Safety of winch launch vrs. aero tow?

Gary Boggs wrote:
I really appreciate all this good input, thank you all for responding. Now
for a new twist, one of our members has built a "pay out winch".

Haven't heard about that, but I _have_ heard about a hairy thing called
"step towing", which is something the hang-glider pilots do from small
fields. They winch up to say 150m, have the winch pay out as the fly
back, turn and take another winch launch from altitude! This can of
course be repeated for as many times as practical, and some respectable
altitudes can be gained.

Imagine this done with a glider and dyneema or spectra cord for wire.
You would of course have to modify the tow-hook to not automatically
back-release (shudder, gulp!)...

Well, if someone actually tries this with a sailplane I'm not sure I'd
want to know. They would certainly not be allowed to fly _my_ glider
anyway.

Christian 8-)

"F.L. Whiteley" wrote in message ...

If it's soarable, one launch should do most days. Most seasons I winch
launched regularly I can count on one hand the number second snaps taken per
season to soar away. Of course, _big wings_ do help, but that's another
thread;^) This season, I only took two aerotows to 2000agl. My other AT
releases were 1200 to 1700agl, that is, at or below winch height and near
enough to the airfield to presume had we been winching, getting away was
pretty likely. For a number of reasons we didn't winch much this season,
but when we did, we soared. This included thermals on New Year's Day and
wave on Feb 1 and thermals each subsequent winch day this season. Looks
like snow for November 1st though. Last Saturday would have been perfect as
lift was 10kts to 12K in a stiff NW breeze. The kind of day we get 2500+agl
on the wire.

Frank Whiteley
************************************************** ********************************
You guys should get a really good winch and pay someone to operate it
during the week. During the summer you could become a vacation
destination. Since there are nonstop flights from Europe to Denver
every day, you could probably get enough Brits and others to pay for
your winch and some rental gliders in a few summers.

"Eric Greenwell" wrote in message
.. .
In article , mowry86
@hotmail.com says...
Beware of the raw statistics.

How about this one:

100% of 2003 US glider fatalities occur after aerotow.

Sounds like a good tag line for a winch manufacturer advertisement

Unfortunately, not true: some have occurred after self-launch, and I
know there have been some ground launch fatalities (how recently, I
can't remember)
--
!Replace DECIMAL.POINT in my e-mail address with just a . to reply
directly

Eric Greenwell
Richland, WA (USA)

The following occured in the launch phase

Two fatals I'm aware of. A homebuilt failed structurally in a winch launch
in Colorado some years ago and apparently another homebuilt crashed in North
Carolina in the past couple of weeks on auto tow. Not clear whether the NC
accident pilot was even trained in ground launch. Perhaps someone in that
neck of the woods can offer more information.

A Russia was damaged in Wyoming a few years back on auto tow at a private
ranch strip, however, the grapevine reported the pilot had no specific
ground launch training and cart-wheeled the glider. IIRC, it was properly
repaired and sold.

A sometimes RAS poster was seriously injured in a winch launch accident
involving a Phoebus C in Georgia a few years ago. (stalled all-flying tail
to excessive pitch-up to wing stall, wing-drop, and rolled inverted to
impact)

Any others? Certainly there have been a few at Torrey Pines over the
decades, though environmental factors have been a big player there.

Frank Whiteley

The HG community used (has used) pay-out winches for a number of years. At
least one major auto maker produced a limited production launch vehicle
pick-up truck as advertised on national TV. Others were retro-fits or home
grown. The current generation of US UL gliders, Sparrowhawk and Lighthawk,
could probably use these as supplied. The Apis and Silent might need
something a bit more stout.

Frank Whiteley


"Gary Boggs" wrote in message
...
I really appreciate all this good input, thank you all for responding.
Now
for a new twist, one of our members has built a "pay out winch". A pay
out
winch is a drum with a break on it. The glider hooks up about 200' behind
the tow vehicle, and as the glider climbs, the line spools out. Does
anybody have any experience with this type of launch? How much runway do
you need for this type of launch, how high can you get, ect?

Boggs

"Stefan" wrote in message
...
Bob Johnson wrote:

Your ability to get 600 m releases with a winch on a 1200 m strip seems
extraordinary.

It all depends on the wind. With zero wind, the rule of thumb is that
you get approximately 1/3 the cable lengh. More with headwind, much more
with strong headwind. With extraordirarily strong headwind, you can even
kite. (Yes, it has been done.)

Stefan

Bob Johnson wrote:

Eggert --

Those are really good numbers for your winch.

