MDC's JSF failed to get off the deck
Lockheed Martin's "low-risk" design
Boeing's bid is a far cry from a widebodied aircraft
Guy Norris/LOSANGELES
Boeing and Lockheed Martin have begun final detailed design work on their respective Joint Strike Fighter (JSF) demonstrator aircraft configurations, both are aiming to make first flights in early 2000.
Boeing's first aircraft will be a combined conventional take-off and landing (CTOL) and carrier (CV) demonstrator. The second aircraft will be the "primary" short take-off and vertical landing (STOVL) demonstrator for the US Marine Corps and Royal Navy JSF versions. It is due to be flown around mid-2000. Boeing JSF aircraft integration manager, Dennis Muilenburg, says both aircraft will be "STOVL capable", to minimise any potential disruptions of the Concept Demonstrator Programme (CDP).
Lockheed Martin's design, considered the lowest risk of the three contenders, will be "effectively frozen within six months", says senior executive Paul Bevilaqua.
The first Lockheed Martin JSF demonstrator (the CTOL) will fly around the end of February 2,000, says Bevilaqua, talking at the AIAA's International Powered Lift Conference in Florida.
Assuming all goes well with the initial flight the STOVL version is due to follow two months later. About three months later the CTOL version will be "re-winged" and equipped with an arrestor hook and other CV trappings to perform its function as a carrier test aircraft.
Pratt & Whitney are moving to define the two versions of the F119 turbofan to meet the same schedule. The most powerful version, rated at around 35,000lb thrust, is being developed for Boeing's direct-lift design. P&W plans to have the first Boeing engine to test in April 1998, but says its internal goal is to begin engine runs in February. The engine will be shipped to Seattle for the first ground runs in 1999. The flight test engines will be delivered later in the year.
Details of the larger fan being fitted to the F119 remain classified. The engine-maker says it will be "around 30% to 40% bigger" than the present unit. Although the bigger fan naturally increases the by -pass ratio, P&W says the rise is not "too dramatic" because the larger fan also pumps more air through the core. "We are talking about a [bypass] ratio similar to the F100," says P&W.
Boeing is equally tight-lipped about what it will do with the extra bypass air in cruise, but says it plans to use the cooler flow to dissipate the main exhaust plume and help reduce the infra-red signature."
The first ground test F119 for the Lockheed Martin JSF will be shipped to Palmdale, California, for installation around May 1999. "Shortly after this we will take the first man-rated engine," says Bevilaqua.
Unlike the Boeing engine, which has two Harrier-like main lift nozzles, the STOVL version of the Lockheed Martin aircraft is fitted with a three-bearing swivel nozzle to vector the main-engine thrust. The unit is loosely based on a similar design used by Yakovlev for the Yak-141 main engine nozzle.
Engine power to the shaft-driven lift fan, is modulated by varying the main exhaust nozzle area. When the area of the nozzle is increased, the engine pressure drop occurs across the turbine itself, rather than in the nozzle area, forcing the turbine to speed up. The turbine is connected. via a hydrostatic clutch and gearbox. to the lift fan, which then speeds up in response. The gear-train handles up to 25,000shp and the fan generates almost 20,000lb of thrust.
At the conference Boeing took the opportunity to reveal more details of its unusual design. The aircraft is just 13.6m long with a wingspan of 9.15m and a wing area of 55m2 able to take up to 15,000lb of fuel. Mission take-off gross weight for the USAF version is 38,000lb, though maximum take-off weight is 50,000lb and interdiction mission combat radius is of "well over" 600nm.
Internal weapons include two 1,000lb JDAMs plus two AIM-120C missiles. Boeing says the CTOL version has growth capability for 2,000lb-class JDAMs with the AIM-120s. It also carries an internal 20mm gun . The USN version has a 60,000lb launch capability and a "bring back" payload of 8,000lb.
More than 90% of the three Boeing JSF variants are common. The afterbody/empennage and forebody of all are identical, as is the single-piece wing structure.
Wingtip extensions are to be added to the wing box of the CV version, which is also fitted with a pop-up leading-edge vortex fence to improve low speed approach characteristics for carrier landings. The fuselage is the same for the CV and CTOL versions.
