Every F/A-18E/F begins life at Northrop Grumman's El Segundo plant, once home to a North American P-51 Mustang production line, and just a stone's throw from Los Angeles International Airport, California.
The E/F programme sustains a 25-year long relationship between the team members that began with Northrop's YF-17 lightweight fighter prototype. McDonnell Douglas (MDC) first teamed with Northrop in 1974, to propose a YF-17 derivative to meet the US Navy's Air Combat Fighter requirement. Their proposal was selected in May 1975 and the scaled-up YF-17 was designated the F/A-18 Hornet. When MDC was awarded the full-scale development contract in December 1975, Northrop became the company's principal subcontractor.
The E/F agreement closely follows the original deal struck 24 years ago. "We have 40% of the programme, which is good business," says Northrop Grumman's F/A-18 business development manager, Kevin O'Mara. "The F/A-18 will become more and more important to us, and in 1999 will be the biggest portion of the business unit for the first time.
"We make the centre and aft fuselage, which is the real muscle of the aircraft. When it goes out the door it is ready to go," he says. Each fuselage takes roughly six months to complete from subassemblies. The completed sections are then trucked across country to Boeing's final assembly line in St Louis, Missouri.
The substantial changes incorporated in the much larger E/F presented opportunities to alter the long standing workshare agreement with MDC, now Boeing. "We did look at it, but we kept virtually the same workshare. We swapped a few items where it made sense, but it is basically the same," says O'Mara.
Key differences from Northrop Grumman's workshare on the C/D include the addition of conformal antennas, titanium bulkheads, engine bay fire protection and the new low-observable inlets and ducts. The company gained responsibility for the increased capacity environmental control system and installation of polyurethane fuel cells. It is also responsible for providing the extra fuel space (3,600lb - 1,600kg) in the E/F and developing the 207/345bar (3,000/5,000lb/in2) hydraulic system. The company lost work on the speedbrake, which has been deleted from the E/F.
Other opportunities for change presented by the E/F upgrade were actively seized on, however, particularly in the areas of advanced materials and manufacturing processes. Northrop Grumman's expertise in large-scale composite manufacturing, honed over years of development work on low-observable aircraft, is coming into its own on the E/F line.
"We learned a lot from the YF-23 and B-2, and the E/F has been an opportunity to use techniques we didn't even know about 15 years ago," says Bob Keller, head of operations for the F/A-18 and product delivery team leader. This is even more significant given the greater use of composites in the E/F - over 20% by weight, compared to around 10% in the C/D.
COMPOSITE FOCUS
The focus for composites manufacturing is an 1,800m2 (20,000ft2) dedicated centre which is organised by product lines to produce skins, bonded assemblies and Kevlar/glassfibre parts. Lean manufacturing principles have been adopted for the centre, which has seen flow times reduced from 30 days to between 8.5 and 10 days as the benefits of a "pulse system" philosophy have been realised. With the winding down of the C/D line, E/F work now makes up 99% of the production work at the site.
A variety of new machines, production and design systems have been introduced into the composite manufacturing centre. These include a tow placement machine which can produce the complex curved structure of the E/F's serpentine engine intake. Large, five-axis waterjet/milling machines have also been introduced to contour and machine parts, while laser ply guidance machines have been installed to mark and align the plies, rather than relying on the time-consuming placement of templates. Other pieces of major equipment include automated Drivmatic rivetting machines, resin transfer moulding machines, Accugraphic computer-aided cutting machines, autoclaves and automated ultrasonic inspection systems.
Changes were also introduced on the final assembly line. "Literally thousands" of these changes were suggested by line workers, more than 500 of whom were retrained to work on the E/F, says Keller. "We surveyed every mechanic on the C/D line and asked them what they'd change. All their suggestions went into the Unigraphics [design] database and that's where we got this manufacturing line from. We captured 20 years of tribal knowledge and put it into the database."
The results range from the setting up of integrated product teams to the use of bar-coded badges that enable planners to keep track of how much sandpaper is being used by each mechanic, and therefore how much more to buy to keep the line supplied.
Innovations include the use of off-the-shelf industrial robotic tools, bought for less than $700,000 to produce the vertical tails during the E/F engineering and manufacturing development (EMD) phase. "The key is that it is off-the-shelf, not custom made," says Keller. Nearly all the E/F tooling is positioned on self-levelling gyro-jacks - an important factor in the Los Angeles basin, which is subject to earthquakes and tremors. "They continuously re-adjust themselves every 20 seconds. If we have a 3.5 [on the Richter scale] or over, we have to re-site every tool, but not these," he adds.
PRODUCTION RAMP-UP
Northrop Grumman completed 10 fuselage shipsets for E/F ground and flight testing under the EMD programme. Under the first phase of low-rate initial production (LRIP) it produced 12 airframes last year, and it plans to deliver 20 this year. The line will ramp up to 30 shipsets in 2000, but further rate increases will depend on funding, says the company. The first full-rate production lot, scheduled for 2001, is planned to include 36 E/Fs. Lot 2, in 2002/3, is planned to be 42 aircraft, while Lots 3 and 4, covering 2003-5, are for 48 aircraft each.
