From 8fdc85ccbead3f276a94162658f480d45bf330aa Mon Sep 17 00:00:00 2001
From: Peter Hall <iampete@hotmail.co.uk>
Date: Sun, 23 Jan 2022 22:22:41 +0000
Subject: [PATCH] AC_AttitudeControl: WeatherVane: add tail in option

---
 libraries/AC_AttitudeControl/AC_WeatherVane.cpp | 11 +++++++++++
 libraries/AC_AttitudeControl/AC_WeatherVane.h   |  1 +
 2 files changed, 12 insertions(+)

diff --git a/libraries/AC_AttitudeControl/AC_WeatherVane.cpp b/libraries/AC_AttitudeControl/AC_WeatherVane.cpp
index e0f5601747..e74a8565ea 100644
--- a/libraries/AC_AttitudeControl/AC_WeatherVane.cpp
+++ b/libraries/AC_AttitudeControl/AC_WeatherVane.cpp
@@ -163,6 +163,17 @@ bool AC_WeatherVane::get_yaw_out(float &yaw_output, const int16_t pilot_yaw, con
             dir_string = "side in";
             break;
 
+        case Direction::TAIL_IN:
+            if (is_negative(pitch_cdeg)) {
+                output = fabsf(roll_cdeg) - pitch_cdeg;
+            } else {
+                output = MAX(fabsf(roll_cdeg) - deadzone_cdeg, 0.0);
+            }
+            if (is_positive(roll_cdeg)) {
+                output *= -1.0;
+            }
+            dir_string = "tail in";
+            break;
     }
 
     if (!active_msg_sent) {
diff --git a/libraries/AC_AttitudeControl/AC_WeatherVane.h b/libraries/AC_AttitudeControl/AC_WeatherVane.h
index 397da41d88..a6cf35139b 100644
--- a/libraries/AC_AttitudeControl/AC_WeatherVane.h
+++ b/libraries/AC_AttitudeControl/AC_WeatherVane.h
@@ -28,6 +28,7 @@ class AC_WeatherVane {
             NOSE_IN = 1, // Only nose into wind
             NOSE_OR_TAIL_IN = 2, // Nose in or tail into wind, which ever is closest
             SIDE_IN = 3, // Side into wind for copter tailsitters
+            TAIL_IN = 4, // backwards, for tailsitters, makes it easier to descend
         };
 
         // Paramaters