This is interesting, from Twin Commander...
https://flightlevelsonline.com/2024/spring-2024/control-column-supplementary-nts-check-procedure-2/?fbclid=IwZXh0bgNhZW0CMTAAAR0JDcKqfxFaISmo5Q1GQwVgZ2FFsCbXo3rZSgyZt07v_3S8N0E5w97pEM4_aem_Ac0YZpQCHtbAap4P7zkuSeOK_vQsNU6oMImBJnjxtR6b85xYxXAz8FH90Wvcx-F3VQxqsn4900RuKOX4_y1wV_AkSUPPLEMENTARY NTS CHECK PROCEDURE:
The NTS system ground check outlined in some aircraft manuals (utilizing the NTS Check or Beta light) verifies operation of the major NTS system components. However, the NTS system ground check does NOT completely verify the operational status of the NTS system. Specifically, the NTS system ground check does not verify whether the oil supply from the Propeller Governor (PG) is available to the NTS system because the check utilizes the propeller unfeather pump, instead of the PG, to supply oil pressure to the NTS system. If the oil passage between the PG and the downstream NTS system is blocked or restricted, the normal ground check procedure may not reveal the inoperative system. In this situation, the affected engine may not NTS in the event of an inflight shutdown, necessitating immediate manual feathering of the propeller to reduce windmilling drag.
One symptom of the loss of PG oil supply to the NTS system is resetting of the PG speed set point to a value 5 to 8 percent rpm above normal (for that Speed Control position) at power lever positions above flight idle. (Normally, the PG reset function increases the PG speed set point only when the power lever is brought below flight idle.) The supplemental NTS check procedure outlined below detects this symptom, which is indicative of a blockage potentially resulting in an inoperative NTS system.
