In the deep mid winter…

Hermione got thrown…

…up into the air at full acceleration!

It was less than -5°C when I took Hermione out wearing her salad bowl lid.  I knew the end result would be a destructive crash but I wanted to compare against Zoe’s inability to get of the ground yesterday.

Before 0.9s, things were looking promising…

Double brrr!

Double brrr!

…right up to the point something went wrong with the I2C readings of the IMU:

WTF?

WTF?

At that point she launched into the air at high speed to counteract the negative vertical distance she was (falsely) sensing.  By the time I hit Ctrl-C, she was 3m up and climbing hard towards the house roof.  When she hit the ground, she was doing about 7ms-1, so unsurprisingly, there was damage.  Luckily minutes later, the postman arrived with the replacement parts – I knew they were coming which is why I could do the flight bound to end in damage.  It’s worth noting that no “FIFO overflows” or “I2C errors” were detected at the point everything went wrong.

Here’s the equivalent of Zoe’s flight yesterday when she couldn’t get off the ground.  She was flying at about +5°C.  I cut this flight because she was sitting on the ground with the props spinning at the minimal speed.

Zoe's cold

Zoe’s cold

They were running identical code but Zoe’s IMU worked perfectly throughout.  I’m assuming Hermione has power brown outs due to her A+ and all her sensors.  I’m not sure why Zoe’s not taking off well – both she and Hermione showed the same temperature change during takeoff, and the corresponding accelerometer drift.  Next step is to take Zoe out into the sub-zero back garden and see how she reacts at that temperature.

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