diff --git a/ArduCopter/Copter.h b/ArduCopter/Copter.h
index f01c1297b9..9dc3780b49 100644
--- a/ArduCopter/Copter.h
+++ b/ArduCopter/Copter.h
@@ -46,8 +46,8 @@
 #include <AP_AccelCal/AP_AccelCal.h>                // interface and maths for accelerometer calibration
 #include <AP_InertialSensor/AP_InertialSensor.h>  // ArduPilot Mega Inertial Sensor (accel & gyro) Library
 #include <AP_AHRS/AP_AHRS.h>
-#include <AP_NavEKF/AP_NavEKF.h>
 #include <AP_NavEKF2/AP_NavEKF2.h>
+#include <AP_NavEKF3/AP_NavEKF3.h>
 #include <AP_Mission/AP_Mission.h>         // Mission command library
 #include <AC_PID/AC_PID.h>             // PID library
 #include <AC_PID/AC_PI_2D.h>           // PID library (2-axis)
@@ -202,9 +202,9 @@ private:
     AP_RPM rpm_sensor;
 
     // Inertial Navigation EKF
-    NavEKF EKF{&ahrs, barometer, rangefinder};
     NavEKF2 EKF2{&ahrs, barometer, rangefinder};
-    AP_AHRS_NavEKF ahrs{ins, barometer, gps, rangefinder, EKF, EKF2, AP_AHRS_NavEKF::FLAG_ALWAYS_USE_EKF};
+    NavEKF3 EKF3{&ahrs, barometer, rangefinder};
+    AP_AHRS_NavEKF ahrs{ins, barometer, gps, rangefinder, EKF2, EKF3, AP_AHRS_NavEKF::FLAG_ALWAYS_USE_EKF};
 
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
     SITL::SITL sitl;
diff --git a/ArduCopter/Log.cpp b/ArduCopter/Log.cpp
index 31345f32d5..14126bbcdf 100644
--- a/ArduCopter/Log.cpp
+++ b/ArduCopter/Log.cpp
@@ -378,9 +378,9 @@ void Copter::Log_Write_Attitude()
     DataFlash.Log_Write_Attitude(ahrs, targets);
 
  #if OPTFLOW == ENABLED
-    DataFlash.Log_Write_EKF2(ahrs,optflow.enabled());
+    DataFlash.Log_Write_EKF(ahrs,optflow.enabled());
  #else
-    DataFlash.Log_Write_EKF2(ahrs,false);
+    DataFlash.Log_Write_EKF(ahrs,false);
  #endif
     DataFlash.Log_Write_AHRS2(ahrs);
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
diff --git a/ArduCopter/Parameters.cpp b/ArduCopter/Parameters.cpp
index bb428ec999..567c9398cb 100644
--- a/ArduCopter/Parameters.cpp
+++ b/ArduCopter/Parameters.cpp
@@ -852,14 +852,14 @@ const AP_Param::Info Copter::var_info[] = {
     // @Path: ../libraries/AP_RCMapper/AP_RCMapper.cpp
     GOBJECT(rcmap, "RCMAP_",        RCMapper),
 
-    // @Group: EKF_
-    // @Path: ../libraries/AP_NavEKF/AP_NavEKF.cpp
-    GOBJECTN(EKF, NavEKF, "EKF_", NavEKF),
-
     // @Group: EK2_
     // @Path: ../libraries/AP_NavEKF2/AP_NavEKF2.cpp
     GOBJECTN(EKF2, NavEKF2, "EK2_", NavEKF2),
     
+    // @Group: EK3_
+    // @Path: ../libraries/AP_NavEKF3/AP_NavEKF3.cpp
+    GOBJECTN(EKF3, NavEKF3, "EK3_", NavEKF3),
+
     // @Group: MIS_
     // @Path: ../libraries/AP_Mission/AP_Mission.cpp
     GOBJECT(mission, "MIS_",       AP_Mission),
diff --git a/ArduCopter/Parameters.h b/ArduCopter/Parameters.h
index bf190bc663..b42fe30ca5 100644
--- a/ArduCopter/Parameters.h
+++ b/ArduCopter/Parameters.h
@@ -51,9 +51,10 @@ public:
         k_param_software_type,
         k_param_ins_old,                        // *** Deprecated, remove with next eeprom number change
         k_param_ins,                            // libraries/AP_InertialSensor variables
-        k_param_NavEKF2_old, // deprecated
+        k_param_NavEKF2_old, // deprecated - remove
         k_param_NavEKF2,
         k_param_g2, // 2nd block of parameters
+        k_param_NavEKF3,
 
         // simulation
         k_param_sitl = 10,
@@ -110,7 +111,7 @@ public:
         k_param_angle_rate_max,         // remove
         k_param_rssi_range,             // unused, replaced by rssi_ library parameters
         k_param_rc_feel_rp,
-        k_param_NavEKF,                 // Extended Kalman Filter Inertial Navigation Group
+        k_param_NavEKF,                 // deprecated - remove
         k_param_mission,                // mission library
         k_param_rc_13,
         k_param_rc_14,
diff --git a/ArduCopter/make.inc b/ArduCopter/make.inc
index 2770398f38..b8c4eeb4ce 100644
--- a/ArduCopter/make.inc
+++ b/ArduCopter/make.inc
@@ -14,7 +14,6 @@ LIBRARIES += AP_Math
 LIBRARIES += AP_InertialSensor
 LIBRARIES += AP_AccelCal
 LIBRARIES += AP_AHRS
-LIBRARIES += AP_NavEKF
 LIBRARIES += AP_NavEKF2
 LIBRARIES += AP_Mission
 LIBRARIES += AP_Rally