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The Boeing 720 is a retired American
narrow-body airliner A narrow-body aircraft or single-aisle aircraft is an airliner arranged along a single aisle, permitting up to 6-abreast seating in a cabin less than in width. In contrast, a wide-body aircraft is a larger airliner usually configured with mul ...
produced by
Boeing Commercial Airplanes Boeing Commercial Airplanes (BCA) is a division of the Boeing Company. It designs, assembles, markets, and sells commercial aircraft, including the 737, 767, 777, and 787, along with freighter and business jet variants of most. The divis ...
. Announced in July 1957 as a 707 derivative for shorter flights from shorter runways, the 720 first flew on November 23, 1959. Its type certificate was issued on June 30, 1960, and it entered service with
United Airlines United Airlines, Inc. is a Major airlines of the United States, major airline in the United States headquartered in Chicago, Chicago, Illinois that operates an extensive domestic and international route network across the United States and six ...
on July 5, 1960. A total of 154 Boeing 720s and 720Bs were built until 1967. As a derivative, the 720 had low development costs, allowing profitability despite relatively few sales. Compared to the 707-120, it has a length reduced by 8.33 feet (2.54 m), a modified wing and a lightened airframe for a lower
maximum takeoff weight The maximum takeoff weight (MTOW) or maximum gross takeoff weight (MGTOW) or maximum takeoff mass (MTOM) of an aircraft, also known as the maximum structural takeoff weight or maximum structural takeoff mass, is the maximum weight at which the p ...
. Originally designed to be powered by four Pratt & Whitney JT3C turbojets, the initial 720 could cover a range with 131 passengers in two classes. The reconfigured 720B, powered by JT3D turbofans, first flew on October 6, 1960, and entered service in March 1961. It could seat 156 passengers in one class over a range. Some 720s were later converted to 720Bs specification. It was succeeded by the
Boeing 727 The Boeing 727 is an American Narrow-body aircraft, narrow-body airliner that was developed and produced by Boeing Commercial Airplanes. After the heavier Boeing 707, 707 quad-jet was introduced in 1958, Boeing addressed the demand for shorter ...
trijet.


Development


Shorter range 707

Boeing announced its plans to develop a new version of the 707 in July 1957.Angelucci, Enzo; Paolo Matricardi and Adriano Zannino. ''The Illustrated Encyclopedia of Civil Aircraft: From Leonardo da Vinci to the Present'', p. 346. Edison, New Jersey US: Chartwell Books, 2001. . 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 United Airlines, Inc. is a Major airlines of the United States, major airline in the United States headquartered in Chicago, Chicago, Illinois that operates an extensive domestic and international route network across the United States and six ...
. Compared to the , it has four fewer frames in front of the wing and one fewer aft: a total length reduction of . The new model was designed to a lower maximum takeoff weight with a modified wing and a lightened airframe. The wing modifications included
Krueger flap Krueger flaps, or Krüger flaps, are lift enhancement devices that may be fitted to the leading edge of an aircraft wing. Unlike Leading-edge slat, slats or leading-edge droop flap, droop flaps, the main wing upper surface and its leading edge is ...
s outboard of the outboard engines, lowering take-off and landing speeds—thus shortening runway length requirements—and a thickened inboard leading edge section, with a slightly greater sweep. This modification increased the top speed over the .Frawley, Gerald. "Boeing 720". ''The International Directory of Civil Aircraft, 2003/2004''. Fishwick, Act: Aerospace Publications, 2003. . It had four Pratt & Whitney JT3C-7 turbojet engines producing each.Donald, David, ed. ''The Complete Encyclopedia of World Aircraft''. New York: Barnes & Noble Books, 1997. . At one point in the development phase, it was known as the , then , although this was the Boeing model designation of the KC-135 and remained unused for a commercial airliner until it was applied to the MD-95, following
Boeing The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...
's merger with
McDonnell Douglas McDonnell Douglas Corporation was a major American Aerospace manufacturer, aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own ...
in 1997. 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.Pither 1998, p. 29. The first 720 took its maiden flight on November 23, 1959. The type certificate for the 720 was issued on June 30, 1960. It first entered service with United Airlines on July 5, 1960; 65 of the original version were built.Boeing 720
. Boeing


