Ever heard of a supersonic airplane that can stop in midair and hover? The F-35B Lightning II can. It’s the world’s first jet fighter to combine stealth technology with short takeoff-vertical landing (STOVL) capability and supersonic speed.
The aircraft depends on a lift fan, which produces 20,000 pounds of thrust. It overcomes many of the temperature, velocity and power challenges of direct-lift systems. The innovative device is assembled by Rolls-Royce in a new, state-of-the-art factory just outside Indianapolis.
The heart of the F-35B is a STOVL propulsion system comprising the most powerful engine ever flown in a jet fighter. It consists of a shaft-driven, counter-rotating lift fan situated behind the cockpit, a roll duct under each wing for lateral stability, and a rear swivel nozzle that vectors engine exhaust in the desired direction.
An F-35B pilot can land and take off just about anywhere. In addition to using traditional runways and aircraft carriers, the plane can land on a parking lot, a patch of grass or a rooftop. It can operate from a variety of ships, roads and austere bases near frontline combat zones.
The F-35B’s flexibility increases sortie rates and provides a broad range of deployment options for military commanders at sea or ashore. That’s why it appeals to the U.S. Marine Corps, which has ordered more than 340 of the jets. Armed forces in England, Italy and elsewhere have also expressed an interest in the fighter.
The Rolls-Royce LiftSystem, which includes the LiftFan located behind the cockpit and the swivel module at the tail, produces lift by directing thrust downward to overcome the weight of the aircraft. It produces a total vertical lifting thrust of more than 40,000 pounds, which is about 10,000 pounds more than the F-35B weighs.
During vertical takeoffs or landings, doors above and below the lift fan open, and a clutch connecting the lift fan to the engine driveshaft engages. A dorsal auxiliary engine inlet opens to increase airflow to the engine.
At the same time, doors beneath the three-bearing swivel nozzle open and the rear nozzle pivots downward in a matter of seconds to deflect engine thrust toward the ground. Roll ducts under each wing also are engaged, keeping the aircraft laterally stable.
In this configuration, the F-35B can hover, land vertically, take off in a few hundred feet fully loaded or take off vertically with a light load. When the aircraft transitions from jet-borne to conventional wing-borne flight, the doors close and the pilot can then accelerate to supersonic speeds. The system is completely automatic.
The F-35B is part of the controversial Joint Strike Fighter (JSF) program, which consists of three variations of the same basic aircraft to serve multiple branches of the U.S. military and its allies. The $400 billion program has been under development for more than a decade.
Pentagon officials believe the one-size-fits-all approach is an effective way to replace their aging fighter fleets, which have an average age of 22 years. The fifth-generation JSF stealth fighter is designed to replace a wide range of existing aircraft, such as A-10s, F-16s and F/A-18 Hornets.
Lockheed Martin Corp. assembles the planes at its factory in Fort Worth, TX. Key partners in the project include Northrop Grumman Corp., which assembles fuselages at a new automated plant in Palmdale, CA, and Pratt & Whitney, which assembles F-35 jet engines in Middletown, CT.
Rolls-Royce is the only company in the world to produce vertical-lift capability for fighter aircraft.
It supplies the LiftSystem as a subcontractor to Pratt & Whitney. Rolls-Royce also builds a wide variety of engines for other types of military applications, in addition to commercial jetliners, business jets and helicopters.
The first three production F-35B aircraft were recently delivered to Eglin Air Force Base in northwest Florida for the start of pilot training. More than 340 vertical landings have been performed so far.
Fresh Thinking
To support the F-35B program, Rolls-Royce built a 37,000-square-foot “focused factory” in Plainfield, IN. The $12 million facility is located a few miles from the company’s much larger and older plants that produce jet and propeller-driven engines and components.
“The focused factory was a paradigm shift in the way we operate from a cost and competitiveness standpoint,” says John Gallo, executive vice president of business operations at Rolls-Royce North America. “By operating under the new structure, we had a tremendous opportunity to be significantly more cost competitive…as well as more flexible [with] work rules regarding the employees.
