On Fri, 17 Apr 2020 06:14:28 -0700, AS wrote:

On Thursday, April 16, 2020 at 5:27:22 PM UTC-4,
wrote:
New people always ask about release altitudes. The more relevant
question is the rate of launches. We learn to fly and gain proficiency
through repetition, we gain altitude in thermals. Ever ask the guy
doing pattern work in a 172 how high he got?

Right on, Doug!
Another question I get from just about everyone who learns that there
are hardly any single drum winches in Europe but most of them have two
or even up to six drums: Wow - isn't that a bit close to launch that
many gliders so close to each other? [insert the sound the little birdie
makes when it comes out of the clock here]

OK, I'll bite:

My club does a lot of winching, usually off a 1km x 175m grass runway
that is fairly well aligned with the prevailing winds (04/22) and use a
two drum Skylaunch winch. Launches are generally to 1400ft but can be a
lot higher given a strong breeze with a good gradient. We have a grass
triangle of runways, but the other two runs are 16/34 and 09/27 are much
narrower and launch rates on them are a lot slower because landings block
those runways until the glider can be towed back to the launch point.

It is possible to get 18 launches an hour with this rig on 22 or 04, but
that needs a big crew. As well as a launch marshal and winch driver you
need:

- a dedicated driver in the Hilux cable truck, who'd chase the first
launch down the field and wait by the winch to bring both cables back.

- a couple of people with golf buggies getting landed gliders off
the landing area, which is behind and to one side of the launch point,
so landing rolls don't normally end up in front of the launch point.

- another one or two people keeping the launch queue moved up to the
launch points (one for each cable, on either side of the control
point table).

- an absence of instructors briefing students at the front of the
launch queue

I understand this setup and its limitations: back when we used a launch
list and I was a new solo, working on Bronze and Silver in the club's
Juniors, there was a gang of us in the same position, so periodically
we'd all get stuck in and push the launch rate, but no matter how we
tried, we never managed more than 18 launches per hour.

These days we use booked training slots and in consequence there just
aren't enough people around the launch point to push the launch rate much
above 10-12 launches/hour.

The London club had a four drum van Gelder winch and tried the same
tricks, but they told me that they also hit a barrier at 18 launches/
hour, probably because, back in the days of steel cable, they used a
tractor to fetch cables rather than the Hiluxes we use - I imagine that a
Hilux would have problems dragging four steel cables at once, especially
on damp or wet grass.


--
Martin | martin at
Gregorie | gregorie dot org