AP_Airspeed: remove airspeed filter and run at 10Hz

this saves on the filter memory, and gives just as good a result

ArduPlane/ArduPlane.pde

@@ -761,14 +761,6 @@ static void fast_loop()
 	// ------------------------------------
 	check_short_failsafe();
 
-	// Read Airspeed
-	// -------------
-	if (airspeed.enabled()) {
-#if HIL_MODE != HIL_MODE_ATTITUDE
-		read_airspeed();
-#endif
-	}
-
 	#if HIL_MODE == HIL_MODE_SENSORS
 		// update hil before AHRS update
 		gcs_update();
@@ -878,6 +870,14 @@ Serial.println(tempaccel.z, DEC);
 		case 2:
 			medium_loopCounter++;
 
+            // Read Airspeed
+            // -------------
+#if HIL_MODE != HIL_MODE_ATTITUDE
+            if (airspeed.enabled()) {
+                read_airspeed();
+            }
+#endif
+
 			// Read altitude from sensors
 			// ------------------
 			update_alt();

libraries/AP_Airspeed/AP_Airspeed.cpp

@@ -69,7 +69,7 @@ void AP_Airspeed::read(void)
 	if (!_enable) {
 		return;
 	}
-	_airspeed_raw 		= _filter.apply(_source->read());
+	_airspeed_raw 		= _source->read();
 	airspeed_pressure 	= max((_airspeed_raw - _offset), 0);
 	_airspeed		= sqrt(airspeed_pressure * _ratio);	
 }

libraries/AP_Airspeed/AP_Airspeed.h

@@ -50,7 +50,6 @@ private:
 	AP_Int8     _enable;
 	float	    _airspeed;
 	float	    _airspeed_raw;
-    AverageFilterFloat_Size5 _filter;
 };