A Convair 990 (CV-990) aircraft formerly used by NASA as a medium-altitude research platform is now a Landing Systems Research Aircraft (LSRA). It is being used to test space shuttle landing gear and braking systems as part of NASA's continuing effort to upgrade and improve space shuttle capabilities.
The aircraft is operated by the NASA Dryden Flight Research Center, Edwards, Calif., where it was modified into a Landing Systems Research Aircraft.
A series of tests with the CV-990 were conducted at Edwards and at the Kennedy Space Center, Fla., in 1993 and 1994 to study shuttle tire wear. The tests were very significant to the space shuttle program by allowing the Return to Landing Site (RTLS) crosswind limits of the orbiters to be increased from 15 to 20 knots. The tests at Kennedy were carried out on several sample runway surfaces that were evaluated for smoothness and tire wear. Tests results aided in the selection of a runway surface that allowed the landings at higher crosswind limits.
The LSRA is considered a unique test and research vehicle that is available for use in programs with other government agencies.
A landing gear retraction system has been installed in the lower fuselage area of the CV-990, between the aircraft's main landing gear. The landing capability of the CV-990 is unaffected by the test components which represent a space shuttle landing gear unit.
During tests, the landing gear unit is lowered by a high-pressure hydraulic system once the CV-990 main landing gear has contacted the runway. The tests allow engineers to assess and document the performance of the space shuttle's main and nose landing gear systems, tires and wheel assemblies, plus braking and nose wheel steering performance. As soon as an individual landing test is completed, the loads on the shuttle gear, up to 150,000 lbs., are reduced and the landing roll is completed on the CV-990's landing gear.
Test sensors give engineers data on tires under varying loads, slip angles, temperatures, and pressures and show how much wear the shuttle tires can withstand under a variety of operational conditions.
Landing gear components already manufactured for the space shuttle fleet are being used in the test program.
The landing gear of the CV-990 is always fully extended and serves as a backup for normal landing if a component of the shuttle gear system fails during the tests.
Many basic aircraft parameters are recorded during the test runs. In addition to instrumentation on the landing gear systems, video and high-speed film cameras are used to record the tests for thorough engineering analysis.
First check flight of the CV-990 with the shuttle test components at Dryden was in April 1993. Tests were subsequently carried out on the dry lakebed at Edwards, and on the main runways at Edwards and the Kennedy Space Center.
Additional flights by the CV-990 are planned at Edwards to test shuttle tires on the main runway at low air pressures, and to conduct additional tests on the natural lakebed surface.
The CV-990 was built by the Convair Division of General Dynamics Corp., Ft. Worth, Tex., in 1962.
The aircraft was used for commercial passenger service by American Airlines and Modern Air Transport until acquired by NASA in 1975 for use as a research aircraft at the Ames Research Center, Moffett Field, Calif.
The aircraft, which has a cruise speed of 432 kph (496 mph), is 139 feet long and has a wing span of 120 feet. Landing speeds of the CV-990 duplicate those of the space shuttle orbiters - about 230 kph (256 mph).
It is powered by four General Electric CJ805-23 engines, each producing 16,000 pounds of thrust.
The Space Shuttle landing gear test project is managed by the Johnson Space Center, Houston, Tex. Other agencies and organizations involved are: Shuttle Landing Facility, Kennedy Space Center, Fla.; Landing Impact Dynamics Facility, NASA Langley
Research Center, Hampton, Va.; Landing Gear Development Facility, Wright-Patterson AFB, Dayton, Ohio; B.F. Goodrich Facility, Troy, Ohio; and Rockwell International's Space Transportation Systems Division, Downey, Calif.; and a special LSRA panel formed by SAE's Aerospace Landing Gear Systems Committee.
The Dryden project pilot is C. Gordon Fullerton, a veteran of two space shuttle missions. Fullerton was also a member of the NASA flight crews that carried out the space shuttle approach and landing tests at Dryden in 1977 with the prototype orbiter Enterprise.