diff --git a/libraries/AP_AHRS/AP_AHRS.cpp b/libraries/AP_AHRS/AP_AHRS.cpp
index 623df872375..ad5c1a0a10f 100644
--- a/libraries/AP_AHRS/AP_AHRS.cpp
+++ b/libraries/AP_AHRS/AP_AHRS.cpp
@@ -272,7 +272,7 @@ void AP_AHRS::init()
 #if !HAL_NAVEKF2_AVAILABLE && HAL_NAVEKF3_AVAILABLE
     if (_ekf_type.get() == 2) {
         _ekf_type.set(EKFType::THREE);
-        EKF3.set_enable(true);
+        ekf3.EKF3.set_enable(true);
     }
 #elif !HAL_NAVEKF3_AVAILABLE && HAL_NAVEKF2_AVAILABLE
     if (_ekf_type.get() == 3) {
@@ -284,7 +284,7 @@ void AP_AHRS::init()
 #if HAL_NAVEKF2_AVAILABLE && HAL_NAVEKF3_AVAILABLE
     // a special case to catch users who had AHRS_EKF_TYPE=2 saved and
     // updated to a version where EK2_ENABLE=0
-    if (_ekf_type.get() == 2 && !EKF2.get_enable() && EKF3.get_enable()) {
+    if (_ekf_type.get() == 2 && !EKF2.get_enable() && ekf3.EK3.get_enable()) {
         _ekf_type.set(EKFType::THREE);
     }
 #endif
@@ -385,7 +385,7 @@ void AP_AHRS::reset_gyro_drift(void)
     EKF2.resetGyroBias();
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.resetGyroBias();
+    ekf3.reset_gyro_drift();
 #endif
 }
 
@@ -716,7 +716,7 @@ void AP_AHRS::update_EKF2(void)
             if (EKF2.getOriginLLH(new_origin)) {
                 done_common_origin = true;
 #if HAL_NAVEKF3_AVAILABLE
-                EKF3.setOriginLLH(new_origin);
+                ekf3.set_origin(new_origin);
 #endif
 #if AP_AHRS_EXTERNAL_ENABLED
                 external.set_origin(new_origin);
@@ -730,7 +730,7 @@ void AP_AHRS::update_EKF2(void)
 #if HAL_NAVEKF3_AVAILABLE
 void AP_AHRS::update_EKF3(void)
 {
-    if (!_ekf3_started) {
+    if (!ekf3.started) {
         // wait 1 second for DCM to output a valid tilt error estimate
         if (start_time_ms == 0) {
             start_time_ms = AP_HAL::millis();
@@ -747,49 +747,19 @@ void AP_AHRS::update_EKF3(void)
         }
 #endif
         if (AP_HAL::millis() - start_time_ms > startup_delay_ms) {
-            _ekf3_started = EKF3.InitialiseFilter();
+            ekf3.started = ekf3.EKF3.InitialiseFilter();
         }
     }
-    if (_ekf3_started) {
-        EKF3.UpdateFilter();
+    if (ekf3.started) {
+        ekf3.update();
+        ekf3_estimates = {};
+        ekf3.get_results(ekf3_estimates);
         if (_active_EKF_type() == EKFType::THREE) {
-            Vector3f eulers;
-            EKF3.getRotationBodyToNED(state.dcm_matrix);
-            EKF3.getEulerAngles(eulers);
-            roll  = eulers.x;
-            pitch = eulers.y;
-            yaw   = eulers.z;
 
-            update_cd_values();
-            update_trig();
-
-            const AP_InertialSensor &_ins = AP::ins();
-
-            // Use the primary EKF to select the primary gyro
-            const int8_t primary_imu = EKF3.getPrimaryCoreIMUIndex();
-            const uint8_t primary_gyro = primary_imu>=0?primary_imu:_ins.get_first_usable_gyro();
-            const uint8_t primary_accel = primary_imu>=0?primary_imu:_ins.get_first_usable_accel();
-
-            // get gyro bias for primary EKF and change sign to give gyro drift
-            // Note sign convention used by EKF is bias = measurement - truth
-            Vector3f drift;
-            EKF3.getGyroBias(-1, drift);
-            state.gyro_drift = -drift;
-
-            // use the same IMU as the primary EKF and correct for gyro drift
-            state.gyro_estimate = _ins.get_gyro(primary_gyro) + state.gyro_drift;
-
-            // get 3-axis accel bias estimates for active EKF (this is usually for the primary IMU)
-            Vector3f &abias = state.accel_bias;
-            EKF3.getAccelBias(-1,abias);
-
-            // use the primary IMU for accel earth frame
-            Vector3f accel = _ins.get_accel(primary_accel);
-            accel -= abias;
-            state.accel_ef = state.dcm_matrix * get_rotation_autopilot_body_to_vehicle_body() * accel;
+            copy_estimates_from_backend_estimates(ekf3_estimates);
 
             nav_filter_status filt_state;
-            EKF3.getFilterStatus(filt_state);
+            ekf3.get_filter_status(filt_state);
             update_notify_from_filter_status(filt_state);
         }
         /*
@@ -797,7 +767,7 @@ void AP_AHRS::update_EKF3(void)
         */
         if (!done_common_origin) {
             Location new_origin;
-            if (EKF3.getOriginLLH(new_origin)) {
+            if (ekf3.get_origin(new_origin)) {
                 done_common_origin = true;
 #if HAL_NAVEKF2_AVAILABLE
                 EKF2.setOriginLLH(new_origin);
@@ -832,7 +802,7 @@ void AP_AHRS::update_external(void)
             EKF2.setOriginLLH(new_origin);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-            EKF3.setOriginLLH(new_origin);
+            ekf3.set_origin(new_origin);
 #endif
         }
     }
@@ -861,9 +831,7 @@ void AP_AHRS::reset()
     }
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    if (_ekf3_started) {
-        _ekf3_started = EKF3.InitialiseFilter();
-    }
+    ekf3.reset();
 #endif
 }
 
