Copter: add air mode aux function

ArduCopter/Copter.h

@@ -374,6 +374,8 @@ private:
 
     ap_t ap;
 
+    AirMode air_mode; // air mode is 0 = not-configured ; 1 = disabled; 2 = enabled
+
     static_assert(sizeof(uint32_t) == sizeof(ap), "ap_t must be uint32_t");
 
     // This is the state of the flight control system

ArduCopter/RC_Channel.cpp

@@ -112,6 +112,7 @@ void RC_Channel_Copter::init_aux_function(const aux_func_t ch_option, const AuxS
     case AUX_FUNC::SUPERSIMPLE_MODE:
     case AUX_FUNC::SURFACE_TRACKING:
     case AUX_FUNC::WINCH_ENABLE:
+    case AUX_FUNC::AIRMODE:
         do_aux_function(ch_option, ch_flag);
         break;
     default:
@@ -593,6 +594,19 @@ void RC_Channel_Copter::do_aux_function(const aux_func_t ch_option, const AuxSwi
             }
 #endif
             break;
+
+        case AUX_FUNC::AIRMODE:
+            switch (ch_flag) {
+            case AuxSwitchPos::HIGH:
+                copter.air_mode = AirMode::AIRMODE_ENABLED;
+                break;
+            case AuxSwitchPos::MIDDLE:
+                break;
+            case AuxSwitchPos::LOW:
+                copter.air_mode = AirMode::AIRMODE_DISABLED;
+                break;
+            }
+        break;
             
     default:
         RC_Channel::do_aux_function(ch_option, ch_flag);

ArduCopter/defines.h

@@ -107,6 +107,13 @@ enum GuidedMode {
     Guided_Angle,
 };
 
+// Airmode
+enum class AirMode {
+    AIRMODE_NONE,
+    AIRMODE_DISABLED,
+    AIRMODE_ENABLED,
+};
+
 // Safe RTL states
 enum SmartRTLState {
     SmartRTL_WaitForPathCleanup,

ArduCopter/land_detector.cpp

@@ -151,7 +151,7 @@ void Copter::update_throttle_mix()
 
     if (flightmode->has_manual_throttle()) {
         // manual throttle
-        if(channel_throttle->get_control_in() <= 0) {
+        if (channel_throttle->get_control_in() <= 0 || air_mode == AirMode::AIRMODE_DISABLED) {
             attitude_control->set_throttle_mix_min();
         } else {
             attitude_control->set_throttle_mix_man();

ArduCopter/radio.cpp

@@ -180,7 +180,7 @@ void Copter::set_throttle_zero_flag(int16_t throttle_control)
     // and we are flying. Immediately set as non-zero
     if ((!ap.using_interlock && (throttle_control > 0) && !SRV_Channels::get_emergency_stop()) ||
         (ap.using_interlock && motors->get_interlock()) ||
-        ap.armed_with_switch) {
+        ap.armed_with_switch || air_mode == AirMode::AIRMODE_ENABLED) {
         last_nonzero_throttle_ms = tnow_ms;
         ap.throttle_zero = false;
     } else if (tnow_ms - last_nonzero_throttle_ms > THROTTLE_ZERO_DEBOUNCE_TIME_MS) {