2003 X-31 VECTOR

It is my special honor to nominate the VECTOR International Test Team for the Kelly Johnson Award for Outstanding Achievement in the Field of Flight Test Engineering.

NOMINATION

The X-31 VECTORING, EXTREMELY SHORT TAKEOFF & LANDING, CONTROL AND TAILLESS OPERATION RESEARCH (VECTOR) International Test Team was formed in 1999 to evaluate proposed flight test of an advanced flush air data system (AADS) and Extremely Short Take-Off and Landing (ESTOL) using the X-31A. The test team was comprised of engineers from the US Navy, Boeing, European Aeronautic Defence and Space Company (EADS), Deutsches Zentrum für Luft-und Raumfahrt e.V. (DLR - the German Aerospace Center), Bundesamt für Wehrtechnik und Beschaffung (BWB - the German Federal Office of Defense Technology and Procurement) and RJK Technologies, LLC. The U.S. Navy and BWB each assigned one test pilot. In virtually every discipline, the Team was "one deep", a very significant challenge it faced each and every day. Only by establishing a very successful ability to properly establish priorities was the Team able to function, though even then, many days were much longer than for 'normal' people.

The VECTOR Team was setting out to do something no one had done before. More, in the case of developing and demonstrating ESTOL, they were embarking upon a program whose risk was going to be substantially greater than most other programs. While the Team had some support from the respective parent industries, in virtually every facet of development the Team 'built' their own products, from aircraft modifications, to control laws, to flight control software.

The Team started with extensive engineering, data formulation and analyses to support comprehensive concept definition and a decision to proceed. Data from the previous X-31A program, "Enhance Fighter Maneuverability" (EFM), was retrieved and subjected to extensive review. Engineering analyses and concept development, safety and flight test analysis ultimately led to a decision to proceed.

With that, the Team set about the Herculean task of expanding the knowledge base of supporting information necessary to such an ambitious undertaking. As engineering analyses and concept definition began to develop design alternatives, new engineering studies were undertaken, wind tunnel runs were made and concepts of operation were formulated. Throughout, flight test planning and safety analyses kept apace.

In the meantime, the Team set out to meet another great challenge, reactivation and refurbishment of the X-31A and all of its special supporting systems, including the complete simulation and software development environment. After initial refurbishment at Palmdale, CA the aircraft was sent to Patuxent River in April 2000 to complete preparations for flight test. The simulation Downey Cockpit was sent to EADS, where it was completely rebuilt. The remainder of the simulation was rebuilt at Patuxent River and the software development environment was refurbished at RJK Technologies, Blacksburg, VA.

With the support of exhaustive engineering refurbishment was completed erasing the rigors of over five years of storage. The Team embarked on a comprehensive flight test program phase to verify aircraft functional operation, aerodynamic and engine performance and to validate modifications and procedures required for operations at Patuxent River. The VECTOR test team completed that first phase of testing in April 2001, determining the aircraft was airworthy and ready to begin ESTOL testing; within a year, the team had a fully operational aircraft with which to move forward with their goals for AADS and ESTOL. The aircraft entered a modification period; the Team continued engineering and planning for the research development and demonstration phases.

In order to conduct the development and demonstration phases, it was necessary to design an autopilot system, an autothrottle system and a navigation system capable of providing aircraft positional data to centimeter level accuracy. A unique aspect of the X-31 test team was that the flight control law and autothrottle system designers were also members of the test team. The combination of control law and subsystem technology engineers and flight test engineers during actual flight test phases proved invaluable in efficiently, accurately and above all, safely, determining overall aircraft system performance real time and quickly resolving issues that arose.

In 2002 the test team concentrated on two missions: Up and Away ESTOL and flush air data system (FADS) testing. The FADS system was designed by Germany's European Aeronautic Defense and Space Company (EADS) to replace the traditional pitot static probe/flush port systems and tactical aircraft angle of attack (AoA) vane systems; it also provided sideslip angle, a new capability. Testing was completed at angles up to 70 degrees AoA, and in supersonic flight up to 1.18 Mach. In addition, FADS was tested during dynamic maneuvering to ensure that aerodynamic data tracked closely with the X-31A calibrated noseboom. This phase of testing ended in March 2003 and proved a promising solution for replacing conventional aircraft systems as well as the long, intrusive nosebooms that have been used for flight testing in the past. The FADS system is already planned for use on the Eurofighter and could some day find its way on an American aircraft.

The ESTOL approach is fully automated, flown at AoAs from 12 (normal approach) to 24 degrees. Typically, the approach starts at 5 degrees gamma and 12 degrees alpha; AoA is increased to the desired value after beginning the descent. Approaching the runway, gamma is decreased greatly and, at a tail height of 2 feet above the runway, the aircraft is derotated at to a normal landing attitude ensuring sufficient tail clearance at touchdown. ESTOL landings were first planned to a 5,000 MSL virtual runway programmed into the navigational systems at as a risk reduction measure. Auto-coupled landing functionality required the Team to design an autopilot system that could control the engine and all the flight control surfaces, including the thrust vectoring vanes such that the aircraft achieved the appropriate glide slope and runway alignment at the target de-rotation point. To incorporate the engine into the ESTOL flight control system, it was necessary to design an autothrottle system that modulated the engine to provide the necessary thrust, thus working in concert with the thrust vectoring vanes to provide the required pitch and yaw inputs. To command the thrust vectoring vanes appropriately, the flight control computers used engine parameters to determine estimated thrust. In-flight thrust calculations have historically proven to be difficult, however the estimated thrust calculation proved successful for the application of the ESTOL approach. In addition to the autopilot and autothrottle systems, a navigational system that could determine aircraft position within the required but heretofore unachieved accuracy of 2 centimeters was developed and integrated into the flight control system. To ensure the ability to safely fly only within the very tight approach tolerances, the Team developed extensive redundancy management schemes and embedded them through the integrated flight/navigation/engine control system. The ability to fly actual ESTOL approaches at high angles of attack and with such tight error tolerances is testimony to their redundancy management approach.

On November 19, 2002 the X-31 test team made the first successful landing to the virtual runway. This was a true milestone for the team, which had spent the previous two and a half years coping with the myriad of the difficulties encountered while designing the detailed and highly advanced systems needed for the autocoupled landing. After completing the first phase of testing to the virtual runway, modifications were made to the software to provide crosswind correction and minor approach parameter selectability. A final operational flight software load was released and night-testing began on 3 April, 2003. After completing numerous approaches to the virtual nmway, the first ESTOL landing to the runway at 12 degrees AoA (normal approach angle of attack) was completed on 22 April, 2003 and the first ESTOL landing with a derotation at 13 degrees AoA was completed on 23 April 2003. Overcoming marginal weather and severe financial and schedule limitations, the test team completed their ESTOL target of a 24 AoA automated landing on 29 April, 2003, thus meeting all ofthe program goals. In the span of 26 days the test team worked 14-hour days, 7 days a week, to achieved the culmination of 4 years of effort, all the while maintaining the utmost safety in high-risks cutting edge, X-plane flight test. The signiicance of the science the test team accomplished, and its impact on the future of the aerospace industry cannot be overstated; their perseverance, dedication and technical excellence are the true key to this triumph.