@@ -885,7 +853,7 @@ bool AP_AHRS::_get_location(Location &loc) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        if (EKF3.getLLH(loc)) {
+        if (ekf3_estimates.get_location(loc)) {
             return true;
         }
         break;
@@ -951,7 +919,7 @@ bool AP_AHRS::_wind_estimate(Vector3f &wind) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getWind(wind);
+        return ekf3.wind_estimate(wind);
 #endif
 
 #if AP_AHRS_EXTERNAL_ENABLED
@@ -1081,7 +1049,7 @@ bool AP_AHRS::_airspeed_EAS(float &airspeed_ret, AirspeedEstimateType &airspeed_
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        have_wind = EKF3.getWind(wind_vel);
+        have_wind = ekf3.wind_estimate(wind_vel);
         break;
 #endif
 
@@ -1168,7 +1136,7 @@ bool AP_AHRS::_airspeed_TAS(Vector3f &vec) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getAirSpdVec(vec);
+        return ekf3.EKF3.getAirSpdVec(vec);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1200,7 +1168,7 @@ bool AP_AHRS::airspeed_health_data(uint8_t instance, float &innovation, float &i
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getAirSpdHealthData(instance, innovation, innovationVariance, age_ms);
+        return ekf3.EKF3.getAirSpdHealthData(instance, innovation, innovationVariance, age_ms);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1231,7 +1199,7 @@ bool AP_AHRS::use_compass(void)
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.use_compass();
+        return ekf3.use_compass();
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1279,11 +1247,8 @@ bool AP_AHRS::_get_quaternion_for_ekf_type(Quaternion &quat, EKFType type) const
 #endif
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        if (!_ekf3_started) {
-            return false;
-        }
-        EKF3.getQuaternion(quat);
-        break;
+        quat = ekf3_estimates.quaternion;
+        return ekf3_estimates.attitude_valid;
 #endif
 #if AP_AHRS_SIM_ENABLED
     case EKFType::SIM:
@@ -1338,8 +1303,10 @@ bool AP_AHRS::_get_secondary_attitude(Vector3f &eulers) const
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
         // EKF3 is secondary
-        EKF3.getEulerAngles(eulers);
-        return _ekf3_started;
+        eulers[0] = ekf3_estimates.roll_rad;
+        eulers[1] = ekf3_estimates.pitch_rad;
+        eulers[2] = ekf3_estimates.yaw_rad;
+        return ekf3_estimates.attitude_valid;
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1407,8 +1374,8 @@ bool AP_AHRS::_get_secondary_position(Location &loc) const
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
         // EKF3 is secondary
-        EKF3.getLLH(loc);
-        return _ekf3_started;
+        ekf3_estimates.get_location(loc);
+        return ekf3.started;
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1446,11 +1413,8 @@ Vector2f AP_AHRS::_groundspeed_vector(void)
 #endif
 
 #if HAL_NAVEKF3_AVAILABLE
-    case EKFType::THREE: {
-        Vector3f vec;
-        EKF3.getVelNED(vec);
-        return vec.xy();
-    }
+    case EKFType::THREE:
+        return ekf3.groundspeed_vector();
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1481,7 +1445,7 @@ bool AP_AHRS::set_origin(const Location &loc)
     const bool ret2 = EKF2.setOriginLLH(loc);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    const bool ret3 = EKF3.setOriginLLH(loc);
+    const bool ret3 = ekf3.set_origin(loc);
 #endif
 #if AP_AHRS_EXTERNAL_ENABLED
     const bool ret_ext = external.set_origin(loc);
@@ -1574,7 +1538,7 @@ void AP_AHRS::use_recorded_origin_maybe()
 bool AP_AHRS::handle_external_position_estimate(const Location &loc, float pos_accuracy, uint32_t timestamp_ms)
 {
 #if HAL_NAVEKF3_AVAILABLE
-    return EKF3.setLatLng(loc, pos_accuracy, timestamp_ms);
+    return ekf3.EKF3.setLatLng(loc, pos_accuracy, timestamp_ms);
 #endif
     return false;
 }
@@ -1606,8 +1570,7 @@ bool AP_AHRS::_get_velocity_NED(Vector3f &vec) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.getVelNED(vec);
-        return true;
+        return ekf3_estimates.get_velocity_NED(vec);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1641,7 +1604,7 @@ bool AP_AHRS::get_mag_field_NED(Vector3f &vec) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.getMagNED(vec);
+        ekf3.EKF3.getMagNED(vec);
         return true;
 #endif
 
@@ -1673,7 +1636,7 @@ bool AP_AHRS::get_mag_field_correction(Vector3f &vec) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.getMagXYZ(vec);
+        ekf3.EKF3.getMagXYZ(vec);
         return true;
 #endif
 