“Additionally, it gave us a green field to optimize the process and layout for flow and lean principles, while taking advantage of the latest assembly technologies,” adds Gallo. “This helped us to create a world-class assembly facility.”
The plant was designed from the ground up with lean manufacturing in mind. “Throughout the project, we drove lean into the facility and processes,” Gallo points out. “[We leveraged] our experiences and the lessons learned with [our] new small-engine assembly line to improve on some technologies and implement new technologies.”
The 24,000-square-foot small-engine line was built several years ago at another Rolls-Royce factory in Indianapolis. It produces turboshaft engines for use in helicopters such as the R66 from Robinson Helicopter Co.
Ideas borrowed from that operation include smart tools that help error-proof the process and capture more fastening data; intelligent tool control systems that alert assemblers when a tool is not in its correct place; and an electronic execution system that can provide 3D models and graphics to aid assemblers.
“We also pioneered completely new technologies and capabilities, including wireless integration of the entire facility,” says Gallo. “[That covers everything] from the use of wireless tools to handheld devices that allow [operators] to navigate the assembly execution system.
“For all areas, we incorporated the latest in visual management, such as using computer modeling for animation and simulation of the assembly area and equipment during concept generation,” Gallo points out. “The dedicated facility also provides a customer showcase for [our] highest technology products.”
The LiftFan factory served as the pilot for a new union contract that has since been incorporated across Rolls-Royce’s Indianapolis operations. It includes flexible work rules, a broader definition of “work,” self-directed work teams and a performance-based bonus.
“The flexible work rules allow our [assemblers] to perform virtually any task within the facility,” says Gallo. “They can do everything from inspection and material handling to light asset maintenance.
“This flexibility gives us the ability to respond to the needs of the operation much more quickly and effectively,” explains Gallo. “Every team member is also completely flexible across assembly stations. If one area needs help to catch up or is undermanned, anyone on the team [can] bounce to the area and help.”
A wide variety of lean manufacturing principles are used in the facility. For example, process management tools include business plan deployment, master planning, PDCA (plan-do-check-act), 3C (concern, cause, countermeasure) and root cause analysis.
Visual management and workplace organization play key roles in the plant. For instance, all subassembly positions are clearly labeled and marked.
A large andon board in the middle of the factory provides production updates to assemblers. “It brings immediate attention to problems as they occur,” says Gallo. “[The scoreboard also] encourages immediate reaction to quality, downtime and safety problems. It improves accountability and [enables us] to quickly identify and resolve manufacturing issues.”
A centralized communications center features two 42-inch touchscreen computers designed for ease-of-use by the entire team. It displays a wide variety of real-time data for responsiveness and flexibility.
Assembly Tools
The heart of the Rolls-Royce LiftSystem is the LiftFan. It consists of a 50-inch, two-stage counter-rotating fan equipped with state-of-the-art hollow-bladed disk technology. The unit is driven from a conventional gas turbine and produces the forward vertical lift of the F-35B.
The complex device contains approximately 3,200 parts, which are supplied by other Rolls-Royce plants and third-party vendors. Key components include rotors, gearboxes and clutchs. Each lift fan requires about 500 hours of manual assembly time. Rolls-Royce assemblers also produce the vane box, which forms the exit through which air from the LiftFan is vectored.
LiftFans are assembled vertically at three main workstations, which the company calls “stack stations.” Subassembly lines on both sides feed into them. The key assembly steps are tightening of threaded fasteners; interference fits, including press fitting and shrink and expansion fits; retaining ring fastening; shim selection; and gear backlash and contact pattern verification.
The assembly process starts with the gearbox modules. Assemblers focus on the clutch at the second workstation. The last stack station is the most complex, with numerous hose and wiring assembly tasks.
Assemblers are equipped with state-of-the-art fastening equipment in the ISO 14001-compliant plant. “We use DC-electric tools throughout the entire assembly process,” says Mike Hess, LiftFan manufacturing engineering manager. Cordless tools are used for some applications and various control and tightening strategies are widely used, including prevailing torque monitoring and statistical and trend deviation alarms.
Manual, transducerized wrenches have interchangeable smart heads that provide different torque capacities with angle readings. “Those tools are used for difficult access or limited-space applications, as well as affordable tube-nut tightening,” explains Hess.
Smart torque tools are equipped with wireless locating technology. “[The positioning system] locates, validates and error-proofs torque sequence patterns,” Hess points out. “An electromagnetic sensing system tracks the X, Y, Z, pitch, roll and yaw positions of the device. It prompts configurable locations to the operator on a graphical user interface.”
Data is automatically collected for all fastening tools. “All tightening results and traces are stored in one common database,” says Hess. “It provides NOK (not OK) reports, event reports and fault history, in addition to providing program change tracking.” The system also produces a variety of statistical reports, such as run charts and process capability indexes.
Tools are equipped with radio frequency identification tags for asset tracking, loss prevention and foreign object detection. A scanner can automatically find tools within a 30-foot radius, in case something is accidentally left in an assembly.
An intelligent tool cabinet dispenses screwdrivers, wrenches, pliers and hammers, using badge scan access. “[This helps us] easily locate the person and area the item was issued to and when it was issued,” says Hess. “[And, it allows] visual inspection of missing items from the touchscreen monitor and audit databases for compliance purposes.”
At the end of the LiftFan assembly line, operators use soft dry ice, accelerated at high speeds, to lift any contaminants off the underlying substrate. “Dry ice cleaning is nonabrasive, nonflammable and nonconductive, contains no secondary contaminants such as solvents, and can be used without damaging active electrical or mechanical parts,” Hess points out. A robot equipped with a vision system inspect each LiftFan prior to shipment for testing.
Ergonomics and Material Handling
Because the LiftFan is 60 inches in diameter and weighs almost 3,000 pounds, ergonomics and material handling play a key role at the new Rolls-Royce plant.
Custom-built assembly platforms for the three workstations on the flow line were constructed to address ergonomic issues. The platforms are 24 feet long and 18 feet wide. They utilize electric cylinders to drive scissor lift mechanisms anywhere from 2 to 10 feet above the plant floor.
Six build stands move between lift platforms via air skids to eliminate the use of forklifts in the assembly area. They move up or down independently of the lift platforms, as well as rotate 90 degrees for specific installation processes.
“This equipment allows operators to always work on the LiftFan in an ergonomically correct position and height,” says Anthony Woodard, senior manager of LiftFan assembly. “The lift platform includes accommodations for toolboxes, parts bins and assembly tools. The build stand fixture facilitates quick mounting and removal of the LiftFan through the use of the clamshell clamps.”
All fastening tools were selected with ergonomics in mind. “The use of battery-powered and wireless torque tools allows the operator to work unhindered in ergonomically [correct] positions, which results in reduced operator fatigue,” explains Woodard. “The cordless tools are ideal for large structures where operators need to cover significant distances.”
Mobile wireless computer stations that resemble hospital carts allow operators to roll work instructions directly to the point of use in the assembly area to reduce wasted motion.
All parts needed to build the LiftFan arrive at the factory in foam cut-outs enclosed in reusable plastic totes and containers. “We use a third-party logistics center to collect and kit all components needed [to assemble the LiftFan],” says Woodard. “All containers are owned by the logistics service, including all maintenance and management. These containers are designed to ensure ergonomic functionality and there is clear visual identification integrated into the kit boxes.”
Visual demand signals determine when kits are needed on the assembly line. Based on the visual signals on the plant floor, the kits are either staged in the logistics area or taken directly to the assembly line. Empty containers are placed in the designated area in the logistics bay and loaded onto a truck to be returned, cleaned, maintained and refilled at the third-party logistics center.
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