Boeing 720

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Boeing 720
Cyprus Airways Boeing 720B G-BCBB LHR 1978-8-24.png
The 720 is similar to the Boeing 707 with a slightly shorter fuselage. Here, a 720 in Cyprus Airways (1947-2015) livery is landing at London Heathrow Airport
General information
Role Narrow-body jet airliner
National originUnited States
Manufacturer Boeing Commercial Airplanes
StatusRetired
Primary users United Airlines
Number built154 [1]
History
Manufactured1959–1967 [2] [3]
Introduction dateJuly 5, 1960, with United Airlines
First flightNovember 23, 1959
RetiredSeptember 29, 2010 [4]
Developed from Boeing 707

The Boeing 720 is a retired American narrow-body airliner produced by Boeing Commercial Airplanes. 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 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.

Contents

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. Originally designed to be powered by four Pratt & Whitney JT3C turbojets, the initial 720 could cover a 2,800 nautical miles [nmi] (5,200 km; 3,200 mi) 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 3,200 nautical miles [nmi] (5,900 km; 3,700 mi) range. Some 720s were later converted to 720Bs specification. It was succeeded by the Boeing 727 trijet.

Development

Shorter range 707

The Boeing 720 made its maiden flight on November 23, 1959. Boeing company Boeing 720 N7201U.jpg
The Boeing 720 made its maiden flight on November 23, 1959.

Boeing announced its plans to develop a new version of the 707 in July 1957. [1] It was developed from the 707-120 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. [5] Compared to the 707-120, it has four fewer frames in front of the wing and one fewer aft: a total length reduction of 8 feet 4 inches (2.54 m). [6]

The new model was designed to a lower maximum takeoff weight with a modified wing and a lightened airframe. The wing modifications included Krueger flaps 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 707-120. [6] It had four Pratt & Whitney JT3C-7 turbojet engines producing 12,500 lbf (55.6 kN) each. [7]

At one point in the development phase, it was known as the 707-020, then 717-020, [5] 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's merger with McDonnell Douglas in 1997. [8]

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. [9] The first 720 took its maiden flight on November 23, 1959. [6] The type certificate for the 720 was issued on June 30, 1960. It first entered service with United Airlines on July 5, 1960; [6] 65 of the original version were built. [10]

Further developments

The 720B version of the 720 had JT3D turbofan engines, [6] producing 17,000 lbf (75.6 kN) each. [7] The JT3D engines had lower fuel consumption and higher thrust. [11] The maximum takeoff weight for the 720B was increased to 234,000 lb (106,000 kg). The 720B first took to the skies on October 6, 1960, and received certification and entered service with American Airlines in March 1961; [7] 89 720Bs were built, [10] in addition to conversions of American's 10 existing 720s. [12]

As a modification of an existing model, the 720 had minimal research and development costs, which allowed it to be successful despite few sales. [13] The company built 154 Boeing 720s and 720Bs from 1959 to 1967. [2] The 720's wing modification was later added on the 707-120B and on 707-120s retrofitted to the B standard. [14]

Design

The 720 is slightly shorter than the 707 and has a modified wing. Maersk 720B (6074178893).jpg
The 720 is slightly shorter than the 707 and has a modified wing.

The Boeing 720 is a four-engined low-wing cantilever monoplane. Although it was similar to the Boeing 707, compared with the 707-120, it was 8 ft 4 in (2.54 m) shorter in length, [5] and had a lighter structure through use of lighter forged metal parts and thinner fuselage skins and structures. [13]

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. [13]

Wings

The 720 uses an improved wing based on the 707 wing. The wingspan remained the same as the 707-120. For the 720, the wing was changed between the fuselage and inner engines by adding a wing root glove. [15] [16] 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. [17]

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. [11]

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.

The Boeing 720 flight deck. Boeing 720-047B AN1535319.jpg
The Boeing 720 flight deck.

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

United Airlines introduced the 720 on July 5, 1960. Boeing 720 United Air Lines (7162682658).jpg
United Airlines introduced the 720 on July 5, 1960.

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 [10] 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′ first Boeing 720B – a Boeing 720-040B (registration AP-AMG) piloted by Captain Abdullah Baig and copilot Captain Taimur Baig – set a world record during the London-to-Karachi leg of its delivery flight to Pakistan for speed over a commercial air route, making the flight in 6 hours 43 minutes 55 seconds at an average speed of 938.78 km/h (583.33 mph). [18] [19]

The 720 was supplanted by the Boeing 727 in the mid-1960s in its medium-range, high-performance market. [5] 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 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.

The Controlled Impact Demonstration used an FAA 720. CID pre-impact.jpg
The Controlled Impact Demonstration used an FAA 720.

