TAP, HSR, and the Early Development of SVS

In 1993, responding to anticipated increases in air travel demand, NASA established a Terminal Area Productivity program to increase airliner throughput at the Nation’s airports by at least 12 percent over existing levels of service. TAP consisted of four interrelated subelements: air traf­fic management, reduced separation operations, integration between aircraft and air traffic control (ATC), and Low Visibility Landing and Surface Operations (LVLASO).[1145]

Of the four Agency subelements, the Low Visibility Landing and Surface Operations project assigned to Langley held greatest signifi­cance for SVS research. A joint research effort of Langley and Ames Research Centers, LVLASO was intended to explore technologies that could improve the safety and efficiency of surface operations, includ­ing landing rollout, turnoff, and inbound and outbound taxi; making better use of existing runways; and thus making obvious the need for expensive new facilities and the rebuilding and modification of older ones.[1146] Steadily increasing numbers of surface accidents at major air­ports imparted particular urgency to the LVLASO effort; in 1996, there had been 287 incidents, and the early years of the 1990s had witnessed 5 fatal accidents.[1147]

LVLASO researchers developed a system concept including two technologies: Taxiway Navigation and Situational Awareness (T-NASA) and Rollout Turnoff (ROTO). T-NASA used the HUD and NAV display moving map functions to provide the pilot with taxi guidance and data link air traffic control instructions, and ROTO used the HUD to guide the pilot in braking levels and situation awareness for the selected run­
way turnoff. LVLASO also incorporated surface surveillance concepts to provide taxi traffic alerting with cooperative, transponder-equipped vehicles. LVLASO connected with potential SVS because of its airport database and GPS requirements.

In July and August 1997, NASA Langley flight researchers undertook two sequential series of air and ground tests at Atlanta International Airport, using a NASA Boeing 757-200 series twin-jet narrow-body transport equipped with Langley-developed experimental cockpit displays. This permitted surface operations in visibility conditions down to a runway visual range (RVR) of 300 feet. Test crews included NASA pilots for the first series of tests and experienced airline captains for the second. All together, it was the first time that SVS had been demon­strated at a major airport using a large commercial jetliner.[1148]

LVLASO results encouraged Langley to continue its research on integrating surface operation concepts into its SVS flight environment studies. Langley’s Wayne H. Bryant led the LVLASO effort, assisted by a number of key researchers, including Steven D. Young, Denise R. Jones, Richard Hueschen, and David Eckhardt.[1149] When SVS became a focused project under AvSP in 1999, these talented researchers joined their col­leagues from the HSR External Vision Systems project.[1150] While LVLASO technologies were being developed, NASA was in the midst of one of the largest aeronautics programs in its history, the High-Speed Research Program. SVS research was a key part of this program as well.

After sporadic research at advancing the state of the art in high­speed aerodynamics in the 1970s, the United States began to look at both supersonic and hypersonic cruise technologies more seriously in the mid – 1980s. Responding to a White House Office of Science and Technology Policy call for research into promoting long-range, high-speed aircraft, NASA awarded contracts to Boeing Commercial Airplanes and Douglas Aircraft Company in 1986 for market and technology feasibility studies
of a potential High-Speed Civil Transport. The speed spectrum for these studies spanned the supersonic to hypersonic regions, and the areas of study included economic, environmental, and technical considerations. At the same time, LaRC conducted its own feasibility studies led by Charles M. Jackson, Chief of the High-Speed Research Division; his dep­uty, Wallace C. Sawyer; Samuel M. Dollyhigh; and A. Warner Robbins. These and follow-on studies by 1988 concluded that the most favorable candidate considering all factors investigated was a Mach 2 to Mach 3.2 HSCT with transpacific range.[1151]

NASA created the High-Speed Research program in 1990 to investigate technical challenges involved with developing a Mach 2+ HSCT. Phase I of the HSR program was to determine if major environmental obstacles could be overcome, including ozone depletion, community noise, and sonic boom generation. NASA and its industry partners determined that the state of the art in high-speed design would allow mitigation of the ozone and noise issues, but sonic boom mitigation remained elusive.[1152]

Buoyed by these assessments, NASA commenced Phase II of the HSR program in 1995, in partnership with Boeing Commercial Airplane Group, McDonnell-Douglas Aerospace, Rockwell North American Aircraft Division, General Electric Aircraft Engines, and Pratt & Whitney as major industry participants. A comprehensive list of technical issues was slated for investigation, including sonic boom effects, ozone deple­tion, aero acoustics and community noise, airframe/propulsion integra­tion, high lift, and flight deck design. One of the earliest identified issues was forward visibility. Unlike the Concorde and the Tupolev Tu-144 Supersonic Transports, the drooping of the nose to provide forward visibility for takeoff and landing was not a given. By leaving the nose undrooped, engineers could make the final design thousands of pounds lighter. Unfortunately, to satisfy supersonic fineness ratio requirements, the postulated undrooped nose would completely obstruct the pilots’ forward vision. A solution had to be found, and the new disciplines of advanced cockpit electronic displays and high-fidelity sensors, in
combination with Langley’s HITS development, suggested an answer. A concept known as the External Vision System was developed, which was built around providing high-quality video signals to the flight deck to be combined with guidance and navigation symbology, creating a virtual out-the-window scene.[1153]

With the extensive general-aviation highway-in-the-sky experience at Langley, researchers began to expand their focus in the early 1990s to include more sophisticated applications to commercial and busi­ness aircraft. This included investigating the no-droop nose require­ments of the conceptual High-Speed Civil Transport, which lacked side windows and had such a forward-placed cockpit in relation to the nose wheel of the vehicle—over 50 feet separated the two—as to pose seri­ous challenges for precise ground maneuvering. As the High-Speed Research program became more organized, disciplines became grouped into Integrated Technology Development (ITD) Teams.[1154] An XVS ele­ment was established in the Flight Deck ITD Team, led by Langley’s Daniel G. Baize. Because the HSR program contained so many member organizations, each with its own prior conceptions, it was thought that the ITD concept would be effective in bringing the disparate organiza­tions together. This did not always lead to an efficient program or rapid progress. Partly, this was due to the requirement that consensus must be reached on all ITD Team decisions, a Skunk Works process in reverse. In the case of the XVS element, researchers from NASA Langley and NASA Ames Research Centers joined industry colleagues from Boeing, Douglas, Calspan, and others in designing a system from the bottom up.[1155]

Different backgrounds led to different choices for system design from the group. For example, at Langley, the HITS concept was favored with a traditional flight director, while at Ames, much work had been
devoted to developing a "follow me” aircraft concept developed by Ames researcher Richard Bray, in which an iconic aircraft symbol portrayed the desired position of the aircraft 5-30 seconds in the future. The pilot would then attempt to use the velocity vector to "follow” the leader aircraft. Subsequent research would show that choices of display symbology types profoundly coupled with the type of control law selected. Certain good display concepts performed poorly with certain good control law implementations. As the technology in both flight displays and digital fly-by-wire control laws advanced, one could not arbitrarily select one without considering the other. Flight tests in the United States Air Force (USAF)/Calspan Total In-Flight Simulator (TIFS) aircraft had shown that flightpath guidance cues could lead to pilot-induced oscilla­tions (PIOs) in the flare when control was dependent upon a flight con­trol system employing rate command control laws. For this reason, the Flight Deck and Guidance and Flight Controls (GFC) ITD Teams worked closely together, at times sharing flight tests to ensure that good concert existed between display and flight control architecture. To further help the situation, several individuals served on both teams simultaneously.

From 1994 to 1996, Langley hosted a series of workshops concern­ing concepts for commercial transports, including tunnel-, pathway-, and highway-in-the-sky concepts.[1156] The first two workshops examined potential display concepts and the maturity of underlying technologies, with attendees debating the merits of approaches and their potential utility. The final workshop, the Third XVS Symbology Workshop (September 4-5, 1996), focused on XVS applications for the HSCT. Led by the Flight Deck Integrated Display Symbology Team of Dr. Terrence Abbott and Russell Parrish, from Langley, and Andrew Durbin, Gordon Hardy, and Mary Kaiser, from Ames, the workshop provided an opportunity for participants from related ITD Teams to exchange ideas. Because the sensor image would be the primary means of traffic sepa­ration in VMC, display clutter was a major concern. The participants developed the minimal symbology set for the XVS displays to include the virtual out-the-window display and the head-down PFD. The theme of the workshop became, "Less is best, lest we obscure the rest.” [1157]

As flight tests would troublingly demonstrate, display clutter (excess symbology) would be one of several significant prob­lems revealed while evaluating the utility of displays for object (traffic) detection.