Further developments

The 720B version of the 720 had JT3D turbofan engines, producing each. The JT3D engines had lower fuel consumption and higher thrust. 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 American Airlines, Inc. is a major airlines of the United States, major airline in the United States headquartered in Fort Worth, Texas, within the Dallas–Fort Worth metroplex, and is the Largest airlines in the world, largest airline in the ...
in March 1961; 89 720Bs were built, in addition to conversions of American's 10 existing 720s.Pither 1998, p. 30 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."Boeing 707/720 Short History."
''Boeing''. Retrieved: December 27, 2009.
The 720's wing modification was later added on the 707-120B and on 707-120s retrofitted to the B standard."Boeing 707."
''airlinercafe.com''. Retrieved: December 27, 2009.


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, and had a lighter structure through use of lighter forged metal parts and thinner fuselage skins and structures.


Fuselage

The rearmost of the 707's over-wing emergency exits was deleted on each side, which reduced passenger capacity, while two over-wing exits were an option for higher-density configurations.


Wings

The 720 uses an improved wing based on the 707 wing. The wingspan remained the same as the . For the 720, the wing was changed between the fuselage and inner engines by adding a wing root glove. 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 The Pratt & Whitney JT3D is an early turbofan aircraft engine derived from the Pratt & Whitney J57, Pratt & Whitney JT3C turbojet. It was first run in 1958 and was first flown in 1959 under a B-45 Tornado test aircraft. Over 8,000 JT3Ds were prod ...
, 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 Cabin pressurization is a process in which conditioned air is pumped into the aircraft cabin, cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for humans flying at high altitudes. For aircraft, this air i ...
. The engines could not supply sufficient
bleed air Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine ...
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 An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115&n ...
, 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

