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Lockheed Martin leads a JSF X-35 team that includes Northrop Grumman, BAE Systems, and Pratt & Whitney as program partners. The Lockheed Martin team capitalizes on the low-cost, rapid-prototyping, and advanced technology experience at the Lockheed Martin Palmdale facility; the integrated product team structure, critical stealth technologies, and lessons learned from the Lockheed Martin F-22 office in Marietta; and the total systems integration and world-class, lean production capability at Lockheed Martin in Fort Worth. Northrop Grumman brings tactical aircraft integration, carrier suitability, stealth technologies, avionics systems integration, sensors, and advanced commercial aircraft manufacturing. BAE SYSTEMS provides its expertise and experience with short take off and vertical landing (STOVL) technology, subcontract management, and lean manufacturing. Though separated geographically, the team members share a virtual workspace created by shared databases and common audio, video, and computer systems. The Lockheed Martin JSF team is currently evaluating their flight demonstrator aircraft, the X-35A/B and X-35C.

The Lockheed Martin JSF team has developed three variants designed to meet the needs of the U.S. Air Force, U.S. Navy, U.S. Marine Corps, and the U.K. Royal Air Force and Royal Navy. These variants share a highly common structure that includes the same fuselage and internal weapons bay. The Lockheed Martin aircraft have common outer mold lines with common structural geometries, identical wing sweeps, and similar tail shapes. The aircraft carry weapons in two parallel bays located aft of the main landing gear. The canopy, radar, ejection system, subsystems, and avionics are common. All of the aircraft are powered by a modification of the same core engine, the Pratt & Whitney F119.

Commonality and flexibility are the basis for the Lockheed Martin JSF design. The high degree of commonality among the service aircraft variants, and across the total development and production program, is a key to affordability. Cooperation allows the participating services to share development costs, which in turn greatly reduces total cost, when compared to an independent program for each service. Together, the services plan to purchase approximately 3,000 aircraft, so this highly common design will benefit from economies of scale. Additional international sales of approximately 2000 JSFs may further reduce costs.

 

 

X-35 Variants

 

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The X-35A
X-35A
X-35B
X-35B

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 operations like catapult launches, control authority at approach speeds and beefed up structure to handle arrested landings do 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.

 

 

Testing

 

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X-35C
X-35C

The first X-35 concept demonstrator aircraft left the runway at Air Force Plant 42, Palmdale, California at 0906 PST on 24 October 2000. The X-35A landed shortly thereafter at Edwards Air Force Base, California and began a rigorous flight test program.

On 7 November 2000, the X-35A took on fuel from a KC-135 tanker for the first time, enabling the aircraft to complete its longest flight to date: 2 hours and 50 minutes. The X-35A successfully completed its flight-test program on 22 November 2000, logging 27 flights in 30 days and achieving the first JSF supersonic flight on 21 November 2000, before it was returned to Palmdale in order to be converted to the STOVL X-35B.

The X-35B was scheduled to fly during spring 2001. The X-35B features a unique shaft-driven lift fan that amplifies engine thrust and reduces exhaust temperature and velocity during STOVL operations.

The X-35C, designed to satisfy U.S. Navy requirements, features a larger wing and control surfaces than the other JSF variants, and has an increased-capacity structure for absorbing catapult launches and arrested landings. This variant of the Lockheed Martin JSF family first flew on 16 December 2000. Afterwards, the X-35C began a series of envelope-expansion flights and on 25 January 2001, the X-35C completed tanker qualification trials with a series of air-to-air refueling behind an U.S. Air Force KC-10. The X-35C then completed its first supersonic flight on 31 January 2001 before being ferried from Edwards Air Force Base, California to Patuxent River Naval Air Station, Maryland.

The X-35C touched down at Patuxent River NAS on 10 February 2001, completing the first-ever transcontinental flight of a JSF demonstrator aircraft and initiating a series of flight tests that demonstrated carrier suitability in sea-level conditions. The X-35C's flight-test program included a series of Field Carrier Landing Practice (FCLP) tests to evaluate the aircraft's handling qualities and performance during carrier approaches and landings at an airfield, and also included up-and-away handling-quality tests and engine transients at varying speeds and altitudes.

 

 

X-35 Technology

 

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X-35 STOVL
Lockheed JSL

Lockheed Martin has developed a STOVL lift system that uses a vertically oriented Lift Fan. A two-stage low-pressure turbine on the engine delivers the horsepower to drive the STOVL Lift Fan. The Lift Fan generates a column of cool air that produces nearly 20,000 pounds of lifting power using variable inlet guide vanes to modulate the airflow, along with an equivalent amount of thrust from the downward vectored rear exhaust to lift the aircraft. The Lift Fan has a clutch that engages for STOVL operations and a telescoping "D" -shaped hood to provide thrust deflection. Because the lift fan extracts power from the engine, exhaust temperatures are reduced by about 200 degrees compared to traditional STOVL systems. The SDLF concept was successfully demonstrated through a Large Scale Powered Model (LSPM) in 1995-96. The lift fan, a patented Lockheed Martin design, was developed and produced by Rolls-Royce Corp. at its North American facility in Indianapolis, Indiana.

