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Aviation History
1991
1991 - 3368.PDF
eating airliners like the Lockheed Super Constellation, the Rare Bear continues to dominate Reno. After scouring^ the engine market, Rutan received the best offer from John Knepp, president of California-based Nissan subsid iary Electramotive. Knepp proposed a ver sion of the Electramotive VG30 engine based on the Vee-6 block used in the Nissan 300ZX car. The liquid-cooled, single- overhead-cam shaft engine has two valves per cylinder and a 3.21itre displacement. Running on methanol, each turbocharged engine will develop 754kW eventually. For all flights under taken to date, the aircraft has flown with two 600kW versions of the VG30. Without the large radiators, cooling ducts and tur- bocharger, the engine weighs in at around 145kg and is packed economically into the 0.6m di ameter of the tube-like nacelle. As indicated by the experi ences at Reno, the engines have proved problematic. Knepp says the failure in Nevada, traced to oil- pump failure, did, however, prove the structural integrity of the engine. He adds: "It ran for 60 seconds without any oil be fore the pilot shut it down. That says a lot about the engine." Electramotive prides itself on the development of a gearbox to convert the racing-car engine's 6,000rpm to an acceptable 2,200rpm. "Although this was not so different from the chal lenge faced by the Rolls-Royce engineers working on the Mer lin, we had to start from scratch. We searched for records of how people did it before, but there were hardly any. Most, if not all, of the engineers who worked on engines of that sort are gone." Electramotive's "re-invention of the wheel" took just over a year, and was introduced to the completed airframe in time for a first flight in March 1991. In early 1992, Electramotive will introduce the uprated VG30 and a new gearbox capable of transforming 8,000rpm into 2,300rpm. The use of methanol as a racing fuel creates a vastly different operating regime for both the crew and the engine. Because of methanol's low specific impulse (thrust divided by rate of fuel consumption per second) compared with standard fuel, the engine requires very high levels of boost to generate more than 700kW. To deliver about 745kW, the engine must be boosted to HOin (0.28m) Hg manifold pressure, because it needs twice as much methanol as gasoline to produce the same power. So, using methanol, which is derived from fermentation and does not detonate like gasoline, reduces the Pond Racer's range significantly. Standard aviation gaso line is used for ferry flights requiring programme changes to the electronic en gine-control processor (EECP) unit. The EECP takes pressure data from the manifold, fuel, oil, coolant and gearbox monitored through Magnetek pressure transducers, as well as digitised signals from potentiometers linked to the throttle and propeller controls. Problems with the unit, which works out timing and duration of the spark and injection, have occurred throughout the development programme, and were believed to be responsible for the rough running experienced during the Reno races. Engi neers believe the problems could be caused by electromagnetic interference generated by the close proximity of the microproces sor to the engine. As a result, it may be moved to a friendlier environment aft of the tyre in one of the undercarriage bays — virtually the only available space remaining in an other wise solid little aircraft. An alternative location — in the cockpit — has been ruled out, because longer wiring looms connect ing the EECP to the sensors would be equally susceptible to interference. Ray- chem, which produced hardened wiring systems for the B-2 strategic bomber, is lending its expertise to solve the problems. The engines drive specially modified Beech King Air propellers adapted by manu facturer Hartzell to control airflow shock waves in the transonic speed range at Mach 0.98. The stubby, 2m-diameter, four-bladed propeller units counter-rotate, the port pro peller clockwise and the starboard anti clockwise. PERFORMANCE Dick Rutan says that the Pond Racer "...is a very nice, agile aircraft with very rapid con trolled bank-to-bank turns with just aileron input. It really flies just like a jet." Early concerns about engine- out performance were dispelled when flight tests showed that, with one engine at 40% power and the other propeller wind- milling at flight idle, only 3cm (15%) rudder deflection is needed to counteract the yaw moment. During tests the aircraft required no trimming between 140kt and 250kt, demonstrating a very small static margin. Although the pilot's view is restricted by his position when taxiing, the airborne view is bet ter. Landing round-out holds no vices, despite the high touch down speed of 120kt. Approach speeds can be reduced partially by lowering the ailerons by up to 15%, to act as flaperons. The starboard aileron has an electri cally operated trim tab. WORLD SPEED RECORD "We've got the thing well and truly under way now towards phase two, the race and record attempt," says Pond. "Now we're getting it into where we want to win races and break that record. Hopefully, we will do that record attempt this summer." Pond has set up a new team to tackle phase two, "...the Rutans having done a wonderful job until now". Chino, Califor nia-based Steve Hinton, a warbird re- builder, will head the team, with Lockheed Skunk works engineering head Bruce Bo- land as head of engineering. Jim Dale, who saw the aircraft through its "blooding" at Reno, will be crew chief. Work on building up for the attempt will begin in earnest in April, 1992. The aircraft is now planned to be based at Pond's Palm Springs headquarters, and will fly to Las Vegas, New Mexico, or possibly Thermal, California, to make the record attempt later that year. "We're getting there and I'm optimistic," says Pond, whose eventual aim is to see Pond Racer-type aircraft competing for honours, like the Formula One racing cars of today. ' 32 FLIGHT INTERNATIONAL 25 December, 1991 - 7 January, 1992
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