diff --git a/libraries/AP_AHRS/AP_AHRS_Quaternion.cpp b/libraries/AP_AHRS/AP_AHRS_Quaternion.cpp
index 7986763c6e..03fe02869d 100644
--- a/libraries/AP_AHRS/AP_AHRS_Quaternion.cpp
+++ b/libraries/AP_AHRS/AP_AHRS_Quaternion.cpp
@@ -321,22 +321,16 @@ void AP_AHRS_Quaternion::update(void)
 
 	// get current IMU state
 	gyro = _imu->get_gyro();
-	accel = _imu->get_accel();
 
-	// Quaternion code uses opposite x and y gyro sense from the
-	// rest of APM
-	gyro.x = -gyro.x;
-	gyro.y = -gyro.y;
-
-	// Quaternion code uses opposite z accel as well
-	accel.z = -accel.z;
+	// the quaternion system uses opposite sign for accel
+	accel = - _imu->get_accel();
 
 	if (_centripetal && _gps && _gps->status() == GPS::GPS_OK) {
 		// compensate for linear acceleration. This makes a
 		// surprisingly large difference in the pitch estimate when
 		// turning, plus on takeoff and landing
 		float acceleration = _gps->acceleration();
-		accel.x -= acceleration;
+		accel.x += acceleration;
 
 		// compensate for centripetal acceleration
 		float veloc;
@@ -344,12 +338,12 @@ void AP_AHRS_Quaternion::update(void)
 		// be careful of the signs in this calculation. the
 		// quaternion system uses different signs than the
 		// rest of APM
-		accel.y -= (gyro.z - gyro_bias.z) * veloc;
-		accel.z += (gyro.y - gyro_bias.y) * veloc;
+		accel.y += (gyro.z - gyro_bias.z) * veloc;
+		accel.z -= (gyro.y - gyro_bias.y) * veloc;
 	}
 
 	if (_compass != NULL && _compass->use_for_yaw()) {
-		Vector3f mag = Vector3f(_compass->mag_x, _compass->mag_y, - _compass->mag_z);
+		Vector3f mag = Vector3f(_compass->mag_x, _compass->mag_y, _compass->mag_z);
 		update_MARG(deltat, gyro, accel, mag);
 	} else {
 		// step the quaternion solution using just gyros and accels
diff --git a/libraries/AP_AHRS/AP_AHRS_Quaternion.h b/libraries/AP_AHRS/AP_AHRS_Quaternion.h
index 921d925155..a5b6583903 100644
--- a/libraries/AP_AHRS/AP_AHRS_Quaternion.h
+++ b/libraries/AP_AHRS/AP_AHRS_Quaternion.h
@@ -34,13 +34,13 @@ public:
 	// get corrected gyro vector
 	Vector3f get_gyro(void) {
 		// notice the sign reversals here
-		return Vector3f(-_gyro_corrected.x, -_gyro_corrected.y, _gyro_corrected.z);
+		return Vector3f(_gyro_corrected.x, _gyro_corrected.y, _gyro_corrected.z);
 	}
 
 	Vector3f get_gyro_drift(void) {
 		// notice the sign reversals here. The quaternion
 		// system uses a -ve gyro bias, DCM uses a +ve
-		return Vector3f(gyro_bias.x, gyro_bias.y, -gyro_bias.z);
+		return Vector3f(-gyro_bias.x, -gyro_bias.y, -gyro_bias.z);
         }
 
 	float get_error_rp(void);