The E/F rate at Northrop Grumman is unaffected by the slow down on the neighbouring C/D line, which is scheduled to go into "deep freeze" in July with delivery of the last fuselage section currently on order - for an aircraft destined for the Finnish air force.
Over in St Louis, meanwhile, the E/F upgrade also presented an opportunity to change the way the F/A-18 is built. It began with the way the aircraft was designed and has expanded to encompass everything from parts manufacture to final assembly.
The biggest change at the outset of the E/F programme was the adoption on an integrated product development approach. Integrated product teams (IPTs) were formed, which brought together the design, manufacturing, quality and procurement resources required to perform the task. The aircraft was broken down into a product hierarchy ranging from the Level 1 IPT responsible for the entire weapon system to the Level 5 teams responsible, for example, for the inner wing.
"Each team has total responsibility, accountability and authority for its product from womb to tomb," says Jim Young, Boeing's division director, F/A-18 programme engineering. "As we transition to production and operation, the teams are shrinking. A year from now there will be no Level 5 IPTs," he says.
The same product breakdown is being used in E/F assembly. "The team leaders looked at how it was done in product definition," says Young. Now the assembly and engineering teams are located next door to each other, and close to the E/F line.
Design for assembly was a guiding principle for the product definition teams, and the focus was on reducing parts count. Examples include the nose barrel bulkhead, which was a 90-piece assembly in the C/D but is now a one-piece machined part in the E/F. Tooling was eliminated and assembly time and cost reduced. High-speed machining has allowed the E/F team to convert numerous sheet-metal assemblies to machined-from-solid parts.
Variability reduction was another key design principle intended to improve assembly, and included modelling of the build-up of tolerances during manufacture, fabrication and assembly. Examples include redesign of the historically troublesome interface splice between the Boeing-produced forward fuselage and Northrop Grumman-built centre/aft fuselage. Redesigning tools and parts to improve the fit resulted in a 23% reduction in shims required and a 28% cut in manhours expended.
ASSEMBLY INNOVATIONS
Production operations are well under way in St Louis, where the first batch of LRIP aircraft are in final assembly. Delivery of the first production E/F to the US Navy, in December last year, was ahead of schedule.
New assembly tooling concepts have been introduced with the E/F. They include the low rate expandable tooling (LRET) used for the forward fuselage. Rather than move the fuselage section down an assembly line, it is built from the keel up in a mainframe tool. Three LRETs were installed for EMD; eight will be needed to support full-rate production. They share auxiliary jigs that are loaded into the tools as required to locate parts.
Assembly teams are assigned to each fuselage or wing LRET and build the entire structure. "There is healthy competition between LRET teams," says F/A-18 programme manufacturing director Kent Beran.
Several innovations are being introduced on the E/F assembly line, to cut costs. These include the paperless assembly data delivery system (PADDS), piloted during EMD on the outer wing and now being deployed throughout the St Louis plant. Using the PADDS, assembly workers can call up job instructions on a workstation adjacent to the tools.
An improved system, which displays three-dimensional graphics showing how to locate parts in the tool, is being piloted on the "mini-LRET" in which the nose keel/drag brace, which forms the backbone of the forward fuselage, is assembled. "It shows you which tool to use, and where not to drill. It's good for training new people and shortens the learning curve," says Beran. Boeing's aim during low-rate initial production is to "beat the learning curve" and drive E/F costs down.
Another innovation is the flexible assembly system, which will drill, countersink and inspect holes and install fasteners in the wing. Beran says this will replace the automatic rivetting machine now used. Liquid shimming is used to ensure a good fit between the carbonfibre wing skins and the metal substructure.
Further cost savings could result from Boeing's work under its advanced technology assembly (ATA) initiative. "We want to move drilling back into fabrication, and put the holes in during machining, "Beran says, adding that ATA changes are just beginning to be applied to the E/F forward fuselage.
Splicing of the forward and centre/aft fuselage is accomplished in a Nicholson alignment tool, which uses laser trackers to guide the two sections together. "The forward fuselage is mobile and the aft fuselage is stationary, and the computer drives them together for a nominal fit," says Beran. "We get perfect alignment."
Fuselage splicing presently takes place in a different building, but Boeing plans to extend the final assembly plant to get everything under on roof. Other investments for E/F production include a new paint facility, where the low-observability coatings also will be applied, and a radar cross-section measurement facility, where their effectiveness will be checked.
Investments will continue to be made, Boeing says, where they promise to reduce the E/F's cost. That includes design changes, which can pay for themselves in reduced fabrication and assembly costs. "Improving the F/A-18 is continuous process," says Young.
Source: Flight International
