The T-3A had no center of gravity maneuver limitations and we never considered it--at all--but we flew with some big football player students, two parachutes and full tanks and would take off and go directly to the area (about 10-15 minutes flight time) and begin spinning. We were told that one or two pilots with any fuel level would always be within CG limits.
Because the entire fleet was new, none of the T-3's had been measured (put on scales) since they left the factory. I asked our maintainers about the weight and balance measurement procedure but no one knew how to level the plane for the measurement. I knew the aircraft's measurement datum line and how to calculate the moments but I needed to know how to level the plane for an accurate measurement. Typically the procedure is to place a level on the cockpit floor or storage compartment floor. I contacted Hondo's maintenance chief and he said he didn't know how to do it since the procedure hadn't been needed yet. I even contacted Slingsby but could not get an answer. I got the feeling they didn't want us to look into the CG issue too closely.
I decided to weigh the aircraft anyway. I put a T-3 on the scales with full wing tanks and oil, plus me and a cadet in the seats with our parachutes on with the canopy closed--exactly the situation for a normal takeoff. The aircraft was scaled inside a hangar with a known level floor. The weights at all three wheels were taken and the numbers crunched. We were over two inches rear of the rear CG limit! I tried to push this info up the chain of command but because the aircraft wasn't leveled to Slingsby's specification (whatever that was) no one believed the numbers. I know that leveling the aircraft will move the CG but there's no way it was going to shift the CG two inches forward--you'd have to stand the aircraft on it's freakin' nose to do that. The bottom line is we were flying the aircraft with an extremely aft center of gravity and no one wanted to admit it.
As wing fuel burned off the aircraft's CG would shift forward so the T-3A would become more stable throughout the flight. It's worth noting the first accident aircraft took off, went directly out to the maneuver area, flew one maneuver--most likely a "spin prevent" (recovery of incipient spin), climbed up to 11,700 feet and entered the fatal spin with nearly full fuel tanks and an aft CG.
Could someone post the maneuvering CG limits for the T67? Are they the same for all the variants?