During OPS 8 major mode 801, the orbital checkout of orbiter systems used during entry is performed, usually the day before deorbit. These activities take about 15 minutes. System checkout is performed in two parts. The first part, which requires the use of one auxiliary power unit/hydraulic system, involves the repositioning of the left and right main engine nozzles for entry and the cycling of aerosurfaces, hydraulic motors and hydraulic switching valves. After the checkout is completed, the auxiliary power unit is deactivated. The second part consists of a check of all the crew dedicated displays; self-test of the microwave scan beam landing system, TACAN, accelerometer assemblies, radar altimeter, rate gyro assemblies and air data transducer assemblies; and a check of the hand controllers, rudder pedal transducer assemblies, speed brake, panel trim switches, RHC trim switches, speed brake takeover push button and mode/sequence push button light indicators.