Customer: Fairchild Republic Co. (general design)
Type: sub-scale demonstrator for USAF two-seat jet trainer
Program: FRC-225 Next Generation Trainer
Powerplant: 2 x 220 lb. Garrett Microturbo Ames TRS-18 turbojet engines
First flight: 10 September 1981
The RAF Model 73 was a scaled flight demonstrator of Fairchild Republic's proposal for the Air Force's Next Generation Trainer (NGT) program. At the beginning of 1981, a request for proposals (RFP) was issued for a New Generation Trainer to Cessna, Fairchild Republic, General Dynamics, Rockwell International and Vought (teamed with MBB in Germany), which called for an aircraft with two turbofans, a pressurised cockpit and a gross weight slightly less than that of the T-37B, which had a gross weight of 2,982 kg.
In terms of performance, the USAF wanted an aircraft capable of 556 km/h at 7,620 m, with the ability to operate from 1,524 m runways in hot and high conditions. The Fairchild Republic Company of Farmingdale, one of the aerospace subsidiaries of Fairchild Industries Incorporated (which had been attemping to sell Fairchild Republic), contracted Ames Industries, in Bohemia, to produce a fiberglass scale model of their contender, which was called NGT Flight Demonstrator. Fairchild supplied accurate lofts of the external shape of the NGT design. Ames hired RAF to design the structure and systems and to conduct the flight test program. The scaled demonstrator was to be 62 percent of the size of the full scale aircraft, and made of composite materials.
Burt Rutan was ordered to develop and test-fly the demonstrator for Ames. The NGT demonstrator (designated Model 73 by Burt Rutan) was an H-tail, high-wing, design with twin engines and a pressurized cockpit. Its structure was the moldless composite sandwich method, using oriented uni-directional carbon fiber or fiberglass for facings and spar caps and rigid closed-cell foams for core. The Model 73 was designed, built, and flown to investigate the handling characteristics and configuration aerodynamics prior to the submission of the proposal for full-scale development. The design and prototype construction effort took eight months. The aircraft was shipped to RAF in early September 1981, and the first flight took place on September 10, controlled by Dick Rutan and powered by two Microturbo TRS-18 engines with 100 kg of thurst each. The scaled prototype could only accomodate the pilot, but if the contract was obtained, the full-scale production version would provide side-by-side seating for two. Rutan flew the Model 73 over 20 hours at Mojave, California, before turning it over to the Air Force. A number of USAF bases were visited to win support form USAF personnel for the design.
The demonstrator was used to collect information for the full-scale NGT in the areas of flight handling qualities, control surfaces and spin recovery. Within eight weeks RAF accomplished all the following tasks: flew four qualitative flights, coordinated the installation of a telemetered instrumentation system, flew 14 stability and control flights, developed and tested a spin recovery parachute, measured and ballasted the three-axis moments of inertia, developed a fuel transfer system for cg control, designed and incorporated several modifications, reduced, analyzed and presented all flight test data, wrote the qualitative flying qualities results, conclusions and recommendations, prepared a 220-page test report and an oral/video tape/slide presentation of the results. Working on a tight schedule, the final report and presentation was presented to Fairchild seven days after the last test flight. The flight demonstration program, which required only a total of ten calendar months (including two months of flight testing with 23 flight-test hours), showed that the stability levels and basic response of the air-frame closely matched the predictions. In addition, the general handling and stalling characteristics of the configuration were explored and refined to the satisfaction of the pilot community who flew it.
FRC used the low-cost demonstrator approach to reduce the risks inherent in the USAF Next Generation Trainer program and secure the T-46 contract for Republic. The flight-test data received by telemetry during the FRC tests proved to be of high quality, and comparable to data normally obtained from well-instrumented conventional means. In fact, the use of the manned, scaled flight demonstrator produced higher quality data than other methods, particularly for areas such as spin susceptibility and departure recovery. The scaled flight demonstrator was built within a schedule and cost framework that compared to conventional static-only wind-tunnel programs. However, the added benefits of dynamic stability data and pilot qualitative information resulted in considerable improvement in the value of the findings.
On 2 July 1982, Fairchild Republic was named winner of the NGT programme, with what became known as the T-46A Eaglet, or more affectionately as the "Thunder Piglet". The fact that FRC won the the T-46A contract was due in part to the excellent technical validation of the basic aircraft concept provided by the NGT Flight Demonstrator.
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The Next Generation Trainer program
The basic NGT Program was initiated in the 1970's with the requirement to replace the T-37. The Fairchild Republic Company started working on the program in August 1977 and responded to the Request for Information in April 1978 and November 1979. The funded program was initiated in 1980 when five contractors were given study contracts which were completed in October 1980. The Request for Proposal was issued by the USAF on October 7, 1981, with the response submitted on December 7, 1981. The Fairchild Republic Company was awarded a fixed price incentive contract for the design, development, fabrication, test, and delivery of two test aircraft, and two durability test articles for full scale development on July 2, 1982. Concurrently, the Garrett Turbine Engine Company was awarded a separate contract for 29 engines also for full scale development. Unfortunately, the NGT program was scrapped altogether when it was decided that existing trainers could be overhauled some more. A larger-scale trainer procurement program was later launched and known as the JPATS, resulting in procurement of a piston-engined type, less costly to operate and maintain.