The first aircraft was a production aircraft for United Airlines which flew on November 23, 1959. The type certificate for the 720 was issued on June 30, 1960. The first service of the 720 was by United Airlines on July 5, 1960 on the Los Angeles-Denver-Chicago route. American Airlines followed by putting the 720 in commercial operation on July 31 that same year. On January 2, 1962,
Pakistan International Airlines Pakistan International Airlines, commonly known as PIA, is the flag carrier of Pakistan. With its primary hub at Jinnah International Airport in Karachi, the airline also operates from its secondary hubs at Allama Iqbal International Airport ...
′ first Boeing 720B – a Boeing 720-040B (registration AP-AMG) piloted by
Captain Captain is a title, an appellative for the commanding officer of a military unit; the supreme leader or highest rank officer of a navy ship, merchant ship, aeroplane, spacecraft, or other vessel; or the commander of a port, fire or police depa ...
Abdullah Baig and copilot Captain Taimur Baig – set a world record during the
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
-to-
Karachi Karachi is the capital city of the Administrative units of Pakistan, province of Sindh, Pakistan. It is the List of cities in Pakistan by population, largest city in Pakistan and 12th List of largest cities, largest in the world, with a popul ...
leg of its delivery flight to
Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...
for speed over a commercial air route, making the flight in 6 hours 43 minutes 55 seconds at an average speed of . The 720 was supplanted by the
Boeing 727 The Boeing 727 is an American Narrow-body aircraft, narrow-body airliner that was developed and produced by Boeing Commercial Airplanes. After the heavier Boeing 707, 707 quad-jet was introduced in 1958, Boeing addressed the demand for shorter ...
in the mid-1960s in its medium-range, high-performance market. In the late 1960s, 720 and 720B aircraft were used by the US military to shuttle troops to the Far-East war efforts. The interiors of these planes were stripped of class partitions. Some of these flights originated at
Travis AFB Travis Air Force Base is a United States Air Force base under the operational control of Air Mobility Command (AMC), located three miles (5 Kilometre, km) east of the central business district of the city of Fairfield, California, Fairfield, i ...
California and flew nonstop to Japan. At least one of the landing sites was Yokota AB, Japan, before the troops traveled to their final destinations. After disposal of 720s by the major airlines, many were acquired by second-rank operators in South America and elsewhere. In 1984, a Boeing 720 flown by remote control was intentionally crashed at Edwards AFB as a part of the FAA and
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
Controlled Impact Demonstration program. The test provided peak accelerations during a crash. The performance of fire-retardant fuel was also tested. 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 Led Zeppelin were an English rock music, rock band formed in London in 1968. The band comprised vocalist Robert Plant, guitarist Jimmy Page, bassist-keyboardist John Paul Jones (musician), John Paul Jones and drummer John Bonham. With a he ...
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 Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building automation, industrial automa ...
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 The Boeing 757 is an American Narrow-body aircraft, narrow-body airliner designed and built by Boeing Commercial Airplanes. The then-named 7N7, a twinjet successor for the trijet Boeing 727, 727, received its first orders in August 1978. The ...
.
Pratt & Whitney Canada Pratt & Whitney Canada (PWC or P&WC) is a Canada-based aircraft engine manufacturer. PWC's headquarters are in Longueuil, Quebec, south of Montreal. It is a division of the larger US-based Pratt & Whitney (P&W), itself a business unit of RTX ...
(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 American Airlines, Inc. is a major airlines of the United States, major airline in the United States headquartered in Fort Worth, Texas, within the Dallas–Fort Worth metroplex, and is the Largest airlines in the world, largest airline in the ...
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 A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft engine, aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the add ...
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 A turboprop is a Gas turbine, gas turbine engine that drives an aircraft Propeller (aeronautics), propeller. A turboprop consists of an intake, reduction drive, reduction gearbox, gas compressor, compressor, combustor, turbine, and a propellin ...
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. In May 2012, the former PWC 720 was flown to
CFB Trenton Canadian Forces Base Trenton (also CFB Trenton), formerly RCAF Station Trenton, is a Canadian Forces base located within the city of Quinte West, Ontario. It is operated as an air force base by the Royal Canadian Air Force (RCAF) and is the hub ...
, Ontario, to be put on display at the
National Air Force Museum of Canada The National Air Force Museum of Canada is an aviation museum dedicated to preserving the history of the Royal Canadian Air Force (RCAF) and is located on the west side of CFB Trenton in Trenton, Ontario. The museum is a permanent archive which c ...
.


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.FAA Type Certificate Data Sheet http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/b72df74d3b1847ad852567240060a02d/$FILE/4a28.PDF ;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

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 February 12, 1963, Northwest Orient Airlines Flight 705, a Boeing 720-051B (reg. N724US), suffered an in-flight break-up over the Florida Everglades about 12 minutes after leaving Miami, bound for Chicago. All 35 passengers and eight crew died. The cause of the crash was determined to be an unrecoverable loss of control due to severe turbulence. * 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 The Eritrean Liberation Front (ELF; ; ; ), colloquially known as Jebha, was the main Eritrean War of Independence, independence movement in Eritrea Province, Eritrea which sought Eritrea's independence from Ethiopia during the 1960s and the ear ...
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 casualtie

