Today's Message Index:
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1. 12:55 AM - 912 S/ULS compression ratio (Remi Guerner)
2. 06:41 AM - Re: 912 S/ULS compression ratio (Roger Lee)
3. 08:39 AM - drop of rpm on take off (georg.stiller@arcor.de)
4. 09:23 AM - Re: drop of rpm on take off (Roger Lee)
5. 04:11 PM - Re: Re: drop of rpm on take off (Noel Loveys)
6. 04:50 PM - Re: drop of rpm on take off (Roger Lee)
7. 04:51 PM - Re: drop of rpm on take off (Roger Lee)
Message 1
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| Subject: | 912 S/ULS compression ratio |
On the last issue (April 1st, 2010) of the Rotax 912 series Operator Manual, the
compression ratio of the 912S/ULS has been increased to 11:1. See page 1-14.
Previously it was 10.5:1. Surprisingly there is no mention of any affected performance
figure. Does anyone know whether this is just a correction of a mistake
in the documentation, or a real modification of the cylinder head or piston
geometry?
Regards
Remi Guerner
Europa F-PGKL
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=327980#327980
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| Subject: | Re: 912 S/ULS compression ratio |
Hi Remi,
Nice catch. I suspect it is a typo, but I'll shoot off an email to Rotax and find
out for sure. It may be a day or so being Sunday, but I'll re-post and let
you know.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328000#328000
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| Subject: | drop of rpm on take off |
Hi,
I started this thread on January, 4. I should like to thank for the advise and
report on my findings:
I changed the needle in the carb from pos. 3 to 4 and made some testflights at
5 - 6 centigrade below zero with carb heat pulled. There was no trouble, no rpm
drop anymore. Power output is okay. Carb heat is nearly ineffective, however,
as I checked the temperature in the air box with a digital thermometer and there
was virtually no difference with or without carb heat.
So the needle position obviously fixed the problem.
I have now a little problem with the warm start of the engine. Seems to be running
somewhat rich, a little bit of grey smoke from the exaust when the engine
catches.
Thanks again!
Regards, Georg
Kitfox, Rotax 912
Message 4
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| Subject: | Re: drop of rpm on take off |
Make sure your idle rpm is set to only 1700-1800, not more it may be hard to start
and less it may be hard to start. No throttle on start up is normal. Once
in a while a 10% throttle opening can help if your normal rpm is a little too
low, but no more than 10%. Make sure that both choke/enricher circuits open fully
and not one more or less than the other. Try one or two different start up
procedures and I'm sure one will work.
Starting is also tied to poor carb balance so make sure they are set.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328039#328039
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| Subject: | Re: drop of rpm on take off |
I'm now installing a 912 to replace a 582. On the 582 I intentionally set
the idle very low so the plane wouldn't drift on touchdown. Once on the
ground I had to add throttle to keep 1800 rpm. Is this used with the 912?
Noel
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Roger Lee
Sent: January 23, 2011 1:51 PM
Subject: RotaxEngines-List: Re: drop of rpm on take off
Make sure your idle rpm is set to only 1700-1800, not more it may be hard to
start and less it may be hard to start. No throttle on start up is normal.
Once in a while a 10% throttle opening can help if your normal rpm is a
little too low, but no more than 10%. Make sure that both choke/enricher
circuits open fully and not one more or less than the other. Try one or two
different start up procedures and I'm sure one will work.
Starting is also tied to poor carb balance so make sure they are set.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328039#328039
Message 6
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| Subject: | Re: drop of rpm on take off |
Hi Noel,
You' re going to like your 912.
1800 rpm is not enough to keep you flying and might extend a glide
50', maybe. I have a plane that has a 14:1 glide ratio and can land in 1K feet
easily with 2800 rpm. I will use 2700-2800 rpm for all flap settings on normal
landings or I can land at idle. It can make a world of difference carrying a
little rpm to touch.
The rest of this post is on my soapbox and not aimed at anyone single person.
If someone can't put their plane down with 1800-2000 idle rpm then they should
look at their landing technique and try a few changes. Remember the stick controls
speed and throttle altitude. So what ever the rpm pulling back the stick
to your desired speed works just fine. Yes I know up to a point it makes a difference,
but not at rpms at or below 2000 rpm. Landing with rpm will also give
you better control surface authority just before touch down. The controls won't
feel mushy and give good solid input. If you can't hit a target landing spot
at 1600 rpm then you can't hit it at 2800 rpm and either way that just means
more focused practice. RPM doesn't decide where or when the wheels or floats
touchdown, you do in your setup and execution of the landing. I can hit my spot
at 1700 or 3000 rpm on landing and I can touch down at the same speed.
Purposely setting an idle rpm so you may loose the engine is, in my opinion, the
wrong way to set up your aircraft. It isn't good for the engine or the pilot
as some day it may cost you.
The more distractions you throw into a landing the more chance of making a mistake
some day. It only takes a second for a normal landing to mess up, keep throwing
distractions in your execution and sooner or later you may not be jolly
on the spot with a correction.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328117#328117
Message 7
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| Subject: | Re: drop of rpm on take off |
Hi All,
Here is a link to the ROAN website to watch a fairly new Rotax engine tips video.
It covers things like start up, carb sync, prop balance, shut down and proper
engine rpm, ect. This video gives proper idle speed. This video is in conjunction
with "Service Letter" 0912-016.
For those who have argued about idle speed for the 912ULS 100 HP I hope this will
clear up any low rpm idle issues. It not only talks about it, but you can see
it on the instrument panel. The 912UL with only a 9.0:1 compression can do
1500 idle rpm, but the 912ULS at 10.5:1 compression has too much compression and
beats up the engine/gearbox, not to mention the chance of loosing an engine
at a 1500 idle approach. Be kind to your engine, it's the only thing that keeps
you off the ground and out of the tress.
The video will tell you to keep rpms at 1800 + rpm and higher depending on the
phase of the engine run. Running a 9121ULS at rpms of 1500-1700 is not good for
your engine as we have discussed here before. This is in writing now and I hope
alleviates some of the confusion from other sources.
http://rotax-owner.c...ning&Itemid=174
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=328118#328118
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