Top Technologies for 2000

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Every month, Aerospace Engineering publishes the latest technologies. The Aerospace Engineering editors have reviewed thousands of reader responses submitted during the past year and, based on your feedback, have chosen the top technologies. Of the winners, "the best of the best" are presented here followed by a list of the runners-up.

New diesels for GA aircraft

Moraine Renault engine.

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 is believed to offer a cleaner and cheaper solution, and 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 could not use Avgas or automobile gasoline, which was considered too dangerous, leaving Jet A kerosene as an option. Jet A kerosene 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%.

In March 1998, the first 200-hp MR200 was subjected to its initial test flight, fitted to a Socata TB20 Trinidad. By the Paris Air Show, it had flown 40 hours, reaching a max-imum altitude of 25,000 ft. More than 1900 static-test hours were accumulated, with pow-er units cover-ing 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 Jean-Mare de Raffin, SMA's President, claimed vibration level of the early-development flight engine was "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. An early 2000 certification date was scheduled, with the MR250 at the end of 2000 and the MR300 in 2001.

Diesel Air focuses on fuel economy

Diesel Air's DAIR 100 focuses on fuel economy.

In the UK, an aviation diesel program is under way. Diesel Air is developing a 100 hp two-cycle engine, the DAIR 100, with the design focus on fuel economy. The company reports that it has designed, built, and tested - for more than 1000 hours - several prototypes. Like SMA, it is planning a "family" of engines but with a maximum output of 600 hp. This first engine resembles a flat four or "boxer" engine but has only two cylinders, each with two pistons. The engine has two outboard crankshafts connected by gears to the propeller drive and accessories. According to the company, this flat plane layout ensures that the engine easily can be retrofitted in place of the popular Continental or Lycoming engines, using the same mounting points in many cases. The engine has liquid cooling for durability and the avoidance of "shock-cooling." It has single-lever control, eliminating separate fuel mixture and carburetor heat controls. Starting is via an integrated electric starter.

Diesel Air says work is progressing to refine the engine's performance and bring it to production status prior to flight trials. The company plans to release a small batch of engines under PFA (Popular Flying Association) regulations for customer evaluation. The first customer for the new engine is Airship Technologies Ltd., who will use the engine in a vectored-thrust propulsion unit. The company feels that the diesel engine offers the best specific fuel consumption of any prime mover, with the two-stroke cycle giving the best efficiency in that class. The engine will run on Avtur or diesel fuel.

Marshalling the X34

The umbilical connections between the X34 and L1011.

Marshall Aerospace in the UK is playing a major role in NASA's X34 reusable launch vehicle program. It has carried out modification work on a Lockheed L1011 TriStar to carry the X34, which was due for its first "live drop" last summer.

Marshall originally modified the L1011, which belongs to Orbital Sciences Corporation of America, in 1994. This effort involved major changes to the aircraft's structure, plus complex alterations to its interior to facilitate launch of Pegasus satellite launch vehicles for Orbital Sciences.

Now the aircraft is being used to carry X34, a NASA hypersonic space research vehicle. All design, modification, and testing of the aircraft systems were carried out at Marshall's UK facility. The X34 weighs about 50,000 lb and, according to Marshall, represents the heaviest object ever dropped from an aircraft in flight. It is carried on hooks. One Marshall design priority was that no single component failure would allow inadvertent release of X34, and that front and rear hooks would open within 50 m of each other. To detach the electrical and nitrogen supplies from X34 via a "diminutive" disconnect pocket, a swinging pantagraph cradle was incorporated into the design. The cradle, which retains three electrical cables and three nitrogen hoses (umbilicals), is attached to the aircraft via lanyard-operated disconnects with varying lanyard length allowing sequencing. The lanyards are secured to the cradle. If a lanyard breaks, a weak joint in the umbilical allows secondary disconnect.

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