X-35 - Joint Strike Fighter (JSF)
The Air Force JSF variant poses the smallest relative engineering challenge. The aircraft has no hover criteria to satisfy. And the characteristics and handling qualities associated with carrier operationslike catapult launches, control authority at approach speeds and beefed up structure to handle arrested landingsdo not come into play. On the other hand, the Air Force airplane will be measured against the high standards set by the F-16. As the biggest customer for the JSF, the service will not accept a multirole fighter replacement that doesn't significantly improve on the original. With the largest planned purchase, the USAF aircraft is also the program's affordability driver.
Carrier operations account for most of the differences between the Navy version and the other JSF variants. The aircraft has larger wing and tail control surfaces to better manage low-speed approaches. The extra wing area is provided by larger leading-edge flaps and foldable wingtip sections. These components attach to the common-geometry wingbox on the production line. The internal structure of the Navy variant is strengthened up to handle the loads associated with catapult launches and arrested landings. The aircraft has a carrier-suitable tailhook. Its landing gear has a longer stroke and higher load capacity. A larger wing span provides increased range and payload capability for the Navy variant. The aircraft has almost twice the range of an F-18C on internal fuel. The design is also optimized for survivability, a key Navy requirement.
The Marine variant of Lockheed Martin's JSF design distinguishes itself from the other variants with its short takeoff/vertical landing capability. The airplane must have more vertical lift than weight. While that requirement is obvious, it is sometimes difficult to meet. The airplane must be light and have a high thrust-to-weight ratio. Good controllability in every axis of the airplane at zero airspeed is a second requirement. The transition between up-and-away flight and hover must be carefully considered. The airplane's hover footprint, the propulsion system's impact on the ground surface or carrier deck, is just as critical. In the JAST program, which preceded JSF Concept Demonstration, the Lockheed Martin team accomplished extensive testing of its propulsion system for the STOVL aircraft. A shaft-driven lift fan system was operated for 200 hours in a 91-percent scale aircraft model, proving the system's feasibility and mechanical integrity.
The UK Royal Navy/Royal Air Force JSF will be very similar to the U.S. Marine variant.
The overall Concept Demonstration Phase has five separate but highly interrelated efforts. JSF Program success depends upon executing and integrating all of these efforts, which include: (1) design, manufacture, and test of concept demonstration aircraft; (2) Preferred Weapon System Concept design refinement; (3) other weapon system concept common and unique demonstrations; (4) Propulsion System development, manufacturing, and test; and (5) successful execution of the Technology Maturation contracts for transition into E&MD. Creating and maintaining an effective Government and Industry Team, and accomplishing these management objectives, are fundamental to successful completion of these efforts.
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