Listening to the verbiage on the tape, the instructions to the in-bounds was "Nxxxx, after TORBY, circle runway 1", so I believe that would make these approaches "formal circles off an instrument approach", which should then give one the confidence to fly the circle like one's flying a jet rather than a single engine prop. It would be easy to understand, however, how peer pressure and subtle "keep it tight" comments could overwhelm one's better angels.
The basic problem on almost any circling approach, especially when executed tightly is the almost inherent instability of the approach. Circling approaches are not necessarily inherently dangerous, but must almost always be flown differently than a straight in. The timing of configuration is the main difference, particularly in a Lear 35. You really, really don't want to drop full flaps until you are lined up on some kind of straight final segment. If you do elect to fully configure early and make the turn with full flaps, you need extra speed and nose down attitude all the way through the turn til you're close to level again. And you'd better be monitoring AOA. And that's in calm conditions. In shear/gusts of the type that day, it would be madness to attempt a fully configured circle to land in a 35. Hell, if it were me, the extra speed I'd be carrying would likely put me above full flap speed anyway. That said, in the heat of the fray, it would be mighty easy to fall into the trap.
No vertical modes are worth a damn with the autopilot on. It may or may not have had VNAV guidance (probably did), and it may or may not have had altitude preselect (probably didn't).
