The TSRV 737's precise data gathering capability also led it to be chosen for NASA research projects that were not within the original parameters of the TCV/ATOPS program. Two different flight experiments, for example, focused on measuring and analyzing air flow over sections of the aircraft wing and fuselage in an effort to help engineers design more efficient transport aircraft in the future. A fullscale aircraft was an important tool in research areas involving air flow and drag analysis, because some of the measurements were sensitive to "scale effects." In other words, some of the flow characteristics observed on small wind tunnel models would not hold true for a fullscale aircraft in flight. The TSRV 737 allowed researchers to obtain accurate flight data that then could be used to update computer models and provide more accurate data to aircraft design engineers.

The Boeing 737 "flying laboratory" operated at Langley Research Center with flaps deployed during high-lift research.

In 1988, researchers used the 737 to measure the air flow around its fuselage as a first step toward evaluating the effectiveness of Large Eddy BreakUp (LEBU) devices. The LEBU concept involved mounting small airfoils on the airframe to help reduce skin friction drag. In order to determine the effect of the LEBU devices, however, researchers first had to have precise information about the standard airflows around a transport airframe. So the upper portion of the 737 fuselage was outfitted with numerous data gathering instruments including pressure belts, pitot rakes, hot wire rakes, hot films, and piezoelectric foil to measure the pressure, speed, flow, and turbulence characteristics of the airflow over the airframe. Data was gathered throughout a range of speeds, attitudes and altitudes from 10,000 feet to 25,000 feet and from Mach .5 to Mach .8. [Ref 8-6] A second set of flight experiments had been planned with LEBU devices installed on the 737 airframe. Further ground testing of the LEBU concept indicated that it would not actually reduce drag in flight conditions, however, so the research was discontinued. [Ref 8-7]

A second research project measured the air flow characteristics of the 737's wing and flap system to help engineers create more efficient highlift designs for future transport aircraft. The TSRV 737 had a typical transport aircraft flap system, known as the "tripleslotted Fowler flap." In addition to a slat that extended from the front of the wing, the aircraft had a threepart flap at the back of the wing that first slid back, and then down, when it was deployed. As the flap slid back and the slat slid forward, the area of the wing, and therefore the lift it could produce, increased. This was critical when the aircraft was flying slowly, such as on approach to landing or immediately after takeoff.

The tripleslotted flap system worked well. When Airbus Industries came out with a simpler, single piece flap for its A310 and A320 aircraft that had the same performance as the threepart design, however, NASA and the U.S. manufacturers realized that the European consortium had edged ahead of the U.S. in high lift technology. To try to correct this perceived lag in U.S. technology, NASA began a multiphased program in subsonic transport highlift research. [Ref 8-8]

One of the first steps in the program was to learn more about the flow characteristics of current transport highlift systems. This data could then be used to create more accurate and precise math and computational fluid dynamics models which, in turn, could be used by engineers to design better systems. In order for the models to be accurate, however, the data had to be obtained from a fullscale transport aircraft in actual flight conditions. Since the TSRV 737 was already set up for extensive and precise data gathering and it was kept at the Langley Research Center, where the highlift research was being conducted, it was the logical choice for the experiments.

For the initial flight tests in 1990, the 737's right wing and flap system were "tufted" with short pieces of string to help researchers visualize the basic air flow patterns across them in various flight configurations. In 1991, a second set of flight tests was conducted with more elaborate instrumentation on the three elements of one right wing flap section. Pressure belts recorded the surface pressure distribution over the flap segments, and instruments called Preston tubes measured the skin friction levels at various locations on the flap surfaces. A third set of flight tests in February 1992 used the same instrumentation, but expanded the test area to a fullchord strip that started at the front of the leading edge slat and ran back across the wing to the trailing edge of the flap. Another set of flights with even more precise instrumentation, including infrared imaging systems, hotfilm sensors and micro vortex generators, was scheduled for the end of 1993. Ê[Ref 8-9]

The large gaps in between the flight tests were one of the main drawbacks to using the TSRV for flight experiments. So many research projects wanted flight time on the airplane that it was difficult to get a place on the schedule. Nevertheless, the data obtained from the 737 flights was very useful to the ongoing highlift research at NASA. The flight test data corroborated some wind tunnel test results, corrected the predictions of others, and gave research engineers additional information about the dynamics of highlift flow physics. That information could help manufacturers design more efficient aircraft and, at the same time, restore the United States' competitive edge in the field of highlift technology.