Plane: Prevent FS action overiding VTOL land

ArduPlane/events.cpp

@@ -171,7 +171,7 @@ void Plane::handle_battery_failsafe(const char *type_str, const int8_t action)
             }
             FALLTHROUGH;
         case Failsafe_Action_RTL:
-            if (flight_stage != AP_Vehicle::FixedWing::FLIGHT_LAND && control_mode != &mode_qland ) {
+            if (flight_stage != AP_Vehicle::FixedWing::FLIGHT_LAND && control_mode != &mode_qland && !quadplane.in_vtol_land_sequence()) {
                 // never stop a landing if we were already committed
                 set_mode(mode_rtl, ModeReason::BATTERY_FAILSAFE);
                 aparm.throttle_cruise.load();

ArduPlane/quadplane.cpp

@@ -3172,3 +3172,11 @@ bool QuadPlane::in_vtol_land_final(void) const
 {
     return in_vtol_land_descent() && poscontrol.state == QPOS_LAND_FINAL;
 }
+
+/*
+  see if we are in any of the phases of a VTOL landing
+ */
+bool QuadPlane::in_vtol_land_sequence(void) const
+{
+    return in_vtol_land_approach() || in_vtol_land_descent() || in_vtol_land_final();
+}

ArduPlane/quadplane.h

@@ -553,6 +553,11 @@ private:
       are we in the final landing phase of a VTOL landing?
      */
     bool in_vtol_land_final(void) const;
+
+    /*
+      are we in any of the phases of a VTOL landing?
+     */
+    bool in_vtol_land_sequence(void) const;
     
 public:
     void motor_test_output();