Plane: removed the old crash_timer code

This code is less relevent with the new L1 navigation, and could cause
issues with the pilot not having control after a long dive.

Thanks to Soren for pointing out the issues

See issue #305

ArduPlane/ArduPlane.pde

@@ -323,9 +323,6 @@ static int16_t failsafe;
 // Used to track if the value on channel 3 (throtttle) has fallen below the failsafe threshold
 // RC receiver should be set up to output a low throttle value when signal is lost
 static bool ch3_failsafe;
-// A timer used to help recovery from unusual attitudes.  If we enter an unusual attitude
-// while in autonomous flight this variable is used  to hold roll at 0 for a recovery period
-static uint8_t crash_timer;
 
 // the time when the last HEARTBEAT message arrived from a GCS
 static uint32_t last_heartbeat_ms;
@@ -1025,7 +1022,6 @@ static void update_GPS(void)
 static void update_current_flight_mode(void)
 {
     if(control_mode == AUTO) {
-        crash_checker();
 
         switch(nav_command_ID) {
         case MAV_CMD_NAV_TAKEOFF:
@@ -1111,7 +1107,6 @@ static void update_current_flight_mode(void)
         case RTL:
         case LOITER:
         case GUIDED:
-            crash_checker();
             calc_nav_roll();
             calc_nav_pitch();
             calc_throttle();

ArduPlane/Attitude.pde

@@ -63,10 +63,6 @@ static bool stick_mixing_enabled(void)
  */
 static void stabilize_roll(float speed_scaler)
 {
-    if (crash_timer > 0) {
-        nav_roll_cd = 0;
-    }
-
     if (inverted_flight) {
         // we want to fly upside down. We need to cope with wrap of
         // the roll_sensor interfering with wrap of nav_roll, which
@@ -279,16 +275,6 @@ static void stabilize()
 }
 
 
-static void crash_checker()
-{
-    if(ahrs.pitch_sensor < -4500) {
-        crash_timer = 255;
-    }
-    if(crash_timer > 0)
-        crash_timer--;
-}
-
-
 static void calc_throttle()
 {
     if (g.throttle_cruise <= 1) {

ArduPlane/commands_logic.pde

@@ -232,7 +232,6 @@ static bool verify_condition_command()          // Returns true if command compl
 static void do_RTL(void)
 {
     control_mode    = RTL;
-    crash_timer     = 0;
     next_WP                 = home;
 
     if (g.loiter_radius < 0) {

ArduPlane/system.pde

@@ -324,7 +324,6 @@ static void set_mode(enum FlightMode mode)
         trim_control_surfaces();
 
     control_mode = mode;
-    crash_timer = 0;
 
     switch(control_mode)
     {