Boeing 720
Encyclopedia
The Boeing 720 is a four-engine narrow-body
short- to medium-range passenger jet airliner
. Developed by Boeing
in the late 1950s from the Boeing 707
, the 720 has a shorter fuselage and less range. The 720 first flew in November 1959 and the model entered service with launch customer United Airlines
in July 1960.
Though only 154 were built, the Boeing 720/720B was still profitable due to the low research and development costs of it being a slightly modified version of the 707-120. It was later replaced by the Boeing 727
.
Boeing announced its plans to develop a new version of the 707 in July 1957. It was developed from the 707-120 to provide for airline operation for short to medium range flights from shorter runways. The model was originally designated 707-020 before being changed to 720 because of all the design changes involved. Compared to the 707-120, it has four fewer frames in front of the wing, and one less aft, for a total of 8 in 4 in (2.54 m) shorter.
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 to lower takeoff and landing speeds and thus shorten field length, and a thickened inboard section at the leading edge, which had a slightly greater sweep. This modification increased the top speed over the -120. It had four Pratt & Whitney JT3C-7
turbojet engines producing 12500 lbf (55.6 kN) each.
At one point in the promotion stage to airlines, it was known as the 717, 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.
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 the November 23, 1959. The Type Certificate for the 720 was issued on June 30, 1960. It was first put into service by United Airlines on July 5, 1960. 65 of the original version were built.
turbofan engines, producing 17000 lbf (75.6 kN) each. As a turbofan variant of the JT3C it had lower fuel consumption and higher thrust. The maximum takeoff weight for the 720B was increased to 234000 lb (106,140.6 kg). The 720B first took to the skies on October 6, 1960 and received certification and entered service with American in March 1961. 89 720Bs were built, in addition to conversions of American's ten existing 720s.
As a modification of an existing model the 720 had minimal research and development costs, which allowed it to be profitable despite few sales. Boeing built 154 720s and 720Bs from 1959 to 1967. The 720's wing modification was later added on the -120B and on -120s retrofitted to the B standard.
, 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 pressurization
. The engines could not supply sufficient bleed air
for this purpose without a serious loss of thrust. The small air inlets are visible just above the main engine inlets on the inner engine pods of all 720s and 720Bs; the lack of the turbocompressor inlets on the outer pods helps spotters distinguish 720/720Bs from most 707s.
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.
Honeywell
operated the last Boeing 720 in operation 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
flew the last 720 until 2010. The final operational flight took place on September 29, 2010 with a decision still to come regarding whether it will be scrapped or placed in a museum. Pratt & Whitney Canada replaced their testbed with a Boeing 747SP
.
720B
Sources:
Narrow-body aircraft
A narrow-body aircraft is an airliner with a fuselage aircraft cabin width typically of 3 to 4 metres , and airline seat arranged 2 to 6 abreast along a single aisle...
short- to medium-range passenger jet airliner
Jet airliner
A jet airliner is an airliner that is powered by jet engines. This term is sometimes contracted to jetliner or jet.In contrast to today's relatively fuel-efficient, turbofan-powered air travel, first generation jet airliner travel was noisy and fuel inefficient...
. Developed by Boeing
Boeing Commercial Airplanes
Boeing Commercial Airplanes designs, assembles, markets and sells large commercial jet aircraft and provides product-related maintenance and training to customers worldwide...
in the late 1950s from the Boeing 707
Boeing 707
The Boeing 707 is a four-engine narrow-body commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". The first airline to operate the 707 was Pan American World Airways, inaugurating the type's first commercial flight on...
, the 720 has a shorter fuselage and less range. The 720 first flew in November 1959 and the model entered service with launch customer United Airlines
United Airlines
United Air Lines, Inc., is the world's largest airline with 86,852 employees United Air Lines, Inc., is the world's largest airline with 86,852 employees United Air Lines, Inc., is the world's largest airline with 86,852 employees (which includes the entire holding company United Continental...
in July 1960.
