Quoting "VSB1976" in a previous thread :
Lockheed L-1011 TriStar Horizontal Stabilizer
There is something about the L-1011 horizontal stabilizer that makes it unique: In the early design stages, the airlines told Lockheed they wanted the pilots to have more power and control over the pitch system, so that in case of a jet upset, the crew could pull the aircraft out of a dive.
Lockheed designed this extra power into the tail: The L-1011 is the only commercial jet that can take off with full nose down trim. This was actually demonstrated to the airlines during the flight testing phase - with full nose down trim (which is a mis-set trim setting but has happened in the past on other aircraft and caused accidents) the pilot is still able to rotate the aircraft and climb away - it takes a lot of control wheel force to do it but it can be done - in other aircraft, the control column can be pulled full aft but with full nose down trim the nose won't come up for rotation. For those who don't know: Jet upset was an early event that happened more in the 1950's and early 1960' with the commercial jets than we see today - via rough air, the aircraft would get knocked out of it's stablized cruise condition until it was diving towards the ground out of control - the pilots would attempt to pull back on the wheel to get the nose to come up but most of the jets of that era did not have the power to overcome the excessive speed and thus they could not pull the aircraft out of the dive - when the L-1011 was being designed, the airlines wanted to make sure the L-1011 had enough pitch force to do this should it happen - to this day, a TriStar has never been lost as a result of jet upset and not being able to pull out of the resulting dive.
Now on to the technical description of the L-1011 pitch control system. The L-1011 incorporates an all-flying horizontal stabilizer to control movement in the pitch axis. This "all flying tail" is unique in the commercial aircraft industry. First of all, pitch control on most airplanes are usually controlled by elevators - on the L-1011 however, the primary part of the tail that controls pitch is the front part called the horizontal stabilizer, the leading edge of which which move up and down - the elevators are attached to the rear spar of this movable stabilizer piece - the elevators do move, yes, but not under direct pilot control. The elevators move as a direct result of stabilizer movement only via a physical mechanical link: When the stabilizer moves it's nose downward, the elevators deflect upward to increase the camber of the entire tail - this causes a downward moment and thus pulls the entire rear portion of the aircraft in a downward direction - this causes the nose of the aircraft to pitch up. When the pilot pushes the control wheel forward, this causes the stabilizer nose to move up, causing the elevators to deflect downward, increasing the camber effect to cause a lifting moment and thus pull the tail of the aircraft upward and this in turn causes the nose to pitch down.
Just to get in before the inevitable ! do you think there is a 1011 alarm in Arizona ?