Troy,
As for your prop/carbs/throttle comments:
Your OK at 5200 RPM static with your prop setting. I wouldn't screw
with it. 5200 is right on with the Rotax recommendations also. That
bit of extra throttle still available most likely means you are "propped
out". That is, the prop has absorbed all the torque the engine can
produce. Static RPM does vary with air density and 5200 RPM static will
allow full power up to about 90 KIAS before the prop unloads to the
engine max of 5800 RPM.
To expand on the build manual, normally, with the throttle idle in the
cockpit each carb should be hard at its stop (both cables tight). At
full, each should just hit the stop at the same time. If not, work on
your cables. You are smart in keeping track of the throttle. I have
seen some setups able to move a 1/2 inch or so from the throttle stop on
the carb until the throttle in the cockpit hits its stop, which is
bending the cables which will cause trouble in the long run. Like you,
I adjust full throttle so as the cockpit throttle lever only barely
allows the cable to bow slightly as the carbs hit their full forward
stop.
As for the carbs, if it runs great at full power / static at 5200,
great. If it is stumbling or rough sounding at full power, you need to
investigate. Changing plugs does make a difference (especially if you
have a turbo that throws a 1/2 cup of oil on start). I have found most
912S/914 have a rough spot between 2500 and 3500 as it is touchy to get
a cable dual carb setup spot on. At full power it should be smooth
sounding. 1/2 inch of MP is not bad, but if it is consistent as you
build rpm, you will hear a stumble and may need to adjust one of your
cables.
My technique when doing a pneumatic carb check, is to note that my carb
pressures are dead even from full rpm, down to 4000. I accept a stumble
---From 2500-3500. I want it smooth at 4000 for the ignition check. If
the idle is bad and the carbs were torn apart and the factory idle
changed, I will adjust the idle setting on the carbs IAW the Rotax line
maintenance manual until it evens out at idle. I only did this once
(three hours of trial and error and two calls to Kerry at Lockwood) as
normally if the factory setting isn't changed during a carb float bowl
and rubber gasket cleanup, no further adjustment is necessary except at
the cable. Once the idle is solid, go up through the RPM ranges again.
The Rotax recommended procedure is available as a DVD/CD video from your
Rotax dealer (I think you may have to pay a pretty penny for it though)
or if you took a Rotax repairman class, it is sometimes a handout. If
you are a registered owner you can download the manuals...Ira told me
that Rotax is now charging for this service also (surprise).
If you take the time, you can get it to run smooth throughout the range.
My old POS 914 is running super smooth now. At least until the stator
went out (defective stator). Ah, the joys of aircraft ownership.
Fly Safe,
Bud Yerly
Custom Flight Creations.
----- Original Message -----
From: Troy Maynor<mailto:wingnut54@charter.net>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Sunday, February 21, 2010 3:24 PM
Subject: Europa-List: Max RPM
Hi All,
Yesterday I took the plane out of the garage and rigged it. Started
the engine, let it warm up, and did the pneumatic carb balancing. They
were within 1/2 in.Hg of each other at 3k rpm when I proclaimed it good
and shut it down. Is this close enough? It ran fairly smooth from 3k up
to 5k. The gages were not so closely matched at around 2k rpm. Just
wondering if this is normal.
When all the hoses were put back in place and vacuum gages removed,
plane tied down securely I did a 2 minute run at max rpm, simulating a
climb to safe landing altitude. All went well at first. However, I only
got 5,200 rpm max. The max rpm was reached without the lever being all
the way forward. The last inch or so of lever travel produced no change.
And, no the cables were not being pushed too far. When the lever stops
in the cockpit, the carb lever just touches the stop. I have a 912S
with the ground adjustable Warp Drive prop set at 17 degrees as per
manual. The analog tach is made by Mitchell and is made for Rotax. Will
the rpm go as high as 5800 when the plane is cut loose or do I need to
flatten the pitch to 16 degrees and try it again?
Thanks again crew.
Troy
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