diff --git a/ArduSub/Parameters.h b/ArduSub/Parameters.h
index 12e300732e..f170667859 100644
--- a/ArduSub/Parameters.h
+++ b/ArduSub/Parameters.h
@@ -49,7 +49,7 @@ public:
         // Layout version number, always key zero.
         //
         k_param_format_version = 0,
-        k_param_software_type, // unusued
+        k_param_software_type, // unused
 
         k_param_g2, // 2nd block of parameters
 
diff --git a/ArduSub/ReleaseNotes.txt b/ArduSub/ReleaseNotes.txt
index 937999ce18..6d68f5216e 100644
--- a/ArduSub/ReleaseNotes.txt
+++ b/ArduSub/ReleaseNotes.txt
@@ -704,7 +704,7 @@ Changes from 3.1.4
 11) CLI removed from APM1/2 to save flash space, critical functions moved to MAVLink:
     a) Individual motor tests (see MP's Initial Setup > Optional Hardware > Motor Test)
     b) compassmot (see MP's Initial Setup > Optional Hardware > Compass/Motor Calib)
-    c) parameter reset to factory defautls (see MP's Config/Tuning > Full Parameter List > Reset to Default)
+    c) parameter reset to factory defaults (see MP's Config/Tuning > Full Parameter List > Reset to Default)
 ------------------------------------------------------------------
 ArduCopter 3.1.5 27-May-2014 / 3.1.5-rc2 20-May-2014
 Changes from 3.1.5-rc1
diff --git a/ArduSub/defines.h b/ArduSub/defines.h
index 170b466966..87e45820bc 100644
--- a/ArduSub/defines.h
+++ b/ArduSub/defines.h
@@ -39,7 +39,7 @@ enum autopilot_yaw_mode {
 #define WP_YAW_BEHAVIOR_NONE                          0   // auto pilot will never control yaw during missions or rtl (except for DO_CONDITIONAL_YAW command received)
 #define WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP               1   // auto pilot will face next waypoint or home during rtl
 #define WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP_EXCEPT_RTL    2   // auto pilot will face next waypoint except when doing RTL at which time it will stay in it's last
-#define WP_YAW_BEHAVIOR_LOOK_AHEAD                    3   // auto pilot will look ahead during missions and rtl (primarily meant for traditional helicotpers)
+#define WP_YAW_BEHAVIOR_LOOK_AHEAD                    3   // auto pilot will look ahead during missions and rtl (primarily meant for traditional helicopters)
 #define WP_YAW_BEHAVIOR_CORRECT_XTRACK                4   // point towards intermediate position target during line following
 
 
diff --git a/ArduSub/mode_poshold.cpp b/ArduSub/mode_poshold.cpp
index 8c1b389464..b85e359ede 100644
--- a/ArduSub/mode_poshold.cpp
+++ b/ArduSub/mode_poshold.cpp
@@ -93,7 +93,7 @@ void ModePoshold::run()
 
     } else { // hold current heading
 
-        // this check is required to prevent bounce back after very fast yaw maneuvers
+        // this check is required to prevent bounce back after very fast yaw manoeuvres
         // the inertia of the vehicle causes the heading to move slightly past the point when pilot input actually stopped
         if (tnow < sub.last_pilot_yaw_input_ms + 250) { // give 250ms to slow down, then set target heading
             target_yaw_rate = 0; // Stop rotation on yaw axis