pole' it too early, you recover
with plenty of time to get your breath back and land. But there have
been incidents where pilots haven't waited for a safe height to pitch
the glider fully up, with a similar outcome to a power plane climbing
out at Vx and losing the motor at 50 feet.

Other interesting things are just with the operation of the winch and
cable. Since we are on a hard surfaced runway (in fairly poor condition)
we use piano wire. A release under tension can create a 'birds nest' -
the wire snarls up on itself, and it's a real bugger to get it
untangled. It's very stiff. Usually we have to resort to cutting the
cable in a couple of strategic places, then tying it (we have tools to
make knots in the cable).

The cable also has a weak link so you don't overstress the glider and
pull the wings off. The Slingsby Swallow, for example, has a different
weak link to the Blanik, being a much lighter ship. Occasionally, a weak
link will get broken when someone gets a bit aggressive on the launch.
There's also a guillotine that chops the cable in case the glider can't
release. Just like pilots are taught a 200-ft turn back to the runway
when being towed by a plane, we also teach launch failures. At sites
with stranded cable or synthetic, the instructor pulls the release
handle on a launch. With piano wire, we simulate it by doing a dive and
a pull up and then the instructor shouts 'BANG!' because when it breaks,
it goes with a bang. (releasing for real on piano wire tends to cause a
birds nest so we avoid it unless we have to!)

How is the behavior of
synthetic rope going to differ from metal cable?

It's a fraction of the weight. The synthetic winch cable for our run (we
have about a mile of cable) weighs something like 25kg, wheras the steel
piano wire probably weighs around 80-100kg. The weight saving translates
into a good couple of hundred extra feet on the launch. Trials at other
clubs shows it's longer lasting than steel (although we have to see how
it goes with our hard surfaced runway) and unlike the piano wire we use
now, it won't snarl up.

Of course, when we get the new winch cable, we're moving from the
carburetted, mechanical points and condenser ignition 6 cylinder engine
to an electronic ignition/electronic fuel injection V12 engine too...

--
Dylan Smith, Port St Mary, Isle of Man
Flying: http://www.dylansmith.net
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de
Frontier Elite Universe: http://www.alioth.net

On 2005-11-14, Jose wrote:
[Power pilots - whenever you see
the glider port symbol on your chart, remember that there may be a winch
there. They are less common in the US than over here, but they are used
in the US, and the 1/8th inch steel cable will not be kind to you if you
run into it. Never directly overfly gliderports below 3000' without
talking to their radio operator]

How is this cable used, and why would it extend up three thousand feet?

The video should explain quite nicely, the cable is very visible
on that. However, normally, without the sunset glinting off the steel,
it's quite invisible until it's too late. The glider pilot may have a
hard time spotting you during the middle stage of the launch since the
glider will be pitched 45 degrees or more nose up.

It's not that the cable will necessarily get to that altitude (but one club
in France has exceeded 3,000 feet on a winch launch, more normally, a
winch launch gets the glider up to between 1,000 and 1,600 feet,
although at our club we've managed a launch of 2,200 ft). Many clubs
also use tow planes, and the tow plane+glider combination (which is
fairly unmanoevrable) generally go up to about that height. Towplanes
may also be doing semi-aerobatic manoevres to get down quickly so they
can go get the next glider - it can be like flies around a cowturd at a
busy gliderport, especially if an event is going on (towplanes, gliders,
winch launches all going on simultaneously).

--
Dylan Smith, Port St Mary, Isle of Man
Flying: http://www.dylansmith.net
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de
Frontier Elite Universe: http://www.alioth.net

Jose wrote:
How is this cable used, and why would it extend up three thousand feet?

have you played with kites when a kid? a bit the same way, but
using a very powerful engine instead of just running holding
the wire (though that technique, running holding the wire,
can also be used, albeit towing it with a car, done it as
well :-) The thing about the warning the previous poster
mentioned: the glider can be sitting on the ground still, and
a minute or two later, be flying full speed at 3000' (rates
of climb to kill for :-); which could be a surprise to the
unsuspecting power pilot overflying the field already, but
the cable might be even more of a surprise as well...
(seriously, if you have a glider port with a winch in your
vicinity, and you never experienced a winch launch, ask for a
ride!)

--Sylvain