Perhaps the most unusual experiment ever conducted with the TSRV 737 was a flight test program for the Air Force in 1985. Air Force officials were apparently concerned that aircraft operating out of the new airport planned for Denver, Colorado would block critical transmissions between defense satellites and receiver antennas at Buckley Air Force Base, which was located just west of the airport site. The best way to determine if the airliners would really cause a problem was simply to fly a transport aircraft through the signal beam and see if it interfered with the transmission. The difficulty with this approach was that to intersect the beam, an aircraft had to navigate through a constantly moving threefoot square hole in the sky. The Air Force also wanted the tests completed in only three or four months. After an unsuccessful search for an aircraft that could perform that kind of demanding precision navigation and could conduct the flight test in that short a period of time, the Air Force finally approached NASA about using the TSRV 737. The 737 had an extremely precise guidance system that could be programmed to indicate course deviations as small as a few feet, and its velocity vector electronic flight displays allowed the pilot to see not only the attitude of the aircraft, but the exact flight path it was following. NASA agreed to support the Air Force effort, and Langley engineers began work on the project in the spring of 1985.

In order for the 737 to achieve the precise accuracy the Air Force tests required, the research flights were designed to use guidance from two different sources. The initial flight path for each run was designed on board the aircraft and put into the navigation computers, which then generated a magnetic course for the pilot to follow. The flight path had to be designed on board the airplane because the target was constantly moving. Each new test run required a different flight path. The second source of guidance came from an extremely precise Marine Corps fire control radar on the ground. The Marine personnel called small course corrections over a radio frequency to the research pilot, as well a a countdown to the intersection point with the target. The countdown was important because at the precise moment the airplane intersected the target, the Air Force wanted the 737 to pitch up to a 30 degree nosehigh attitude. Although the approach to the target had to be flown from the aft cockpit to control the flight path with the precision the tests required, the aft cockpit flight controls could only command half deflection of the 737's control surfaces. To get an rapid pitchup of 30 degrees, command of the airplane had to be handed over to the front cockpit. The countdown helped the research pilots execute the transfer of command and the pitchup maneuver at the exact moment the plane intersected the target.

A 1/8th scale model of th eBoeing 737 undergoing wing test in the Langley Research Center wind tunnel. This research tested flow physics over the aircraft wing. Over 700 pressure ports were placed on the right-hand wing to measure airflow.

To add to the challenge of the flight tests, all the electronic displays in the 737's aft cockpit malfunctioned just before the Denver flights. In 1985, the airplane was still equipped with the original, experimental, monochrome General Electric flight displays, and they had a history of maintenance difficulties. Unfortunately, there was not enough time to repair the displays and still get the Air Force tests done on time. So NASA research pilot Lee Person had to fly the tests with only an electromechanical Course Deviation Indicator (CDI) in the aft cockpit for course guidance. The CDI was a standard navigation instrument that indicated the aircraft's relative position to a selected course. If the needle on the CDI was centered, the plane was on course. If the needle was left or right of center, it indicated that the airplane needed to turn left or right to get back on the correct path. Since the CDI NASA used for the Air Force flight tests received its guidance from the Marine Corps fire control radar, however, it indicated much smaller course deviations than a standard instrument would. The autopilot control knobs were also modified to allow much more precise corrections in the flight path. Instead of the usual configuration, in which each click of a knob altered the airplane's track angle by one degree, the controls were altered so that each click changed the track angle only onetenth of a degree. As a result, Person was able to make corrections as small as one or two feet. [Ref 8-20]

Between the computergenerated flight paths on board the airplane, the course corrections radioed from the Marine fire control radar and the precision autopilot control of the airplane, the NASA research pilots were able to repeatedly find and intersect the moving, onemeter cube in space they were seeking. The Air Force was extremely satisfied with the results, and the NASA personnel who worked on the project were justifiably proud of what they had done. The task they had undertaken had been so difficult that not even military aircraft had been able to accomplish it. Yet the 20year old 737 at Langley and its crew of researchers had not only completed the mission successfully, but they had done it on budget, and on time. The 737 was proving itself a much more flexible and capable resource the early TCV program researchers had ever imagined it could be.