With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
laid out, we are getting the rule of thumb 1/3 cable length releases of
1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
the Blanik in the barn!

BJ
Midland, Texas



Eggert Ehmke wrote:

Bob Johnson wrote:

Mr. Ehmke --

Your ability to get 600 m releases with a winch on a 1200 m strip seems
extraordinary. Is your cable length just 1200 m also or is it greater
than your strip length?

That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
What I told is the normal range - with strong wind aligned to the runway we
had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
launch, but it sounds reasonable. 650 m I have experienced myself.
Eggert


1/3 cable length seems low. There was in France an experiment showing
40% cable length without wind with cable length from 1000 to 2000 m.
See HTTP://www.gliderforum.com/thread-vi...geID=1466#1466

soarski wrote:
...
As for Gary Boggs, the only thing I can suggest is to go to Germany
for a summer and learn the trade. Winches, how to run them, including
the infrastructure. (Telephone)


Why telephone rather than radio? Radio let everybody know what is
happening, rather than only the two persons at bot end of telephone.
Likely mandatory when there is some other activity in parallel (aero
tow, power flying ...).

On the other hand, with more reasonable selflaunchers coming out, the
winch effort may not be the answer anymore in the US. There are enough
reasons mentioned in this thread.


What does "reasonable" mean here? Selflaunchers are a way to increase
the cost of flying, winch is a way to decrease it.

Robert --

I would like to learn how they do this. Our Blanik has perhaps the best
located CG hook on any sailplane I'm aware of, although some would say
the bridle is somewhat awkward to use.
On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
winch engine throttle is advanced to the forward stop in 3 seconds and
at this time the engine is already rapidly approaching redline 5000 RPM.
At this point the Blanik is already beginning its climb and the throttle
is eased.

This quick takeoff and climb performance is still not fast enough to
load the ship and its occupants to more than about 0.8 - 0.9 G
horizontal acceleration, which I think one would have do to attain any
more than the 1/3 line length releases we are attaining.

We limit our climb airspeed to 55-60 kt, which I believe is the POH
recommendation. Very little if any back stick is necessary, and the
Blanik attains the 55 kt climb pretty much on its own until the last
part of the 45 second tow, when some back stick is applied to counter
the downward (with respect to the ground) pull of the rope. Our
Spectra/Dyneema/Plasma plastic rope weighs less than its full 66 lb when
partially wound on the drum, so line weight (and its necessary
acceleration and ground contact friction) for us is practically
negligible.

If there is a better setup anywhere in the world, I would sure
appreciate a description.

Thanks for your reply,

BJ
Midland, Texas
http://www.permiansoaring.us/

Robert Ehrlich wrote:

Bob Johnson wrote:

Eggert --

Those are really good numbers for your winch.

With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line
laid out, we are getting the rule of thumb 1/3 cable length releases of
1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave
the Blanik in the barn!

BJ
Midland, Texas



Eggert Ehmke wrote:

Bob Johnson wrote:

Mr. Ehmke --

Your ability to get 600 m releases with a winch on a 1200 m strip seems
extraordinary. Is your cable length just 1200 m also or is it greater
than your strip length?

That's 1200 m of cable laid out, with a V8 240 HP engine at the other end.
What I told is the normal range - with strong wind aligned to the runway we
had 750 m (2460 feet) agl with a double seated ASK21. I did not see this
launch, but it sounds reasonable. 650 m I have experienced myself.
Eggert

1/3 cable length seems low. There was in France an experiment showing
40% cable length without wind with cable length from 1000 to 2000 m.
See HTTP://www.gliderforum.com/thread-vi...geID=1466#1466

Mike Borgelt wrote in message . ..
On Sat, 25 Oct 2003 12:43:35 -0700, "Gary Boggs"
wrote:

Someone must have already compared the safety of these tow launch methods.
What do the statistics show is the safer method of launch? Aero tow seems
to involve more inherent dangers to me. For one thing, there is just more
time for things to go wrong. What could be more dangerous than to tie tow
airplanes together and try to fly?

Gary Boggs


I've only done about two winch launches but have done several hundred
car tows and driven several hundred also.

Two winch launches. Helps to understand why you say what you say later
on.


Ground launches involve lots of wire, rope etc. It is probably a good
observation that the more rope you have the more trouble you can get
into! With one exception below.

I've had the glider run over the wire and tangle in the wheel well.
Not good as you now cannot release and depend on the tow driver..

