RV Jet Plane 3.8 diving to the ground

I’ve had dozens of successful flights with my RV Jet since it first took to the skies in 2015. Since upgrading to Plane 3.8 the plane constantly dives to the ground on launch in any mode other than “manual”. I managed to get the plane to take off in manual mode and maintain altitude in “stabilised” mode after adding a lot of elevon up trim. CG has remained constant since upgrading to plane 3.8. On engaging RTH the plane lost altitude quickly and I had to switch back to another mode (Stabilise or manual) to save it. I’m really not sure what parameter has changed to cause this? The FBWmin and other parameters seem to be the same as they were before. Compass 2 is disabled as error variances were always too great to arm the plane, despite being fine before upgrading. I have attached the Bin file in the dropbox link below.

Any help would be greatly appreciated!

can you post a DF log of a previous successful flight with the same airframe with an earlier version? I suspect the auto-upgrade of parameters didn’t go well.

I’m having the same symptoms after upgrading to 3.8.2. PDIP.I is positive (as it’s trying to climb), airspeed is well above the FBW min of 12 but the plane (FX-79) dives into the ground just after take-off on Autotune and FBWA. It needs a new airspeed sensor after the crash this morning but will fix, reset parameters and try again. This aircraft has been flying (mostly successfully) for about 6 months until today. There’s no physical changes since the last flight apart from upgrading the servo links.

Meanwhile, here’s this morning’s logs and a few successful autotune flights from July. I don’t usually keep the bin files, I just keep a battery and flight log.


Thanks, Tim

Hi Tridge, here are links to two previous flights (Bin files) . I’m not much good at reviewing logs yet…

Appreciate your help!

Hi Tridge, I managed to have a slightly more successful flight - still strange behaviour here and there. A dropbox link to the Bin file is below. Any help would be greatly appreciated!

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Hi, I was interested in analyzing the flight logs that you posted but they have been deleted. Could you post them again if you still have them?