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Need help with a G-61 problem

Old 10-30-2011, 02:51 PM
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Default Need help with a G-61 problem

Hey guys. I have an Italian-made G-61 powering an Escapade 60 that I've been having some problems with and I'm hoping someone can help. Here's the scenario: She idles great for as long as you care to let it do so. Runs solid at high-speed as well. Transitions from low to high on the bench with no issues, but put it in the air and that's where the problems come in. I'll take off, fly a couple of circuits, and come in for a touch-and-go. It's at this point that I'm experiencing the problem. After landing (or even during aborted landings), I'll give more throttle from low or idle to climb back into the air, and the engine either stumbles or outright dies. We've tried both high and low needle tuning, and switched fuels and glow plugs. I thought we had it licked, as the problem seemed to clear up for a few days. The first two flights this morning were just fine, but then the problem came back on the third flight and stayed the rest of the day, resulting in a dead-stick each time.

I should note that the transition from low to high is fine on the bench (no matter what we do to try to duplicate the issue), and is also just fine during normal flight.

I'm using O.S. #7 and #8 plugs, and have used Omega 10% and 15% and Cool Power 10%. The Cool Power seemed to help a bit (the problem was very consistent with the Omega), but that's what I was using today, both for the good flights as well as the dead-sticks. One of the guys at the field told me that the Italian STs really didn't like anything more than 5% nitro, and suggested I try some FAI (0% nitro) fuel.

I'm at a loss. My father, who uses and swears by STs, along with several other experienced tuners at the field haven't been able to eradicate the problem and I'm sure I'm running out of luck with my dead-stick landings. So far I've been fortunate to have it always die upwind (mostly because the problem seems to usually happen after an aborted landing or touch-and-go takeoff).

Help me, Obi-Wan. You're my only hope...
Old 10-31-2011, 06:08 AM
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Default RE: Need help with a G-61 problem

You may not have the carb well-balanced. Here's the carb setup: http://www.rcuniverse.com/forum/m_1579985/tm.htm

Also, if the temperature of the day changes a lot during your flying session (morning to afternoon), then you'll also have to change carb settings.

Mainly, setting a very-low idle is the culprit. Get the top-end set first, and then the idle. Work out an idle mixture and RPM that will allow a good transition. Any idle RPM 2,500 RPM or lower is excellent.
Old 10-31-2011, 07:26 AM
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Default RE: Need help with a G-61 problem

Thanks for the info. The transition between low and high works very well on the bench and during normal flying, with not even a hint of stumble other than during the circumstances I described. I *think* the balance is good between the LSN and HSN, or I would expect to experience the problem more consistently. As far as the idle speed, although we did not use a tach to measure it, it does not seem overly low. Actually, at one point we had to lower it because it was high enough that the plane wouldn't land - it would just glide right by a foot off the runway!

Why would the engine act differently (to this extent) in the air vs. on the bench? I live in Florida, so my altitude is either 4' ASL or 40' ASL, depending on whether it's on the bench or in the air...

Fun times.

 
Old 10-31-2011, 06:58 PM
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Default RE: Need help with a G-61 problem


ORIGINAL: 7kings

Why would the engine act differently (to this extent) in the air vs. on the bench?
Fun times.


When the airplane is in the air the engine is under less load than stationary on the ground
thus the fuel/carbueration requirements are different.

Happy flying, Oscar
Old 11-01-2011, 06:12 AM
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Default RE: Need help with a G-61 problem

You must tune the engine to the way it behaves in flight. As the model flies, loads on the engine will change. You have to adjust the engine as needed to accomodate what happens in the air. Setting it on the ground is fine, but you then have to listen and observe to see how it act once you take off. Also, the more the engine is run, the better it will handle.

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