I have a low time Behotec 180 that flamed out twice in flight at the Route 66 jet rally this past weekend and I am at a loss to explain why it happened. Both times the flameouts occurred right at 4 minutes into the flight at the same steady throttle setting with no noticeable thing amiss during the flight up to that point. Can the timing of when the flameouts occurred just be coincidence?

The first thing one suspects and the first we eliminated is the fuel system. No sign of air bubbles in the fuel line, the filter or anywhere else except the UAT and that volume of air was pretty small; about what you would expect from a normal flight. We pulled the tank and checked the clunk and that was in good shape as well.

There is one thing different from the previous flights where the engine performed normally. I sent the transmitter in for service because the speaker had completely quit working. I was told by EspritRC that they replaced the main board in the transmitter, (Jeti DS-16), tested it to make sure all was good and returned it to me shortly before the rally. The engine started normally, just like always, so I didn’t suspect there was any effect from the service work that might have caused the flameouts. I have yet to redo the stick setup on the ECU but that will happen before I do ground testing. Since the engine started normally and ran fine for 4 minutes I really don’t suspect that redoing the ECU/stick learning process will solve the issue.

Of course, I discussed the flameouts with various other pilots at the rally. One asked what battery I was using to power the ECU. The battery is an HRB 3s 4000mah 100C battery. They said the voltage was too high and was heating up the ECU. This evening I charged the battery and it was at 12.5 volts coming off the charger. A manual for the type ECU the engine uses says power should be 12 volts maximum. The battery was freshly charged prior to the first flameout flight. That extra .5 volt doesn’t seem to be enough to create issues?

Fuel doesn’t seem to be an issue because the same fuel, Jet A with 5% Kingtech oil, was used in another smaller engine for many flights at the rally with no issues.

Anyone have similar experience with this engine?

Unknown or unknowable causes are the worst!!