Lockheed Martin has decided to stick with the final design of allowing the main and lift nozzle to vector thrust forward by 20¹.o
Guy Norris/LOSANGELES
Boeing and Lockheed Martin have begun final detailed design work on their respective Joint Strike Fighter (JSF) demonstrator aircraft configurations, both are aiming to make first flights in early 2000.
Boeing's first aircraft will be a combined conventional take-off and landing (CTOL) and carrier (CV) demonstrator. The second aircraft will be the "primary" short take-off and vertical landing (STOVL) demonstrator for the US Marine Corps and Royal Navy JSF versions. It is due to be flown around mid-2000. Boeing JSF aircraft integration manager, Dennis Muilenburg, says both aircraft will be "STOVL capable", to minimise any potential disruptions of the Concept Demonstrator Programme (CDP).
Lockheed Martin's design, considered the lowest risk of the three contenders, will be "effectively frozen within six months", says senior executive Paul Bevilaqua.
The first Lockheed Martin JSF demonstrator (the CTOL) will fly around the end of February 2,000, says Bevilaqua, talking at the AIAA's International Powered Lift Conference in Florida.
Assuming all goes well with the initial flight the STOVL version is due to follow two months later. About three months later the CTOL version will be "re-winged" and equipped with an arrestor hook and other CV trappings to perform its function as a carrier test aircraft.
Pratt & Whitney is moving to define the two versions of the F119 turbofan to meet the same schedule. The most powerful version, rated at around 35,000lb thrust, is being developed for Boeing's direct-lift design. P&W plans to have the first Boeing engine to test in April 1998, but says its internal goal is to begin engine runs in February. The engine will be shipped to Seattle for the first ground runs in 1999. The flight test engines will be delivered later in the year.
Details of the larger fan being fitted to the F119 remain classified. The engine-maker says it will be "around 30% to 40% bigger" than the present unit. Although the bigger fan naturally increases the by -pass ratio, P&W says the rise is not "too dramatic" because the larger fan also pumps more air through the core. "We are talking about a [bypass] ratio similar to the F100," says P&W.
Boeing is equally tight-lipped about what it will do with the extra bypass air in cruise, but says it plans to use the cooler flow to dissipate the main exhaust plume and help reduce the infra-red signature."
The first ground test F119 for the Lockheed Martin JSF will be shipped to Palmdale, California, for installation around May 1999. "Shortly after this we will take the first man-rated engine," says Bevilaqua.
Unlike the Boeing engine, which has two Harrier-like main lift nozzles, the STOVL version of the Lockheed Martin aircraft is fitted with a three-bearing swivel nozzle to vector the main-engine thrust. The unit is loosely based on a similar design used by Yakovlev for the Yak-141 main engine nozzle.
Engine power to the shaft-driven lift fan, is modulated by varying the main exhaust nozzle area. When the area of the nozzle is increased, the engine pressure drop occurs across the turbine itself, rather than in the nozzle area, forcing the turbine to speed up. The turbine is connected. via a hydrostatic clutch and gearbox. to the lift fan, which then speeds up in response. The geartrain handles up to 25,000shp and the fan generates almost 20,000lb of thrust.
At the conference Boeing took the opportunity to reveal more details of its unusual design. The aircraft is just 13.6m long with a wingspan of 9.15m and a wing area of 55m2 able to take up to 15,000lb of fuel. Mission take-off gross weight for the USAF version is 38,000lb, though maximum take-off weight is 50,000lb and interdiction mission combat radius is of "well over" 600nm.
Internal weapons include two 1,000lb JDAMs plus two AIM-120C missiles. Boeing says the CTOL version has growth capability for 2,000lb-class JDAMs with the AIM-120s. It also carries an internal 20mm gun. The USN version has a 60,000lb launch capability and a "bring back" payload of 8,000lb.
More than 90% of the three Boeing JSF variants are common. The afterbody/empennage and forebody of all are identical, as is the single-piece wing structure.
Wingtip extensions are to be added to the wing box of the CV version, which is also fitted with a pop-up leading-edge vortex fence to improve low speed approach characteristics for carrier landings. The fuselage is the same for the CV and CTOL versions.
Lockheed Martin has decided to stick with the final design of allowing the main and lift nozzle to vector thrust forward by 20¹.
Source: Flight International
