Slaved or non-slaved, electronic or mechanical, a thorough understanding of your HSI system is critical for proper use and early recognition of failure.
While the HSI was a game-changer for the instrument pilot by raising the bar on situational awareness, it introduced more avionics complexity, especially when connected to multiple nav sources. In failure mode, and for the pilot who doesnít know how to operate it, the instrument can be a killer.
When I was a new avionics technician, Narcoís DGO-series HSI system was the ground breaker. But, not all pilots fully understood what an HSI would do, and fewer yet understood how they worked. Thatís somewhat true even today.