@@ -1720,8 +1683,7 @@ bool AP_AHRS::get_vert_pos_rate_D(float &velocity) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        velocity = EKF3.getPosDownDerivative();
-        return true;
+        return ekf3_estimates.get_vert_pos_rate_D(velocity);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1752,7 +1714,7 @@ bool AP_AHRS::get_hagl(float &height) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getHAGL(height);
+        return ekf3.get_hagl(height);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -1798,7 +1760,7 @@ bool AP_AHRS::get_relative_position_NED_origin(Vector3p &vec) const
     case EKFType::THREE: {
             Vector2p posNE;
             postype_t posD;
-            if (EKF3.getPosNE(posNE) && EKF3.getPosD(posD)) {
+            if (ekf3.EKF3.getPosNE(posNE) && ekf3.EKF3.getPosD(posD)) {
                 // position is valid
                 vec.x = posNE.x;
                 vec.y = posNE.y;
@@ -1866,7 +1828,7 @@ bool AP_AHRS::get_relative_position_NE_origin(Vector2p &posNE) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE: {
-        bool position_is_valid = EKF3.getPosNE(posNE);
+        bool position_is_valid = ekf3.EKF3.getPosNE(posNE);
         return position_is_valid;
     }
 #endif
@@ -1932,7 +1894,7 @@ bool AP_AHRS::get_relative_position_D_origin(postype_t &posD) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE: {
-        bool position_is_valid = EKF3.getPosD(posD);
+        bool position_is_valid = ekf3.EKF3.getPosD(posD);
         return position_is_valid;
     }
 #endif
@@ -2073,16 +2035,16 @@ AP_AHRS::EKFType AP_AHRS::_active_EKF_type(void) const
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE: {
         // do we have an EKF3 yet?
-        if (!_ekf3_started) {
+        if (!ekf3.started) {
             return fallback_active_EKF_type();
         }
         if (always_use_EKF()) {
             uint16_t ekf3_faults;
-            EKF3.getFilterFaults(ekf3_faults);
+            ekf3.EKF3.getFilterFaults(ekf3_faults);
             if (ekf3_faults == 0) {
                 ret = EKFType::THREE;
             }
-        } else if (EKF3.healthy()) {
+        } else if (ekf3.healthy()) {
             ret = EKFType::THREE;
         }
         break;
@@ -2119,8 +2081,8 @@ AP_AHRS::EKFType AP_AHRS::_active_EKF_type(void) const
 #endif
 #if HAL_NAVEKF3_AVAILABLE
         case EKFType::THREE:
-            EKF3.getFilterStatus(filt_state);
-            should_use_gps = EKF3.configuredToUseGPSForPosXY();
+            ekf3.get_filter_status(filt_state);
+            should_use_gps = ekf3.EKF3.configuredToUseGPSForPosXY();
             break;
 #endif
 #if AP_AHRS_SIM_ENABLED
@@ -2213,7 +2175,7 @@ AP_AHRS::EKFType AP_AHRS::fallback_active_EKF_type(void) const
 #endif
 
 #if HAL_NAVEKF3_AVAILABLE
-    if (_ekf3_started) {
+    if (ekf3.started) {
         return EKFType::THREE;
     }
 #endif
@@ -2322,9 +2284,8 @@ bool AP_AHRS::healthy(void) const
 #endif
 
 #if HAL_NAVEKF3_AVAILABLE
-    case EKFType::THREE: {
-        bool ret = _ekf3_started && EKF3.healthy();
-        if (!ret) {
+    case EKFType::THREE:
+        if (!ekf3.healthy()) {
             return false;
         }
         if ((_vehicle_class == VehicleClass::FIXED_WING ||
@@ -2335,7 +2296,6 @@ bool AP_AHRS::healthy(void) const
             return false;
         }
         return true;
-    }
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2411,11 +2371,7 @@ bool AP_AHRS::pre_arm_check(bool requires_position, char *failure_msg, uint8_t f
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        if (!_ekf3_started) {
-            hal.util->snprintf(failure_msg, failure_msg_len, "EKF3 not started");
-            return false;
-        }
-        return EKF3.pre_arm_check(requires_position, failure_msg, failure_msg_len) && ret;
+        return ekf3.pre_arm_check(requires_position, failure_msg, failure_msg_len) && ret;
 #endif
     }
 
@@ -2442,7 +2398,7 @@ bool AP_AHRS::initialised(void) const
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
         // initialisation complete 10sec after ekf has started
-        return (_ekf3_started && (AP_HAL::millis() - start_time_ms > AP_AHRS_NAVEKF_SETTLE_TIME_MS));
+        return (ekf3.started && (AP_HAL::millis() - start_time_ms > AP_AHRS_NAVEKF_SETTLE_TIME_MS));
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2474,7 +2430,7 @@ bool AP_AHRS::get_filter_status(nav_filter_status &status) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.getFilterStatus(status);
+        ekf3.get_filter_status(status);
         return true;
 #endif
 
@@ -2498,7 +2454,7 @@ void  AP_AHRS::writeOptFlowMeas(const uint8_t rawFlowQuality, const Vector2f &ra
     EKF2.writeOptFlowMeas(rawFlowQuality, rawFlowRates, rawGyroRates, msecFlowMeas, posOffset, heightOverride);
 #endif
 #if EK3_FEATURE_OPTFLOW_FUSION
-    EKF3.writeOptFlowMeas(rawFlowQuality, rawFlowRates, rawGyroRates, msecFlowMeas, posOffset, heightOverride);
+    ekf3.EKF3.writeOptFlowMeas(rawFlowQuality, rawFlowRates, rawGyroRates, msecFlowMeas, posOffset, heightOverride);
 #endif
 }
 
