4.7:Heli throttle notch

common/source/docs/common-imu-notch-filtering.rst

@@ -53,7 +53,10 @@ Key to the dynamic notch filter operation is control of its center frequency. Th
 
 #. :ref:`INS_HNTCH_MODE <INS_HNTCH_MODE>` = 0. **Static center frequency**. Dynamic notch frequency control is disabled. The center frequency is fixed and is static. Often used in Traditional Helicopters with external governors for rotor speed, either incorporated in the ESC or separate for ICE motors.
 #. :ref:`INS_HNTCH_MODE <INS_HNTCH_MODE>` = 1. (Default) **Throttle position based**, where the frequency at hover throttle is determined by analysis of logs, and then variation of throttle position above this is used to track the increase in noise frequency. See :ref:`throttle-based<common-imu-notch-filtering-throttle-based-setup>` for further setup details.
-#. :ref:`INS_HNTCH_MODE <INS_HNTCH_MODE>` = 2 (RPM Sensor 1) or 5(RPM Sensor2). **RPM sensor based**, where an external :ref:`RPM sensor <common-rpm>` is used to determine the motor frequency and hence primary vibration source's frequency for the notch. Often used in Traditional Helicopters (See :ref:`Helicopters<common-imu-notch-filtering-helicopter-setup>`) using the ArduPilot Head Speed Governor feature. See :ref:`RPM Sensor<common-rpm-based-notch>` for further setup instructions.
+
+.. note:: this type of notch filter cannot be used in Traditional Helicopters since throttle stick position does not relate to motor throttle, but rather collective and will result in a configuration error being declared at boot. The **Static center frequency** type is usually used since helis usually use constant motor speed.
+
+3. :ref:`INS_HNTCH_MODE <INS_HNTCH_MODE>` = 2 (RPM Sensor 1) or 5(RPM Sensor2). **RPM sensor based**, where an external :ref:`RPM sensor <common-rpm>` is used to determine the motor frequency and hence primary vibration source's frequency for the notch. Often used in Traditional Helicopters (See :ref:`Helicopters<common-imu-notch-filtering-helicopter-setup>`) using the ArduPilot Head Speed Governor feature. See :ref:`RPM Sensor<common-rpm-based-notch>` for further setup instructions.
 #. :ref:`INS_HNTCH_MODE <INS_HNTCH_MODE>` = 3. **ESC Telemetry based**, where the ESC provides motor RPM information which is used to set the center frequency. This can also be used for the forward motor in fixed wing flight, if the forward motor(s) ESCs report RPM. This requires that your ESCs are configured correctly to support BLHeli telemetry via :ref:`a serial port<blheli32-esc-telemetry>`. See :ref:`ESC Telemetry<common-esc-telem-based-notch>` for further setup instructions. If :ref:`INS_HNTCH_OPTS<INS_HNTCH_OPTS>`, or :ref:`INS_HNTC2_OPTS<INS_HNTC2_OPTS>` if the second set of notches is enabled, has bit 1 set, then a set of notches for each motor will be created, tracking its RPM telemetry, otherwise, the average frequency of all motors will set the center frequency.
 #. :ref:`INS_HNTCH_MODE <INS_HNTCH_MODE>` = 4. **In-Flight FFT based**, where a running FFT is done in flight to determine the primary noise frequency and adjust the notch's center frequency to match. This probably the best mode if the autopilot is capable of running this feature. It requires that the autopilot firmware supports it (see :ref:`common-limited_firmware` for GyroFFT feature) and has sufficient cpu power (F7/H7 autopilots). See :ref:`In-Flight FFT <common-imu-fft>` for further setup instructions.