Flight Determined Subsonic Lateral Directional Stability And Control Derivatives Of The Thrust Vectoring F 18 High Angle Of Attack Research Vehicle Harv And Comparisons To The Basic F 18 And Predicted Derivatives

The subsonic, lateral-directional, stability and control derivatives of the thrust-vectoring F-1 8 High Angle of Attack Research Vehicle (HARV) are extracted from flight data using a maximum likelihood parameter identification technique. State noise is accounted for in the identification formulation and is used to model the uncommanded forcing functions caused by unsteady aerodynamics. Preprogrammed maneuvers provided independent control surface inputs, eliminating problems of identifiability related to correlations between the aircraft controls and states. The HARV derivatives are plotted as functions of angles of attack between 10deg and 70deg and compared to flight estimates from the basic F-18 aircraft and to predictions from ground and wind tunnel tests. Unlike maneuvers of the basic F-18 aircraft, the HARV maneuvers were very precise and repeatable, resulting in tightly clustered estimates with small uncertainty levels. Significant differences were found between flight and prediction; however, some of these differences may be attributed to differences in the range of sideslip or input amplitude over which a given derivative was evaluated, and to differences between the HARV external configuration and that of the basic F-18 aircraft, upon which most of the prediction was based. Some HARV derivative fairings have been adjusted using basic F-18 derivatives (with low uncertainties) to help account for differences in variable ranges and the lack of HARV maneuvers at certain angles of attack.Iliff, Kenneth W. and Wang, Kon-Sheng CharlesArmstrong Flight Research CenterF-18 AIRCRAFT; ANGLE OF ATTACK; MAXIMUM LIKELIHOOD ESTIMATES; DIRECTIONAL STABILITY; CONTROL SURFACES; AIRCRAFT CONTROL; WIND TUNNEL TESTS; PARAMETER IDENTIFICATION; LATERAL STABILITY

The X-31 Enhanced Fighter Maneuverability Demonstrator was unique among experimental aircraft. A joint effort of the United States and Germany, the X-31 was the only X-plane to be designed, manufactured, and flight tested as an international collaboration. It was also the only X-plane to support two separate test programs conducted years apart, one administered largely by NASA and the other by the U.S. Navy, as well as the first X-plane ever to perform at the Paris Air Show. Flying Beyond the Stall begins by describing the government agencies and private-sector industries involved in the X-31 program, the genesis of the supermaneuverability concept and its initial design breakthroughs, design and fabrication of two test airframes, preparation for the X-31's first flight, and the first flights of Ship #1 and Ship #2. Subsequent chapters discuss envelope expansion, handling qualities (especially at high angles of attack), and flight with vectored thrust. The book then turns to the program's move to NASA's Dryden Flight Research Center and actual flight test data. Additional tasking, such as helmet-mounted display evaluations, handling quality studies, aerodynamic parameter estimation, and a "tailless" study are also discussed.The book describes how, in the aftermath of a disastrous accident with Ship #1 in 1995, Ship #2 was prepared for its outstanding participation in the Paris Air Show. The aircraft was then shipped back to Edwards AFB and put into storage until the late 1990s, when it was refurbished for participation in the U. S. Navy's VECTOR program. The book ends with a comprehensive discussion of lessons learned and includes an Appendix containing detailed information.