@@ -2506,7 +2462,7 @@ void  AP_AHRS::writeOptFlowMeas(const uint8_t rawFlowQuality, const Vector2f &ra
 bool AP_AHRS::getOptFlowSample(uint32_t& timeStamp_ms, Vector2f& flowRate, Vector2f& bodyRate, Vector2f& losPred) const
 {
 #if EK3_FEATURE_OPTFLOW_FUSION
-    return EKF3.getOptFlowSample(timeStamp_ms, flowRate, bodyRate, losPred);
+    return ekf3.EKF3.getOptFlowSample(timeStamp_ms, flowRate, bodyRate, losPred);
 #endif
     return false;
 }
@@ -2515,7 +2471,7 @@ bool AP_AHRS::getOptFlowSample(uint32_t& timeStamp_ms, Vector2f& flowRate, Vecto
 void  AP_AHRS::writeBodyFrameOdom(float quality, const Vector3f &delPos, const Vector3f &delAng, float delTime, uint32_t timeStamp_ms, uint16_t delay_ms, const Vector3f &posOffset)
 {
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.writeBodyFrameOdom(quality, delPos, delAng, delTime, timeStamp_ms, delay_ms, posOffset);
+    ekf3.EKF3.writeBodyFrameOdom(quality, delPos, delAng, delTime, timeStamp_ms, delay_ms, posOffset);
 #endif
 }
 
@@ -2526,7 +2482,7 @@ void AP_AHRS::writeExtNavData(const Vector3f &pos, const Quaternion &quat, float
     EKF2.writeExtNavData(pos, quat, posErr, angErr, timeStamp_ms, delay_ms, resetTime_ms);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.writeExtNavData(pos, quat, posErr, angErr, timeStamp_ms, delay_ms, resetTime_ms);
+    ekf3.EKF3.writeExtNavData(pos, quat, posErr, angErr, timeStamp_ms, delay_ms, resetTime_ms);
 #endif
 }
 
@@ -2537,7 +2493,7 @@ void AP_AHRS::writeDefaultAirSpeed(float airspeed, float uncertainty)
     EKF2.writeDefaultAirSpeed(airspeed);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.writeDefaultAirSpeed(airspeed, uncertainty);
+    ekf3.EKF3.writeDefaultAirSpeed(airspeed, uncertainty);
 #endif
 }
 
@@ -2548,7 +2504,7 @@ void AP_AHRS::writeExtNavVelData(const Vector3f &vel, float err, uint32_t timeSt
     EKF2.writeExtNavVelData(vel, err, timeStamp_ms, delay_ms);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.writeExtNavVelData(vel, err, timeStamp_ms, delay_ms);
+    ekf3.EKF3.writeExtNavVelData(vel, err, timeStamp_ms, delay_ms);
 #endif
 }
 
@@ -2586,7 +2542,7 @@ void AP_AHRS::getControlLimits(float &ekfGndSpdLimit, float &ekfNavVelGainScaler
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.getEkfControlLimits(ekfGndSpdLimit,ekfNavVelGainScaler);
+        ekf3.get_control_limits(ekfGndSpdLimit,ekfNavVelGainScaler);
         break;
 #endif
 
@@ -2636,7 +2592,7 @@ bool AP_AHRS::getMagOffsets(uint8_t mag_idx, Vector3f &magOffsets) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getMagOffsets(mag_idx, magOffsets);
+        return ekf3.EKF3.getMagOffsets(mag_idx, magOffsets);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2671,8 +2627,8 @@ void AP_AHRS::_getCorrectedDeltaVelocityNED(Vector3f& ret, float& dt) const
 #endif
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        imu_idx = EKF3.getPrimaryCoreIMUIndex();
-        EKF3.getAccelBias(-1,accel_bias);
+        imu_idx = ekf3.EKF3.getPrimaryCoreIMUIndex();
+        accel_bias = ekf3_estimates.accel_bias;
         break;
 #endif
 #if AP_AHRS_SIM_ENABLED
@@ -2740,9 +2696,9 @@ bool AP_AHRS::attitudes_consistent(char *failure_msg, const uint8_t failure_msg_
 #if HAL_NAVEKF3_AVAILABLE
     // check primary vs ekf3
     if (configured_ekf_type() == EKFType::THREE || active_EKF_type() == EKFType::THREE) {
-        for (uint8_t i = 0; i < EKF3.activeCores(); i++) {
+        for (uint8_t i = 0; i < ekf3.EKF3.activeCores(); i++) {
             Quaternion ekf3_quat;
-            EKF3.getQuaternionBodyToNED(i, ekf3_quat);
+            ekf3.EKF3.getQuaternionBodyToNED(i, ekf3_quat);
 
             // check roll and pitch difference
             const float rp_diff_rad = primary_quat.roll_pitch_difference(ekf3_quat);
@@ -2760,7 +2716,7 @@ bool AP_AHRS::attitudes_consistent(char *failure_msg, const uint8_t failure_msg_
                 return false;
             }
         }
-        total_ekf_cores += EKF3.activeCores();
+        total_ekf_cores += ekf3.EKF3.activeCores();
     }
 #endif
 
