From abd5f8351d86ef44bddd7df4e7cb905d9d7bb12d Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 15 Dec 2020 08:47:46 +1100
Subject: [PATCH] Plane: don't reset yaw target in TRANSITION_TIMER for
 tilt-vectored quadplanes

---
 ArduPlane/quadplane.cpp | 20 +++++++++++---------
 ArduPlane/quadplane.h   |  1 +
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/ArduPlane/quadplane.cpp b/ArduPlane/quadplane.cpp
index be24f5865a..452582808d 100644
--- a/ArduPlane/quadplane.cpp
+++ b/ArduPlane/quadplane.cpp
@@ -736,9 +736,9 @@ bool QuadPlane::setup(void)
         AP_BoardConfig::config_error("unknown Q_FRAME_TYPE %u", (unsigned)frame_type.get());
     }
 
-    if (motors_var_info == AP_MotorsMatrix::var_info &&
-        tilt.tilt_mask != 0 &&
-        tilt.tilt_type == TILT_TYPE_VECTORED_YAW) {
+    tilt.is_vectored = tilt.tilt_mask != 0 && tilt.tilt_type == TILT_TYPE_VECTORED_YAW;
+
+    if (motors_var_info == AP_MotorsMatrix::var_info && tilt.is_vectored) {
         // we will be using vectoring for yaw
         motors->disable_yaw_torque();
     }
@@ -1737,9 +1737,7 @@ void QuadPlane::update_transition(void)
         }
         hold_hover(climb_rate_cms);
 
-        if (tilt.tilt_mask == 0 ||
-            tilt.tilt_type != TILT_TYPE_VECTORED_YAW ||
-            now - transition_start_ms < 100) {
+        if (!tilt.is_vectored || now - transition_start_ms < 100) {
             // set desired yaw to current yaw in both desired angle
             // and rate request. This reduces wing twist in transition
             // due to multicopter yaw demands. This is disabled when
@@ -1794,9 +1792,13 @@ void QuadPlane::update_transition(void)
         // set desired yaw to current yaw in both desired angle and
         // rate request while waiting for transition to
         // complete. Navigation should be controlled by fixed wing
-        // control surfaces at this stage
-        attitude_control->set_yaw_target_to_current_heading();
-        attitude_control->rate_bf_yaw_target(ahrs.get_gyro().z);
+        // control surfaces at this stage.
+        // We disable this for vectored yaw tilt rotors as they do need active
+        // yaw control throughout the transition
+        if (!tilt.is_vectored) {
+            attitude_control->set_yaw_target_to_current_heading();
+            attitude_control->rate_bf_yaw_target(ahrs.get_gyro().z);
+        }
         break;
     }
 
diff --git a/ArduPlane/quadplane.h b/ArduPlane/quadplane.h
index 4c333888b3..91b2cc3113 100644
--- a/ArduPlane/quadplane.h
+++ b/ArduPlane/quadplane.h
@@ -481,6 +481,7 @@ private:
         float current_throttle;
         bool motors_active:1;
         float transition_yaw;
+        bool is_vectored;
     } tilt;
 
     // bit 0 enables plane mode and bit 1 enables body-frame roll mode