Hi all, checking in again with updates to the debug process:
Based on @rollys’s suggestions, we have narrowed down the following parameters that may help in reducing altitude drop:
- TRIM_ARSPD_CM: Airspeed which the autopilot aims for in auto flight. This should be set to the desired cruise speed
- Preliminary runs in SITL (bin file attached) also show that increasing TRIM_ARSPD_CM results in a higher throttle output during transition. This is desired, as it will help build up airspeed quickly to reach the required cruise speed.
- ARSPD_FBW_MIN: Minimum airspeed in FBWA mode, which also determines the transition speed after which the autopilot drops throttle in auto mode. This parameter was recommended to be set to equal or slightly lower than the cruise speed.
- Q_TRAN_PIT_MAX: Maximum pitch during transition to fixed-wing flight. Will reducing the value of this parameter help to reduce the amount of negative pitch experienced during transition?
- A test run in SITL (see bin. file over here) shows that when this parameter is set to 0, the amount of negative pitch decreases from -5 to -2. This is a desired outcome, but why is there still -2 pitch when the limit is set to zero? What else is over-riding the parameter to generate negative pitch?
We will look at how these parameters affect the quadplane’s performance for our next test flight. In the meantime, if anyone else out there has experienced the same altitude drop problem and has been able to solve the issue (thanks again to rollys for sharing!), we would really appreciate if you could share with us your debug process!