I was a bit slimmer in those days, but I regularly flew Bill Dean's K18 at
Lasham, which only had a belly hook. It had also been fitted with a
castoring tail wheel, which made take offs and landings in a cross wind
quite 'interesting' as it was a taildragger. I remember that even with
the trim hard forward, you still had to push a bit to stop it climbing too
high on aerotow, as it basically wanted to do a winch launch. I agree that
the type became much easier to aerotow when fitted with a nose hook, and I
did fly the Booker ones and the one at Sandhill Farm as a visitor when so
fitted.

As an instructor, I would recommend setting the trimmer slightly too far
forward, rather than slightly too far back, for the early part of the
launch as this minimises the tendency to zoom too high. You can always
retrim when you get to a safe height.

After said aerotow accidents we were definitely instructed to aerotow in a
slightly lower position, just above the slip stream but definitely not in
it. If you are not sure where the correct position is, just move down a
bit until you feel a little bit of buffeting and then move back up a few
feet. You should definitely not be looking down at the tug. The
Australians generally use the low tow position below the wake.

Derek Copeland


At 14:15 07 September 2009, Chris Rollings wrote:
The graphic in the BGA Instructors Manual was based on the photos
mentioned
(as was an Australian Safety Poster from around that time). The Ka18
isn't particularly prone to the accident, it's just that the small
number imported into the UK all only had C of G Hooks, no nose hooks,
but
were quite often aerotowed with low experience pilots. The problem can
arise with anything aerotowed on a C of G Hook. When we bought two used
Ka18's from Dunstable at around that time we did not allow them on site
until nose-hooks were fitted.

There were never as many as three or four such fatals in one year in the
UK, but a year with two such accidents was enought to start us on the
tests described, as Booker was the busiest aerotow operation in the UK
at
that time and I wanted to try to ensure we never had one.

The standard towing position was not moved down, it remained unchanged.
To go to a lower towing position (or worse still to trasit to
"low-tow")
would put the glider close to, or in, the turbulent prop wash and wake
of
the tow-plane, and getting bounced around by that is one of the possible
causes of the momentary, inadvertant, pitch-up that can cause the
accident.

As in almost all phases of flight the glider should be trimmed for as
close to zero forward or back pressure on the stick as can be pre-set.
Having to hold a substantial back-pressure on the stick would be
un-helpful.

In the last sentance delete the word "almost".


At 11:00 07 September 2009, Derek Copeland wrote:
At 20:10 06 September 2009, OregonGliderPilot wrote:

GARY BOGGS;705095 Wrote:
Are any of the pictures still around? I would love to see them.
I'm
sure others would too.

Gary Boggs

I think they were posted on the BGA website once?

OGP

I have looked in the BGA website, but can't find these photos. If you
have access to the BGA Instructors Manual there is a graphic in Section
17
which shows the sequence of events. It shows that if the glider gets
too
high and kites on a belly hook, the tug can be pulled into a stalled
and
near vertically downwards attitude within 3 seconds! There is a note
saying that it takes at least 800 feet to recover from this!

At about the time I started gliding in the early 1980s, I remember
there
were three or four such accidents to tugs in one year in the UK, all
unfortunately fatal. Also from memory I think most of them involved
K18s
fitted only with belly hooks. This type is particularly prone to kite.

As a result of these and the Booker experiments, the standard towing
position was moved down a bit and glider pilots were briefed to release
if
they started to get significantly too high or lost sight of the tug
altogether. Also tug rope releases where improved to make them more
accessible to the pilot, and there was a recommendation that all new
gliders should be fitted with nose hooks for aerotowing.

The main danger of getting too high is shortly after take off, when the
combination is still accelerating and the glider's wings are making
more
and more lift due the increasing airspeed. The glider pilot needs to
keep
easing the stick forward so that the glider does not get much higher
than
the top of the tug's tail fin. It is probably a good idea to trim well
forward for this stage of the launch. If a tug upset does occur at this
stage of the launch there is almost no chance of the tug pilot being
able
to recover before hitting the deck.

Derek Copeland