To Pawnee or not to Pawnee...that is the question...

Not could - DO!

We winch only - in vintage rag and tube mostly and we seem to be able to attract
teenagers with our equally old winch.

309 wrote:
On Oct 20, 9:45 am, "Bill Daniels" bildan@comcast-dot-net wrote:
I don't think any tow plane ever pays for itself once all 'hidden' costs are
considered. Operating an old rag and tube airplane of any kind is fraught
with 'nickel & dime' costs that add up. The last time I took a hard look, a
Pawnee runs about $150 USD/hour. With rapidly escalating costs of fuel and
insurance, it will probably be $200/hour by next summer. You don't operate
small airplanes to make money, you do it because you either need to or want
to. Tugs are cost centers not profit centers.

I think any club interested in lowering operating costs should be
investigating winches.

Bill Daniels

I forgot to add my "turbine tow would require winch launch
authorization" punch line. ;-) Thanks, Frank.

If somebody made a twin-turbine-taildragger tug, you could get the tow
pilots to PAY for that time (building time for th airlines...).
Turbine Beech-18 gets logged as Complex-Multi-Taildragger-Turbine-High
Performance time...worth $200.00 per hour for training to be a line
pilot. Yeah, I'd go back to the club and put up with the politics for
that!

Since AUTO fuel will quickly be over $4.00 per gallon (it already has
"traded" above that in Beverly Hills), the winches aren't going to be
a hell of a lot better -- if we must insist on suckering, er I mean
recruiting teenagers into our dying sport. (Flame away, guys...I'm
trying to get my kids interested -- _I_ have a hard time competing
with video games, even when I shut the power off).

I suspect we'll soon be back to hilltops and bungee cords... Quick,
we must assemble a protest march to SAVE TORREY PINES (Gliderport)!!!!

-Pete
#309
(I just donned my flame retardant suit).

P.S.: For the record, I agree with Bill -- EVERY "club" should have a
winch. And I think winch launches COULD compete with video games.

Frank Whiteley wrote:

Actually, a winch launch to 2000agl uses very little fuel. Getting to
the gliderport will use far more.

Solar cells charging batteries all week for the electric winch, and ride
your bike to the airport. Save the gas for the retrieves :-)



Shawn

"309" wrote in message
ups.com...
On Oct 20, 9:45 am, "Bill Daniels" bildan@comcast-dot-net wrote:
I don't think any tow plane ever pays for itself once all 'hidden' costs
are
considered. Operating an old rag and tube airplane of any kind is
fraught
with 'nickel & dime' costs that add up. The last time I took a hard
look, a
Pawnee runs about $150 USD/hour. With rapidly escalating costs of fuel
and
insurance, it will probably be $200/hour by next summer. You don't
operate
small airplanes to make money, you do it because you either need to or
want
to. Tugs are cost centers not profit centers.

I think any club interested in lowering operating costs should be
investigating winches.

Bill Daniels

I forgot to add my "turbine tow would require winch launch
authorization" punch line. ;-) Thanks, Frank.

If somebody made a twin-turbine-taildragger tug, you could get the tow
pilots to PAY for that time (building time for th airlines...).
Turbine Beech-18 gets logged as Complex-Multi-Taildragger-Turbine-High
Performance time...worth $200.00 per hour for training to be a line
pilot. Yeah, I'd go back to the club and put up with the politics for
that!

Since AUTO fuel will quickly be over $4.00 per gallon (it already has
"traded" above that in Beverly Hills), the winches aren't going to be
a hell of a lot better -- if we must insist on suckering, er I mean
recruiting teenagers into our dying sport. (Flame away, guys...I'm
trying to get my kids interested -- _I_ have a hard time competing
with video games, even when I shut the power off).

I suspect we'll soon be back to hilltops and bungee cords... Quick,
we must assemble a protest march to SAVE TORREY PINES (Gliderport)!!!!

-Pete
#309
(I just donned my flame retardant suit).

P.S.: For the record, I agree with Bill -- EVERY "club" should have a
winch. And I think winch launches COULD compete with video games.


As frank pointed out, winches comsume very, very little energy. Roughly
1kW/Hr or a liter of diesel which could easily be biodiesel. An electric
winch, if it could be powered from the grid, would comsume less than 10
cents worth of power per launch.

Bill Daniels

Bill Daniels wrote:

I don't think any tow plane ever pays for itself once all 'hidden' costs are
considered.

A club which wants to survive *must* charge tows at full cost. At my
club, the tow plane *does* pay for itself. Which means that tows aren't
exactly cheap.

"John Smith" wrote in message
...
Bill Daniels wrote:

I don't think any tow plane ever pays for itself once all 'hidden' costs
are considered.

A club which wants to survive *must* charge tows at full cost. At my club,
the tow plane *does* pay for itself. Which means that tows aren't exactly
cheap.

"Not exactly cheap" tows leads to an activity called "assembly practice".
This is where a pilot drives to the gliderport, assembles his glider but
then decides the conditions aren't worth the cost of a tow so he de-rigs
without flying.