* On January 1, 1976,
Middle East Airlines Flight 438 Middle East Airlines Flight 438 was an international passenger flight operated by a Boeing 720 from Beirut, Lebanon, to Muscat, Oman, with a stopover in Abu Dhabi, United Arab Emirates. On 1 January 1976, the aircraft operating the flight was de ...
, 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 The Republic of China Air Force ( Chinese, 中華民國空軍), or the ROCAF; known colloquially as the Taiwanese Air Force ( Chinese, 臺灣空軍) by Western or mainland Chinese media, or commonly referred as the National Military Air Force ...
VIP aircraft, is on display at Kangshan, Taiwan.Pither 1998, p. 311. *720-047B ''AP-AXL'' is on display at PIA Planetarium,
Lahore Lahore ( ; ; ) is the capital and largest city of the Administrative units of Pakistan, Pakistani province of Punjab, Pakistan, Punjab. It is the List of cities in Pakistan by population, second-largest city in Pakistan, after Karachi, and ...
(Pakistan) standing in a park for the public. *720-047B ''AP-AXM'' is on display at PIA Planetarium,
Karachi Karachi is the capital city of the Administrative units of Pakistan, province of Sindh, Pakistan. It is the List of cities in Pakistan by population, largest city in Pakistan and 12th List of largest cities, largest in the world, with a popul ...
(Pakistan). *720-023B ''C-FETB'' was donated to the
National Air Force Museum of Canada The National Air Force Museum of Canada is an aviation museum dedicated to preserving the history of the Royal Canadian Air Force (RCAF) and is located on the west side of CFB Trenton in Trenton, Ontario. The museum is a permanent archive which c ...
in 2012 after its last flight. *720-030B ''HK-749'' is on display at Museo de los Niños ( Children's Museum of Bogotá),
Bogotá Bogotá (, also , , ), officially Bogotá, Distrito Capital, abbreviated Bogotá, D.C., and formerly known as Santa Fe de Bogotá (; ) during the Spanish Imperial period and between 1991 and 2000, is the capital city, capital and largest city ...
,
Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
in Avianca Colombia livery.Pither 1998, p. 308. It was the first jet airplane delivered to a Colombian airline.


Specifications (Boeing 720-048)


See also


References


Notes


Bibliography

*


Further reading

* * Caidin, Martin. ''Boeing 707''. New York: Bantam Books, 1959. * Price, Alfred. ''The Boeing 707''. Leatherhead, Surrey, UK: Profile Publications, 1967. * Schiff, Barry J. ''The Boeing 707''. Blue Ridge Summit, PA: Tab Books, 1982, First edition 1967, . . * Whittle, John A. ''The Boeing 707 and 720''. Tonbridge, Kent: Air Britain (Historians), 1972. . * * Lloyd, Alwyn T. ''Boeing 707 & AWACS in Detail and Scale''. Falbrook, CA: Aero Publishers, 1987. . * * Cook, William H. ''Road to the 707: The Inside Story of Designing the 707''. Bellevue, WA: TYC Publishing Company, 1991. . * Cearley, George Walker. ''Boeing 707 & 720: A Pictorial History.'' Dallas, TX: G.W. Cearley Jr, 1993. No ISBN. * Smith, Paul Raymond. ''Boeing 707 – Airline Markings No. 3''. Shrewsbury, Shropshire, UK: Swan Hill Press, 1993. . * * Wilson, Stewart. ''Boeing 707, Douglas DC-8, and Vickers VC-10.'' Fyshwick, Australia, ACT: Aerospace Publications Pty Ltd., 1998. 1-875671-36-6. * Francillon, René. ''Boeing 707: Pioneer Jetliner''. Shrewsbury, Shropshire, UK: Motor Books International, 1999. * * * Winchester, Jim. ''Boeing 707''. Shrewsbury, Shropshire, UK: Airlife, 2002. . * Stachiw, Anthony L. and Andrew Tattersall. ''Boeing CC137 (Boeing 347C) in Canadian Service''. St. Catherines, ON: Vanwell Publishing Ltd., 2004. . * Breffort, Dominique. ''Boeing 707, KC-135 and Civilian and Military Versions''. Paris: Histoire & Collections, 2008. . {{Authority control 720 1950s United States airliners Quadjets Boeing 707 Low-wing aircraft Aircraft first flown in 1959 Aircraft with retractable tricycle landing gear