for more research on other types of airplanes. As a result, a program was started by Robert R. Gilruth with Melvin N. Gough as the chief test pilot. Evaluation of flying qualities The technique for the study of flying qualities requirements used by Gilruth was first to install instruments to record relevant quantities such as control positions and forces, airplane angular velocities, linear accelerations, airspeed, and altitude. Then a program of specified flight conditions and maneuvers was flown by an experienced test pilot. After the flight, data were transcribed from the records and the results were correlated with pilot opinion. This approach would be considered routine today, but it was a notable original contribution by Gilruth that took advantage of the flight recording instruments already available at Langley and the variety of airplanes available for tests under comparable conditions. An important quantity in flying qualities measurements in turns or pull-ups is the variation of control force on the control stick or wheel with the value of acceleration normal to the flight direction expressed in g units. This quantity is usually called the force per g. Relation to Spacecraft A new generation of spacecraft now under development by NASA to replace the Space Shuttle and return astronauts to the Moon will have a manual control capability for several mission tasks, and the ease and precision with which pilots can execute these tasks will have an important effect on performance, mission risk and training costs. No reference standards currently exist for flying qualities of piloted spacecraft. See also Flight test Cooper-Harper rating scale Pilot-induced oscillation Longitudinal static stability Flight envelope References External links Airplane Stability and Control by Malcolm L. Abzug Stengel R F: Flight Dynamics. Princeton University Press 2004, . Aerospace engineering