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Aviation History
1986
1986 - 0535.PDF
The chances of this happening are real, for in order to achieve the 28,000-mile range required for the 12-day trip, system redundancy has been eliminated to save every last ounce of weight. Voyager has 17 fuel tanks with a total capacity of 1,489 US gal, weighing 8,9341b, and allowing one day's reserve. Exact fuel carried will depend on prevailing winds. At take off, 80 per cent of Voyager's weight will be taken up by fuel. Wing, canard, boom tanks, and fuselage all carry fuel, fed to the engines via a collector tank to the left of the pilot's legs. Fuel transfer, via two rotary selectors, will be calculated using the sidestick's position indicator, and a spirit level to maintain correct e.g. and deck angle. A panel-mounted computer ensures exact fuel transfer monitoring. The Voyager's structure is totally composite. Wing spars and skin are oven- cured Hercules Magnamite graphite with Magnamite sandwich. A Hexcel honey comb core is used for most of the aircraft's skin. Voyager's structural flexibility is essen tial for strength in turbulence. While The strength of Voyager lies in its flexibility. While the wings droop on the ground, increased dihedral effect allows positive spiral stability in flight Burt Rutan estimates that up to 30ft flex is tolerable, excessive bending is undesirable. The outboard wing tanks have been subdivided, allowing fuel to be retained at the wingtips to counter wing bending as fuel burns off. Early flight-tests in 1984 proved that Voyager had adequate range. Take-off and climb performance was better than esti mated, but the search for the right engines added over a year to the project. After much research, the liquid-cooled 110 h.p. Teledyne Continental IOL-200 was chosen as the rear engine, capable of deliv ering a specific fuel consumption of less than 0-41b/h.p./hr at 20-30 per cent power. It drives a variable-pitch reversing propeller designed to produce drag for descent and landing. Voyager is the first aircraft to fly with this engine, and estab lishing its reliability and performance is essential. The front engine is a standard air- cooled Teledyne Continental VO-240 engine driving a variable-pitch feathering propeller. This engine will be shut down after the first two days and, unlike the rear engine, can be restarted in flight. The propellers, which are controlled by elec tronic switches, were manufactured in West Germany. Engine oil can be replen ished from on-board storage tanks. Voyager's cabin measures only 2ft wide by 7ft long. The pilot sits in a specially moulded seat enclosed by a close fitting bubble canopy. The nonflying crew member lies on a bed with little view outside except for two small side windows. The combination of sunlight, cloud, and a flexing structure makes for a nauseous ride. "It's rather like being below decks at sea," says Yeager, whose petite build is clearly an advantage in the confined space. The crew have worked out a routine for changing places in flight, which must require the skill of a contortionist to achieve. "It really makes your eyes water," says Rutan. Neither will be able to move to any great degree during the flight, and exercising limbs will be difficult. Different types of food packs are being evaluated. Sealed packs of bland food stuffs seem best. Highly spiced food is definitely unwise. Plenty of drinking water will be essential to avoid dehy dration and blood coagulation, and water supplies will be carried beneath the rear cabin; 20 per cent of the cabin space is taken up with water, food, oxygen, radios, and equipment. A portable electric heat ing element, designed for camping, can be used to boil water and heat food. Special flight suits are being developed which fit loosely and minimise chafing. They will probably be more like pyjamas, made from material that will maintain body temperature and absorb sweat. Jeana King develops Voyager avionics King Radio has worked closely with the Voyager programme to develop a comprehensive avionics package which is reliable and ultra-light. None of the avionics aboard have been duplicated and there is no backup for the King 150 autopilot which has been modified for Voyager's unusual handling character istics. Rutan says that a serviceable autopilot is essential for flight. Due to its flexible structure the aircraft is a handful to fly in turbulence; not some thing to relish after several days in the air. "It has to work," says Rutan. "We just can't lose it. If we do, the mission will have to be aborted, unless we are very close to the finish." This package is now installed and includes a King four-colour digital weather radar with phase array antenna, vital for avoiding weather and turbulence, a KNS-660 Omega/VLF for instant position fixing and point-to- point area navigation, and a KHF-990 HF radio for long-range commu nications. Line-of-sight VHF commu nication is via a KX-165 nav/comm which includes a VOR/ILS facility and a KT-76A transponder to assist easy radar identification. Heading and atti tude reference is achieved using a KCS- 55A gyro-stabilised heading reference system. Location of radio antennas is critical with composite aircraft, and the HF antenna has been mounted so that it sticks out behind the port tail boom. The H-field Omega/VLF antenna is mounted in the upper skin of the sleep ing compartment which, being made of glass/aramid fibre, is electronically transparent. The weather radar antenna is mounted in the nose of the starboard boom tank, while the VHF aerial is buried in the starboard vertical fin. A portable backup VHF will be carried in the cockpit. The antenna for the transponder is mounted under the aircraft and its drag is negligible. The Argos satellite-based data collection system will be used to track en-route progress. This system, in service since 1979, is primarily for envi ronmental use. The satellite system will act as a data link between the aircraft and Voyager Mission Control in the Air & Space Museum in Wash ington. This position information will then be regularly transmitted to the Voyager crew by HF radio, thus acting as backup and update for the Omega/ VLF. Voyager's crew will not be able to receive navigation information directly from the satellite, but should a ditching or emergency landing occur, the satellite system can assist rapid location. FLIGHT INTERNATIONAL, 8 March 1986 39
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