Though only 154 were built, the Boeing 720/720B was still profitable due to the low research and development costs of it being a slightly modified version of the 707-120. It was later replaced by the Boeing 727
Boeing 727
The Boeing 727 is a mid-size, narrow-body, three-engine, T-tailed commercial jet airliner, manufactured by Boeing. The Boeing 727 first flew in 1963, and for over a decade more were built per year than any other jet airliner. When production ended in 1984 a total of 1,832 aircraft had been produced...
.
Shorter range 707
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
Krueger flaps
Krueger flaps are lift enhancement devices that may be fitted to the leading edge of an aircraft wing. Unlike slats or drooped leading edges, the main wing upper surface and its nose is not changed...
outboard of the outboard engines to lower takeoff and landing speeds and thus shorten field length, and a thickened inboard section at the leading edge, which had a slightly greater sweep. This modification increased the top speed over the -120. It had four Pratt & Whitney JT3C-7
Pratt & Whitney JT3C
|-Specifications :-See also:-References:NotesBibliography* Francillon, René J. McDonnell Douglas Aircraft since 1920. London: Putnam, 1979. ISBN 0-370-00050-1.-External links:* * *...
turbojet engines producing 12500 lbf (55.6 kN) each.
At one point in the promotion stage to airlines, it was known as the 717, 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
Boeing 717
The Boeing 717 is a twin-engine, single-aisle jet airliner, developed for the 100-seat market. The airliner was designed and marketed by McDonnell Douglas as the MD-95, a third-generation derivative of the DC-9. Capable of seating of up to 117 passengers, the 717 has maximum range of...
following Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
's merger with McDonnell Douglas
McDonnell Douglas
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It formed from a merger of McDonnell Aircraft and Douglas Aircraft in 1967. McDonnell Douglas was based at Lambert-St. Louis International Airport...
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. The first 720 took its maiden flight on the November 23, 1959. The Type Certificate for the 720 was issued on June 30, 1960. It was first put into service by United Airlines on July 5, 1960. 65 of the original version were built.
Further developments
The 720B was the version of the 720 with JT3DPratt & Whitney JT3D
|-See also:-External links:*...
turbofan engines, producing 17000 lbf (75.6 kN) each. As a turbofan variant of the JT3C it had lower fuel consumption and higher thrust. The maximum takeoff weight for the 720B was increased to 234000 lb (106,140.6 kg). The 720B first took to the skies on October 6, 1960 and received certification and entered service with American in March 1961. 89 720Bs were built, in addition to conversions of American's ten existing 720s.
As a modification of an existing model the 720 had minimal research and development costs, which allowed it to be profitable despite few sales. Boeing built 154 720s and 720Bs from 1959 to 1967. The 720's wing modification was later added on the -120B and on -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 707-120 it was 9 ft (2.73 m) shorter in length and was built using a lighter gauge of aluminum to reduce weight.Fuselage
Compared to the 707-120, the 720 had one 20 inch frame section removed ahead of the wing and four removed aft for a total reduction of 100 inches. The rearmost of the 707's over-wing emergency exits was deleted on each side which, under FAA exit regulations, limited passenger capacity to 149. However, two over-wing exits were an option, which allowed a capacity increase to 165 passengers.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. This glove reduced the drag of the wing by decambering the root, which reduced the "middle effect", thereby increasing the effective local wing sweep. It is reported that the wing root glove increased the drag divergence Mach number of the wing by .02 Mach.Engines
Though initially fitted with turbojet engines, the dominant engine for the Boeing 720 was the Pratt & Whitney JT3DPratt & Whitney JT3D
|-See also:-External links:*...
, 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
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
to supply high-pressure air for pressurization
Cabin pressurization
Cabin pressurization is the pumping of compressed air into an aircraft cabin to maintain a safe and comfortable environment for crew and passengers when flying at altitude.-Need for cabin pressurization:...
