Boeing 737-400 History

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 In December 1985, Boeing decided to offer a 737 twin jet with a 10-foot (290-cm) fuselage stretch
 that would add three more seat rows, or 18 more passengers in six-across when compared to the
 earlier -300.

 Boeing engineers had been studying a larger 737 for a number of years - one with a fuselage
 lengthened just enough to bring capacity to about 145 seats in mixed-class service. Airlines
 operating the -300 model had been pleased with its low fuel consumption and high dispatch
 reliability, and urged the development of an airplane with slightly more capacity, but one which
 would blend easily into existing fleets of 737s.

 Airlines especially liked the fact that the 737-400 is a straightforward derivative of the 737-300 so
 that -300 pilots could be cross-qualified. Flight crews who can operate both a -300 and -400 give
 airlines great flexibility in scheduling and subsequent savings in fleet operations.

 The -400 was formally launched in June 1986 to augment the fleets of carriers needing more
 capacity to meet traffic growth. Roll out of the first 737-400 was Jan. 26, 1988. Following an
 eight-month flight test program, first delivery was Sept. 15, 1988, to kickoff customer Piedmont
 Airlines.

 The -400 twin jet retains basic systems commonality with the -300. Thus, it is a short-to-medium
 range airliner with increased passenger seating, low noise levels, low fuel consumption and high
 dispatch reliability.

 Apart from the longer fuselage, other changes from the 737-300 are engines of slightly higher thrust,
 strengthened wing components and landing gear and the environmental control system (the airplane's
 "air conditioning") is enlarged to handle higher passenger loads. The airplane is 119 ft. 7 in. (36.4
 m.) long with a tail height of 36 ft. 6 in. (11.1 m.) and wingspan of 94 ft. 9 in. (28.9 m.).

 The engines which power the -400 are the CFM56-3B2 built by CFM International, a company
 owned by General Electric of the U.S. and Snecma of France. The -3B2 engine is a
 high-bypass-ratio power plant rated at 22,000 lbs. thrust and offers a 19 percent fuel burn
 improvement over engines powering early models of the 737 and 727. The quietness of takeoffs is
 surprising - generally the takeoff noise cannot be heard outside of the airport boundaries. Much of
 the noise reduction and low fuel consumption of the 737-400 is due to this superior engine.

 Other advances in the 737-400 stemmed from basic design.

 During development work on the airplane, Boeing kept as a goal long service life and low
 maintenance, as well as elimination of any excess weight in the airplane. The latest aluminum alloys
 are used in the structure, along with increased carbon composite parts. A special program of
 corrosion prevention is designed to assure customers that the airplane will maintain its original
 structural soundness in any operating environment.

 Some operators fit additional seats into the 737-400. The basic U.S. configuration is 146 seats
 (138 economy with 32-inch (800 mm) pitch between seats and 8 first class at 36-inch (900 mm)
 pitch). Other options include 159 all-economy seats at 32-inch (800 mm) pitch, and an
 inclusive-tour layout of 168 passengers at 30-inch (750 mm) pitch.

 No matter which seating arrangement is chosen, passengers benefit from the 737-400's roomy
 interior with large overhead stowage bins for carry-on baggage and a 20-inch (500 mm) center
 aisle.

 With the longer fuselage, airlines gain larger cargo areas. With a total usable cargo volume of 1,373
 cu. ft. (38.9 cu. m.), the 737-400 still offers a freight hold accessible from the ground without
 ladders.

 The basic airplane gross weight is 138,500 lbs. (62,820 kg.), with an optional high-gross-weight
 version of 150,000 lbs. (68,040 kg.). Fuel capacity is 5,311 gals. (20,105 L.).

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