A piece of aviation history for 30 October

The Boeing 747SP is a modified version of the Boeing 747 jet airliner which was designed for ultra-long-range flights. The SP stands for "Special Performance". Compared with its predecessor, the 747-100, the 747SP retains its wide-body, four-engine layout, along with its double-deck design, but has a shortened fuselage, larger tailplane, and simplified trailing edge flaps. The weight saved by the shortened fuselage permits longer range and increased speed relative to other 747 configurations.

Known during development as the short-body 747SB, the 747SP was designed to meet a 1973 joint request from Pan American World Airways and Iran Air, who were looking for a high-capacity airliner with sufficient range to cover Pan Am's New York–Middle Eastern routes and Iran Air's planned Tehran–New York route. The aircraft also was intended to provide Boeing with a mid-size wide-body airliner to compete with existing trijet airliners.

The 747SP first entered service with Pan Am in 1976. The aircraft was later acquired by VIP and government customers. While in service, the 747SP set several aeronautical performance records, but sales did not meet the expected 200 units, and production ultimately totaled 45 aircraft.

Development

The idea for the 747SP came from a request by Pan Am for a 747 variant capable of carrying a full payload non-stop on its longest route between New York and Tokyo.Joined with Pan Am's request was Iran Air; their joint interest was for a high capacity airliner capable of covering Pan Am's New York–Middle Eastern routes and Iran Air's planned New York-Tehran route. (New York to Tehran may have been the longest non-stop commercial flight in the world for a short time, until Pan Am started Tokyo to New York in mid-1976.) The aircraft was launched with Pan Am's first order in 1973 and the first example delivered in 1976.

Bahrain Royal Flight Boeing 747SP takes off at London Heathrow Airport

A shorter derivative of the 747-100, the SP was developed to target two market requirements. The first was a need to compete with the DC-10 and L-1011 while maintaining commonality with the 747, which in its standard form was too large for many routes. Boeing lacked a mid-sized wide-body to compete in this segment. The second market requirement was an aircraft suitable for the ultra-long-range routes emerging in the mid-1970s following the joint request. These routes needed not only longer range, but also higher cruising speeds. Boeing could not afford to develop an all-new design, instead opting to shorten the 747 and optimize it for speed and range, at the expense of capacity. Production of the 747SP ran from 1976 to 1983. However a VIP order for the Royal Flight of Abu Dhabi led Boeing to produce one last SP in 1987.

A special 747SP is the Stratospheric Observatory for Infrared Astronomy (SOFIA) astronomical observatory which has its airframe modified to carry a 2.5-meter-diameter reflecting telescope to high altitude, above 99.9% of the light-absorbing water vapor in the atmosphere. The telescope and its detectors cover a wide wavelength range from the near infrared to the sub-milimeter region; no window material is transparent over this whole range, so the observations are made through a 13 ft (3.96 m) square hole in the port upper quarter of the rear fuselage, aft of a new pressure bulkhead. A sliding door covers the aperture when the telescope is not in use. Astronomers take data and control the instrument from within the normally pressurised cabin. Originally delivered to Pan Am and titled "Clipper Lindbergh", NASA has the name displayed in Pan Am script on the plane.

Design

Apart from having a significantly shorter fuselage and one fewer cabin door per side, the 747SP differs from other 747 variants in having simplified flaps and a taller vertical tail to counteract the decrease in yaw moment-arm from the shortened fuselage. The 747SP uses single-piece flaps on the trailing edges, rather than the smaller triple-slotted flaps of standard 747s. The SP was also the first— and until the introduction of the Boeing 777-200LR the only—Boeing wide-body with a wingspan greater than the length of the fuselage.

Iran Air 747SP at London Heathrow Airport

The SP could accommodate 230 passengers in a 3-class cabin or 331 in a (303 economy, 28 business) 2-class cabin, and a maximum of 440 passengers in one class. Originally designated 747SB for "short body", it later was nicknamed "Sutter's balloon" by employees after 747 chief engineer Joe Sutter. Boeing later changed the production designation to 747SP for "special performance", reflecting the aircraft's longer range and faster cruise speed. Pan Am was the launch customer for the 747SP, taking the first delivery, Clipper Freedom, on March 5, 1976, followed by Iran Air.

The 747SP was the longest-range airliner available until the 747-400 entered service in 1989. Despite its technical achievements, the SP never sold as well as Boeing hoped. Increased fuel prices in the mid 1970s to early 1980s, the SP's heavy wings, expensive cost, reduced capacity, and the increased ranges of forthcoming airliners were some of the many factors that contributed to its low sales. Only 45 were built and of those remaining, most are used by operators in the Middle East. However, some of the engineering work on the 747SP was reused with the development of the 747-300 and 747-400. In the 747SP, the upper deck begins over the section of fuselage that contains the wingbox, not ahead of the wingbox as is the case with the 747-100 and 747-200. This same design was used in the 747-300 and 747-400 resulting in a stretched upper deck.

[edit]Operators

Saudi Royal Flight Boeing 747SP arrives at Baden Airpark

Forty-five 747SP aircraft were built between 1974 and 1989. As of December 2008, 17 are still flying, 16 have been scrapped, and 12 are in storage, awaiting salvage or on display in museums

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