When you see "assembly practice" or pilots driving to the gliderport without
flying, it's a sign your aero tow operation is verging on an economic death
spiral. You'll reach a point where tow costs are so high that you can't do
enough tows to pay the fixed overhead which, in turn, requires still further
increases in tow costs.

At $5 - $10 for a winch launch, you'll never see "assembly practice". At
$15/launch, a winch can not only support itself, it can support that tug and
some nice glub gliders. Even if you will never take a winch launch, get one
anyway just for the revenue stream.

Bill Daniels

Frank Whiteley wrote:
Not positive, but I don't think multiple glider tows are allowed under
the SSA insurance plan.

The SSA insurance plan isn't the only one available. Double tows to the
mountains are pretty routinely used at Williams Soaring Center in
California...

Marc

A club which wants to survive *must* charge tows at full cost. At my
club, the tow plane *does* pay for itself. Which means that tows aren't
exactly cheap.[/quote]

How much?
and, what is the breakdown, for instance, 2000' agl, + per minute or + per 100' ?

does the tow charge cover all the a/c costs, like insurance, maintenance, replacement after time etc?

curios bagger

On 21 Oct, 01:03, "Bill Daniels" bildan@comcast-dot-net wrote:

As frank pointed out, winches comsume very, very little energy. Roughly
1kW/Hr or a liter of diesel which could easily be biodiesel. An electric
winch, if it could be powered from the grid, would comsume less than 10
cents worth of power per launch.

I'm bored, so thought I'd play with some numbers ...

I've launched ASH-25's to 1,600' on the wire. At 750kg that's a PE
gain of 750kg x 10 N/kg x 500m = 3.75MJ. There's also a PE gain in
half a ton of wire rope going up 250m: 500kg x 10 N/kg x 250m =
1.25MJ. KE is small in comparison, so that's a nice round 5MJ per
launch.

That's 1.4kWh, but allowing for 85% efficiency in the electric motor
you'd need 1.6kWh. Typical domestic prices here are around 12.5p /
kWh, so that's a nice cheap 20p/launch.

The downside is that you need that energy awful fast. 5MJ over 50
seconds is 100 kW (probably what 200bhp diesel winches get to wire
after transmission losses). That gives two problems.

First of all, you need a very hefty supply. On 415V 3-phase AC, and
assuming a 0.85 power factor, that's a line current of 100 kW /
[sqrt(3) x 415 x 0.85] = 163A. That's definitely non-trivial.

Secondly, you wouldn't get the electricity on a domestic tariff.
Industrial contracts take account of peak power as well as energy
used: the club would need a 100kW supply infrastructure despite only
using, on average, a tiny fraction of that capacity. The power company
will want to recoup the cost of the supply, and that will push the
price up considerably.

The logical alternative would be to use a local energy storage
facility: a great big Li-ion battery bank in the winch would help a
lot. With a 20% service factor (one launch every five minutes) the
average power requirement would come down to 20kW. Still too much for
a standard domestic supply, but a 40A 3-phase supply is pretty
standard. The downside there is that the batteries and associated
supply kit would be horribly expensive.

I believe Tost used to offer a (mobile?) electric winch, and I'd be
interested to know what the power supply arrangements were. As far as
I can see they don't do winches of any sort any more.

I'm sure electric winches could work very well, but I think they'd do
best as fixed installations. Are any in use?

Ian

On 16 Oct, 13:54, Martin Gregorie wrote:
Dan G wrote:
Why is it only old Pawnee vs. new Husky? Are there not used efficient
180hp tugs available in the US?

I was up at Milfield with my Libelle a week ago, where they run three
tow planes: 150 Pawnee, 180 Supercub, 235 Pawnee. I couldn't see much
difference between the Supercub and the 235 Pawnee but the 150 Pawnee
had a much slower climb rate than either of the others: more like my
club's 160hp Rallye.

It's actually a 160hp Pawnee - it was uprated a few years back.
Although there have been 150bhp - 180bhp conversion in the US, 160bhp
(it's a helicopter engine) was as far as the CAA would allow without a
complete new set of stress calculations.

When the wee Pawnee arrived it had a four blade prop and a good
silencer: amazingly silent but couldn't pull the skin off a rice
pudding. I remember circling overhead in weak wave for some time
before landing once, waiting for it to get a Bocian off. Three
circuits of the airfield, got to 350', gave up.

Ian

Bill Daniels schrieb:

"Not exactly cheap" tows leads to an activity called "assembly practice".

I've never seen this. The glider pilots I know want to fly, that's why
they are glider pilots, after all.

When you see "assembly practice" or pilots driving to the gliderport without
flying, it's a sign your aero tow operation is verging on an economic death
spiral.

If you operate tow planes that don't pay for themselves, then your aero
tow operation is certainly verging on an economic death spiral.

At $5 - $10 for a winch launch, you'll never see "assembly practice".

Unfortunately, there are airfields from wich you can't reach thermals
from the winch. Or, if you reach them, you do so only three ours later
than with aerotow, which makes big flights impossible. I *know* there
are pilots lucky enough to operate from airfileds where you reach your
first thermal reliably from the winch at 10 a.m. I just don't happen to
operate from such a field.