diff --git a/ArduCopter/control_acro.pde b/ArduCopter/control_acro.pde
index 64bcb5b2fb..9a65b18c1f 100644
--- a/ArduCopter/control_acro.pde
+++ b/ArduCopter/control_acro.pde
@@ -127,17 +127,17 @@ static void get_pilot_desired_angle_rates(int16_t roll_in, int16_t pitch_in, int
             rate_bf_level = rate_bf_level*acro_level_mix;
 
             // Calculate rate limit to prevent change of rate through inverted
-            rate_limit = fabs(fabs(rate_bf_request.x)-fabs(rate_bf_level.x));
+            rate_limit = fabsf(fabsf(rate_bf_request.x)-fabsf(rate_bf_level.x));
             rate_bf_request.x += rate_bf_level.x;
             rate_bf_request.x = constrain_float(rate_bf_request.x, -rate_limit, rate_limit);
 
             // Calculate rate limit to prevent change of rate through inverted
-            rate_limit = fabs(fabs(rate_bf_request.y)-fabs(rate_bf_level.y));
+            rate_limit = fabsf(fabs(rate_bf_request.y)-fabsf(rate_bf_level.y));
             rate_bf_request.y += rate_bf_level.y;
             rate_bf_request.y = constrain_float(rate_bf_request.y, -rate_limit, rate_limit);
 
             // Calculate rate limit to prevent change of rate through inverted
-            rate_limit = fabs(fabs(rate_bf_request.z)-fabs(rate_bf_level.z));
+            rate_limit = fabsf(fabsf(rate_bf_request.z)-fabsf(rate_bf_level.z));
             rate_bf_request.z += rate_bf_level.z;
             rate_bf_request.z = constrain_float(rate_bf_request.z, -rate_limit, rate_limit);
         }
diff --git a/ArduCopter/control_drift.pde b/ArduCopter/control_drift.pde
index 046f19d0ab..555727d61b 100644
--- a/ArduCopter/control_drift.pde
+++ b/ArduCopter/control_drift.pde
@@ -66,7 +66,7 @@ static void drift_run()
     float pitch_vel = vel.y * ahrs.sin_yaw() + vel.x * ahrs.cos_yaw(); // body pitch vel
 
     // gain sceduling for Yaw
-    float pitch_vel2 = min(fabs(pitch_vel), 2000);
+    float pitch_vel2 = min(fabsf(pitch_vel), 2000);
     target_yaw_rate = ((float)target_roll/1.0f) * (1.0f - (pitch_vel2 / 5000.0f)) * g.acro_yaw_p;
 
     roll_vel = constrain_float(roll_vel, -DRIFT_SPEEDLIMIT, DRIFT_SPEEDLIMIT);
diff --git a/ArduCopter/control_flip.pde b/ArduCopter/control_flip.pde
index 0475cb37b8..1d89de7824 100644
--- a/ArduCopter/control_flip.pde
+++ b/ArduCopter/control_flip.pde
@@ -188,14 +188,14 @@ static void flip_run()
 
         if (flip_roll_dir != 0) {
             // we are rolling
-            recovery_angle = fabs(flip_orig_attitude.x - (float)ahrs.roll_sensor);
+            recovery_angle = fabsf(flip_orig_attitude.x - (float)ahrs.roll_sensor);
         } else {
             // we are pitching
-            recovery_angle = fabs(flip_orig_attitude.y - (float)ahrs.pitch_sensor);
+            recovery_angle = fabsf(flip_orig_attitude.y - (float)ahrs.pitch_sensor);
         }
 
         // check for successful recovery
-        if (fabs(recovery_angle) <= FLIP_RECOVERY_ANGLE) {
+        if (fabsf(recovery_angle) <= FLIP_RECOVERY_ANGLE) {
             // restore original flight mode
             if (!set_mode(flip_orig_control_mode)) {
                 // this should never happen but just in case
diff --git a/ArduCopter/control_poshold.pde b/ArduCopter/control_poshold.pde
index cbb00e966f..53096698c2 100644
--- a/ArduCopter/control_poshold.pde
+++ b/ArduCopter/control_poshold.pde
@@ -247,7 +247,7 @@ static void poshold_run()
                 }
 
                 // if velocity is very low reduce braking time to 0.5seconds
-                if ((fabs(vel_right) <= POSHOLD_SPEED_0) && (poshold.brake_timeout_roll > 50*LOOP_RATE_FACTOR)) {
+                if ((fabsf(vel_right) <= POSHOLD_SPEED_0) && (poshold.brake_timeout_roll > 50*LOOP_RATE_FACTOR)) {
                     poshold.brake_timeout_roll = 50*LOOP_RATE_FACTOR;
                 }
 
@@ -341,7 +341,7 @@ static void poshold_run()
                 }
 
                 // if velocity is very low reduce braking time to 0.5seconds
-                if ((fabs(vel_fw) <= POSHOLD_SPEED_0) && (poshold.brake_timeout_pitch > 50*LOOP_RATE_FACTOR)) {
+                if ((fabsf(vel_fw) <= POSHOLD_SPEED_0) && (poshold.brake_timeout_pitch > 50*LOOP_RATE_FACTOR)) {
                     poshold.brake_timeout_pitch = 50*LOOP_RATE_FACTOR;
                 }
 
diff --git a/ArduCopter/motors.pde b/ArduCopter/motors.pde
index dcfff8346e..f32c3a0feb 100644
--- a/ArduCopter/motors.pde
+++ b/ArduCopter/motors.pde
@@ -308,7 +308,7 @@ static bool pre_arm_checks(bool display_failure)
         nav_filter_status filt_status = inertial_nav.get_filter_status();
         bool using_baro_ref = (!filt_status.flags.pred_horiz_pos_rel && filt_status.flags.pred_horiz_pos_abs);
         if (using_baro_ref) {
-            if (fabs(inertial_nav.get_altitude() - baro_alt) > PREARM_MAX_ALT_DISPARITY_CM) {
+            if (fabsf(inertial_nav.get_altitude() - baro_alt) > PREARM_MAX_ALT_DISPARITY_CM) {
                 if (display_failure) {
                     gcs_send_text_P(SEVERITY_HIGH,PSTR("PreArm: Altitude disparity"));
                 }
@@ -674,7 +674,7 @@ static bool arm_checks(bool display_failure, bool arming_from_gcs)
     nav_filter_status filt_status = inertial_nav.get_filter_status();
     bool using_baro_ref = (!filt_status.flags.pred_horiz_pos_rel && filt_status.flags.pred_horiz_pos_abs);
     if (((g.arming_check == ARMING_CHECK_ALL) || (g.arming_check & ARMING_CHECK_BARO)) && using_baro_ref) {
-        if (fabs(inertial_nav.get_altitude() - baro_alt) > PREARM_MAX_ALT_DISPARITY_CM) {
+        if (fabsf(inertial_nav.get_altitude() - baro_alt) > PREARM_MAX_ALT_DISPARITY_CM) {
             if (display_failure) {
                 gcs_send_text_P(SEVERITY_HIGH,PSTR("Arm: Altitude disparity"));
             }