Avionics
A sophisticated computer system installed on board the STA simulates the flight dynamics of the orbiter with nearly perfect accuracy. The STA's highly realistic simulation of the Orbiter is not limited to handling characteristics, but also implements the shuttle control interfaces for the pilot.
The pilot then navigates the STA around a heading alignment cone (HAC), a maneuver which aligns the shuttle's (or training aircraft's) flight path with the landing runway.
An onboard computer called the Advanced Digital Avionics System (ADAS) controls the Direct Lift Control (DLC) and the in-flight reverse thrust during Simulation Mode.
Every Shuttle Commander has practiced at least 1000 landings in this manner, as has each mission's Shuttle Pilot.
Read more about this topic: Shuttle Training Aircraft