TacomaSailor wrote on Dec 21^st, 2009 at 3:24am:

NOW I UNDERSTAND!! - It is a DEEP STALL and Captain Sim modeled it perfectly - as far as I can tell from my limited experience. [...] I'm sure many of you know about deep stalls but since it is a phenomena pretty much restricted to T-Tails it is something I had never experienced or read about.

Back in the Dark Ages (around the time that early 727's were rolling off the Boeing assembly line) I remember a lively "hangar talk" session about the new Piper Arrows being given T-Tails for no reason other than "visual style" and/or "ramp appeal." Somehow, Piper's Marketing people had prevailed over the aerodynamicists and engineers and convinced Management that the airplane would sell better if it looked more like a jet.

The conclusion of the assembled sages that day was that Piper had shot itself in the foot, and that the adverse aerodynamic characteristics of T-Tails (elevator blanking) at rotation, in the flare and (as you have discovered with the 727) in "slow flight" when level would basically "kill" the Arrow as a marketable airplane. As evidence, they discussed the elevator blanking so painfully obvious in Piper's attempt to unseat the Cessna 150/152 as the most widely-used primary trainer: the Tomahawk, which also had a T-Tail purely for misguided aesthetic reasons and whose entire empennage would shake visibly and audibly while practicing stalls. I turned around to look at it once while it was shaking and flapping around at the onset of a stall, and I immediately released back pressure, resumed normal flight, returned SLOWLY AND GENTLY to the airport and refused to ever fly a Tomahawk again. It's the only time in my long and mostly-routine flying career that I was AFRAID of what was happening and genuinely fearful that I would not make it back alive.

Turns out the sages were right about the T-Tail Arrow- it wasn't long before poor sales moved Piper to have the same epiphany- they put the horizontal stab back where it came from, i.e. where the engineers said it should be. Also, on the used airplane market, the T-Tails are generally the cheapest and least-desirable of all the Arrows, other factors being equal.

Of course, the T-Tails on 727's, DC-9's (etc. etc.) were put there due to engine placement, not aesthetics, but the result is that elevator blanking at high AoA is a very real phenomenon in pretty much ANY T-Tail airplane, large or small. That's why the "normal configuration" for horizontal stabs has them mounted on or very close to the fuselage.

The only part of your post that I'm having any difficulty understanding is where you appear to say that you are reading Mach .71 and 140 KIAS simultaneously at 12,000 ft MSL. Just "don't seem right" to me.  :o

Also, I was under the impression that ALL autopilots would "kick off" at the onset of the stick shaker. I have no personal RL experience with the 727's Sperry, but I thought that this was a certification requirement. Many large airplanes even have "stick pushers" that take affirmative action to cure an incipient stall- I wonder if the 727 had a stick pusher as well as a stick shaker?