Thankyou Dave
This is certainly an enlightenment. I am pleased that people with the
foresight and persistence that you have stay with the gliding movement. It
must have been a long, tough road. Although I can not speak for my club, I
would imagine that the Adelaide Soaring Club, would certainly be on the list
for a proven conversion.
Go for the Aussie product everytime !
PS You mentioned the need for a commercial concern to take this on and
make a buck out of conversions. What about Gippsland Aeronautics?
Even further, has GA considered an auto engine in the GA 200? We would
then have a totally home grown towplane. With the dollar so low any
Aussie product will export like wildfire!
You never know, Jabiru might then consider making and/or exporting a
cheap GRP single seat 15m wingspan club class glider or a two seater
glider. Am I dreaming?
From: "Dave Sharples" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Subject: Re: [aus-soaring] Autotug
Date sent: Thu, 15 Mar 2001 11:16:58 +1000
Send reply to: [EMAIL PROTECTED]
Andrew
The Autotug project is still going and by no means
abandoned. A full report was published in (I think) May's
AG, followed by another auto engine report in September. In
November I sent a circular to all aerotowing clubs with a
report and asked for expressions of interest, responses
have been minimal. Rather than go through it all again the
following is a copy of the latest (brief) update which
another party requested and where the project is now.
It's 100hourly is now due, not because of hours
but the 12 months is up, however we were able to
do 80 hours in that 12 month period, it has now
done around 400 launches. The only defect
during that period was a leaking head gasket
which appeared ok and was not blown, but tests
showed there were traces of CO in the coolant.
Head gaskets and head bolts were replaced. I
also replaced the re-drive belt, not because of
any visual defect but because the manufacturers
claim they have a shelf life of 10 years and
this one was 12 years old. The engine itself
has not missed a beat and has not dropped any
power (RPM,s) at all since it's first start up
in 1992.
Performance and economy is better than expected, especially fuel costs
which shows an unbelievable (conservative) saving of $2000.00 per 100
hours.
This is the breakdown:
According to reports from several
clubs that operate PA25,s with 0-540
engines (which they all have) their
fuel consumption varies from 58 to 60
litres per hour towing. The reason
for this high consumption is that
they all operate at full throttle
with full rich mixture to assist in
cooling. Upon glider release
(usually at 2000 ft) the throttle is
left fully open on the initial
letdown or until the speed builds up
from towing speed of around 65 knots
to 100 - 110 knots IAS with the RPM
getting close to the redline, this is
done to reduce the incidence of shock
cooling, then the power is trickled
back to maintain that speed slowly
reducing RPM,s (fixed pitch props) to
around 2000rpm until final approach.
Thus a lot of fuel is consumed on the
decent (still at full rich). Any
deviation from this practice has
shown to cause cracked pots.
On the other hand the auto engine (spinning the same standard PA25 prop
at the same rpm) does not have to run at excessively rich mixture because
of the ability of water internally cooling the valve stems and seats.
Upon glider release the throttle is immediately fully closed and only a
trickle of opening is required if decent is too severe, thus little or no
fuel is used on decent (when the coolant drops by approx 15deg c the
thermostat closes thus shutting off the coolant circulation). Records
over a long period show fuel consumption at 32 litres per hour towing.
Therefore:
At 58 litres per hour at 90c a litre for 100 hours (58 * 100 * .90)
= $5220
At 32 litres per hour at 90c a litre for 100 hours (32 * 100 * 90) =
2880
$2340 saving
These figures are assuming that both fuel prices are the same.
Until recently mogas was 10c a litre cheaper than avgas which
would improve the situation further should that variation return.
Further to this the auto engine (because of faster letdowns) is capable
of at least one extra tow per hour. We often do ten tows in the hour and
frequently do 30 tows without refueling with a good reserve left, the
tank holds 151 litres.
I sent a circular to all clubs with performance/economy details requesting
expressions of interest in financially supporting us obtaining limited
certification for dedicated glider tugs, the response has been
disappointing. It's strange but every time a club finds itself due for
an engine overhaul I get a call, "when can we get one of your engines"
Regards
Dave.
----- Original Message -----
From: ANDREW WRIGHT
To: [EMAIL PROTECTED]
Sent: Thursday, March 15, 2001 10:04 AM
Subject: [aus-soaring] Autotug
With the Aussie dollar continuing it's downward slide, why is it that we
are still powering our tugs with imported engines. The costs associated
with engine overhauls and replacement are escalating as the dollar
declines. Can anyone answer these questions. 1. Where is our Autotug
project? 2. Why was it abandoned? 3. Is an Aussie made, auto engine
viable as a tug engine. 4. Where is all that money the GFA membership
sunk into the project all those years ago?
I have launched behind a Pawnee with an auto engine many years ago
when
it visited Gawler. (I think it came from Port Lincoln). Is there now a
economic incentive to get this thing off the ground?
Am I wrong or am I not right?
Comments appreciated?
PS In anticipation of this one, some might say that the answer is winch
or auto-wire launching. Unfortunately in many cases wire launching is
not practical, ie in the presence of nearby main roads, powerlines,
built-up areas or at airfields used by lots of GA. Aerotow is a very
popular launch mechanism.
Andrew Wright (VH GAM)
--
* You are subscribed to the aus-soaring mailing list.
* To Unsubscribe: send email to [EMAIL PROTECTED]
* with "unsubscribe aus-soaring" in the body of the message
* or with "help" in the body of the message for more information.
ANDREW WRIGHT
--
* You are subscribed to the aus-soaring mailing list.
* To Unsubscribe: send email to [EMAIL PROTECTED]
* with "unsubscribe aus-soaring" in the body of the message
* or with "help" in the body of the message for more information.
