Shuttle Training Aircraft

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The Shuttle Training Aircraft is oriented sharply nose-down during training exercises in order to mimic the Space Shuttle's steep glide angle during its descent from orbit. Note the lowered landing gear, which provides added drag.

The Shuttle Training Aircraft (STA) is a NASA training vehicle that duplicates the Space Shuttle's approach profile and handling qualities, allowing astronaut pilots to simulate Shuttle landings under controlled conditions before attempting the task on board the orbiter. It is a modified Gulfstream II business jet originally manufactured by Grumman Aerospace, a unit of U.S. defense contractor General Dynamics.

The aircraft's exterior has been modified in order to allow it to withstand the high aerodynamic forces incurred during each training sortie. Inside the aircraft, a redesigned cockpit provides a high-fidelity simulation of the Shuttle Orbiter's controls and pilot vantage point; even the seats are fitted in the same position as those in the Space Shuttle.

The STAs are located at Ellington Field, approximately 2-3 miles from Johnson Space Center in Houston, Texas. The STA is also used at Kennedy Space Center in Florida. It is primarily flown by astronauts practicing landings at the Shuttle Landing Facility and to assess weather conditions prior to Space Shuttle launches.

The STA is particularly critical for Shuttle pilots in training because the Orbiter lacks the atmospheric engines that would allow the craft to "try again" after a poor approach. After re-entry, the Shuttle is a very heavy glider (it is sometimes referred to as a 'flying brick'), and as such has only one chance to land.

In order to match the descent rate and drag profile of the real Shuttle, the main landing gear is lowered (the nose landing stays retracted due to wind load constraints) and engine thrust is reversed. Its flaps 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).

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, and also includes:

cockpit
motion
handling qualities.

To simulate the events in the STA cockpit at 37,000 feet (11,300 m), and abeam the intended point of landing, the instructor pilot performs the following:

lowers the Main landing gear to act as speed brakes/increase drag
selects reverse thrust,
activates simulation mode, activating the shuttle pilot's controls.

The Shuttle Training Aircraft's cockpit. The commander's side of the cockpit, at left, features a Shuttle-type heads-up display (HUD), a rotational hand controller (RHC) used to fly the vehicle, and multi-function displays. The instructor pilot, who occupies the right-hand side of the STA cockpit, has access to a similar heads-up display, as well as conventional aircraft controls and instruments.

The pilot then navigates the STA around a heading alignment circle, 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. 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. At 1,750 feet (533 m) the pilot flares to reduce the descent angle to a more gradual 3 degrees. 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 flies around the runway, never actually landing the aircraft. Every Shuttle Commander has practiced at least 900 landings in this manner, as has each mission's Shuttle Pilot. [1]

Four Gulfstream II aircraft constitute the current STA fleet, although other Gulfstream II aircraft, lacking STA capabilities, are also used by NASA for personnel transport purposes. Although the majority of the fleet have markings similar to those pictured above, paint schemes do vary slightly across aircraft. Current STA tail numbers are:

N944NA (sn144)
N945NA (sn118)
N946NA (sn146)
N947NA (sn147)

In the event NASA's T-38 Talons are not in use, the STAs are used for transporting crewmembers between major sites, namely from Johnson Space Center in Houston to Kennedy Space Center in Cape Canaveral, Florida.