VTOL land detector: extend fall_detection from multicopter land detector and disable in fixed-wing mode

Extend the get_freefall_state() from MC land detector to have a VTOL-specific
one that just enables free fall detection if in rotary wing or transition mode.
This is done to prevent wrong free-fall detected warnings while doing low-G maneuvers
(parabolic flights). Land detection is anyway disabled in FW flight for VTOL so
no logic change.

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

src/modules/land_detector/VtolLandDetector.cpp

@@ -40,6 +40,7 @@
  */
 
 #include <drivers/drv_hrt.h>
+#include <matrix/math.hpp>
 
 #include "VtolLandDetector.h"
 
@@ -94,4 +95,13 @@ bool VtolLandDetector::_get_landed_state()
 	return landed;
 }
 
+bool VtolLandDetector::_get_freefall_state()
+{
+	bool free_fall_detected =
+		MulticopterLandDetector::_get_freefall_state(); // true if falling or in a parabolic flight (low gravity)
+
+	// only return a positive free fall detected if not in fixed-wing mode
+	return _vehicle_status.vehicle_type != vehicle_status_s::VEHICLE_TYPE_FIXED_WING && free_fall_detected;
+}
+
 } // namespace land_detector

src/modules/land_detector/VtolLandDetector.h

@@ -59,6 +59,7 @@ protected:
 	void _update_topics() override;
 	bool _get_landed_state() override;
 	bool _get_maybe_landed_state() override;
+	bool _get_freefall_state() override;
 
 private: