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X-35 - Joint Strike Fighter (JSF)


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.

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Page last modified: 07-07-2011 02:39:36 ZULU