Pilots training for a specific mission receive more intensive instruction in orbiter approach and landing in Shuttle Training Aircraft (STA), which are four Gulfstream II business jets modified to perform like the orbiter during landing. Because the Orbiter approaches landings at such a steep angle (17-20 degrees) and high speed (over 300 miles per hour), the STA approaches with its engines in reverse thrust and main landing gear down to increase drag and duplicate the unique glide characteristics of the orbiter. Assigned pilots receive about 100 hours of STA training prior to a flight, which is equivalent to 600 Shuttle approaches.. .. . <a href="http://www.wstf.nasa.gov/WSSH/Default.htm" target="_blank">Photo</a> . . <a href="http://quest.arc.nasa.gov/people/journals/aero/ringo/shuttle.html" target="_blank">NASA diagram & Trip Report</a>. .. .They also have a KC-135A, the "Vomit Comet", however, apart from some minor modifications to the hydraulic system to keep the pressure from dropping to zero during the periods of zero-G, the structure itself has not been strengthened, as the NASA missions are still within its normal certified operating envelope of +2.5/-1.0 Gs.. .. . <a href="http://www.avweb.com/articles/vcomet/" target="_blank">KC-135A</a>. . . . <small>[ 27 March 2002, 19:36: Message edited by: ORAC ]</small>