Today's Message Index:
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1. 05:02 AM - Re: Rotax throttle return springs (Catz631@aol.com)
2. 08:31 AM - Re: Re: Replacing throttle return springs (Hugh)
3. 09:24 AM - Re: Replacing throttle return springs (Thom Riddle)
4. 01:15 PM - Re: Re: Replacing throttle return springs (Hugh)
5. 03:36 PM - Engine ID (CHUCK RHOADS)
6. 05:42 PM - Re: Engine ID (ElleryWeld@aol.com)
7. 07:02 PM - Re: Replacing throttle return springs (Thom Riddle)
8. 07:19 PM - Re: Re: Replacing throttle return springs (Paul McAllister)
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| Subject: | Re: Rotax throttle return springs |
Thom,
Thanks for your reply. I have put the original springs back on.They look
identical to the springs I just saw in the "hombuilders aid' dvd on the Rotax
engine (912UL).They have a unique shape and thickness so I am sure they are the
originals.
With the installation of a vernier throttle I can now control the rpm alot
better and I will get used to the surge forward and react acordingly when I
push the throttle button.
Acording to the Lockwood Aviation dvd and the homebuilders aid dvd as well
as my Rotax books they are all calling for an idle of 1800 to 2000 rpm on the
912 UL If I were try to idle it at 1600 and if it didn't quit,it would sound
like a thrashing machine.It is much smoother and easier on the gearbox, I
believe, at the higher rpm.I have tried to pull it back that far in flight and
it
has quit.(3 times) In fact on my first flight in the aircraft it did that and
I deadsticked from about 30 ft.
Dick Maddux
Kitfox 4-1200
Rotax 912UL
Pensacola, Fl
(http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004)
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| Subject: | Re: Replacing throttle return springs |
Thom:
I have been following some of this discussion and since you and I both have
an Allegro 2000 with a 912UL engine I was curious as to how you are able to
idle your 912 at 1500-1600 rpm with out having the engine come off the mount
our tearing up your gearbox? I read Dick Maddux's reply stating that he had
terrible engine vibration and an actual in-flight engine stop at that low of
throttle setting. Have you changed something on the carbs (on your Allegro)
to allow such a low rpm? My 912UL begins to shake at about 1700. I try not
to go below 1800. From my experience, I agree with Dick that you cannot idle
a 912UL in the 1500-1600 rpm range and not have the engine violently
shaking.
I am also curious as to what airspeed you hold in your Allegro on your final
approach (under normal conditions), and what engine rpm you are turning on
final approach, and what your final touchdown speed is. As I turn from base
to final I am turning at 3000 rpm and an air speed from 65 to 70 with flaps.
>From that point until I am over the runway threshold I try to hold a minimum
air speed of 65. After that I back off the throttle and as you say the
Allegro does want to "float" until touchdown. What is your experience?
Hugh
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Thom
Riddle
Sent: Friday, December 28, 2007 6:12 PM
Subject: RotaxEngines-List: Re: Replacing throttle return springs
Dick,
Most of the guys responding to you so far are flying airplanes with the
912ULS (100 hp) but your question was about the 912UL (80 hp) which is what
we have in our Allegro 2000. The 100 hp engine may indeed need 1800 rpm idle
but the 912UL does not. Ours is set for 1500-1600 rpm idle speed when fully
warmed up. Setting it cold won't do you much good because it will change
when warm.
The Allegro is a floater too and anything above 1600 rpm idle (912UL) will
make final approach difficult, just as you have experienced in your Kitfox.
Roger and I have had this discussion before.... search the archives.
One thing no one has mentioned yet is this. When you buy someone else's
experimental aircraft, you may be in for some unexpected surprises. Are you
sure you have the Rotax/Bing supplied springs on the carburetors? If a
previous owner lost them and bought stronger hardware store springs, instead
of the more costly Rotax springs, this could explain the difficulty your
were having with holding throttle position.
Thom Riddle
FAA Powerplant Mechanic
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=154798#154798
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| Subject: | Re: Replacing throttle return springs |
Hugh,
To get a 912 series engine to idle smoothly in the 1500-1600 rpm range requires
careful mechanical and pneumatic (vacuum) synchronization of the carbs. The mechanical
adjustments must be done first and can be done without running the engine.
Once that is done, the engine must be fully warmed up to do a proper vacuum
synchronization job. The best way to ensure it is warm enough is to fly it
and then do the vacuum balance. This requires dual vacuum gauges. We bought
ours from Lockwood (I think). The proper procedure for doing both of these is
in the Rotax Line Maintenance manual.
If after reading the manual you have any questions, let me know. I know of several
Rotax 912 owners who never synch their carburetors but it does make a difference
if you want a smooth idle at 1600 rpm or less (warm).
