Using Your King Air Bus Sense Test Switch and the Effect on Your HEDS

This is a good tip for pilots and mechanics alike. The Bus Sense switch is a three-position switch with “RESET” on top, “NORMAL” in the middle, and “TEST” on the bottom. Default has the switch in the NORMAL position with the Up RESET and Down TEST positions being spring loaded and intended for momentary use only. For those of you who follow the full After Start Checklist as well as the Abnormal Electrical Condition Checklist and use the TEST portion of this switch, the correct use is a momentary tap and let go in order to test the system. Holding the switch down in the TEST position for any length of time more than just a momentary tap will risk damaging your HEDs. On the other hand, holding the switch up in the RESET position for longer durations does not cause any issues. This is not to say that the incorrect use of this switch is always to blame for HED failures, but sometimes it is. So do yourself a favor and just give it a quick tap. Hope this helps save you a few dollars.