Pilot reactions to a low altitude winch launch failure are utterly
critical. I suspect we've killed dozens if not hundreds over the years
this way around the world.

Yes, the reaction is critical. But even more important is the correct
attitude corresponding to airspeed and altitude at all times. This
does make the reaction when something goes wrong a quite a bit less
critical.
I guess we have about 0.5 cable breaks and 2 or 3 weak link breaks per
1000 launches. We do about 3500 winch launches a year. It can happen
and if the pilot is properly instructed he knows this and is prepared.
I do not consider cable break or engine failure to be a _problem_ when
launching even when it happens.


You may need more than one launch to get away(rare with aerotow).

Normally not.

Someone mentioned the stresses in the wire and the glider. Both are
much lower in properly executed arotow.

Stresses are normally higher, but where's the problem in that? The
glider is built to easily take those stresses and we change the wire
once a year anyway.


Aero tow may have a higher exposure to an off airport landing in
unsuitable terrain but the failures seem to be much more rare than
winch wire breaks. If you don't use toy towplanes(less than 180HP)
then any place suitable for winching probably gives you the
opportunity to do a 180 or land straight ahead from an aerotow.

Definite 'No' on the 'probably gives you' bit.
From a winch launch you should _always_ be able to land on the
runwyay. I know lots of airfields where you have a certain time,
sometimes only two or three seconds, sometimes ages, in the aero tow
when you definitely do _not_ want _anything_ to go wrong. The
suitability of the airfield for whinch launching has no relevance
here.


If you want gliding to be popular aerotow involves less running around
on the ground per flight hour.

Don't see why. Only thing to do additionally is retrieveing the winch
cable. And the guy drives, he doesn't run.
And: If you want gliding to be more popular among the people living
near the airfield you should stop making such a racket with those
ancient technology fuel to noise converters. Instead we do 80% of our
launches with 0.4 litres of Diesel.


Flying towplanes is more fun than driving a winch or tow
car.(Allegedly - I last sat in a towplane in 1971 writing down CHT's
for the cooling test for 4 tows in a row and haven't felt motivated to
get into a towplane since despite the aquisition of a PPL 9 years ago)

Aerotowing danger can be reduced by using a longer rope. One of the
local clubs around here tried it and liked it so much the towpilots
won't fly with short ropes. The long rope gives everyone more time to
handle upsets. I suspect the rise of the towplane upset accident
coincided with using shorter ropes.

Agree to all that.

Regards
Marcel

On Wed, 29 Oct 2003 10:02:06 +0000, Robert Ehrlich
wrote:


Why telephone rather than radio? Radio let everybody know what is
happening, rather than only the two persons at bot end of telephone.
Likely mandatory when there is some other activity in parallel (aero
tow, power flying ...).

Nothing worse than someone else interfering during the critical phase
of a winch launch (initial acceleration).

Bye
Andreas

Bob Johnson wrote:

I would like to learn how they do this. Our Blanik has perhaps the best
located CG hook on any sailplane I'm aware of, although some would say
the bridle is somewhat awkward to use.
On a typical tow, with the Blanik weighing about 1100 lb, the 300 hp
winch engine throttle is advanced to the forward stop in 3 seconds and
at this time the engine is already rapidly approaching redline 5000 RPM.
At this point the Blanik is already beginning its climb and the throttle
is eased.

As a winch driver, I allways try to leave the throttle in the position it
has when the plane leaves the ground, for about the first 1/3 of the climb.
Then I slightly slow down, depending on the wind and the climb angle of the
plane. This can mean full throttle for a double seater and almost idle for
a Ka8 with strong headwind. This method works in all wind conditions.

With an ASK21 or Grob G103, the ground roll is not longer than 2 or 3
seconds. The first ca. 100 feet we keep a flat attitude, than we go
slightly into a climb angle of about 40 degrees.

We limit our climb airspeed to 55-60 kt, which I believe is the POH
recommendation.

This seems a bit slow for me, but may be correct for the Blanik. The ASK21
has a recommended speed of about 60 kt, and 65 is no problem. More speed
means more lift too.

Very little if any back stick is necessary, and the
Blanik attains the 55 kt climb pretty much on its own until the last
part of the 45 second tow, when some back stick is applied to counter
the downward (with respect to the ground) pull of the rope.

In the last part of the climb it is even important to give the stick a
little forward, so the angle between cable and plane does not exceed the
point where the backrelease is triggered. That way you can stay longer on
the rope, getting higher. Also the release is much softer.

Just my 2 cents...
Eggert