The flight deck of a 757/767, incorporating systems that
the NASA 737 aided in research and development..

When the Terminal Configured Vehicle (TCV) program began in 1973, the air transport industry was facing some dramatic changes in aircraft design and operation. The development of the computer driven cathode ray tube (CRT) made a whole new kind of aircraft display possible, and the advancement of digital technology was preparing to revolutionize aircraft operations.

By the early 1970s, digital technology was beginning to be considered reliable enough to be incorporated into commercial transport aircraft. Wide body airliners had already begun to use digital equipment for numerous subsystems, and the next generation transport airplanes were expected to incorporate digital techniques in many more areas, including automatic flight control and guidance systems. The technology was attractive because it promised potentially significant savings in fuel consumption and cost of equipment ownership for the airlines. These savings were possible because digital equipment was lighter and generally required fewer components than analog systems. It was also proving to be highly reliable, easy to troubleshoot, and could often incorporate updates in capability through simple computer software changes. As a result, digital systems were predicted to reduce maintenance costs and equipment weight and volume as much as 2540%. Digital technology also offered the opportunity to control many aircraft guidance and navigation functions by computer, allowing much more precise and fuelefficient flight profiles.[Ref 3-1] This capability became increasingly important to the airlines as jet fuel prices soared throughout the 1970s. [Ref 3-2]

Computer driven CRTs, like those used for the displays in the aft cockpit of NASA's 737 airplane, had not been incorporated into any commercial transport airplanes when the TCV program began, but they were not an entirely new concept. Electronic displays had been used extensively in military aircraft since 1960, and they were considered important components not only for the SST design, but for the new NASA Space Shuttle, as well. Electronic displays could help reduce a pilot's workload by integrating separate instrument readings and pieces of information into a comprehensive picture of the flight situation. They were also considered vastly superior to conventional analog instruments for monitoring automatic guidance and navigation systems, which was an important consideration in the case of the space shuttle. [Ref 3-3]

The control tower at Wallops Flight Facility. Many of the NASA 737
aircraft research activities have taken place at this installation.

Prior to the 1970s, air transport operations were not considered sufficiently demanding to require advanced equipment like electronic flight displays. The increasing complexity of transport aircraft, the advent of digital systems and the growing air traffic congestion around airports began to change that, however.

In order to solve the capacity and noise problems of busy commercial airports, future airline operations were expected to include more complex approaches to airports and more closely spaced air traffic operations. Instead of the 10 mile, straight final approaches that were typical with the Instrument Landing System (ILS) that had been in use since the 1940s, future air traffic operations were expected to rely on steep, curved approach paths with final legs as short as a mile. Airlines were also beginning to look at improving low visibility landing capabilities of their aircraft, including the use of automatic landing systems. In order to accomplish all these maneuvers safely, airline pilots were going to need a much more accurate picture of the airplane's position at all times. They also had to be able to control the airplane's progress precisely and accurately monitor any automatic systems so they could take over if necessary.[Ref 3-4]

This kind of precise knowledge about the aircraft situation would have been difficult, if not impossible, to gather from the instrumentation in most airline cockpits at the time. [Ref 3-5] The average transport aircraft in the mid1970s had more than 100 cockpit instruments and controls,[Ref 3-6] and the primary flight instruments were already crowded with indicators, crossbars, and symbols. Airline pilots were having to monitor and manage more complex aircraft systems and operations, and there was a growing consensus among research and industry engineers that conventional instrumentation was simply no longer adequate for the job. What was needed were displays that could process the raw aircraft system and flight data into an integrated, easily understood picture of the aircraft situation, position and progress, not only in horizontal and vertical dimensions, but with regard to speed and time, as well.[Ref 3-7] This was one of the strengths of CRT displays, and it was the reason the NASA engineers at Langley wanted to include electronic display research in the TCV program.

The forward flight deck of the NASA 737 near the time of arrival at the NASA Langley Research Center in 1974. Note the profusion of gauges and dials and the yokes used to control the aircraft. The co-pilot's position, however, has received an upgrade of electronic flight displays for research into SST technology.