Towing performance SF25C Rotax Falke 912S?

I am looking for some reliable data on the Rotax Falkes towing performance,
but I have until now not found any consistent values.



I would therefore very much appreciate if you would send me some
information, if you have any experience in this area.





To put it simple, I would like to know how many minutes it takes for a Rotax
Falke with the 912S engine, to tow an ASK-21 (fully loaded, or close to) to
4.000 ft./1.200 meters, in calm air?





My question arises because I have heard one club say 12 minutes, and others
say 25 minutes.



Maybe both answers are true, and the difference is due to different power
settings, towing speed and propeller. In a manual (from 1999), I have read
that the 912S engine may run with a maximum of 5.800 rpm for 5 minutes, and
4.800 rpm for continues flight. I would therefore also like to know the
power setting during tow, for which you have provided the time:





First part of the tow: XXX rpm for YYY minutes

Remaining part of the tow: ZZZ rpm for NNN minutes

Propeller (fixed or variable):

Landing gear:



Please do not hesitate to answer the first question, even if you don't know
the answers for the last 4 questions.



Thank you in advance!



Steen

To put it simple, I would like to know how many minutes
it takes for a
Rotax
Falke with the 912S engine, to tow an ASK-21 (fully
loaded, or close to)
to
4.000 ft./1.200 meters, in calm air?

Is that 4,000 ft above amsl, or above site?

What ambient temperature etc?

My only experience of being towed by this type was
in (or should I say
on) a Primary, at a very steady 42 mph! I would be
surprised if it gave
acceptable performance for really high wing loadings
though.

Ray

Hi Ray

Thank you for the answers, and pointing out two very important aspects that
I have left out of the equation.



Height of site and temperature would be to very useful information in order
to evaluate the data.



I live in Denmark, and here it is just a little bit less flat compared to
the Netherlands, so MSL would be the most relevant height of site. Average
temperature (spring, summer, autum) would be something like 15 deg. Celsius.


Steen

"Ray Hart" wrote in message
...


Is that 4,000 ft above amsl, or above site?

What ambient temperature etc?

My only experience of being towed by this type was
in (or should I say
on) a Primary, at a very steady 42 mph! I would be
surprised if it gave
acceptable performance for really high wing loadings
though.

Ray

Another question you might want to ask is what is the
distance taken to reach 300 feet with a K21 on tow.
If you have trees at the end of your field this could
be important. Sorry I don't know the answer myself.

Hi Alan

That is true, but in our case we have 1.200 meters asphalt runway, so it is
not my biggest concern right now.

The key issue for me, is that the Falke must have resonable towing
perfomance (time) up to 4.000 ft., before it can be taken into further
consideration.

Steen

Fly the right side up - the upside down :-)


"Alan Garside" skrev i en
meddelelse ...
Another question you might want to ask is what is the
distance taken to reach 300 feet with a K21 on tow.
If you have trees at the end of your field this could
be important. Sorry I don't know the answer myself.

Hi Steen

we've got a SF25C Rotax Falke with only 80 hp and use it for towing,
although our airfiel is small ( 1000 m) and there is a sailing port at one
side of the airfield and the first buildings of our town are directly behind
the other end of it.
You can have a look at it if you follow this link:
http://www.lsf-wesel.de/index.php?size=1024&seite=index

Nevertheless we tow an ASK21 double seated up to 4.000 ft. and back in about
21 min.
ASK21 double seated to 5.000 ft about 25 up to 28 min. depending on the
weather situation.

There is hope that the 912S engine you have has got 100 hp. Towing
performans should be much better!

Jürgen
LS8-18-YO



"Steen Thomasberg" schrieb im Newsbeitrag
...
Hi Alan

That is true, but in our case we have 1.200 meters asphalt runway, so it
is not my biggest concern right now.

The key issue for me, is that the Falke must have resonable towing
perfomance (time) up to 4.000 ft., before it can be taken into further
consideration.

Steen

Hi Steen,

one of our club members told me to mention that our "Falke" has got a
variable-pitch propeller. Compared to anothers one with 100 hp but without a
pitch prop, our SF25C Rotax Falke with only 80 hp tows better.

If you need further informations don't hesitate to ask!

Jürgen


"Jürgen Becker" schrieb im Newsbeitrag
...
Hi Steen

we've got a SF25C Rotax Falke with only 80 hp and use it for towing,
although our airfiel is small ( 1000 m) and there is a sailing port at one
side of the airfield and the first buildings of our town are directly
behind the other end of it.
You can have a look at it if you follow this link:
http://www.lsf-wesel.de/index.php?size=1024&seite=index

Nevertheless we tow an ASK21 double seated up to 4.000 ft. and back in
about 21 min.
ASK21 double seated to 5.000 ft about 25 up to 28 min. depending on the
weather situation.

There is hope that the 912S engine you have has got 100 hp. Towing
performans should be much better!

Jürgen
LS8-18-YO



"Steen Thomasberg" schrieb im Newsbeitrag
...
Hi Alan

That is true, but in our case we have 1.200 meters asphalt runway, so it
is not my biggest concern right now.

The key issue for me, is that the Falke must have resonable towing
perfomance (time) up to 4.000 ft., before it can be taken into further
consideration.

Steen

Steen Th. Pedersen schrieb:
I am looking for some reliable data on the Rotax Falkes towing performance,
but I have until now not found any consistent values.



I would therefore very much appreciate if you would send me some
information, if you have any experience in this area.


Our club doesn´t own a SF-25C but we did a Tow-Training this weekend
with a 80hp Rotax SF-25C owned by a another club. It has a mt electric
constant speed prop. Landing Gear: I´m not sure how you say in English
but it´s a taildrager with a two point main landing gear.

Elevation is 1500ft. Temperature about 15°C. Tows were to 200m-300m.
Climbrate with double seated ASK-21 was 1.5m/s-2m/s (300-400ft/min).

Turn around time with cable-winch: 4-5min

Maximum power can be maintained for 5min. The towpilot told us that
after that in hot conditions there isn´t much climbrate left when towing
their double seated Bergfalke.

I have almost no tow-experience but everyone included me liked it very
much. Very smooth ride with 100km/h.

Bernhard