Today's Message Index:
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1. 08:31 AM - Re: ROTAX 912UL/912ULS Frequently Asked Questions (Thumper)
2. 09:11 AM - Re: Re: ROTAX 912UL/912ULS Frequently Asked Questions (John Hauck)
3. 09:36 AM - Re: ROTAX 912UL/912ULS Frequently Asked Questions (Thumper)
Message 1
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| Subject: | Re: ROTAX 912UL/912ULS Frequently Asked Questions |
FYI. The RPM number is used for take off. What two different Rotax forum guys
said is: the takeoff rpm should not be lower than 5300, which means prop loading
should be set to keep the engine higher than 5300 period during takeoff load.
They intended that for those guys running clean airplanes not to prop them
for their top speed and forget minimum takeoff RPM's. After takeoff you can
fly at whatever reduced rpm you want without harm. The Engine was designed to
run at cruise of 5500 all day if you want to but it is not a requirement to
do so. Once you reduce throttle you reduce load on the internal engine parts
so they are not concerned with that. It has been a big confusion and people saying
you are supposed to cruise at 5500 minimum but that was refuted by Phil
Lockwood and the other man at another 912 forum. So just as long as the takeoff
full load RPM = 5300 they are OK. The book says 5500 but they both admitted
that 5300 was OK with them. I like that 3800-5000 range myself for cruise, makes
a difference in noise and fuel burn change of 1.5GPH. On those days when
I'm flying with my Cub friends, Challenger or Trike buddys I smoke them on fuel
burn at equal speeds. Not a Kolb though, BUT I will have another one when the
right deal comes along. See you at the Homecoming I hope. Dennis, Aeroprakt
A20/Kolb like airplane.
--------
Dennis Long
Oakland TN
2000 Aeroprakt A20 Vista Cruiser
Previously Kolb Mark IIIC, 94 Firestar, 84 Ultrastar.
600+hours since 1/1/2009
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=396325#396325
Message 2
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| Subject: | Re: ROTAX 912UL/912ULS Frequently Asked Questions |
I like that 3800-5000 r!
ange myself for cruise, makes a difference in noise and fuel burn change of
1.
Dennis Long
Oakland TN
2000 Aeroprakt A20 Vista Cruiser
Previously Kolb Mark IIIC, 94 Firestar, 84 Ultrastar.
600+hours since 1/1/2009
Kolbers:
Been flying 912's on my MKIII for the past 20 years and more than 3,000.0
flight hours.
Seems I have a difficult time maintaining a minimum engine oil temp of 190F
if I don't fly at least 5,000 rpm. Engine temps drop rapidly below 5,000
rpm. Besides, with my airplane, in order to cruise at least 80 mph, I need
5,000.
Flying with a ground adjustable prop it is necessary for me to pitch for
best take off and cruise. To do this, I pitch for 5,500 rpm, wide open
throttle, straight and level flight. With this pitch setting I get aprx'ly
5,400 rpm during takeoff and climb.
If I flew at sea level all the time I might be able to pull a tiny bit more
pitch. However, on my flights West, it is necessary to climb to
12,000-13,000 feet ASL, and my flight environment and field elevations are
generally 4,000 to 8,000 feet. If I can pull 5,400 rpm climbing at
home/near sea level, I'm down to 5,100 to 5,200 rpm out West. So what I do
is set my pitch for about 5,600 rpm straight and level, wide open throttle
at home. Then when I get out West I still have respectable performance.
I am a firm believer in freeing up the engines and let them turn as they
were designed. Overpitching, to me, has the same results of lugging down a
car or truck when they are equipped with a 5 or 6 speed transmission. It
hammers them to death.
john h
mkIII
Titus, Alabama
Message 3
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| Subject: | Re: ROTAX 912UL/912ULS Frequently Asked Questions |
Absolutely John. No lugging occurs if the takeoff RPM stays above 5300 per Phil.
In flight we can cruise where we want with no harm as long as the prop is not
the limiting factor, that would be lugging. NOW, I see guys with in-flight
adjustable props doing just that by loading up the engine at reduced RPM, that
is lugging the engine, but it is a habit they learned on high performance GA
aircraft and can't seem to explain it to them. Yours is set up like mine. If
I want to fly slow no harm because the engine isn't lugging. Same thing on the
two strokes although on those if you reduce throttle a lot carbon build up
will occurr quickly. See you at Sun-N-Fun maybe, weather permitting.
--------
Dennis Long
Oakland TN
2000 Aeroprakt A20 Vista Cruiser
Previously Kolb Mark IIIC, 94 Firestar, 84 Ultrastar.
600+hours since 1/1/2009
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=396332#396332
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