Boeing 720

Shorter range 707 Boeing announced its plans to develop a new version of the 707 in July 1957. It was developed from the to provide for short- to medium-range flights from shorter runways. The model was originally designated 707-020 before being changed to 720 at the input of United Airlines. Compared to the , it has four fewer frames in front of the wing and one fewer aft: a total length reduction of . It had four Pratt & Whitney JT3C-7 turbojet engines producing each. At one point in the development phase, it was known as the , then , Because the aircraft systems were similar to the Boeing 707, no prototype Boeing 720 was built; any different systems were tested on the Boeing 367-80. The first 720 took its maiden flight on November 23, 1959. Further developments The 720B version of the 720 had JT3D turbofan engines, The maximum takeoff weight for the 720B was increased to . The 720B first took to the skies on October 6, 1960, and received certification and entered service with American Airlines in March 1961; As a modification of an existing model, the 720 had minimal research and development costs, which allowed it to be successful despite few sales. The company built 154 Boeing 720s and 720Bs from 1959 to 1967. The 720's wing modification was later added on the 707-120B and on 707-120s retrofitted to the B standard. ==Design==

The Boeing 720 is a four-engined low-wing cantilever monoplane. Although it was similar to the Boeing 707, compared with the , it was shorter in length, This glove reduced the drag of the wing by decambering the root, which reduced the "middle effect", thereby increasing the effective local wing sweep. The wing root glove reportedly increased the drag divergence Mach number of the wing by Mach 0.02. Engines Though initially fitted with turbojet engines, the dominant engine for the Boeing 720 was the Pratt & Whitney JT3D, a turbofan variant of the JT3C with lower fuel consumption and higher thrust. JT3D-engined 720s had a "B" suffix; some of American's 720Bs were conversions of JT3C-powered 720s. Like the 707, the 720/720B used engine-driven turbocompressors to supply high-pressure air for cabin pressurization. The engines could not supply sufficient bleed air for this purpose without a serious loss of thrust. The small air inlets and associated humps are visible just above the main engine inlets on the two inner engine pods of all 720s and 720Bs; the lack of the turbocompressor inlet on the outer starboard pod (number 4 engine) helps spotters distinguish 720/720Bs from most 707s, which had three turbocompressors. Other equipment The Boeing 720 lacked an auxiliary power unit, and relied instead on ground power and pneumatic air to power the aircraft's systems, provide air conditioning, and start the engines while on the ground. The normal practice for Boeing 720 aircraft was to start the number three (inner starboard) engine first, then disconnect ground power and air. With one engine running, bleed air from that engine could be used to provide necessary air pressure to start the other engines one by one. On ground, with ground starting crew at hand, all four engines were usually started with ground crew help: this was more reliable and faster. ==Operational history==

introduced the 720 on July 5, 1960. The 720 was supplanted by the Boeing 727 in the mid-1960s in its medium-range, high-performance market. The first 720 (N7201U) was later renamed "The Starship" and became a private charter jet used mainly by touring rock bands. Its main user was Led Zeppelin in the 1970s. The seating capacity was reduced and a bar with a built-in electric organ was added, along with beds, a shower, a lounge area, a TV, and video cassette player. Honeywell operated the last Boeing 720 in the United States, flying out of Sky Harbor Airport in Phoenix. The aircraft had been modified with an extra engine nacelle mounted on the right side of the fuselage to allow testing of a turbine engine at altitude, operating on special certification allowing it to be used for experimental use. This 720B was scrapped on June 21 and 22, 2008. Honeywell replaced their aircraft with a Boeing 757. Pratt & Whitney Canada (PWC) operated the last flying 720 (C-FETB) until 2010. C-FETB was built as N7538A in 1960 and was initially flown by American Airlines and later by Middle East Airlines as OD-AFQ. It was purchased by PWC in December 1985 and between October 1986 and January 1988 it was modified for use as a flying engine test bed. Internally it was known as FTB1 (Flying Test Bed 1). C-FETB was used to test a variety of engines with it being capable of carrying a large turbofan in place of the right wing's inner engine. Alongside this a small turbofan could be mounted on the right side of the front fuselage while a turboprop could be mounted in the modified nose. Its final operational flight occurred on September 29, 2010. Pratt & Whitney Canada replaced the testbed with a Boeing 747SP. ==Variants==

;720 :First production variant with four Pratt & Whitney JT3C turbojet engines :Several high-density seat configurations delivered to Eastern Airlines included four over-wing escape hatches and brake cooling fans to effect quick turns on short-haul sectors. These aircraft, designated "720-025", were certificated to carry up to 170 passengers, provided that certain safety requirements were met. ;720B :Improved variant with four Pratt & Whitney JT3D turbofan engines; American Airlines converted its 720s to 720B standard. ==Operators==

The Boeing 720 was operated/leased by 57 different airlines . These operators flew Boeing 720/720Bs (● = Original Operators): ==Accidents and incidents==

720 destroyed during Operation Peace for Galilee. The Boeing 720 has had 23 hull-loss accidents during its career; it was also involved in a number of incidents including nine hijack incidents and one aircraft destroyed by a bomb in mid-air in 1976. Only 12 of the hull-loss accidents included fatalities which totaled 175 deaths in addition to the 81 deaths on the aircraft destroyed in mid-air by a bomb. The worst of these accidents were: • On May 20, 1965, Pakistan International Airlines Flight 705, a Boeing 720-040B (reg AP-AMH), crashed short of the runway at Cairo International Airport, killing 121 of the 127 people on board. • On December 8, 1972, seven members of the Eritrean Liberation Front hijacked Ethiopian Airlines Flight 708, a Boeing 720-060B, on its way to Paris. Security forces on the plane immediately opened fire, killing all but one of the hijackers (the last surviving hijacker later died in hospital). During the altercation, a hand grenade was detonated that damaged control cables under the cabin floor. However, the pilot put the plane into a controlled dive and managed to land the plane safely back in Addis Ababa with no further casualties. • On January 1, 1976, Middle East Airlines Flight 438, a Boeing 720-023B (reg. OD-AFT), was destroyed en route from Beirut to Dubai by a bomb in the forward cargo hold. All 66 passengers and 15 crew were killed. ==Aircraft on display==

• 720-051B 18351 "Chung Mei", a former Republic of China Air Force VIP aircraft, is on display at Kangshan, Taiwan. • 720-047B AP-AXL is on display at PIA Planetarium, Lahore (Pakistan) standing in a park for the public. • 720-047B AP-AXM is on display at PIA Planetarium, Karachi (Pakistan). • 720-023B C-FETB was donated to the National Air Force Museum of Canada in 2012 after its last flight. • 720-030B HK-749 is on display at Museo de los Niños (Children's Museum of Bogotá), Bogotá, Colombia in Avianca Colombia livery. It was the first jet airplane delivered to a Colombian airline. == Specifications (Boeing 720-048)==