Technology update
New diesels for GA aircraft
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Morane Renault engine was flight- tested in a TB20 Trinidad.
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Aerospatiale Matra and Renault Sport's partnership to create a new diesel engine for general aviation aircraft is progressing. Socata is developing an aircraft based on its new MS fleet (a design extrapolated from the TB line) which could use the new power unit with deliveries in 2001. Thinking behind the project centered on the cost of Avgas 100LL and its limited availability at airfields, particularly in Europe, and also on the fact that as a leaded fuel it is regarded as environmentally undesirable. A turbocharged compression-ignition engine running on Jet A1 fuel was seen as offering a cleaner and cheaper solution. The market for such an engine is potentially very large.
Working on this basis, Aerospatiale Matra and Renault Sport began weighing up new candidate powerplants for all aircraft types equipped with piston engines (e.g., single and twin-engined airplanes, light helicopters, airships). These powerplants would use neither Avgas nor automobile gasoline, which was considered too dangerous. This left Jet A kerosene as an option, which at the same time overcame the problem of fuel cost, which along with other consumable items like lubricant and wear-prone parts, accounts for 60% of the cost per flight hour. The use of Jet A1 kerosene opened up the prospect of reducing this figure by 30-50%.
Morane Renault engine.
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Early stages in the 50/50 partnership date back to 1995. Aerospatiale Matra and Renault Sport formed a joint subsidiary, Societe de Motorisation Aeronautique (SMA) with headquarters at Les Ulis, near Paris, to develop the engine. The engine under development is designated the MR (Morane Renault) series. Morane is a name that links back to the earliest days of aviation. During the MR's development phase, SMA functions as a procurement structure for design studies on behalf of the two partners and is responsible for marketing and customer support. It will also carry out assembly and testing.
SMA explains that despite Renault's long experience in the design and production of piston engines for cars, commercial vehicles, and boats, the design departments of both partner companies rejected the possibility of creating an aeronautical derivative of car or marine engines. Jean-Marc de Raffin, SMA's President, explains the philosophy: "We started from scratch, but with a very precise and demanding set of specifications which notably included a time between overhauls (TBO) of 3000 hours, compared with 2000 hours for existing engines. We opted for a 'family' of versions, ranging from 180-300 hp, developed from a basic module with four cylinders, a 5.0-L capacity, supercharged direct injection, air/oil cooled, a propeller rotation speed of 2000 rpm, and component commonality throughout the range." It was also decided that the pilot should be able to fly an aircraft powered by such an engine using a single control without the need for "checking the inlet pressure, adjusting mixture richness, etc."
In March last year, the first 200-hp MR200 was subjected to its initial test flight, fitted to a Socata TB20 Trinidad. By the time of the Paris Air Show, it had flown for 40 hours, reaching a maximum altitude of 25,000 ft. More than 1900 static-test hours were accumulated with power units covering the entire projected power range of 180-200 hp (MR200); 250 hp (MR250) and 300 hp (MR300). Vibration was a notable problem that had to be met during development but de Raffin claims vibration level of the early-development flight engine is "below that of existing engines," with fuel consumption and performance "as expected." Engine weight and long-term reliability targets are said to have been achieved for the MR200 for which a certification date of early next year is scheduled, with the MR250 at the end of 2000 and the MR300 for 2001.
Work is also moving ahead with Hartzell to develop a propeller optimized for the new engines. "The prototype has been flying with a three-bladed propeller, but should have a two-bladed type after the Paris Air Show," says SMA. In the U.S., the GAP program to revive light aviation is under way and includes development of a diesel engine. Several companies are involved.
Stuart Birch
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