Flight Profile
The STA was particularly critical for Shuttle pilots in training because the Orbiter lacks the atmospheric engines that would allow the craft to "go around" after a poor approach. After re-entry, the Shuttle was a very heavy glider (it is sometimes referred to as a 'flying brick') and as such had only one chance to land.
In order to match the descent rate and drag profile of the real Shuttle at 37,000 feet (11,300 m), the main landing gear was lowered (the nose gear stayed retracted due to wind load constraints) and engine thrust is reversed. Its flaps may deflect upwards to decrease lift as well as downwards to increase lift.
Covers are placed on the left hand cockpit windows to provide the same view as from a Shuttle cockpit, and the left-hand pilot's seat is fitted with the same controls as a Shuttle. The STA's normal flight controls are moved to the right, where the instructor sits. Both seat positions have a Head Up Display (HUD).
In a normal exercise, the pilot descends to 20,000 feet (6,000 m) at an airspeed of 280 knots (519 km/h), 15 miles (24 km) from the landing target. The pilot then rolls the STA at 12,000 feet (3,700 m), 7 miles (11 km) from landing. The nose of the aircraft is then dropped to increase speed to 300 knots (560 km/h), descending at a 20-degree angle on the Outer Glide Slope (OGS). The Outer Glide Slope aiming point is 7500ft short of the runway threshold, and uses PAPI's for visual guidance in addition to the MLS system. At 2000ft the guidance system changes to pre-flare and shortly after, at 1,700 feet (518 m), the pilot starts the flare maneouver to gradually reduce the descent angle and transition to the Inner Glide Slope (IGS) which is 1.5 degrees from 300ft onwards, using a "Ball-bar" system for visual guidance. The shuttle landing gear release is simulated at 300 feet (90 m) above the ground surface, since the STA main gear has been down for the whole simulation. The nose gear of the STA is lowered at 150 ft (46 m) AGL in case of an inadvertent touchdown with the runway surface.
If the speed is correct, a green light on the instrument panel simulates shuttle landing when the pilot's eyes are 32 feet (10 m) above the runway. This is the exact position that the pilot's head would be in during actual landing. In the exercise, the STA is still flying 20 feet (6 m) above the ground. The instructor pilot deselects the simulation mode, stows the thrust reversers, and the instructor executes a go-around, never actually landing the aircraft (on training approaches).
Read more about this topic: Shuttle Training Aircraft
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