During the summer of 1997, Allison conducted testing of a model of the Lift Fan nozzle at the NASA-Lewis Powered Lift Facility in Ohio. The test results validated the computational fluid dynamics predictions of exhaust nozzle performance. B.F. Goodrich conducted testing of the Lift Fan clutch that is being developed under a subcontract to Allison. Testing demonstrated high-speed clutch engagements that were representative of the X-35 STOVL operating conditions. A favorable clutch plate wear rate translated into a clutch plate life of over four times the X-35 flight demonstration requirement.

The exhaust from the engine flows through the 3 Bearing Swivel Nozzle (3BSN). The 3BSN nozzle, developed by Rolls-Royce, was patterned along the lines of the exhaust system on the Yakovlev Yak-141 STOVL prototype that flew at the 1992 Farnborough air show. A US Navy program also developed swivel nozzles in the late 1960's and was proposed for a supersonic STOVL design by Convair (one of the Lockheed Martin heritage companies) in the early 1970's.

Lockheed Martin has developed and prototyped state of the art manufacturing concepts, tooling, and techniques as part of the JSF Concept Development Program. Lockheed Martin completed a comprehensive Airframe Affordability Demonstration (AAD), which demonstrated innovative fabrication, assembly, and tooling techniques for use on JSF. In addition, Northrop-Grumman and BAE SYSTEMS demonstrated advances in composite technologies and flexible tooling which will greatly reduce the cost and time for manufacturing.

Lockheed Martin prototyped, integrated, and tested the advanced avionics required to meet JSF requirements aboard Northrop Grumman's BAC-111 Avionics Test Bed. This testing enabled early evaluation of technology in the airborne environment to ensure risks were reduced early in the development cycle.

Lockheed Martin fabricated and tested a full-scale model of their JSF aircraft to demonstrate key low observability technologies, as well as innovative support concepts for low-observable designs. Testing with full scale prototypes early in the design stage enabled Lockheed Martin to verify their design capabilities, identify areas for potential improvements early in the development cycle, and verify key support concepts required to ensure affordable operation once aircraft are fielded. Lockheed Martin developed another full-scale model to support avionics integration testing to verify performance of key avionics systems in the proposed aircraft configuration early and affordably in the program.

Lockheed Martin has developed full-mission simulation capabilities for all JSF variants. This simulation capability allows pilot-in-the-loop testing to verify operational concepts, system requirements, and derived requirements on the aircraft and mission systems. Lockheed Martin has successfully used these simulations with pilots from the US and Allied Services who will be flying JSF.

Once test pilots begin evaluating the JSF, they will be looking at several key features that have been designed specifically for its pilots and ground crews. The fighter's most unique safety characteristic is its prognostic health management system, which begins working before the aircraft returns from a mission. With this system, the aircraft relays key maintenance information to ground support people who can then assemble the right skills, technical data and aircraft spares needed to quickly return the jet to the air.

If a system, such as the aircraft's radar, were to fail or sustain battle damage, the health management technology would signal an in-flight reconfiguration thus allowing the pilot to link to a wingman's radar system to complete the mission. The reliability and fault-isolation data offered by the system will also help JSF maintenance crews identify when an aircraft is meeting mission and reconfiguration requirements.

The fighter's ground collision avoidance system also has been developed to assist a pilot in a situation where he or she might be task-saturated or temporarily incapacitated. If such a situation arises, the aircraft will automatically maneuver to avoid hitting terrain or obstacles.

The system uses digitally stored databases including one containing terrain representative data to predict when a collision with the ground is imminent, said Crawford. A fly-up is commanded prior to impact signaling the flight controls to execute an automatic fly-up. The mission computer terrain database can be updated flight to flight to support the current mission plan. Pilots will also have the ability to add man-made features to the terrain if needed, said Crawford.

The new fighter also represents a significant step forward in safety of short takeoff and vertical landing, or STOVL, operations as compared to older aircraft such as the British Harrier. The airframe of the Marine version of the JSF has been modified to allow for STOVL operations and is slated to replace the Marine's current fleet of AV-8B Harrier jump jets.

The JSF flight control system will take inputs from the pilot and through its sophisticated software algorithms will determine the safest and most effective method to accomplish the pilot's desired task. The computer system will also correct for environmental and other external influences on the aircraft including wind and ship movement to safely land the F-35 on a carrier deck.

Global Security

 

F-35 Lightning II.

 

 

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