. The engines could not supply sufficient bleed air
Bleed air
Bleed air in gas turbine engines is compressed air taken from within the engine, after the compressor stage and before the fuel is injected in the burners. While in theory bleed air could be drawn in any gas turbine engine, its usage is generally restricted to jet engines used in aircraft...
for this purpose without a serious loss of thrust. The small air inlets are visible just above the main engine inlets on the inner engine pods of all 720s and 720Bs; the lack of the turbocompressor inlets on the outer pods helps spotters distinguish 720/720Bs from most 707s.
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 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, 1960. The 720 remained in service until airlines replaced it with the Boeing 727 after the mid-1960s.In 1984 a Boeing 720 flown by remote control was intentionally crashed at Edwards AFB
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...
as a part of the FAA
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
and NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Controlled Impact Demonstration
Controlled Impact Demonstration
The Controlled Impact Demonstration was a joint project between NASA and the Federal Aviation Administration aimed at acquiring data, as well as demonstrating and testing new technologies, with the intent of improving occupant crash survivability, by crashing a Boeing 720 aircraft...
program. The test provided peak accelerations during a crash.
Honeywell
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
operated the last Boeing 720 in operation in the United States, flying out of Sky Harbor
Phoenix Sky Harbor International Airport
Phoenix Sky Harbor International Airport is a joint civil-military public airport located southeast of the central business district of the city of Phoenix, in Maricopa County, Arizona, United States...
airport in Phoenix
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
. 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
Boeing 757
The Boeing 757 is a mid-size, narrow-body twin-engine jet airliner manufactured by Boeing Commercial Airplanes. Passenger versions of the twinjet have a capacity of 186 to 289 persons and a maximum range of , depending on variant and cabin configuration...
.
Pratt & Whitney Canada
Pratt & Whitney Canada
Pratt & Whitney Canada is a Canadian aircraft engine manufacturer. PWC's headquarters are in Longueuil, Quebec, just outside Montreal. It is a division of the larger US-based Pratt & Whitney , itself a business unit of United Technologies...
flew the last 720 until 2010. The final operational flight took place on September 29, 2010 with a decision still to come regarding whether it will be scrapped or placed in a museum. Pratt & Whitney Canada replaced their testbed with a Boeing 747SP
Boeing 747SP
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...
.
Variants
720- First production variant with four Pratt & Whitney JT3C turbojet engines.
720B
- Improved variant with four Pratt & Whitney JT3D turbofan engines. American Airlines converted its 720s (10 aircraft) to 720B standard.
Original operators
The following operators took delivery of new Boeing 720/720Bs:- AviancaAviancaAvianca S.A. is the flag carrier airline of Colombia since December 5, 1919 when it was initially registered under the name SCADTA. It is headquartered in Bogotá, D.C. with its hub at the El Dorado International Airport...
3 x 720B, two delivered in 1961 and one in 1965
- Ethiopian AirlinesEthiopian AirlinesEthiopian Airlines , formerly Ethiopian Air Lines, often referred to as simply Ethiopian, is an airline headquartered on the grounds of Bole International Airport in Addis Ababa, Ethiopia. It serves as the country's flag carrier, and is wholly owned by the Government of Ethiopia...
3 x 720Bs, two delivered in 1962 and one in 1965
- LufthansaLufthansaDeutsche Lufthansa AG is the flag carrier of Germany and the largest airline in Europe in terms of overall passengers carried. The name of the company is derived from Luft , and Hansa .The airline is the world's fourth-largest airline in terms of overall passengers carried, operating...
8 x 720B delivered 1961-1962
- Aer LingusAer LingusAer Lingus Group Plc is the flag carrier of Ireland. It operates a fleet of Airbus aircraft serving Europe and North America. It is Ireland's oldest extant airline, and its second largest after low-cost rival Ryanair...
3 x 720 delivered 1960-1961
- El AlEl AlEl Al Israel Airlines Ltd , trading as El Al , is the flag carrier of Israel. It operates scheduled domestic and international services and cargo flights to Europe, North America, Africa and the Far East from its main base in Ben Gurion International Airport...