In 1984, a Boeing 720 flown by remote control was intentionally crashed at Edwards AFB as a part of the FAA and NASA Controlled Impact Demonstration program. The test provided peak accelerations during a crash. The performance of fire-retardant fuel was also tested. [20]

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. [21]

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. [22] 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. [23] Its final operational flight occurred on September 29, 2010. [24] Pratt & Whitney Canada replaced the testbed with a Boeing 747SP. [4] In May 2012, the former PWC 720 was flown to CFB Trenton, Ontario, to be put on display at the National Air Force Museum of Canada. [25]

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.[ citation needed ] These aircraft, designated "720-025", were certificated to carry up to 170 passengers, provided that certain safety requirements were met. [26]
720B
Improved variant with four Pratt & Whitney JT3D turbofan engines; American Airlines converted its 720s to 720B standard. [11]

Operators

The Boeing 720 was operated/leased by 57 different airlines [ citation needed ]. These operators flew Boeing 720/720Bs (● = Original Operators):

Flag of the Taliban.svg  Afghanistan
Flag of Belize.svg  Belize
Flag of Cambodia.svg  Cambodia
Flag of Ceylon.svg  Ceylon
Flag of Colombia.svg  Colombia
Flag of the Democratic Republic of the Congo.svg  Democratic Republic of the Congo
Flag of Denmark.svg  Denmark
Flag of the Dominican Republic.svg  Dominican Republic
Flag of Ecuador.svg  Ecuador
Flag of Ethiopia.svg  Ethiopia
Flag of France.svg  France
Flag of Germany.svg  Germany
Flag of Greece.svg  Greece
Flag of Iceland.svg  Iceland
Flag of India.svg  India
Flag of Indonesia.svg  Indonesia
Flag of Ireland.svg  Ireland
Flag of Israel.svg  Israel
Flag of Jordan.svg  Jordan
Flag of Kenya.svg  Kenya
Flag of Lebanon.svg  Lebanon
Flag of Malta.svg  Malta
Flag of Nicaragua.svg  Nicaragua
Flag of Norway.svg  Norway
Flag of Pakistan.svg  Pakistan
Flag of Papua New Guinea.svg  Papua New Guinea
Flag of Rhodesia (1968-1979).svg  Rhodesia
Flag of Saudi Arabia.svg  Saudi Arabia
Flag of Tanzania.svg  Tanzania
Flag of the United Kingdom.svg  United Kingdom
Flag of the United States (23px).png  United States
Flag of Yemen.svg  Yemen

Accidents and incidents

A Middle East Airlines 720 destroyed during Operation Peace for Galilee. Destroyed MEA aircraft 1982.jpg
A Middle East Airlines 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. [47]

The worst of these accidents were: [47]

Aircraft on display

Specifications (Boeing 720-048)

Boeing 720 3-view.svg

Data from [60] [61]

