It's part of my manufacturer issued type certificate as well as a part 91 reg. As a professional pilot, I just assume not hang my livelihood out there with some hokie backup compass. That being said, I agree that it's useless with the exception of a very few scenarios. I do love the DC9 series compass. So much swing error that it has to be mounted on the aft cockpit bulkhead. Seen it many times. Awesome. Incredible that thing was designed looking at slide rules through thick glasses before we even engineered the Lunar Lander. What a TANK.

Jordan
E