This is a minor release to fix a single important bug in speed/height handling. The bug was in the TECS (total energy control system) and could cause a sustained pitch down due to a transient glitch in airspeed demand resulting in a large negative pitch integrator.
The log that found the bug was of a quadplane in CRUISE mode, and resulted in the aircraft forcing nose down for long enough to crash.
The fix includes both protections for the pitch integrator and a fix for the cause of the transient in airspeed demand affecting the TECS demanded airspeed.
Many thanks to ArduPilot partner FoxtechFPV for reporting this bug!
Some extra notes:
- the bug affected both normal planes and quadplanes
- the bug was rare. We only have one sample log showing it happening
- if you suspect you may have been bitten by the bug then look at the TECS.iph value in the log. The distinctive feature is that TECS.iph suddenly drops to a very low value while flying