Speaking of gearboxes, we just finished removing, disassembling and inspecting
our gearbox. The teeth on both gears looked new and only normal wear on the dog
parts. The springs were still in new spec range too after over 500 hours in
service. Lockwood gets a bundle for doing this, so if you want it done cheaper,
send it to me. I'll do it for $100 plus parts and you pay the shipping. I'm
an FAA certificated Power Plant Mechanic so can do it for any Rotax 9 series,
including type certificated aircraft. Rotax recommends the gearbox inspection
at 400 hour intervals and is required on S-LSAs, but not on experimentals.
Our airspeed indicator reads a good bit high, about 7-8% in the final approach
speed range so take that into account when I quote the IAS speeds I use.
On downwind I trim for 75 mph IAS with no flaps and about 3400-3600 rpm on the
tach depending upon flying weight. Abeam the numbers I pull the throttle back
to idle (don't recall what the tach speed is in flight) and maintain 75 mph through
the turn to base and to final, gliding at idle all the way. Once on final
the speeds I use depend on whether I'm flying solo or with a passenger. When
dual, I use 70 IAS with zero flaps, then reduce IAS to 65 mph with 15 degrees
of flaps, and then 60 mph IAS with full flaps until flare. When flying solo,
I reduce these three final approach speeds by 5 mph each.
As I said, I can't tell you what the engine rpm is in flight with the throttle
at idle but I suspect it is in the 2200-2300 range and perhaps a bit less as my
speed is reduced to 60 mph or less. Next time I fly I'll try to remember to
note these tach speeds and let you know. This time of year we don't get many decent
flying days.
--------
Thom in Buffalo
N221FA Allegro 2000 912UL
N197BG FS1/447
--------------------
Believe nothing, no matter where you read it or who has said it, not even if I
have said it, unless it agrees with your own reason and your own common sense.
- Buddha
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=154872#154872
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| Subject: | Re: Replacing throttle return springs |
Thom:
I have not yet pneumatically balanced my carbs. I have a friend who has a
912S on his amphibian at our airport who has pneumatically balanced his and
has offered to help me do mine. I have read the Rotax procedure and I have
the equipment. At the moment, we, like you are waiting for some descent
weather to fly and do the sync. procedure. If we can get the idle speed down
to the 1500-1600 rpm range, I'll let you know.
My ASI is the one that came from Fantasy Air. I don't know how accurate it
is, but the numbers I quoted in my previous email to you are as INDICATED on
that instrument. It was interesting to hear that you pull the throttle back
to "idle" (1500-1600 rpm) and glide the plane all the way. Does this mean
you have pulled the throttle back to the throttle stop (i.e. can't pull it
back any farther)? How do you control your rate of descent if you do not use
your throttle? If you are a little low as you turn on final, I assume you
use the throttle to decrease your rate of descent as necessary to bring you
back to proper glide slope. Anyway, it was interesting to hear how you
handle your Allegro on landing.
Hugh
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Thom
Riddle
Sent: Saturday, December 29, 2007 12:24 PM
Subject: RotaxEngines-List: Re: Replacing throttle return springs
Hugh,
To get a 912 series engine to idle smoothly in the 1500-1600 rpm range
requires careful mechanical and pneumatic (vacuum) synchronization of the
carbs. The mechanical adjustments must be done first and can be done without
running the engine. Once that is done, the engine must be fully warmed up to
do a proper vacuum synchronization job. The best way to ensure it is warm
enough is to fly it and then do the vacuum balance. This requires dual
vacuum gauges. We bought ours from Lockwood (I think). The proper procedure
for doing both of these is in the Rotax Line Maintenance manual.
If after reading the manual you have any questions, let me know. I know of
several Rotax 912 owners who never synch their carburetors but it does make
a difference if you want a smooth idle at 1600 rpm or less (warm).
Speaking of gearboxes, we just finished removing, disassembling and
inspecting our gearbox. The teeth on both gears looked new and only normal
wear on the dog parts. The springs were still in new spec range too after
over 500 hours in service. Lockwood gets a bundle for doing this, so if you
want it done cheaper, send it to me. I'll do it for $100 plus parts and you
pay the shipping. I'm an FAA certificated Power Plant Mechanic so can do it
for any Rotax 9 series, including type certificated aircraft. Rotax
recommends the gearbox inspection at 400 hour intervals and is required on
S-LSAs, but not on experimentals.
Our airspeed indicator reads a good bit high, about 7-8% in the final
approach speed range so take that into account when I quote the IAS speeds I
use.