2 x 720B delivered in 1962
- Pakistan International AirlinesPakistan International AirlinesPakistan International Airlines Corporation commonly known as PIA, is the flag carrier airline of Pakistan. The airline has its head office on the grounds of Jinnah International Airport in Karachi. and operates scheduled services to 24 domestic destinations and 38 international destinations in 27...
4 x 720B delivered 1961-1962 and one in 1965
- American AirlinesAmerican AirlinesAmerican Airlines, Inc. is the world's fourth-largest airline in passenger miles transported and operating revenues. American Airlines is a subsidiary of the AMR Corporation and is headquartered in Fort Worth, Texas adjacent to its largest hub at Dallas/Fort Worth International Airport...
10 x 720 delivered in 1960 and 15 x 720Bs delivered in 1961, the ten 720s were converted to turbofan powered B models in 1961 - Braniff Airways 5 x 720 delivered 1961-1963, an additional aircraft was sold to the Federal Aviation Authority before delivery
- Continental AirlinesContinental AirlinesContinental Airlines was a major American airline now merged with United Airlines. On May 3, 2010, Continental Airlines, Inc. and UAL, Inc. announced a merger via a stock swap, and on October 1, 2010, the merger closed and UAL changed its name to United Continental Holdings, Inc...
8 x 720B delivered 1962-1966 - Eastern Airlines 15 x 720 delivered 1961-1962
- Federal Aviation Authority one 720 delivered in 1961
- Northwest AirlinesNorthwest AirlinesNorthwest Airlines, Inc. was a major United States airline founded in 1926 and absorbed into Delta Air Lines by a merger approved on October 29, 2008, making Delta the largest airline in the world...
13 x 720B delivered 1961-1964 - Pacific Northern Airlines 2 x 720 delivered in 1962
- United AirlinesUnited AirlinesUnited Air Lines, Inc., is the world's largest airline with 86,852 employees United Air Lines, Inc., is the world's largest airline with 86,852 employees United Air Lines, Inc., is the world's largest airline with 86,852 employees (which includes the entire holding company United Continental...
29 x 720 delivered 1960-1962 - Western AirlinesWestern AirlinesWestern Airlines was a large airline based in California, with operations throughout the Western United States, and hubs at Los Angeles International Airport, Salt Lake City International Airport, and the former Stapleton International Airport in Denver...
27 x 720Bs delivered 1961-1967
Notable accidents
- On February 12, 1963, Northwest Orient Airlines Flight 705Northwest Orient Airlines Flight 705Northwest Orient Airlines Flight 705 was a scheduled passenger flight operated on 12 February 1963 by a Boeing 720 aircraft which broke up in midair and crashed into The Everglades shortly after take-off from Miami International Airport in a severe thunderstorm...
, a Boeing 720B, suffered an in-flight break-up over the Florida Everglades approximately 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 AirlinesPakistan International AirlinesPakistan International Airlines Corporation commonly known as PIA, is the flag carrier airline of Pakistan. The airline has its head office on the grounds of Jinnah International Airport in Karachi. and operates scheduled services to 24 domestic destinations and 38 international destinations in 27...
Flight PK 705PIA Flight 705Pakistan International Airlines Flight 705 was a Boeing 720–040B that crashed while descending to land on Runway 34 at Cairo International Airport on May 20, 1965 resulting in 119 fatalities.-Details:...
, a 720, crashed short of the runway at Cairo International AirportCairo International AirportCairo International Airport is the busiest airport in Egypt and the primary hub for Star Alliance member EgyptAir. The airport is located to the north-east of the city around from the business area of the city.The airport is administered by the Egyptian Holding Co...
, killing 119 of the 125 people on board. - On January 1, 1976, Middle East Airlines Flight 438Middle East Airlines Flight 438Middle East Airlines Flight 438 a Boeing 720B, callsign CEDAR JET 438, was en route from Beirut to Dubai on 1 January 1976 when a bomb exploded in the forward cargo compartment. The aircraft broke up at an altitude of and crashed 37 km northwest of Al Qaysumah, Saudi Arabia.The bombers were...
