The RFB Fantrainer (or Fan Trainer) is a two-seat flight training aircraft which uses a mid-mounted ducted fan propulsion system. Developed and manufactured by German aircraft company Rhein-Flugzeugbau GmbH (RFB), it has been used by the Royal Thai Air Force. Development of the Fantrainer commenced during the 1970s. In Germany, it was selected as the winner of a competition for the Luftwaffe's Basic Trainer Requirement, having beaten both the Pilatus PC-7 and Beechcraft Mentor. However, no orders were forthcoming from Germany as it had committed to buying American fighters (F4 Phantom and F-104 Starfighter) which included a deal for pilot training in the United States. At one point, German flag carrier Lufthansa also reportedly took an interest in the aircraft, noting its jet-like handling. Pilots have confirmed the type to be relatively fuel-efficient and capable of providing a true "jet feel" for a reasonable price. The Royal Thai Air Force operates the FT400 and FT600 versions, using it to train ab initio pilots who then went on to fly the Northrop F-5E fighter aircraft.
Development
Origins In the 1960s the German company Rhein Flugzeugbau developed an interest in aircraft powered by ducted fans integrated into the fuselage, flying a pair of modified gliders as flying testbeds in 1969 and 1971. During 1970, the company announced that it had embarked upon a new project to develop a two-seat ducted-fan military trainer, intending to offer an aircraft that possessed jet-like handling at a low cost. In March 1975, RFB received a contract from the German Defence Ministry to produce and fly a pair of prototype Fantrainers; these would be evaluated as replacements for Luftwaffe's existing fleet of Piaggio P.149 initial trainers. According to aerospace periodical Flight International, the initial production process only took seven months to complete a single prototype. On 27 October 1977, the first prototype (registration D-EATJ), powered by a pair of EA871 110 kW (150 hp) NSU Wankel engines, made its maiden flight. The EA871 engine installation proved to be troublesome, thus the second prototype (D-EATI) was furnished with a single 310 kW (420 shp) Allison 250-C20B turboshaft engine, making its first flight on 31 May 1978. The second prototype crashed on 7 September 1978, which resulted in the first prototype being modified to Fantrainer 400 standard, being furnished with an Allison engine and revised air intakes. The Fantrainer was evaluated by the Luftwaffe against the Beechcraft T-34C and Pilatus PC-7 turboprop powered trainers, but although it was considered to be the most suitable of the three aircraft, being cheaper both to purchase (at DM 1 million per aircraft) and to operate, no orders resulted as it was decided that the Piaggio P.149 was still adequate for the Luftwaffe's needs. Despite failing to secure an order from the Luftwaffe, during May 1982, RFB announced that it was set to commence mass production of the Fantrainer within the next few months. By this point, the prototype had accumulated 500 flight hours, which included a five week-long marketing tour around America, have flown an average of 6.5 hours per day during this sojourn. While the company had forecast a wider market for trainer aircraft of roughly 5,000 aircraft over the following decade, it stated that it was aiming for an initial market share of 4 per cent (equivalent to 200 aircraft) due to the unorthodox nature of the Fantrainer. During 1983, the prototype was refitted, its seven-bladed ducted fan being substituted for a five-bladed production standard counterpart, while the cockpit was also improved; the changes reportedly enabled a significant noise reduction and superior external visibility.
Production
The aircraft has been produced in two principal models, these being the Fantrainer 400, powered by a 545 shp (406 kW) Allison 250-C20B, and the Fantrainer 600, which was powered by a 650 shp (480 kW) Allison 250-C30. According to aerospace publication Flight International, the market had a more favourable reaction to the Fantrainer 600 during the 1980s. In August 1982, the Royal Thai Air Force signed a contract with RFB to purchase 47 aircraft, 31 of the model 400 and 16 of the 600. Upon introduction, they were assigned to the 402 Squadron and used as a step-up trainer for their future F-5 Freedom Fighter pilots. The step-up characteristic of the Fantrainer is generally one of its main advantages; the abilities of the Fantrainer in a training capacity is such to almost fully cover a pilot's entire syllabus, only needing to be supplemented by an Advanced Trainer for the purpose of building direct experience with high performance jets. The first four aircraft were constructed in Germany while the remaining aircraft were assembled in Thailand from kits shipped from RFB, which were assembled at a peak rate of six Fantrainers per month. After an initial period of operation, the RTAF elected to replace the aircraft's glass fiber wings with locally-produced aluminium wings, even when the original fiber glass wings proved to endure well in the hot and humid Thailand weather, which was a main concern of the manufacturer. During the 21st century, FanJet Aviation GmbH set about reviving production of the Fantrainer 600, aiming to re-introduce the type under the new name Fanjet 600. During 2010, the company purchased all documentation related to the design, testing and type certification of the original aircraft, followed by the acquisition of associated tools, spare parts inventory, and the trademarks for Rhein-Flugzeugbau and Vereinigte Flugtechnische Werke. FanJet Aviation believes that, following the adoption of a glass cockpit to modernise it, the aircraft remains both valid and cost-competitive for current-day pilot training purposes compared to contemporary jet-powered competitors.
Design
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