Plane: improved crash detection

- fixes bug where a bungee launch is configured but the aircraft gets bumped and triggers the prop to spin up. This will now detect that and "crash' and disable the motor

ArduPlane/Plane.h

@@ -515,6 +515,9 @@ private:
         // debounce timer
         uint32_t debounce_timer_ms;
 
+        // delay time for debounce to count to
+        uint32_t debounce_time_total_ms;
+
         // length of time impact_detected has been true. Times out after a few seconds. Used to clip isFlyingProbability
         uint32_t impact_timer_ms;
     } crash_state;

ArduPlane/is_flying.cpp

@@ -6,7 +6,7 @@
   is_flying and crash detection logic
  */
 
-#define CRASH_DETECTION_DELAY_MS            300
+#define CRASH_DETECTION_DELAY_MS            500
 #define IS_FLYING_IMPACT_TIMER_MS           3000
 
 /*
@@ -197,25 +197,39 @@ void Plane::crash_detection_update(void)
     bool been_auto_flying = (auto_state.started_flying_in_auto_ms > 0) &&
                             (now_ms - auto_state.started_flying_in_auto_ms >= 2500);
 
-    if (!is_flying() && been_auto_flying)
+    if (!is_flying() && arming.is_armed())
     {
         switch (flight_stage)
         {
         case AP_SpdHgtControl::FLIGHT_TAKEOFF:
-        case AP_SpdHgtControl::FLIGHT_NORMAL:
-            if (!in_preLaunch_flight_stage()) {
+            if (g.takeoff_throttle_min_accel > 0 &&
+                    !throttle_suppressed) {
+                // if you have an acceleration holding back throttle, but you met the
+                // accel threshold but still not fying, then you either shook/hit the
+                // plane or it was a failed launch.
                 crashed = true;
+                crash_state.debounce_time_total_ms = CRASH_DETECTION_DELAY_MS;
             }
             // TODO: handle auto missions without NAV_TAKEOFF mission cmd
             break;
 
+        case AP_SpdHgtControl::FLIGHT_NORMAL:
+            if (!in_preLaunch_flight_stage() && been_auto_flying) {
+                crashed = true;
+                crash_state.debounce_time_total_ms = CRASH_DETECTION_DELAY_MS;
+            }
+            break;
+
         case AP_SpdHgtControl::FLIGHT_VTOL:
             // we need a totally new method for this
             crashed = false;
             break;
             
         case AP_SpdHgtControl::FLIGHT_LAND_APPROACH:
-            crashed = true;
+            if (been_auto_flying) {
+                crashed = true;
+                crash_state.debounce_time_total_ms = CRASH_DETECTION_DELAY_MS;
+            }
             // when altitude gets low, we automatically progress to FLIGHT_LAND_FINAL
             // so ground crashes most likely can not be triggered from here. However,
             // a crash into a tree would be caught here.
@@ -228,8 +242,10 @@ void Plane::crash_detection_update(void)
             // but go ahead and notify GCS and perform any additional post-crash actions.
             // Declare a crash if we are oriented more that 60deg in pitch or roll
             if (!crash_state.checkedHardLanding && // only check once
-                (fabsf(ahrs.roll_sensor) > 6000 || fabsf(ahrs.pitch_sensor) > 6000)) {
+                been_auto_flying &&
+                (labs(ahrs.roll_sensor) > 6000 || labs(ahrs.pitch_sensor) > 6000)) {
                 crashed = true;
+                crash_state.debounce_time_total_ms = CRASH_DETECTION_DELAY_MS;
 
                 // did we "crash" within 75m of the landing location? Probably just a hard landing
                 crashed_near_land_waypoint =
@@ -259,7 +275,7 @@ void Plane::crash_detection_update(void)
         // start timer
         crash_state.debounce_timer_ms = now_ms;
 
-    } else if ((now_ms - crash_state.debounce_timer_ms >= CRASH_DETECTION_DELAY_MS) && !crash_state.is_crashed) {
+    } else if ((now_ms - crash_state.debounce_timer_ms >= crash_state.debounce_time_total_ms) && !crash_state.is_crashed) {
         crash_state.is_crashed = true;
 
         if (g.crash_detection_enable == CRASH_DETECT_ACTION_BITMASK_DISABLED) {