@@ -2781,7 +2737,7 @@ bool AP_AHRS::attitudes_consistent(char *failure_msg, const uint8_t failure_msg_
         // and if not using an external yaw source (DCM does not support external yaw sources)
         bool using_noncompass_for_yaw = false;
 #if HAL_NAVEKF3_AVAILABLE
-        using_noncompass_for_yaw = (configured_ekf_type() == EKFType::THREE) && EKF3.using_noncompass_for_yaw();
+        using_noncompass_for_yaw = (configured_ekf_type() == EKFType::THREE) && ekf3.EKF3.using_noncompass_for_yaw();
 #endif
         if (!always_use_EKF() && !using_noncompass_for_yaw) {
             Vector3f angle_diff;
@@ -2816,7 +2772,7 @@ uint32_t AP_AHRS::getLastYawResetAngle(float &yawAng)
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getLastYawResetAngle(yawAng);
+        return ekf3.getLastYawResetAngle(yawAng);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2849,7 +2805,7 @@ uint32_t AP_AHRS::getLastPosNorthEastReset(Vector2f &pos)
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getLastPosNorthEastReset(pos);
+        return ekf3.getLastPosNorthEastReset(pos);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2882,7 +2838,7 @@ uint32_t AP_AHRS::getLastVelNorthEastReset(Vector2f &vel) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getLastVelNorthEastReset(vel);
+        return ekf3.getLastVelNorthEastReset(vel);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2915,7 +2871,7 @@ uint32_t AP_AHRS::getLastPosDownReset(float &posDelta)
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getLastPosDownReset(posDelta);
+        return ekf3.getLastPosDownReset(posDelta);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -2939,7 +2895,7 @@ void AP_AHRS::resetHeightDatum(void)
     WITH_SEMAPHORE(_rsem);
 
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.resetHeightDatum();
+    ekf3.resetHeightDatum();
 #endif
 #if HAL_NAVEKF2_AVAILABLE
     EKF2.resetHeightDatum();
@@ -2979,7 +2935,7 @@ void AP_AHRS::send_ekf_status_report(GCS_MAVLINK &link) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.send_status_report(link);
+        return ekf3.send_ekf_status_report(link);
 #endif
 
     }
@@ -3001,7 +2957,7 @@ bool AP_AHRS::_get_origin(EKFType type, Location &ret) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getOriginLLH(ret);
+        return ekf3.get_origin(ret);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -3120,7 +3076,7 @@ bool AP_AHRS::get_hgt_ctrl_limit(float& limit) const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getHeightControlLimit(limit);
+        return ekf3.get_hgt_ctrl_limit(limit);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -3162,7 +3118,7 @@ void AP_AHRS::set_terrain_hgt_stable(bool stable)
     EKF2.setTerrainHgtStable(stable);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.setTerrainHgtStable(stable);
+    ekf3.set_terrain_hgt_stable(stable);
 #endif
 }
 
@@ -3186,7 +3142,7 @@ bool AP_AHRS::get_innovations(Vector3f &velInnov, Vector3f &posInnov, Vector3f &
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
         // use EKF to get innovations
-        return EKF3.getInnovations(velInnov, posInnov, magInnov, tasInnov, yawInnov);
+        return ekf3.get_innovations(velInnov, posInnov, magInnov, tasInnov, yawInnov);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -3209,7 +3165,7 @@ bool AP_AHRS::is_vibration_affected() const
     switch (configured_ekf_type()) {
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.isVibrationAffected();
+        return ekf3.EKF3.isVibrationAffected();
 #endif
 #if AP_AHRS_DCM_ENABLED
     case EKFType::DCM:
@@ -3252,8 +3208,7 @@ bool AP_AHRS::get_variances(float &velVar, float &posVar, float &hgtVar, Vector3
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE: {
         // use EKF to get variance
-        Vector2f offset;
-        return EKF3.getVariances(velVar, posVar, hgtVar, magVar, tasVar, offset);
+        return ekf3.get_variances(velVar, posVar, hgtVar, magVar, tasVar);
     }
 #endif
 
@@ -3304,7 +3259,7 @@ bool AP_AHRS::get_vel_innovations_and_variances_for_source(uint8_t source, Vecto
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
         // use EKF to get variance
-        return EKF3.getVelInnovationsAndVariancesForSource((AP_NavEKF_Source::SourceXY)source, innovations, variances);
+        return ekf3.get_vel_innovations_and_variances_for_source(source, innovations, variances);
 #endif
 
 #if AP_AHRS_SIM_ENABLED
@@ -3334,7 +3289,7 @@ uint8_t AP_AHRS::get_active_airspeed_index() const
 // we only have affinity for EKF3 as of now
 #if HAL_NAVEKF3_AVAILABLE
     if (active_EKF_type() == EKFType::THREE) {
-        uint8_t ret = EKF3.getActiveAirspeed();
+        uint8_t ret = ekf3.EKF3.getActiveAirspeed();
         if (ret != UINT8_MAX && airspeed->healthy(ret) && airspeed->use(ret)) {
             return ret;
         }
@@ -3367,7 +3322,7 @@ uint8_t AP_AHRS::_get_primary_IMU_index() const
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
         // let EKF2 choose primary IMU
-        imu = EKF3.getPrimaryCoreIMUIndex();
+        imu = ekf3.EKF3.getPrimaryCoreIMUIndex();
         break;
 #endif
 #if AP_AHRS_SIM_ENABLED
@@ -3412,7 +3367,7 @@ int8_t AP_AHRS::_get_primary_core_index() const
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.getPrimaryCoreIndex();
+        return ekf3.EKF3.getPrimaryCoreIndex();
 #endif
     }
 
@@ -3460,7 +3415,7 @@ void AP_AHRS::check_lane_switch(void)
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.checkLaneSwitch();
+        ekf3.EKF3.checkLaneSwitch();
         break;
 #endif
     }
@@ -3492,7 +3447,7 @@ void AP_AHRS::request_yaw_reset(void)
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        EKF3.requestYawReset();
+        ekf3.request_yaw_reset();
         break;
 #endif
     }
@@ -3502,7 +3457,7 @@ void AP_AHRS::request_yaw_reset(void)
 void AP_AHRS::set_posvelyaw_source_set(AP_NavEKF_Source::SourceSetSelection source_set_idx)
 {
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.setPosVelYawSourceSet((uint8_t)source_set_idx);
+    ekf3.EKF3.setPosVelYawSourceSet((uint8_t)source_set_idx);
 #endif
 }
 
@@ -3510,7 +3465,7 @@ void AP_AHRS::set_posvelyaw_source_set(AP_NavEKF_Source::SourceSetSelection sour
 uint8_t AP_AHRS::get_posvelyaw_source_set() const
 {
 #if HAL_NAVEKF3_AVAILABLE
-    return EKF3.get_active_source_set();
+    return ekf3.EKF3.get_active_source_set();
 #else
     return 0;
 #endif   
@@ -3522,7 +3477,7 @@ void AP_AHRS::Log_Write()
     EKF2.Log_Write();
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.Log_Write();
+    ekf3.EKF3.Log_Write();
 #endif
 
     Write_AHRS2();
@@ -3546,7 +3501,7 @@ bool AP_AHRS::using_noncompass_for_yaw(void) const
 #endif
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.using_noncompass_for_yaw();
+        return ekf3.EKF3.using_noncompass_for_yaw();
 #endif
 #if AP_AHRS_SIM_ENABLED
     case EKFType::SIM:
@@ -3573,7 +3528,7 @@ bool AP_AHRS::using_extnav_for_yaw(void) const
 #endif
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.using_extnav_for_yaw();
+        return ekf3.EKF3.using_extnav_for_yaw();
 #endif
 #if AP_AHRS_SIM_ENABLED
     case EKFType::SIM:
@@ -3602,7 +3557,7 @@ bool AP_AHRS::using_gps(void) const
 #endif
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.using_gps();
+        return ekf3.EKF3.using_gps();
 #endif
 #if AP_AHRS_SIM_ENABLED
     case EKFType::SIM:
@@ -3652,7 +3607,7 @@ void AP_AHRS::set_alt_measurement_noise(float noise)
     EKF2.set_baro_alt_noise(noise);
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    EKF3.set_baro_alt_noise(noise);
+    ekf3.EKF3.set_baro_alt_noise(noise);
 #endif
 }
 
@@ -3667,14 +3622,14 @@ const EKFGSF_yaw *AP_AHRS::get_yaw_estimator(void) const
 #if AP_AHRS_DCM_ENABLED
     case EKFType::DCM:
 #if HAL_NAVEKF3_AVAILABLE
-        return EKF3.get_yawEstimator();
+        return ekf3.EKF3.get_yawEstimator();
 #else
         return nullptr;
 #endif
 #endif
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        return EKF3.get_yawEstimator();
+        return ekf3.EKF3.get_yawEstimator();
 #endif
 #if AP_AHRS_SIM_ENABLED
     case EKFType::SIM:
diff --git a/libraries/AP_AHRS/AP_AHRS.h b/libraries/AP_AHRS/AP_AHRS.h
index 052145e49b2..3bed655b97d 100644
--- a/libraries/AP_AHRS/AP_AHRS.h
+++ b/libraries/AP_AHRS/AP_AHRS.h
@@ -27,7 +27,7 @@
 
 #include "AP_AHRS_Backend.h"
 #include <AP_NavEKF2/AP_NavEKF2.h>
-#include <AP_NavEKF3/AP_NavEKF3.h>
+#include "AP_AHRS_NavEKF3.h"
 #include <AP_NavEKF/AP_Nav_Common.h>              // definitions shared by inertial and ekf nav filters
 
 #include "AP_AHRS_DCM.h"
@@ -74,6 +74,10 @@ public:
         return _singleton;
     }
 
+#if AP_AHRS_NAVEKF3_ENABLED
+    AP_AHRS_NavEKF3 ekf3;
+#endif
+
     // periodically checks to see if we should update the AHRS
     // orientation (e.g. based on the AHRS_ORIENTATION parameter)
     // allow for runtime change of orientation
@@ -473,7 +477,7 @@ public:
 #if AP_AHRS_DCM_ENABLED
         DCM = 0,
 #endif
-#if HAL_NAVEKF3_AVAILABLE
+#if AP_AHRS_NAVEKF3_ENABLED
         THREE = 3,
 #endif
 #if HAL_NAVEKF2_AVAILABLE
@@ -500,9 +504,6 @@ public:
 #if HAL_NAVEKF2_AVAILABLE
     NavEKF2 EKF2;
 #endif
-#if HAL_NAVEKF3_AVAILABLE
-    NavEKF3 EKF3;
-#endif
 
     // for holding parameters
     static const struct AP_Param::GroupInfo var_info[];
@@ -818,7 +819,6 @@ private:
     bool _ekf2_started;
 #endif
 #if HAL_NAVEKF3_AVAILABLE
-    bool _ekf3_started;
     void update_EKF3(void);
 #endif
 
@@ -1060,9 +1060,12 @@ private:
     AP_AHRS_DCM dcm{_kp_yaw, _kp, gps_gain, beta, _gps_use, _gps_minsats};
     struct AP_AHRS_Backend::Estimates dcm_estimates;
 #endif
+#if AP_AHRS_NAVEKF3_ENABLED
+    struct AP_AHRS_Backend::Estimates ekf3_estimates;
+#endif
 #if AP_AHRS_SIM_ENABLED
 #if HAL_NAVEKF3_AVAILABLE
-    AP_AHRS_SIM sim{EKF3};
+    AP_AHRS_SIM sim{ekf3.EKF3};
 #else
     AP_AHRS_SIM sim;
 #endif
diff --git a/libraries/AP_AHRS/AP_AHRS_NavEKF3.cpp b/libraries/AP_AHRS/AP_AHRS_NavEKF3.cpp
new file mode 100644
index 00000000000..737e2f49fb9
--- /dev/null
+++ b/libraries/AP_AHRS/AP_AHRS_NavEKF3.cpp
@@ -0,0 +1,83 @@
+#include "AP_AHRS_config.h"
+
+#if AP_AHRS_NAVEKF3_ENABLED
+
+#include "AP_AHRS_NavEKF3.h"
+#include <AP_AHRS/AP_AHRS.h>
+#include <AP_HAL/AP_HAL.h>
+
+extern const AP_HAL::HAL& hal;
+
+void AP_AHRS_NavEKF3::get_results(AP_AHRS_Backend::Estimates &results)
+{
+    /*
+     * attitude estimates:
+     */
+    EKF3.getRotationBodyToNED(results.dcm_matrix);
+
+    Vector3f eulers;
+    EKF3.getEulerAngles(eulers);
+    results.roll_rad  = eulers.x;
+    results.pitch_rad = eulers.y;
+    results.yaw_rad   = eulers.z;
+
+    EKF3.getQuaternion(results.quaternion);
+    results.quaternion.rotate(-AP::ahrs().get_trim());
+
+    results.attitude_valid = started;
+
+    /*
+     * rotational rate estimates:
+     */
+    const AP_InertialSensor &_ins = AP::ins();
+
+    // Use the primary EKF to select the primary gyro
+    const int8_t primary_imu = EKF3.getPrimaryCoreIMUIndex();
+    const uint8_t primary_gyro = primary_imu>=0?primary_imu:_ins.get_first_usable_gyro();
+    const uint8_t primary_accel = primary_imu>=0?primary_imu:_ins.get_first_usable_accel();
+
+    // get gyro bias for primary EKF and change sign to give gyro drift
+    // Note sign convention used by EKF is bias = measurement - truth
+    Vector3f drift;
+    EKF3.getGyroBias(-1, drift);
+    results.gyro_drift = -drift;
+
+    // use the same IMU as the primary EKF and correct for gyro drift
+    results.gyro_estimate = _ins.get_gyro(primary_gyro) + results.gyro_drift;
+
+    /*
+     * acceleration estimates
+     */
+    // get 3-axis accel bias estimates for active EKF (this is usually
+    // for the primary IMU)
+    EKF3.getAccelBias(-1, results.accel_bias);
+
+    // use the primary IMU for accel earth frame
+    Vector3f accel = _ins.get_accel(primary_accel);
+    accel -= results.accel_bias;
+    results.accel_ef = results.dcm_matrix * AP::ahrs().get_rotation_autopilot_body_to_vehicle_body() * accel;
+
+    /*
+     * velocity estimates
+     */
+    EKF3.getVelNED(results.velocity_NED);
+    results.velocity_NED_valid = true;
+    results.vert_pos_rate_D = EKF3.getPosDownDerivative();
+    results.vert_pos_rate_D_valid = true;
+
+    /*
+     * position estimates
+     */
+    results.location_valid = EKF3.getLLH(results.location);
+}
+
+bool AP_AHRS_NavEKF3::pre_arm_check(bool requires_position, char *failure_msg, uint8_t failure_msg_len) const
+{
+    if (!started) {
+        hal.util->snprintf(failure_msg, failure_msg_len, "EKF3 not started");
+        return false;
+    }
+    return EKF3.pre_arm_check(requires_position, failure_msg, failure_msg_len);
+}
+
+#endif  // AP_AHRS_NAVEKF3_ENABLED
diff --git a/libraries/AP_AHRS/AP_AHRS_NavEKF3.h b/libraries/AP_AHRS/AP_AHRS_NavEKF3.h
new file mode 100644
index 00000000000..be268912bc7
--- /dev/null
+++ b/libraries/AP_AHRS/AP_AHRS_NavEKF3.h
@@ -0,0 +1,153 @@
+#pragma once
+
+/*
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ *  shim AP_NavEKF3 into AP_AHRS_Backend
+ */
+
+#include "AP_AHRS_config.h"
+
+#if AP_AHRS_NAVEKF3_ENABLED
+
+#include <AP_NavEKF3/AP_NavEKF3.h>
+#include "AP_AHRS_Backend.h"
+
+class AP_AHRS_NavEKF3 : public AP_AHRS_Backend {
+public:
+
+    /* Do not allow copies */
+    CLASS_NO_COPY(AP_AHRS_NavEKF3);
+    AP_AHRS_NavEKF3() {}
+
+    bool healthy(void) const override {
+        if (!started) {
+            return false;
+        }
+        if (!EKF3.healthy()) {
+            return false;
+        }
+        return true;
+    }
+
+    void reset_gyro_drift() override { EKF3.resetGyroBias(); }
+
+    void update() override { EKF3.UpdateFilter(); }
+
+    void get_results(Estimates &results) override;
+    void reset() override {
+        if (!started) {
