Servers by jDrones

Quadplane speeding up past TRIM_ARSPD during RTL descent

(Sriram Sami) #1

Hi there,

Recently during the RTL phase of a quadplane test flight my aircraft was commanded to speed up past its TRIM_ARSPD_CM of 18 m/s to reach 21.1 m/s. With reference to my previous post, this caused the aircraft to overshoot the landing zone and crash into a tree - this problem has been mitigated with the addition of Q_TRANS_DECEL in the latest Plane release to dynamically change the transition point based on expected stopping distance.

However, this still doesn’t clear up why the aircraft was asked to exceed TRIM_ARSPD_CM in the first place. On inspection of previous logs, in previous flights with this and other aircraft, TECS.spdem on RTL was always between TRIM_ARSPD and ARSPD_FBW_MAX, leaning towards being closer to ARSPD_FBW_MAX, even though the aircraft is descending.

Is this expected behavior? What I naturally expect during RTL is that the aircraft keeps to TRIM_ARSPD_CM or less during descent.

Crash into tree:
(TRIM_ARSPD_CM = 18 m/s, ARSPD_FBW_MAX = 24 m/s, RTL TECS.spdem = 21.21 m/s)

Previous flight before crash:
(TRIM_ARSPD_CM = 18 m/s, ARSPD_FBW_MAX = 30 m/s, RTL TECS.spdem = 21.68 m/s)

Flight on another day: (TRIM_ARSPD_CM = 18 m/s, ARSPD_FBW_MAX = 19 m/s, RTL TECS.spdem = 18.6445 m/s)