On downwind I trim for 75 mph IAS with no flaps and about 3400-3600 rpm on
the tach depending upon flying weight. Abeam the numbers I pull the throttle
back to idle (don't recall what the tach speed is in flight) and maintain 75
mph through the turn to base and to final, gliding at idle all the way. Once
on final the speeds I use depend on whether I'm flying solo or with a
passenger. When dual, I use 70 IAS with zero flaps, then reduce IAS to 65
mph with 15 degrees of flaps, and then 60 mph IAS with full flaps until
flare. When flying solo, I reduce these three final approach speeds by 5 mph
each.
As I said, I can't tell you what the engine rpm is in flight with the
throttle at idle but I suspect it is in the 2200-2300 range and perhaps a
bit less as my speed is reduced to 60 mph or less. Next time I fly I'll try
to remember to note these tach speeds and let you know. This time of year we
don't get many decent flying days.
--------
Thom in Buffalo
N221FA Allegro 2000 912UL
N197BG FS1/447
--------------------
Believe nothing, no matter where you read it or who has said it, not even if
I have said it, unless it agrees with your own reason and your own common
sense.
- Buddha
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=154872#154872
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I am interested in finding out more about a used Rotax 912 engine. The serial
number is 4425597. Specificly I want to know the year of manufacture and is it
a 80 or 100 HP engine.
Thanks,
Chuck Rhoads
__________________________________________________________
Be a better friend, newshound, and
know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
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80 Hp has black Valve covers and the 100 Hp has well some call them blue and
others call them Green valve covers
Im not sure how you would check the SN# Good luck
Ellery in Maine
do not archive
(http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004)
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| Subject: | Re: Replacing throttle return springs |
Hugh,
The idle rpm I'm talking about (1500-1600) is on the ground with the throttle fully
closed. In flight that fully closed throttle (to the throttle stop) in a
glide at 75 mph results in a good bit higher rpm which I am guessing to be in
the 2200-2300 range, but this is just a guess.
The secret to near perfect landings every time in any airplane is a stabilized
approach. In the Allegro, I always plan my pattern (800' AGL) so that when abeam
the numbers at idle power I can glide to an easy power off landing. This turns
out to be about 1/4-1/2 mile away from the runway on downwind depending upon
cross wind. Abeam the numbers I close the throttle and hold 75 mph and begin
my idle power glide. I continue the downwind leg past the numbers about 15 seconds
(adjusting for headwind component by subtracting one(1) second for each
5 mph of headwind component) and turn base, then turn final when I get there
and stabilize approach on final and slow to 70 mph. From abeam the numbers up
to this point I am at fully closed throttle and gliding. Once stabilized on final
I can tell if my current glide path is about right or too long (never short)
and apply flaps and hold the speeds I stated before depending upon my anticipated
touch down point. Using approximately a 15 second downwind extension I
am always plenty high to make the runway if I have a power failure. If the pattern
altitude is 1000' AGL I would have to make the downwind extension longer
than 15 seconds, closer to 20 seconds. I adjust the flaps and speed as necessary
on short final to touchdown where I want, sometimes needing to slip to get
it down shorter. I never have to add throttle once I begin my stabilized approach
abeam the numbers. All I have to do is judge my landing point once on final
and use the flaps and stated speeds as required to make my intended landing
point.
This is NOT how I was taught 40+ years ago. It is what I found to be the easiest
and safest approach method for me in simple aircraft. I am not a big fan of
big patterns for many reasons, not the least of which is that when in the pattern
I want to always be able to glide power off to a safe landing. We are not
flying 747s on 3 degree glide slopes on ILS approaches, so this method keeps the
pattern small and operations quicker for everyone in the pattern. I hope this
helps.
--------
Thom in Buffalo
N221FA Allegro 2000 912UL
N197BG FS1/447
--------------------
Believe nothing, no matter where you read it or who has said it, not even if I
have said it, unless it agrees with your own reason and your own common sense.
- Buddha
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=154948#154948
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| Subject: | Re: Replacing throttle return springs |
Hi all,
I just wanted to share my experience with carburettor balancing. I purchased the
vacuum gaauges from Lockwood aviation, but for some reason I was never able
to get them balanced nicely. In particular I would find I had a vibration in
the range of 3200 ~ 3500 RPM.
Any how I purchased a TwinMax carburettor balancer. This thing is awesome, it has variable sensitivity and I can get them nuts on using this thing. I am able to idle my 914T ar 1500 RPM nicely. It makes quite a difference to my Europa during the landing phase. If you google TwinMax you can find several suppliers. Try http://www.adventuremotogear.com/twinmax.mgi?mgiToken=29HJXUUF
Cheers, Paul
N378PJ
http://www.europa.net.nz/363/index.html
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