On Nov 19, 10:59Â*pm, "noel.wade" wrote:

 Can anyone out there with experience behind both 2-bladed and 4-
bladed
Pawnees give me an idea of what the performance losses are?

My club has debated this off and on, but I was recently at a field
with a 4-bladed Pawnee and was much impressed with the lower noise.

Lower noise is the point. If you have problems with local residents,
or might have in the
future, then lower-noise tugs will help your Public Relations effort.
The very fact that you
have done something, rather than nothing, will help in itself.

In the UK we have had some air tow operations closed down after local
objections about
noise, although winch launching continues at these sites.

I fly from Lasham Gliding Centre in the UK, West of London. Although
Lasham is in the country (“sticks�, “boondocks� ?), it is not truly
rural because many locals who work in the Big City value a quiet time
in the country, particularly at
weekends.

Over the years we have had noise complaints from individuals and, more
difficult to deal with,
from organised groups. We have been air towing from Lasham since 1950
and most of these
people will have moved in since then. However, with over 200 gliders
on site we are very
busy on soarable days, and even on those that are not particularly
soarable, with instructional
flying.

Many years ago, we therefore agreed a programme to reduce tug noise.
This included fitting
better silencers to all tug engines (on the other side of the pond you
call them mufflers) such as
the German Gomolzig series (www.gomolzig.de). Then we fitted four
bladed props to all tugs
to which this was possible. Cost-wise we staggered this over several
years. Lasham owns
three 180hp Robin DR400, a 230hp Pawnee and a 180hp Super Cub. All
now have four
bladers except the Super Cub, which is noticeably more noisy than all
of the others. For some
reason our engineers found it difficult to fit a four blader to the
Cub, although I am aware that
they are fitted elsewhere (advice welcome!). Anyway, that is what we
did, and we get very
few noise complaints today. In addition, our tug pilots are briefed
to avoid flying over the
local villages below 1500ft AGL. If, on rare occasions now, if we get
a complaint from one
place, we simply switch the tow pattern to another direction.

Conditions with little wind and a low inversion are the worst case for
noise on the ground, and
in our area Sundays are more sensitive than other days.

There was even a time where one of the villages asked the club to
attend a village meeting to
explain the noise situation. Although this was a tough one, the fact
that we were able to say
that we had made modifications both to propellors and exhaust noise,
and have a map of
“avoid areas� went down well. We have few complaints from that area
now.

Problem is, I've got club members claiming that it'll cost over $10k
to do the job, and we'd give up 25% to 30% in performance due to the
extra blades.

In my experience as a tug pilot both before and after the noise
reduction programme, the
performance reduction is much less than this. Others who are better
qualified will no doubt
produce figures, but I would suggest between 5 and 10%.

However, if it prevents local inhabitants trying to close your gliding
operation down, then it’s
worth it!

Ian Strachan
Lasham Gliding Centre, UK