OS .61 dies when flying inverted
Stormlord
I have a fairly new (less than a year old) OS .61FX mounted upright in a
Twist 3D 60 with a 13x6 prop. The engine has been properly broke in and
has about 20 flights on it.
I'm having a problem that I'm not sure how to solve.
When flying the plane at around 1/4 throttle, if I fly inverted, it
will die and I have to dead-stick the plane to the ground.
It doesn't seem to happen when I do this at 3/4 or higher throttle, but
it does stutter from time to time, it just doesn't quit.
I never have a problem whatsoever if I don't fly inverted ... runs
through a tank of fuel just fine and I can do anything I want with the
plane.
At first, I thought the clunk was getting stuck and sucking air, but
this is not the case.
The clunk is free and not getting hung up anywhere ... also, when the
plane lands dead-stick, upon inspection, there is fuel in the fuel line
all the way to the carb with no air bubbles in it.
Is there a way to correct this problem? Anyone ever had this happen
before? I'm not sure where to start, I've never had this issue
previously.
I've tried leaning and richening the engine with the main needle valve
(no difference - the problem is repeatable), and I've changed to a
hotter glow plug (from an OS 8 to a 3) so far.
I'm just not sure what's causing the condition, so I'm not sure what to
try to fix it.
Could the engine be flooding itself upside down somehow, causing the
glow plug to foul out? What would cause that and how can it be
corrected?
I pulled the glow plug after one of the dead-stick landings and it was
not wet, but with a hot engine, I thought maybe it had evaporated after
normal level flight had resumed (even though the engine was not
running).
Just not sure where to go with this and I'm searching for some ideas to
try ....
--
Stormlord
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Dave Plumpe
IF, when upright, your tank centerline is below the carb jet, then when
inverted it will be above the jet by the same amount, for a difference of
twice the distance. The fuel mixture, properly adjusted for upright flight,
will become rich - possibly too rich - and the engine will load up.
Midrange throttle typically is a bit rich anyway. Try raising the tank.
If that's not the problem, try adding landing gear on the top.
-Dave
"Stormlord" <Stormlor...@rcgroups.com> wrote in message
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(snip)
Worn Out Retread
"Stormlord" <Stormlor...@rcgroups.com> wrote in message
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>
Like the other reply, I think that the fuel tank is probably set too low
causing a tank high position when inverted. This can easily drown your
engine with an overly rich mixture. I would set the tank up dead centre with
the needle valve (had to for pattern flying where there is a lot of inverted
and outside manoeuvres). Then very carefully adjust the low end mixture so
that it isn't too rich. You have to make adjustments to both the low and
high end mixtures as you are tuning. You know that you have the low end
mixture pretty close if you have the engine at idle for several seconds and
then pinch off the fuel line and the engine dies without a great increase in
rpm. There should be a slight rpm increase before dying. Properly tuned
there should be little to no hesitation when going from idle to full
throttle.
Good luck
--
Ron P
If we are what we eat then: I'm fast,
cheap and easy and past my best before date
Tim Wescott
For a diagnostic, why not put the plane on a stand and run it inverted
on the ground, at the deadly throttle setting? Then you can see what's
going on close up, you can see if you can adjust the mixture to keep it
going, you can maybe pinch the fuel tubing to see if it's too rich or
lean (if it's too rich pinching the line will make it speed up, too lean
it'll sag or die immediately instead of after a bit).
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Ted Campanelli
so great) words of knowledge:
I agree with the others - the tank is set too low.
Position the tank so that where the fuel line exits the stopper on the
tank is even with the SPRAY BAR in the carb. You MAY need to readjust
the carb settings.
Lyman Slack
I concur with the others that the tank is too low in relation to the
carb. However, I'm also aware that you realistically cannot raise the tank
on the Twist. Talking to one of our resident experts at the field today, he
said his fix was to rotate the engine sidewise; i.e., the cylinder on the
right side on the model.
Ideally, the tank center line should be at or no more than 1/2" below
the carb spraybar.
If you still prefer to keep your original set up, an alternate solution
is to add a Perry Pump in the fuel system.
Cheers -- \_________Lyman Slack________/
\_______Flying Gators R/C___/
\_____AMA 6430 LM____ /
\___Gainesville FL_____/
Visit my Web Site at www.LymanSlack.com
"On so-called global warming or climate change, let us not scare ourselves
with catastrophic forecasts, or use them to defend and promote irrational
interventions in human lives."
"Stormlord" <Stormlor...@rcgroups.com> wrote in message
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>
Lyman Slack
I concur with the others that the tank is too low in relation to the
carb. However, I'm also aware that you realistically cannot raise the tank
on the Twist. Talking to one of our resident experts at the field today, he
said his fix was to rotate the engine sidewise; i.e., the cylinder on the
right side on the model.
Ideally, the tank center line should be at or no more than 1/2" below
the carb spraybar.
If you still prefer to keep your original set up, an alternate solution
is to add a Perry Pump in the fuel system.
Cheers -- \_________Lyman Slack________/
\_______Flying Gators R/C___/
\_____AMA 6430 LM____ /
\___Gainesville FL_____/
Visit my Web Site at www.LymanSlack.com
"On so-called global warming or climate change, let us not scare ourselves
with catastrophic forecasts, or use them to defend and promote irrational
interventions in human lives."
Lyman Slack
Can you rotate the engine so the cylinder is on the right side of the
Twist? This will get the carb spraybar in line with the tank CL. If you
can't, another option would be to add a Perry pump.
Cheers -- \_________Lyman Slack________/
\_______Flying Gators R/C___/
\_____AMA 6430 LM____ /
\___Gainesville FL_____/
Visit my Web Site at www.LymanSlack.com
"Stormlord" <Stormlor...@rcgroups.com> wrote in message
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>
Jim
running engines in an upright position for this reason. I know you'd have to
do some surgery on the twist to change it though.
"Lyman Slack" <lys...@bellsouth.net> wrote in message
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