I keep wondering if there is a particular reason for the question.
G3X Touch? ;-)
GLOOORRRRYYY!!!We obviously need some more guidance. Otherwise this will quickly degenerate into arguments over the value of a tire pressure gauge as one's sole instrument.
It's one of the drawbacks of surfing by "New Posts" instead of by sub-forums....I didn't realize this was in the IMC forum until after my first couple of posts. If I was in IMC, I might not just want the oil pressure gauge to be my last remaining instrument....
As for "why post the question"; I suspect since the IMC Club was recently assimilated into EAA, they want to ensure some life is shown in the group. On the downside, they get people like me and Marty participating.....
Given a choice for which instrument to smash, most would choose the hobbs meter.
Coming back to this, a friend of mine wrote to say that he solo'd a Breezy yesterday, the three instruments on board and how you really didn't need to look at any of them. (This is especially true as they are far apart from each other and moving the head to see any one of them means one is not paying attention to everything else outside the plane -- "outside" not being the most precise term when discussing a breezy.) Anyway, apart from the theoretical answer being "none" it also reminded me that some years ago I used to teach CAP cadets to fly at the encampment at OSH after AirVenture. At the time, the boys were all MS FS aces. The challenge was to break them of fixating on instruments and fly the D@#$% Plane! So I covered up everything except the tach and had them fly vertical S's. (It helps with dead straight farm rows and roads laid out like a compass.) After awhile you are familiar enough with the sound of the engine and you don't need the tach either.
All in all it comes back to being conditional. What the most important instrument is depends upon what you are trying to do with the plane. (And what kind of plane.)