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Aviation History
2002
2002 - 0203.PDF
General aviation Advantages claimed for modern digitally controlled, turbocharged diesels over con ventional engines include 30% to 40% lower specific fuel consumption, turbine like single-lever control and constant-rpm operation, simplified maintenance and longer overhaul intervals. In Europe, the wider availability and lower price of Jet A fuel compared with avgas are also factors which favour diesels. In November, Austria's Diamond Aircraft began flight-testing the DA40-TDI version of its Diamond Star four-seater, powered by a Thielert TAE 135 direct- injection turbo-diesel. The German-made lOOkW engine is scheduled for European certification this month, with aircraft certi fication planned for October. Initially, the aircraft and engine will only be marketed in Europe. According to Diamond, replac ing the basic DA40's 135kW Lycoming IO-360 with a diesel results in fuel cost sav ings of 80%, when the lower fuel con sumption and fuel price are combined. Similar savings are claimed for SMA Engines' SR305, also a flat-four, direct- injection, turbo-diesel but rated at 170kW. The Jet A-burning engine received Euro pean certification in April last year, and US approval is imminent. A joint venture between EADS, Renault and Snecma, SMA is working with EADS Socata to certificate the SR305 in the TB20 four-seat light air craft. Engine production is to begin in France "no later than September", says EADS Al Beech, sales director of SMA's US arm. Socata is In the USA, SMA is working with Embry- still Riddle Aeronautical University to re- planning a engine the Cessna 182 with the SR305, and version of award of a supplemental type certificate its TBGT (STC) is expected in the third quarter. In series addition, the company is working with powered by Cirrus Design and Maule Air on new SMA diesel-powered versions of their light air- Engine's craft. SMA says the Cirrus SR21tdi and SR305 Maule MX-9-230 are scheduled for certifi- diesel cation in the fourth quarter, but Cirrus says it will wait until production engines are available before beginning its programme. Single fuel or diesels "The biggest market in the USA is the after- market," says Beech. "The original equip ment manufacturers are hesitant to go into new technology. Cessna, [New] Piper and Raytheon will wait and see, but they will not wait very long. They are already talk ing to us." In the USA, where fuel cost and avail ability are less factors than in Europe, he believes diesels will sell initially to cus tomers interested in new technology. "The key is to get a couple of STCs under our belt and then start flying people," he says. Criticisms levelled against diesels include high cost and lack of support. Beech admits the SR305's base price is $52,000, against $25,000-530,000 for a comparable Teledyne Continental avgas engine, but adds that the target time between overhauls (TBO) is 3,000h, com pared to 2,000h for a piston engine. Tackling the cost issue was the principal goal of NASA's General Aviation Propulsion (GAP) programme, under which Continental began development of a 150kW diesel intended as a direct replacement for its IO-360 piston engine. After much delay, the technology demon strator is expected to fly in a Cessna 337 testbed in February, replacing the forward engine. GAP's goals for the diesel engine include a 50% lower cost, 75% longer TBO and 25% lower fuel consumption compared with the piston engine. The GAP programme, under which NASA was also sponsoring the develop ment of a small turbofan by Williams International, ended in 2000, but work on both engines has continued under co-oper ative research and development agree ments which are scheduled to end soon. Continental is then expected to take its new diesel to certification, with the engine likely to become commercially available within the next two to three years. Even if the cost and support issues can be overcome, the desire for a single fuel could still stand in the way of the USA fol lowing the European lead towards diesel engines. "I don't know where diesels will go," says the EAA's Lawrence. "The US goal is one fuel. If we have to have separate avi ation diesel [and unleaded avgas] supplies we are back to the old problem." • www.flightinternational.com FLIGHT INTERNATIONAL 22-28 JANUARY 2002 37
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