, a 720B, 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
- 4X-JYG Model 720-023B (msn. 18013, no. 120) Former American Airlines (N7527A) aircraft sold to the Israel Air Force, aircraft on display at the Israel Air Force Museum, Beersheba - Hatzerim (LLHB).
- 18351 Model 720-047B (msn. 18351, no. 211) Taiwan Air Force VIP aircraft on display at Kangshan AFB, Taiwan.
- N93143 Model 720-047B (msn. 18063, no. 213) Nose section of former Western AirlinesWestern AirlinesWestern Airlines was a large airline based in California, with operations throughout the Western United States, and hubs at Los Angeles International Airport, Salt Lake City International Airport, and the former Stapleton International Airport in Denver...
on display at the Pima Air and Space Museum, Tucson, AZ. - HK-749 Model 720-030B (msn. 18248, no. 258) Airframe preserved at Museo de los Ninos, Bogota, Colombia.
- AP-AXL Model 720-047B (msn. 18818, no. 390) ex-Pakistan International AirlinesPakistan International AirlinesPakistan International Airlines Corporation commonly known as PIA, is the flag carrier airline of Pakistan. The airline has its head office on the grounds of Jinnah International Airport in Karachi. and operates scheduled services to 24 domestic destinations and 38 international destinations in 27...
aircraft. After being hijacked for 13 days in 1981, it was withdrawn from service, and is now displayed at PIA Planetarium Karachi.
Specifications
| 720 | 707-120B | 707-320B | |
|---|---|---|---|
| Cockpit crew | Three | ||
| Passengers | 167 | 110 (2 class) 179 (1 class) |
147 (2 class) 202 (1 class) |
| Length | 136 ft 2 in (41.25 m) | 145 ft 1 in (44.07 m) | 152 ft 11 in (46.61 m) |
| Wingspan | 130 ft 10 in (39.90 m) | 145 ft 9 in (44.42 m) | |
| Tail height | 41 ft 7 in (12.65 m) | 42 ft 5 in (12.93 m) | |
| Maximum Takeoff Weight (MTOW) | 222,000 lb (100,800 kg) | 257,000 lb (116,570 kg) | 333,600 lb (151,320 kg) |
| Empty weight | 103,145 lb (46,785 kg) | 122,533 lb (55,580 kg) | 146,400 lb (66,406 kg) |
| Runway needed at MTOW | 8,300 ft (2,515 m) | 11,000 ft (3,330 m) | 10,840 ft (3,280 m) |
| Fuel Capacity | 16,060 US gal (60,900 l) | 17,330 US gal (65,590 l) | 23,820 US gal (90,160 l) |
| Landing run | 5,750 ft (1,740 m) | 6,200 ft (1,875 m) | 5,950 ft (1,813 m) |
| Operating range (Max Payload) | 3,680 nmi Nautical mile The nautical mile is a unit of length that is about one minute of arc of latitude along any meridian, but is approximately one minute of arc of longitude only at the equator... (6,820 km) |
3,735 nmi (6,920 km) | |
| Range at MTOW (max fuel) | 3800 nmi (7,040 km) | 4,700 nmi (8,704 km) | 5,750 nmi (10,650 km) |
| Cruising speed | 540 kn (1000 km/h) | 525 kn (972 km/h) | |
| Fuselage width | 12 ft 4 in (3.76 m) | ||
| Powerplants (4 x) | Pratt & Whitney JT3C-7: 12,000 lbf Pound-force The pound force is a unit of force in some systems of measurement including English engineering units and British gravitational units.- Definitions :... (53.3 kN) |
Pratt & Whitney JT3D-1 Pratt & Whitney JT3D |-See also:-External links:*... : 17,000 lbf (75.6 kN) |
PW JT3D-3 Pratt & Whitney JT3D |-See also:-External links:*... : 18,000 lbf (80 kN) PW JT3D-7 Pratt & Whitney JT3D |-See also:-External links:*... : 19,000 lbf (84.4 kN) |
Sources: