diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.cpp b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
index b23c1ef381..cb691f5f89 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
@@ -1272,7 +1272,12 @@ check_sample:
     }
 
     now = hal.scheduler->micros();
-    _delta_time = (now - _last_sample_usec) * 1.0e-6f;
+    if (_hil_mode && _hil.delta_time > 0) {
+        _delta_time = _hil.delta_time;
+        _hil.delta_time = 0;
+    } else {
+        _delta_time = (now - _last_sample_usec) * 1.0e-6f;
+    }
     _last_sample_usec = now;
 
 #if 0
@@ -1336,6 +1341,37 @@ void AP_InertialSensor::set_gyro(uint8_t instance, const Vector3f &gyro)
     }
 }
 
+/*
+  set delta time for next ins.update()
+ */
+void AP_InertialSensor::set_delta_time(float delta_time)
+{
+    _hil.delta_time = delta_time;
+}
+
+/*
+  set delta velocity for next update
+ */
+void AP_InertialSensor::set_delta_velocity(uint8_t instance, float deltavt, const Vector3f &deltav)
+{
+    if (instance < INS_MAX_INSTANCES) {
+        _delta_velocity_valid[instance] = true;
+        _delta_velocity[instance] = deltav;
+        _delta_velocity_dt[instance] = deltavt;
+    }
+}
+
+/*
+  set delta angle for next update
+ */
+void AP_InertialSensor::set_delta_angle(uint8_t instance, const Vector3f &deltaa)
+{
+    if (instance < INS_MAX_INSTANCES) {
+        _delta_angle_valid[instance] = true;
+        _delta_angle[instance] = deltaa;
+    }
+}
+
 #if INS_VIBRATION_CHECK
 // calculate vibration levels and check for accelerometer clipping (called by a backends)
 void AP_InertialSensor::calc_vibration_and_clipping(uint8_t instance, const Vector3f &accel, float dt)
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.h b/libraries/AP_InertialSensor/AP_InertialSensor.h
index c10a785cc9..6e61b83de1 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.h
@@ -112,7 +112,6 @@ public:
     ///
     const Vector3f     &get_gyro(uint8_t i) const { return _gyro[i]; }
     const Vector3f     &get_gyro(void) const { return get_gyro(_primary_gyro); }
-    void               set_gyro(uint8_t instance, const Vector3f &gyro);
 
     // set gyro offsets in radians/sec
     const Vector3f &get_gyro_offsets(uint8_t i) const { return _gyro_offset[i]; }
@@ -144,7 +143,6 @@ public:
     ///
     const Vector3f     &get_accel(uint8_t i) const { return _accel[i]; }
     const Vector3f     &get_accel(void) const { return get_accel(_primary_accel); }
-    void               set_accel(uint8_t instance, const Vector3f &accel);
 
     uint32_t get_gyro_error_count(uint8_t i) const { return _gyro_error_count[i]; }
     uint32_t get_accel_error_count(uint8_t i) const { return _accel_error_count[i]; }
@@ -233,6 +231,17 @@ public:
     uint32_t get_accel_clip_count(uint8_t instance) const;
 #endif
 
+    /*
+      HIL set functions. The minimum for HIL is set_accel() and
+      set_gyro(). The others are option for higher fidelity log
+      playback
+     */
+    void set_accel(uint8_t instance, const Vector3f &accel);
+    void set_gyro(uint8_t instance, const Vector3f &gyro);
+    void set_delta_time(float delta_time);
+    void set_delta_velocity(uint8_t instance, float deltavt, const Vector3f &deltav);
+    void set_delta_angle(uint8_t instance, const Vector3f &deltaa);
+
 private:
 
     // load backend drivers
@@ -347,6 +356,13 @@ private:
     LowPassFilterVector3f _accel_vibe_filter;
 #endif
 
+    /*
+      state for HIL support
+     */
+    struct {
+        float delta_time;
+    } _hil {};
+
     DataFlash_Class *_dataflash;
 };