From e1ad1b60d03095e52fb396ec7a67d111b8bc4f89 Mon Sep 17 00:00:00 2001
From: Silvan Fuhrer <silvan@auterion.com>
Date: Thu, 11 Jan 2024 13:35:01 +0100
Subject: [PATCH] VTOL: change transition airspeed threshold: only look at
 VT_ARSP_TRANS (#22581)

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>
---
 src/modules/vtol_att_control/vtol_type.cpp | 13 +++++++------
 src/modules/vtol_att_control/vtol_type.h   |  9 +--------
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/src/modules/vtol_att_control/vtol_type.cpp b/src/modules/vtol_att_control/vtol_type.cpp
index 2695da5cf2..6fd14359f5 100644
--- a/src/modules/vtol_att_control/vtol_type.cpp
+++ b/src/modules/vtol_att_control/vtol_type.cpp
@@ -598,18 +598,19 @@ float VtolType::getOpenLoopFrontTransitionTime() const
 }
 float VtolType::getTransitionAirspeed() const
 {
-	return  math::max(_param_vt_arsp_trans.get(), getMinimumTransitionAirspeed());
-}
-float VtolType::getMinimumTransitionAirspeed() const
-{
+	// Since the stall airspeed increases with vehicle weight, we increase the transition airspeed
+	// by the same factor.
+
 	float weight_ratio = 1.0f;
 
 	if (_param_weight_base.get() > FLT_EPSILON && _param_weight_gross.get() > FLT_EPSILON) {
-		weight_ratio = math::constrain(_param_weight_gross.get() / _param_weight_base.get(), kMinWeightRatio, kMaxWeightRatio);
+		weight_ratio = math::constrain(_param_weight_gross.get() /
+					       _param_weight_base.get(), kMinWeightRatio, kMaxWeightRatio);
 	}
 
-	return sqrtf(weight_ratio) * _param_airspeed_min.get();
+	return sqrtf(weight_ratio) * _param_vt_arsp_trans.get();
 }
+
 float VtolType::getBlendAirspeed() const
 {
 	return _param_vt_arsp_blend.get();
diff --git a/src/modules/vtol_att_control/vtol_type.h b/src/modules/vtol_att_control/vtol_type.h
index c8cecb8fb0..3707acb68e 100644
--- a/src/modules/vtol_att_control/vtol_type.h
+++ b/src/modules/vtol_att_control/vtol_type.h
@@ -237,12 +237,6 @@ public:
 	*/
 	float getOpenLoopFrontTransitionTime() const;
 
-	/**
-	 *
-	 * @return The minimum calibrated airspeed compensated for weight [m/s]
-	 */
-	float getMinimumTransitionAirspeed() const;
-
 	/**
 	 *
 	 * @return The calibrated blending airspeed [m/s]
@@ -371,8 +365,7 @@ protected:
 					(ParamFloat<px4::params::MPC_LAND_ALT2>) _param_mpc_land_alt2,
 					(ParamFloat<px4::params::VT_LND_PITCH_MIN>) _param_vt_lnd_pitch_min,
 					(ParamFloat<px4::params::WEIGHT_BASE>) _param_weight_base,
-					(ParamFloat<px4::params::WEIGHT_GROSS>) _param_weight_gross,
-					(ParamFloat<px4::params::FW_AIRSPD_MIN>) _param_airspeed_min
+					(ParamFloat<px4::params::WEIGHT_GROSS>) _param_weight_gross
 
 				       )