General characteristics

Performance

See also

Related development

Aircraft of comparable role, configuration, and era

Related lists

References

Notes

  1. 1 2 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. ISBN   0-7858-1389-6.
  2. 1 2 "Boeing 707/720 Short History." Archived June 29, 2011, at the Wayback Machine Boeing. Retrieved: December 27, 2009.
  3. 707/720 Commercial Transport — Historical Snapshot Archived January 29, 2023, at the Wayback Machine Retrieved: January 29, 2023
  4. 1 2 Niles, Russ. "Last Boeing 720 Retired". avweb.com, October 5, 2010. Retrieved: October 18, 2020.
  5. 1 2 3 4 "Boeing 720". Boeing Commercial Airplanes. Archived from the original on September 3, 2011. Retrieved July 7, 2011.
  6. 1 2 3 4 5 Frawley, Gerald. "Boeing 720". The International Directory of Civil Aircraft, 2003/2004. Fishwick, Act: Aerospace Publications, 2003. ISBN   1-875671-58-7.
  7. 1 2 3 Donald, David, ed. The Complete Encyclopedia of World Aircraft. New York: Barnes & Noble Books, 1997. ISBN   0-7607-0592-5.
  8. Lombardi, Michael. "The first KC-135 rolled out 50 years ago this month." Historical Perspective, Start of a Proud Mission: Boeing Frontiers. Boeing, July 2006. Retrieved: April 17, 2010.
  9. Pither 1998, p. 29.
  10. 1 2 3 4 Boeing 720 Archived September 3, 2011, at the Wayback Machine . Boeing
  11. 1 2 3 "Boeing 720". Airliners.net. Retrieved January 10, 2012.
  12. Pither 1998, p. 30
  13. 1 2 3 Proctor, Jon; Mike Machat; Craig Kodera (2010). From Props to Jets: Commercial Aviation's Transition to the Jet Age 1952–1962. North Branch, MN: Specialty Press. pp. 118–120. ISBN   978-1-58007-146-8.
  14. "Boeing 707." Archived March 17, 2021, at the Wayback Machine airlinercafe.com. Retrieved: December 27, 2009.
  15. "The Boeing 720". Flight, August 19, 1960.
  16. The Ultimate Boeing 707 Guide Archived March 17, 2021, at the Wayback Machine Retrieved September 5, 2011.
  17. Cook, William H. The Road to the 707: The Inside Story of Designing the 707. Bellevue, Washington: TYC Publishing, 1991. ISBN   978-0-9629605-0-5.
  18. "FAI Record ID #7679". Archived from the original on September 22, 2017. Retrieved January 1, 2017.
  19. fai.org via historyofpia.com "1962 - PIA Boeing 720B Record Flight Info on FAI Website"
  20. "Flight test experience and controlled impact of a remotely piloted jet transport aircraft, NASA-TM-4084." NASA, November 1, 1988. Retrieved: December 27, 2009.
  21. Film The Song Remains The Same
  22. "Resident Boeing 720B." visitingphx.com. Retrieved: December 27, 2009.
  23. Kelly, Michael (September 23, 2013), Pratt & Whitney Boeing 720 C-FETB , retrieved January 18, 2023
  24. "P&WC Boeing 720B "Red" Flying Test Bed bids farewell". Archived from the original on February 22, 2022. Retrieved October 20, 2020.
  25. Lessard, Jerome (May 10, 2012). "Historic landing a success". Trentonian.ca. Trenton Trentonian. Archived from the original on September 12, 2012. Retrieved March 27, 2013.
  26. FAA Type Certificate Data Sheet http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/b72df74d3b1847ad852567240060a02d/$FILE/4a28.PDF Archived October 24, 2020, at the Wayback Machine
  27. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Pither 1998, pp. 116-219.
  28. "Israeli Upstart: MAOF Airlines". YESTERDAY'S AIRLINES. May 5, 2020. Retrieved July 21, 2020.
  29. "History of Air Rhodesia." Archived August 24, 2020, at the Wayback Machine Viscounts in Africa: The Air Rhodesia Story. Retrieved: 7 February 2014.
  30. "Alaska Airlines" by Cliff & Nancy Hollenbeck, 2012, published by Hollenbeck Productions, http://www.hollenbeckproductions.com Archived January 25, 1999, at the Wayback Machine
  31. "Character & Characters: The Spirit of Alaska Airlines" by Robert J. Serling, 2008, published by Documentary Media LLC, http://www.documentarymedia.com
  32. Pither 1998, p. 133.
  33. Pither 1998, p. 142.
  34. Bohl, Walt, The Aircraft History of Capital Airlines, American Aviation Historical Society Journal, Aviation Historical Society, Huntington Beach, California, Spring 2001, page 23
  35. Pither 1998, p. 151.
  36. Pither 1998, pp. 154–155.
  37. Federal Aviation Administration (September 1987). "Full-Scale Transport Controlled Impact Demonstration Program" (PDF). Atlantic City International Airport, New Jersey: FAA Technical Center. p. 5. DOT/FAA/CT-87/10, NASA-TM-89642. Retrieved September 2, 2014. This was the first time that a four-engine jet aircraft (Boeing 720) had been flown successfully by remote control. It was also the first time that an aircraft was flown solely and successfully on antimisting kerosene fuel (AMK).
  38. Pither 1998, p. 158.
  39. Pither 1998, pp. 183–184.
  40. Pither 1998, pp. 186–187.
  41. "The Only Way To Fly" by Robert J. Serling, page 381, published in 1976 by Doubleday & Company, Inc.
  42. Pither 1998, pp. 187.
  43. "N421MA | Boeing 720-022 | Southeast Airlines | Mesquita Collection".
  44. Pither 1998, p. 211
  45. Pither 1998, pp. 212–213.
  46. Pither 1998, pp. 215-216.
  47. 1 2 "Boeing 720". Aviation Safety Network. Retrieved October 19, 2013.
  48. "Northwest Airlines flight 705." Aviation-Safety.net. Retrieved: December 27, 2009.
  49. "ASN Aircraft accident Boeing 720-040B AP-AMH Cairo International Airport (CAI)". Aviation-safety.net. May 20, 1965. Retrieved March 27, 2013.
  50. Bladd, Joanne. "MEA flight 438." Aviation-Safety.net. Retrieved: December 27, 2009.
  51. Pither 1998, p. 311.
  52. 郭韋綺 (July 21, 2017). "岡山航空教育展示館 門票被嫌貴" (in Chinese). China Times. Retrieved July 21, 2017.
  53. PIA Planetarium, Lahore
  54. "AP-AXL - All Pakistan Aircraft Registration Marks". www.aparm.net. Retrieved August 26, 2017.
  55. PIA Planetarium, Karachi
  56. "AP-AXM - All Pakistan Aircraft Registration Marks". www.aparm.net. Retrieved August 26, 2017.
  57. "B720 « National Air Force Museum of Canada". airforcemuseum.ca. Archived from the original on August 27, 2017. Retrieved August 26, 2017.
  58. Pither 1998, p. 308.
  59. Franco, Javier (February 29, 2012). "Uniendo el maletín retro de Avianca con sus Boeing 720 y 727" . Retrieved December 26, 2014.
  60. "707 Airplane characteristics for airport planning" (PDF). Boeing. May 2011. Archived from the original (PDF) on January 4, 2015.
  61. "Type certificate data sheet No. 4A28" (PDF). FAA. May 1, 1973. Archived from the original (PDF) on October 24, 2020. Retrieved March 21, 2020.

Bibliography

Further reading