Whoops, wrecked my Libelle again…


Broken Libelle

I was trying out a launch preset switch today to give me some reflex and up-elevator on takeoff (instead of trying to control the elevator manually during the throw, which I found difficult to make repeatable).

I got about 5 or 6 nice throws, adjusting the elevator launch preset strength to tune in the climb rate I wanted. There were a few gusts of wind coming by occasionally, and when they sometimes ended up being tail gusts this was a bit annoying for the airspeed drop, but wasn’t a huge issue.

Then for some reason on my last toss, instead of climbing upwards, the Libelle nosed straight down, as if the launch preset’s direction got reversed, and ended up with its nose buried about 10cm into the mud. I have no idea what happened with that. I double checked the launch preset after the crash and I definitely hadn’t accidentally reversed its elevator direction. I wish I had set up the Taranis to log its data to its MicroSD card so I could see what went wrong. I might even see if I can shoehorn an AfroMini 32 onboard in order to log my flight with Cleanflight’s Blackbox feature.

My first guess is that I wasn’t touching the right stick with my thumb, so I might have been unaware that it was being bumped by my clothing or something. I think I’ll program the Taranis to sound a warning tone if the right stick moves off-centre while the launch momentary switch is being held down, or program it to ignore the right stick during launch.

My other guess is that I simply forgot to hold down the launch switch at all, or released it during the rotation. I’ll add an audio notification for the switch being released.

It looks like the wings separated very cleanly, with just one of the locking tabs ending up being stolen by the other side. The two dihedral braces and the wing top plate all shattered, but interestingly both wing bolts survived. I think this suggests that my wing gluing wasn’t strong enough. I believe that the wings should be held together strongly enough that the nylon wing bolts fail before the wing does (making the nylon bolts a sacrificial failure point).

My electronics and the boom/pod assembly are all pristine, making this hopefully an easy fix once I receive new braces from dream-flight.

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