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Aviation History
1988
1988 - 0086.PDF
Left White epoxy paint in the 747-400 hold shows Boeing's new anti-corrosion care. Right Boeing's Elizabeth Reese checks the 747-400's first production carbon winglet n.m. Fuel measurement is digital, more accurate, and with more redundancy. Like fuel management it is automatic, with no crew action required during the cruise. A redesign of the outboard tanks, combining two into one, has taken care of previous airspeed limits (330kt) and tank- sequencing procedures. Undercarriage: The 747's five-truck, eighteen-wheel undercarriage architecture is unchanged but the wheels, tyres and brakes are different. The wheels are 22in diameter (2in more) to house the fatter carbon brake packs; the tyres are lower- profile to give the same overall diameter. This is the sixteenth model of 747 wheel, each one strengthening up previous crack- prone weak spots found in service. Radial tyres are not an option yet. Boeing and the airlines agree that cross- plies are more damage-resistant and retreadable. British and French customers have specified what could prove to be a most important new safety and reliability inno vation: cockpit tyre pressure indication (Tpis). By Labinal of France, Tpis costs about $100,000 per aircraft, which could be less than the cost of one tyre-burst inci dent and its effects. Tyre failure has never caused the loss of a 747 hull, but the new device gives double assurance by telling the pilot (on the synoptics screen, like door status) if pressures are below or above safe limits. Twenty 747 operators are talking to Boeing about Tpis. The brakes are Goodrich carbon, instead of steel, saving 8001b or the equiv alent of six passengers. Though much more expensive than steel, and requiring torque control, carbons last longer and save worthwhile weight on long ranges. Some customers have obtained a guaran teed price per landing. Structure: The 747's structural design may have had testing moments, and involved the airlines in some expensive inspections and repairs, but structural failure has never appeared in the "hull- loss" cause column. The 747's remarkable damage-tolerance and strength have in fact allowed more than one 747 crew to get home in circumstances which might well have been fatal. Examples are the US airline 747 which struck approach-light gantries while taking off from San Francisco, returning with two undercarriage trucks wiped off and a steel girder penetrating the floor up into the fin; and a Taiwanese 747 which the crew allowed to fall out of control violently enough to snap off the outboard elevators. The Japanese 747 structural failure was attributed to poor repairs after a heavy landing, rather than to structural design. Boeing has beefed up and corrosion- treated all structural areas which have given trouble. For example, the great pear- sectioned front end now has thicker frames, skins and doublers. These are the "Section 41" modifications which airlines had to make to higher-time aircraft when cracks were found in some frames. The floor in this area has also been strengthened, as it has in the main cabin to avoid the major mid-life reflooring task which has been unpopular with operators. Says one airline engineer: "Boeing's inadequate corrosion protection was the problem, especially against galley and lavatory spillage. We've had to change all our 747 floors." The 400 will have better protection including more wet-sealing of fasteners, more painting, and a waterproof membrane or dampcourse. Boeing is well aware of its earlier manu facturing shortcomings, and in fact most of the structural improvements in the 747-400 have already been progressively incorporated in all 747 production, and better corrosion protection is apparent in all Boeing models. The 747-400 "economic design life" is 60,000hr, 20,000 flights, or 20 years. More than sixty 747s have so far clocked up 60,000hr. Cabin: The 747-400 cabin has been restyled to give an even wider "look", and remarkably this has been achieved with bigger baggage lockers or bins (see draw ing, page 23). Customers expect Boeing to meet the new fireworthiness rules—plastic panel ling with a heat-release of 65kW/m2—in the first aircraft delivered next year. The aircraft manufacturers and suppliers are required by the airworthiness authorities to install "65" materials by August 1990 but are allowed "100" materials mean while. Airbus has already said that it cannot meet the 1990 deadline with "65" materials. A senior Boeing engineer admits that this target is tough. The airlines want 65 this year. One airline engineer says: "We certainly don't want to have to renew all our panelling a year after delivery". Everyone's objective is the same: to carry passengers in cabins made of nonflammable, nonsmoking and nontoxic plastics. This could be done today, but only with materials which nobody can easily fabricate or afford. Meanwhile, Boeing is making the 747-400 cabin out of phenolic rather than epoxy plastics to make it fireworthier, even though the 747 cabin has never been cited in the hull-loss or fatalities columns. Customers are specifying the smoke and toxicity standards set out by Airbus in its ATS.1000 document, which has become an industry standard in the absence .of US or European rules. Boeing has matched ATS. 1000 with its own similar internal guidelines. Seats are the customer's choice. It seems that seat suppliers are still having a hard time beating steel frames with carbon composites. Metal still wins on strength (to meet the new 16g rule) and on fireworthiness, maintainability, and price. One airline has specified metal seats on the calculation that the cost of the extra weight even in a 550-seat aircraft will be recouped in lower maintenance. The 747-400 can be plumbed for up to 26 lavatory locations, now vacuum-flush units which are cleaner, odourless, and more corrosion-resistant. The greater flexibility of location will ease seating reconfiguration. Right aft is an optional upstairs loft for resting cabin crew. Typically it has eight bunks and two seats, with variations avail able. This little penthouse is in addition to the pilots' two bunks on the flightdeck. It saves the 20-odd passenger seats dis placed by the "Portakabin" which some longhaul 747 operators fit in the aft main cabin. The first has been fitted in a Thai 747-300. Smoke extraction, a growing problem as nonsmokers become more vociferous, has been improved by revised zoning and circulation of cabin air. The 747-400 has five instead of three air-conditioning zones, with a higher ventilation rate. 32 FLIGHT INTERNATIONAL, 16 January 1988
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