Postponed 3 students due to TSA

On Sun, 31 Oct 2004 15:51:07 +0100, Stefan wrote:

Olfert Cleveringa wrote:

At least for this part of Europe, I think a Diesel in a Robin-like
airframe would be a very nice replacement.

I don't think so, there are better solutions.

This year, in Switzerland, we've carried out serious experiments with
those new ultra lights as tow planes, with the allowance and under the
supervision of the FOCA. The results were unexpected and spectacular.
(For our American friends: I'm not speaking of those flying lawn-movers,
but of the new high tech airplanes rated as Ultra Lights in Europe. Look
at http://www.remos.com/ and http://www.lightwing.ch/ for two examples.)

As I said, the results were astonishing. Powered with a 100 hp Rotax
engine, they performed as well if not better than a typical "classic"
180 hp towplane! Even a heavy two seater on wet grass wasn't a problem!
Start roll was even shorter, the noise level was much lower (important
in Europe), and all with a gas burn of 12l/h instead of 40l/h. (Or
similiar, I don't have the exact numbers handy.) Even when high tows
lasted a little longer (i.e. 15 instead of 12 minutes), they were much
cheaper.

We discussed why those planes would perform so well with only 100 hp. We
think, there are mainly two reasons. First, as the name says, they are
very light. It makes a difference whether the plane weights 1000 kg or
400. Then, "traditional" airplanes fly way too slowly on tow. They are
operated far away from their best climb speed, while those ultralights
are operated very near best climb speed. But for whatever reason, in
Switzerland it is common belief now that those ultra lights are the
future of towing.

Stefan

Stefan,
Have they done any tests at high altitude airfields ? My memory of
Swiss gliding fields is that they are in valleys, with reasonably low
altitude. If I am wrong, please correct me, as my knowledge is
fragmentary regarding your lovely country.
We have discussed ultralight tow planes, but the consesus seems to be
that with high temperatures (40 C is not at all uncommon) the high
density altitude will reduce the performance to an unacceptable level.
I have also heard some rumours that the high speed Rotax engines don't
take kindly to the extended full power operation necessary when
towing, and the lifetime is shortened. Can you comment on this please
?
Cheers, John G. (Victoria, Australia)

John Giddy wrote:

Have they done any tests at high altitude airfields ?

How high is high enough? Is a 800 meter paved runway at 1328 m (4354 ft)
altitude high enough? I took off in a Janus last summer there behind an
ultralight. It wasn't 40°C, though.

... regarding your lovely country.

You may spare the flattery, I'm not American. ;-)

We have discussed ultralight tow planes, but the consesus seems to be
that with high temperatures (40 C is not at all uncommon) the high
density altitude will reduce the performance to an unacceptable level.

We've discussed it, too, and all experts said that it wasn't possible.
The experiments showed it was. If you want to know, you must do the
experiments in the conditions which are important to you. No way to know
otherwise.

I have also heard some rumours that the high speed Rotax engines don't
take kindly to the extended full power operation necessary when
towing, and the lifetime is shortened. Can you comment on this please

I've heard all kinds of rumours. No, I can't comment on the lifetime of
Rotaxen, sorry.

Stefan

At 00:24 01 November 2004, John Giddy wrote:
........
Stefan,
Have they done any tests at high altitude airfields
? My memory of
Swiss gliding fields is that they are in valleys, with
reasonably low
altitude. If I am wrong, please correct me, as my knowledge
is
fragmentary regarding your lovely country.
We have discussed ultralight tow planes, but the consesus
seems to be
that with high temperatures (40 C is not at all uncommon)
the high
density altitude will reduce the performance to an
unacceptable level.
I have also heard some rumours that the high speed
Rotax engines don't
take kindly to the extended full power operation necessary
when
towing, and the lifetime is shortened. Can you comment
on this please
?
Cheers, John G. (Victoria, Australia)


John,
talk to the South African guys here. At Gariep Dam
they use a Samba (Rotax engined microlight) for towing
and that is 4000+ft and hot.
http://www.gariepgliding.com/airfield_data.htm#space
http://aeroklubuo.macroware.cz/Lambadaen.html