+            return;
+        }
+        started = EKF3.InitialiseFilter();
+    }
+
+    bool get_origin(Location &ret) const override {
+        return EKF3.getOriginLLH(ret);
+    }
+    bool set_origin(const Location &loc) override {
+        return EKF3.setOriginLLH(loc);
+    }
+
+    // return a wind estimation vector, in m/s
+    bool wind_estimate(Vector3f &wind) const override {
+        return EKF3.getWind(wind);
+    }
+
+    Vector2f groundspeed_vector(void) override {
+        Vector3f vec;
+        EKF3.getVelNED(vec);
+        return vec.xy();
+    }
+
+    bool            use_compass() override {
+        return EKF3.use_compass();
+    }
+
+    // Set to true if the terrain underneath is stable enough to be used as a height reference
+    // this is not related to terrain following
+    void set_terrain_hgt_stable(bool stable) override {
+        EKF3.setTerrainHgtStable(stable);
+    }
+
+    uint32_t getLastYawResetAngle(float &yawAng) override {
+        return EKF3.getLastYawResetAngle(yawAng);
+    };
+    uint32_t getLastPosNorthEastReset(Vector2f &pos) override WARN_IF_UNUSED {
+        return EKF3.getLastPosNorthEastReset(pos);
+    };
+    uint32_t getLastVelNorthEastReset(Vector2f &vel) const override WARN_IF_UNUSED {
+        return EKF3.getLastVelNorthEastReset(vel);
+    };
+    uint32_t getLastPosDownReset(float &posDelta) override WARN_IF_UNUSED {
+        return EKF3.getLastPosDownReset(posDelta);
+    };
+    void resetHeightDatum(void) override {
+        EKF3.resetHeightDatum();
+    }
+    void request_yaw_reset() override {
+        EKF3.requestYawReset();
+    }
+    // get latest altitude estimate above ground level in meters and validity flag
+    bool get_hagl(float &hagl) const override WARN_IF_UNUSED {
+        return EKF3.getHAGL(hagl);
+    }
+
+    bool pre_arm_check(bool requires_position, char *failure_msg, uint8_t failure_msg_len) const override;
+
+    void get_control_limits(float &ekfGndSpdLimit, float &controlScaleXY) const override {
+        return EKF3.getEkfControlLimits(ekfGndSpdLimit, controlScaleXY);
+    }
+    bool get_hgt_ctrl_limit(float &limit) const override WARN_IF_UNUSED {
+        return EKF3.getHeightControlLimit(limit);
+    }
+
+    void send_ekf_status_report(class GCS_MAVLINK &link) const override {
+        EKF3.send_status_report(link);
+    }
+
+    // get_filter_status - returns filter status as a series of flags
+    bool get_filter_status(nav_filter_status &status) const override {
+        EKF3.getFilterStatus(status);
+        return true;
+    }
+
+    // return the innovations for the specified instance
+    // An out of range instance (eg -1) returns data for the primary instance
+    bool get_innovations(Vector3f &velInnov, Vector3f &posInnov, Vector3f &magInnov, float &tasInnov, float &yawInnov) const override {
+        return EKF3.getInnovations(velInnov, posInnov, magInnov, tasInnov, yawInnov);
+    }
+
+    bool get_variances(float &velVar, float &posVar, float &hgtVar, Vector3f &magVar, float &tasVar) const override {
+        Vector2f offset;
+        return EKF3.getVariances(velVar, posVar, hgtVar, magVar, tasVar, offset);
+    }
+
+    bool get_vel_innovations_and_variances_for_source(uint8_t source, Vector3f &innovations, Vector3f &variances) const override WARN_IF_UNUSED {
+        return EKF3.getVelInnovationsAndVariancesForSource((AP_NavEKF_Source::SourceXY)source, innovations, variances);
+    }
+
+    void request_yaw_reset(void) override {
+        EKF3.requestYawReset();
+    }
+
+    // this is out here so parameters can be poked into it
+    NavEKF3 EKF3;
+
+    bool started;
+};
+
+#endif  // AP_AHRS_NAVEKF3_ENABLED
diff --git a/libraries/AP_AHRS/AP_AHRS_config.h b/libraries/AP_AHRS/AP_AHRS_config.h
index 91d82b14a12..8fef368d2e1 100644
--- a/libraries/AP_AHRS/AP_AHRS_config.h
+++ b/libraries/AP_AHRS/AP_AHRS_config.h
@@ -32,6 +32,11 @@
 #ifndef HAL_NAVEKF3_AVAILABLE
 #define HAL_NAVEKF3_AVAILABLE AP_AHRS_BACKEND_DEFAULT_ENABLED && AP_INERTIALSENSOR_ENABLED
 #endif
+#endif
+
+#ifndef AP_AHRS_NAVEKF3_ENABLED
+#define AP_AHRS_NAVEKF3_ENABLED HAL_NAVEKF3_AVAILABLE
+#endif
 
 #ifndef AP_AHRS_SIM_ENABLED
 #define AP_AHRS_SIM_ENABLED AP_AHRS_BACKEND_DEFAULT_ENABLED && AP_SIM_ENABLED && AP_INERTIALSENSOR_ENABLED