I broke that rule a few times. Twice it was to avoid dying and a third time when a student was entering a spin a few knots fast and loaded up the airplane to accelerate the stall. Left wing went first and we were upside down before you could say "hey, look we're upside down!" in an inverted spin. If we were in an aerobatic airplane I may have given then a couple turns to get things sorted out. We weren't so I didn't and we barely went past a half a turn.
If you never break a reg how do you answer the question in an interview "tell me about a time you broke a reg?"
If it was positive G spin it wasn't really an "inverted spin"... You were just in an accelerated spin entry or developing spin, and the roll oscillations resulted in the aircraft being inverted. A true inverted spin is negative Gs from an inverted (low AOA vs. high AOA) stall.
The dudes who wrote the T-6A manual made the same mistake, writing "inverted stalls" as a prohibited maneuver. So every time a student pulls on the stick a bit too much during a loop and the plane stalls just a tiny bit while inverted, I've now just done a prohibited maneuver? Nonsense. They wanted to prohibit negative G stalls, not inverted stalls. But the morons who wrote the manual don't have an understanding of basic aerodynamics so they put that little bit of nonsense in and refuse to change it, because they can't imagine the plane being inverted and a stall not being negative G. I think they're afraid of 3D maneuvering and aerobatics really, and can't be troubled to take the time to learn better.
These are the same people who ignore the single line in the manual about reducing power when approaching a stall when excessively nose high, to avoid prop torque and P-factor causing the plane to depart controlled flight to the left. Instead, they treat it as an out of control situation and immediately jump to the OCF recovery procedure, where anything could happen. I had a student who pretty much ran out of ideas during formation flying and we ended up heading straight up with the airspeed rapidly decaying below 120 kts (stall was approx. 85 kts). Per the recommendations of the fine large aircraft drivers who taught me to fly the T-6, I *should* have pulled the throttle to idle, neutralized the controls, and let the plane flop wherever it wanted, hoping to not ram my flight lead as I abdicated my responsibility as pilot in command. I guess I'd be giving the plane to Allah, since I was flying with an Iraqi student at the time. Instead, I did that pilot stuff, and per the flight manual pulled the power to 60% to reduce torque while ensuring continued airflow over the tail surfaces, and with very careful application of stick and rudder pressure I flew the plane out of it while maintaining visual on my flight lead and even maintained a safe position behind his aircraft. The slowest we got was approx. 40 kts, fully controllable as long as I didn't ask the plane to exceed stall AOA or abuse any other flight control inputs. I think "stall" at that speed was about 0.4 Gs, which is plenty to maneuver a plane in a near-ballistic arc and certainly better than relying on dumb luck to not whip stall or ram the other aircraft.
Anyhow... "inverted spin"? Really? Or was it just an incipient spin with pre-spin gyrations (aerodynamically not much different than a really low speed snap roll) that had you inverted as the aircraft energy bled off during the accelerated spin entry? If you didn't shove the stick fwd inducing a negative G negative AOA stall with the nose still slicing, I'm not sure it could be considered a true inverted spin.
BTW, the T-6 and T-37 would do that, predictably. Certain spin entries in the T-37 were high enough energy that you might go 'round and 'round at least twice in energy dissipating rolls before the plane settled into a developed upright spin. The rolling entry wasn't considered an inverted spin because the people who wrote the manual for the T-37 actually understood aerodynamics, plus an inverted spin in the T-37 was an actual "really bad thing" if handled incorrectly, so they took the effort to make sure we knew the difference. Sitting on your butt in the seat = "upright" spin even if the post stall pre-spin gyrations took the plane inverted, hanging in the straps with helmet pushed up against the canopy = inverted spin even if the plane was temporarily upright at any time during the spin entry.
