document new option to disable IMU checks with ICE running

Author: tridge

common/source/docs/common-ice.rst

@@ -140,3 +140,17 @@ Vibration isolation
 -------------------
 
 The high vibration from internal combustion engines means that :ref:`vibration dampening <common-vibration-damping>` is critical.  It is often necessary to mount the autopilot on a plate with `self-adhesive lead weights <https://www.amazon.com/Great-Planes-Segmented-Weights-6-Ounce/dp/B0015KLJE0>`__ added to increase its mass.
+
+.. note::
+
+   When using Internal Combustion Engine (ICE) motors, vibration during
+   engine run-up can cause the IMU consistency checks to fail, preventing
+   arming.
+   In ArduPilot 4.7 and later an option has been added to :ref:`ARMING_OPTIONS<ARMING_OPTIONS>`:
+
+   **Bit 2 – Skip IMU consistency checks when ICE motor running**
+
+   When this bit is set, ArduPilot will bypass the IMU consistency check
+   if an ICE motor is running. This is intended for setups
+   where ICE engines are typically started before arming, and their
+   vibration may otherwise trigger false failures.

common/source/docs/common-prearm-safety-checks.rst

@@ -41,7 +41,7 @@ Pre-arm checks that are failing will also be sent as messages to the GCS while d
     ======================================================= =================================================== ====================================================
     3D Accel calibration needed                             Accelerometer calibration has not been done         Complete the :ref:`accel calibration <common-accelerometer-calibration>`
     Accels calibrated requires reboot                       Autopilot must be rebooted after accel calibration  Reboot autopilot
-    Accels inconsistent                                     Two accelerometers are inconsistent by 0.75 m/s/s   Re-do the :ref:`accel calibration <common-accelerometer-calibration>`.  Allow autopilot to warm-up and reboot.  If failure continues replace autopilot
+    Accels inconsistent                                     Two accelerometers are inconsistent by 0.75 m/s/s   Re-do the :ref:`accel calibration <common-accelerometer-calibration>`.  Allow autopilot to warm-up and reboot.  If failure continues replace autopilot. If ICE engine runs before arming, see :ref:`ARMING_OPTIONS<ARMING_OPTIONS>` bit 2 as a possible solution.
     ADSB out of memory                                      Autopilot has run out of memory                     Disable features or replace with a higher powered autopilot
     Accels not healthy                                      At least one accelerometer is not providing data    Reboot autopilot.  If failure continues replace autopilot
     AHRS: not using configured AHRS type                    EKF3 is not ready yet and vehicle is using DCM      If indoors, go outside.  Ensure good GPS lock.  Check for misconfiguration of EKF (see :ref:`AHRS_EKF_TYPE<AHRS_EKF_TYPE>`)
@@ -122,7 +122,7 @@ Pre-arm checks that are failing will also be sent as messages to the GCS while d
     GPS x: was not found                                    GPS disconnected or incorrectly configured          Check GPSs physical connection to autopilot and  :ref:`configuration <common-positioning-landing-page>`
     GPSx yaw not available                                  GPS-for-yaw configured but not working              Move to location with better GPS reception.  Check :ref:`GPS-for-yaw <common-gps-for-yaw>` configuration
     Gyro x rate yHz < loop rate z Hz                        Loop rate is faster than Gyro data                  Lower :ref:`SCHED_LOOP_RATE<SCHED_LOOP_RATE>`
-    Gyros inconsistent                                      Two gyros are inconsistent by at least 5 deg/sec    Reboot autopilot and hold vehicle still until gyro calibration completes.  Allow autopilot to warm-up and reboot.  If failure continues replace autopilot
+    Gyros inconsistent                                      Two gyros are inconsistent by at least 5 deg/sec    Reboot autopilot and hold vehicle still until gyro calibration completes.  Allow autopilot to warm-up and reboot.  If failure continues replace autopilot. If ICE engine runs before arming, see :ref:`ARMING_OPTIONS<ARMING_OPTIONS>` bit 2 as a possible solution.
     Gyros not calibrated                                    Gyro calibration normally run at startup failed     Reboot autopilot and hold vehicle still until gyro calibration completes
     Gyros not healthy                                       At least one gyro is not providing data             Reboot autopilot.  If failure continues replace autopilot
     Hardware safety switch                                  Hardware safety switch has not been pushed          Push safety switch (normally on top of GPS) or disable by setting :ref:`BRD_SAFETY_DEFLT<BRD_SAFETY_DEFLT>` to zero and reboot autopilot