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Aviation History
1988
1988 - 0088.PDF
engine operations). The 737 family CFM56 is the -3. The extra power of the -5 version (as fitted to the A320) is not needed. A CFM56-3 engine on a 737-300 has nearly 8,000hr, and total time for the Franco-American engine (including -2s in Super DC-8s) is approaching two million hours. Boeing claims that CFM56-3 shop-visit rates, which are what really cost the airlines money, are 0-054/l,000hr, the lowest in airline operation including the exemplary RB.211-524E. Inflight shutdowns have been fewer than 0-01/l,000hr. Early Boeing concern that the low intake might invite foreign-object damage (Fod) has been dispelled in practice, and the Fod-repelling vortex bleed is not needed, for the flattened lower lip of the CFM56 intake appears to serve the pur pose. Fod rates are in fact lower than for the JT8D (0-01 u 0-02 removals/l.OOOhr). Reverse thrust is not as good as on the JT8D, and so the CFM56 737s have auto matic maximum braking, dialled in. Pilots do not need to "hold off" their feet. The Collins Efis cockpit is the same as that of 757/767 and common to all three 737 models, with different software. Boeing still offers the conventional elec tromechanical panel. "Some customers feel strongly about retaining that", says a Boeing engineer. The 737-300 kick-off customers like USAir, Southwest, and Orion did not want the glass cockpit, the push for which really came from Ansett and Lufthansa. Most customers now want glass. It costs perhaps $1 million more but, to quote Lufthansa, which was the first to buy 737s a quarter-century ago, "this is a long, long time aircraft". The Sperry autopilot is upgraded to full digital on all three models, driving "one of the best autothrottles" (Smiths). The flight management system (FMS, by Smiths/Lear-Siegler) and Honeywell laser gyro provide the navigation inputs to Efis, so-called LNav and VNav for lateral vertical flight, again owing much to 757/767 technology. So similar are the 757/767 cockpits that Boeing is often asked why not a single ticket for all the company's twins. With training allowances for handling differ ences this is not an impossible prospect. Boeing is pleased with the Honeywell laser gyro, which provides much more information for off-airway navigation, minimum fuel profiles, and windshear direction and alerting. In windshear the pilot just flies the pitchbar. "Honeywell think they've gone to Heaven, the number of laser gyros we're buying from them", says a Boeing engineer. A new version, smaller and lighter, is on the way. Navigation extras include time control, so that if ATC asks a pilot "can you make Chicago S beacon by three zero"? he can give an immediate answer and perhaps get an earlier landing slot. As one 737 pilot says, "They aren't supposed to give you preference, but they do". This is 4D or Required Time of Arrival (RTA) naviga tion, and it will be available from September. The new 737s come with steel brakes, which soak up braking energy faster than carbons in the lOmin turnround culture. Two overwing exits distinguish the 737-400 from its smaller sisters Carbons might save 2001b and are reliable, "but at the moment they aren't worth the redesign", according to one Boeing engineer. "They could happen when we've teethed them out on other aircraft". Simi larly the 737 is not yet ready for radial tyres. Despite being lighter and stronger they cannot yet be economically retreaded. Tyre pressure indication (Tpis) can be fitted as an option. The new 737s use more composites, now metal-matrixed for better lightning protection. Kevlar has been dropped for external surfaces because it absorbs mois ture which freezes at high altitudes and breaks it down. Spoilers, which get a hard bashing, have reverted from composite to tougher light alloy. Composites account for about 10 per cent of the new 737s' empty weight. Example applications are elevators, rudder, and dorsal fairing. Aluminium-lithium is still not being delivered in workable or affordable quan tities, and the 737, like other Boeing types, is made of 7000 and 2000 aluminium alloys. Corrosion protection is a great improvement on that of earlier 737s with wet sealing of fasteners, painting, and enamelling. As with the 747, 757 and 767, Boeing promises to meet the US Air Transport Association (ATA) standard of no significant corrosion for 20 years. Cabin plastics will meet the new fire- worthiness requirements, and Boeing's 737 people seem more confident than their 747 colleagues of complying with the "65kW" heat-release rule by August 1990. The new "sculptured" wide-look cabin is standard. Video monitors down the aisle show films and safety briefings without needing the shades pulled down. The galley is transverse aft, as in the 757/767, giving the staff more room. The cabin is quieter than that of the JT8D 737, with added soundproofing as well as a much quieter engine. External noise "footprint" is said to be one-seventh that of the -200's, meeting not only Stage 3 rules but allowing all three new 737 models to operate out of John Wayne Airport (Orange County, California) which has its own "Stage 4" noise- worthiness regulations. The -400 is offered for delivery in 1990 at a basic price of $33 million. E The 737 family CFM56-3s are "the most reliable engines going" 34 FLIGHT INTERNATIONAL, 16 January 1988
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