Did they ever remove the broken up concrete or resurface the runway? It was
in a state 25 years ago. Would have been lethal to aerotow there then.

Are you still using that old piano wire winch with the big 'drum'?

Frank

"Chris Reed" wrote in message
...
My club (Rattlesden in Suffolk, England) operates both winch and aerotow
simultaneously. From 8 years flying there I'd say that the most important
factor for winching is the layout of the site. If it is possible for
aircraft to land without interrupting winch launching then it's very
satisfactory as a launch method, and you might consider moving to winch
only.

Our site is more difficult - an ex WW2 USAF airfield with a main 3,000 ft
runway and a shorter 1,600 ft cross runway. We can only winch from the
main
runway, which means a crosswind component on the majority of days. In a
typical (!) single-seater like a Grob Astir you could expect 800-1,000 ft
on
a 90 degree crosswind day, and 1,400 ft plus with a 20kt headwind. A
reasonable soaring day with, say, a 30 degree crosswind at 10kt should
give
you around 1,300 ft. From this, if you are a reasonably competent soaring
pilot, I estimate you have a 50/50 chance of soaring. This increases if
you
can delay the launch until "your" cloud arrives over the winch.

Frank Whiteley makes some highly relevant points:

3. Launch rate is important. With our single drum winch, I can drive a
launch, drag the wire, return to the winch, and launch again with an 8
minute cycle time on a 5000ft run. If the headwind is good, I can have
both
CG equipped two-seaters in the air at the same time. When there's lift,
we
launch about every 15 minutes, giving each training sorty about 20-25
minutes. I will chastise anyone who is not ready to launch when the
wire
arrives. Do your ground school after hours or week nights, not at the
launch point.

All this is very true, but on a restricted site the launch rate also
suffers
from aircraft landing on the main run, used for winching. Trainees and
early
solo pilots will use the main runway most of the time, as will the tug
aircraft. Practice winch failures at low hight will land straight ahead.
The
sudden appearance of three gliders will require at least one to use the
main
runway. All this means you need to be well organised, so as to clear the
gliders waiting to launch if necessary.

Given these potential frustrations of the winch launch, unnecessary delays
by pilots waiting to launch are to be avoided at all costs.

We use a Skylaunch twin drum winch with braided wire cable, and on a good
summer day might achieve 50 launches, 35 winch and 15 aerotow. On an
evening
when instructors fly introductory flights, using two two-seater gliders
launching from the main runway and landing on the cross we have achieved
16
launches per hour (6 min flights), winching only.

6. If you get a ground launch endorsement in six launches, you've been
cheated. Don't expect to exercise your privileges at my club. There
are
some insidious things about ground launching that could bite you, and
you
will practice and understand avoiding them. They can't be exercised in
six
launches. No matter how many winch launches we've flown or driven,
we're
still learning. I, for one, haven't seen it all, nor do I care to.

Absolutely! From memory from the BGA instructor's manual you need to learn
at least:

1. The ground run (quite different from aerotow);

2. A safe transition to the climb, so that a 50ft cable break doesn't
leave
you with insufficient energy to push over, regain flying speed and round
out. Correct use of the airbrakes in this situation is critical.

3. Recovery from a low cable break with a straight ahead landing.

4. Recovery from an "awkward" height cable break, where you can't land
ahead
but have too little height for a normal circuit.

5. Recovery from a mechanical failure of the winch (usually a gradual loss
of power).

6. Signalling too fast and too slow, and what to do if the winch doesn't
respond.

7. Laying off for crosswinds to prevent the cable falling off the runway
on
release.

8. Avoiding over-speeding and under-speeding. This includes understanding
the changes in stresses on the glider throughout the launch and the
symptoms
of an impending stall on the wire (very nasty!).

9. Stalling and spinning from launch failures - these will be simulated at
height, e.g. dive to 70kt, pull up into 45 degree climb, as speed falls to
around 50kts instructor announces cable break. It takes a second or two to
react and push over, by which time speed will be down to 30 kt or so. If
you
stop the pushover at the normal gliding attitude and turn immediately most
gliders will roll smoothly into a spin with no warning signs - don't try
this on your own if you haven't been well trained on spin recovery!

10. Inadvertent launching into cloud.

This list may sound alarming, but we regularly solo students on the winch
with, say, 7 hrs flying time. However, there's no way these matters can be
covered in a handful of launches.

The UK consensus seems to be that winch launching is as safe as aerotow
but
*only* if pilots are well trained.

So why do we aerotow as well? Obviously, some aspects of pilot training
require more height than a winch launch will give. More important, for
pilots setting off on a task an aerotow takes you to the lift at a height
where it's easier to work. Less mental energy used to get started means
more
left over to complete the task.