Copter: add option to disable RTL flight mode

ArduCopter/APM_Config.h

@@ -28,6 +28,7 @@
 //#define MODE_GUIDED_ENABLED   DISABLED            // disable guided mode support
 //#define MODE_LOITER_ENABLED   DISABLED            // disable loiter mode support
 //#define MODE_POSHOLD_ENABLED  DISABLED            // disable poshold mode support
+//#define MODE_RTL_ENABLED DISABLED                 // disable rtl mode support
 //#define MODE_SMARTRTL_ENABLED DISABLED            // disable smartrtl mode support
 //#define MODE_SPORT_ENABLED DISABLED               // disable sport mode support
 

ArduCopter/Copter.h

@@ -978,7 +978,9 @@ private:
 #if MODE_POSHOLD_ENABLED == ENABLED
     ModePosHold mode_poshold;
 #endif
+#if MODE_RTL_ENABLED == ENABLED
     ModeRTL mode_rtl;
+#endif
 #if FRAME_CONFIG == HELI_FRAME
     ModeStabilize_Heli mode_stabilize;
 #else

ArduCopter/config.h

@@ -297,6 +297,12 @@
 # define MODE_POSHOLD_ENABLED ENABLED
 #endif
 
+//////////////////////////////////////////////////////////////////////////////
+// RTL - Return To Launch
+#ifndef MODE_RTL_ENABLED
+# define MODE_RTL_ENABLED ENABLED
+#endif
+
 //////////////////////////////////////////////////////////////////////////////
 // SmartRTL - allows vehicle to retrace a (loop-eliminated) breadcrumb home
 #ifndef MODE_SMARTRTL_ENABLED

ArduCopter/events.cpp

@@ -189,8 +189,10 @@ void Copter::failsafe_terrain_on_event()
 
     if (should_disarm_on_failsafe()) {
         init_disarm_motors();
+#if MODE_RTL_ENABLED == ENABLED
     } else if (control_mode == RTL) {
         mode_rtl.restart_without_terrain();
+#endif
     } else {
         set_mode_RTL_or_land_with_pause(MODE_REASON_TERRAIN_FAILSAFE);
     }

ArduCopter/mode.cpp

@@ -76,9 +76,11 @@ Copter::Mode *Copter::mode_from_mode_num(const uint8_t mode)
             ret = &mode_land;
             break;
 
+#if MODE_RTL_ENABLED == ENABLED
         case RTL:
             ret = &mode_rtl;
             break;
+#endif
 
 #if MODE_DRIFT_ENABLED == ENABLED
         case DRIFT: