Since the focus of the work was to improve operations for commercial transport airplanes, the researchers at Langley argued that the program needed to include flight tests with a transportsize CTOL aircraft. The only large aircraft owned by NASA were a C141A and a Convair 990 located at the Ames Research Center in California. The cost of using one of these fourengine airplanes for a 68 year research program was too high, however, and all the other NASAowned airplanes were too small, or lacked the capabilities necessary to carry out the TCV research. Langley personnel working on the project also believed that in order for the results of their research to be accepted and used by the air transport industry, the technology had to be tested and developed on a commercial transport class airplane.

The best candidate for a test airplane appeared to be either a DC9 or a Boeing 737, since both had adequate room and capability as well as manageable operating costs. The Boeing 737 was Langley's number one choice, however, since it had a slightly wider fuselage and an advanced, highlift flap system. Money, however, was extremely tight. The market value of a used 737 in 1972 was about $3.5 million, but the Boeing Company had one particular 737 that its sales people said they might be willing to sell for substantially less.[Ref 2-11]

The Boeing aircraft was the original prototype 737100, used for FAA certification tests on the model. The Dash 100 model, which had a length only one foot longer than its wingspan, was nicknamed"Fat Albert" because its shape was so stubby compared to most airliners. The prototype flew for the first time on April 9, 1967 and had only 978 flight hours on its airframe. Since the first order for 737100s was from Lufthansa Airlines, Boeing had designated the prototype as PA099: PA for Lufthansa, and 099 as the last one in a block of 100 aircraft numbers Boeing had reserved for the airline. The prototype was never sold, however, because it was only certified for experimental use. With all the holes, wiring and other modifications that were made in the airplane for certification tests, bringing it up to the standards of a commercial transport airplane would have been too expensive. Boeing used the airplane for a few additional flight tests and then simply set it aside.[Ref 2-12]

In fact, when the Langley engineers first travelled to Seattle to look at the plane, it was a dismal sight. The engines had been removed, and the airplane was sitting at the end of the ramp at Boeing's facility in Renton, Washington with cement blocks hanging off the engine pylons to keep the airplane from falling on its tail. The interior had been stripped out, and where the cockpit instruments should have been, there were only bundles of wire dangling from the remains of a panel. Nevertheless, the plane had several characteristics that appealed to NASA. First, Boeing was willing to bring it back to flightworthy status, complete with overhauled engines, and sell it to NASA for only $2.2 million. Second, while the modifications and special instrumentation wiring and plumbing in the airplane were useless for an airline, they made PA099 more suitable as a research airplane.[Ref 2-13]

Flight deck of the future NASA Langley 737 testbed aircraft as it appeared after completion of Boeing prototype test and before refurbishments for NASA. Its engines had been removed and the interior, including the instrument panel, had been stripped.

The Boeing plane also had one other significant advantage. Boeing had been awarded the contract to build the U.S. Supersonic Transport (SST) aircraft, which included advanced avionics, displays and flight control systems. The program had become very controversial, however, with substantial opposition from communities and groups who were concerned about the environmental impact the plane would have. Finally, on March 24, 1971, Congress voted to cancel the SST.[Ref 2-14] But in an effort to keep all the technology development efforts for the plane from being wasted, Congress authorized Boeing to do a small amount of followon research in a number of technology areas. Two of these areas were advanced electronic displays and digital flight controls.

Boeing had contracted with the Department of Transportation (DOT) to develop the SST Advanced Digital Electronic Displays (ADEDS) and the Automatic Guidance and Control (AGCS) digital flight control system to a point where they could be flight tested. The Boeing plans called for very limited flight testing of the experimental equipment, after which the equipment would be returned to the DOT.[Ref 2-15]

When the Langley engineers approached Boeing about a 737, however, they and Boeing both realized the potential benefits of integrating this advanced equipment into the prototype 737 as a research airplane for NASA. NASA would get the opportunity to experiment with the most advanced display and flight control technology available, and Boeing would get a chance to test the equipment in a specially equipped research airplane with an extensive datagathering capability.

The DOT, in the fall of 1971, had asked NASA to support the Boeing followon tests of the SST electronic displays.[Ref 2-16] To put the DOT-owned display and flight control equipment in a NASA airplane on a permanent basis, however, would require a cooperative agreement between NASA and the FAA.

While cooperative efforts between the two government agencies were not unheard of, the separate roles and responsibilities of the two organizations with regard to national problems in aeronautics and civil aviation were not clearly defined. The agencies also had different mandates. NASA was a research agency, tasked with furthering new technology. It did not have to worry about certifying production equipment, or regulating its operation. The FAA's primary responsibility, on the other hand, was to keep the national air traffic system operating smoothly and safely on a day to day basis. Consequently, the two agencies' research priorities and approaches often differed.

There were some people in the FAA who thought that NASA should concern itself only with airplane technology and should leave issues such as more efficient operating procedures for the terminal area to the FAA. The problem was that the FAA had fewer resources to devote to such research. NASA's aeronautics research budget and personnel typically exceeded that of the FAA's R&D department by a magnitude of at least 10. At the same time, NASA research in new air transportation technology and procedures would not have any practical impact without the FAA's involvement on some level, since the FAA had to approve any changes in air transport equipment or operations. But while it may have made sense for the agencies to work together on the problems, there were still areas of tension over turf, priorities, and working relationships that persisted long after a cooperative working agreement was signed.[Ref 2-17]

In May 1973, a cooperative agreement between NASA and the FAA was reached. In exchange for putting the SST technology in the new NASA airplane, NASA agreed to allow Boeing to use the plane first to conduct the DOT flight tests of the SST equipment. After that, the FAA would be entitled to up to 25% of the aircraft's flying time for its own research projects.[Ref 2-18]

On July 26, 1973, NASA officially purchased Boeing's prototype 737100 aircraft. Boeing spent most of the next 10 months outfitting the aircraft to NASA's specifications and completing the DOT flight tests.[Ref 2-19] Wearing its new tail number of N515NA, the airplane finally arrived at Langley to begin its remarkable career as NASA's Transport Systems Research Vehicle (TSRV) on May 17, 1974.[Ref 2-20]