I've just spent some time trying to tune altitude hold. I had been making reasonable progress, until my copter took off at full throttle while in position hold. At the time, I had PH engaged, and I was flying it back towards me, but it was going quite slowly, so i think I ended up giving it full pitch stick, and it just took off full speed upwards. I flipped it back into manual to save it and bring it back and land. I'm very keen to try and understand how and why this happened to make sure it cannot happen again. I have a serious lack of trust in this thing at the moment.
Just before this flight I changed the throttle factor to be in line with the formula to make it hover at 700 on the radio. (Corrected Factor Throttle = Current Factor Throttle * Value read from graph / 700). My previous throttle factor was 0.53 which made it more or less hover in manual mode (~830 on the radio channel), and pretty much hold altitude in PH, whereas following the formula it suggested 0.63, which makes the copter climb rapidly if I switch out of position hold back to manual, but brings my radio hover throttle to 700 in manual mode. I still needed to have the throttle at about 860 on the radio to hold alt in PH after changing this.
My alt hold PIDS are:
Nav Alt Speed P = 200
Nav Alt Speed I = 3
Nav Alt Position P = 0.2
Here's the clip of the log which shows it. You can see while in position hold earlier it made a single large jump in altitude that I caught (around 10k in the log).
Please help!