Model-based Instructions Help Streamline Avionics Refit

Model-based instructions (MBIs) are shop floor work instructions generated from engineering 3D models of the aircraft for assembly tasks. MBIs, now being used in the largest known aircraft modernization program to date, give mechanics the same 3D visual images available to the designer. They are the culmination of years of efforts to get paper off the shop floor throughout the aerospace industry.


Model-based instructions (MBIs) are shop floor work instructions generated from engineering 3D models of the aircraft for assembly tasks. MBIs, now being used in the largest known aircraft modernization program to date, give mechanics the same 3D visual images available to the designer. They are the culmination of years of efforts to get paper off the shop floor throughout the aerospace industry.

Avionics is shorthand for aviation electronics, such as for flight control, navigation, and communications. “We found that many programs within the company had used elements of virtual manufacturing,” said Martin E. Kret, director of production operations for the Boeing C- 130 Avionics Modernization Program (AMP), “but nobody had taken it to its fullest capacity. We have!”

Many of the aircraft in the AMP are approaching 30 years old. As many as 70 aircraft will be modernized each year, and by 2014, the front ends and cockpits of roughly 400 aircraft are to be gutted, re-quipped and rewired at Robins Air Force Base, GA, and at a second air logistics center (ALC) in Ogden, UT. This will add another 20 years to the service life of these powerful, versatile, and ruggedly built aircraft.

Productivity gains

Benefits to the “owners” of the modified and updated C-130s include newly standardized aircraft controls, meaning that any qualified C-130 crew will be able to fly almost any C-130. This will solve huge scheduling problems. Aircrew tasks will also be simplified with easy to comprehend and easy to use digital displays that are far more informative than the old analog displays they replace. And the aircraft will at last be fully qualified for international flight.

Kret predicted even bigger gains “as the word spreads about how MBI can revitalize any shop-floor operation. We get calls every week from all over the company.” A 25-year veteran of Boeing with lots of shop-floor experience, Kret is an electrical engineer with an MBA in finance.

Model-based instructions have helped boost mechanics’ productivity by 57% in The Boeing Company’s AMP for the C-130 Hercules military transport aircraft. As a result, C-130 AMP managers believe they can cut the turnaround time per aircraft by one-third to four months from six. The C-130 MBIs are being developed with software from Delmia in Auburn Hills, MI.

Boeing calls the gains so far “very conservative,” based solely on shop-floor hours worked on the first aircraft and projected for the second. Hours worked, or “touch labor,” is by far the biggest variable cost in aircraft modifications. The 57% gain has three elements: reducing time spent interpreting paper drawings on the shop floor, better availability of kits and parts, and shortening the learning curve.

The software is Delmia Digital Process for Manufacturing (DPM) software for process validation, resource modeling and simulation, DPM Work for work instruction authoring, and DPM Shop for sharing and deploying electronic work instructions or MBI. The C-130 AMP uses the Dassault Systemes Version 5 for the Microsoft Windows environment, Releases 16 and 17. Delmia is the Digital Manufacturing brand of Dassault, Suresnes, France.

There is an essential hardware component, too. Tablet PCs will be given to the ALC mechanics so that they can access the digital MBIs as needed in real time, even if they are working inside or on top of the aircraft. “The beauty of MBIs,” said Kret, “is that they keep the mechanics on the aircraft so they can get their jobs done.”

Boeing C-130 (AMP) ergonomics analysis as developed with Delmia Human. The MBIs have four aspects:

  • Producibility and ergonomic analyses,

  • Generating 3D work instructions from digital models,

  • Providing networks for online engineering data that is current and cannot be changed, and

  • Electronic buyoffs based on the MBI.

Paper and the learning curve

Soon after Boeing landed the C-130 AMP contract in 2002, Kret and members of his integrated product team (IPT) realized that no two of these aircraft are alike—even those designed and built for identical missions. Work instructions specific to each aircraft would be needed, which pointed to large learning curves.

The engineers quickly realized the C-130 program’s demands could not be met with the accepted methods. They “hit the road” to study Boeing operations in Seattle, St. Louis, and Philadelphia, “searching for new ideas that would work better than what we had,” Kret said. That search evolved into the MBIs. “This is the most complex aircraft modification in history,” Kret added, “with 14 versions of the C-130 being taken to one. Boeing does not own the legacy data on these aircraft, and after 20 years of mods for many different missions, often at multiple depots and ALCs, parts and wiring can vary widely from plane to plane. Wiring harnesses, a major portion of the shop-floor work, often have to be rerouted on the spot, making their installation much more complicated.”

“Mechanics rarely spent less than two hours a day looking for information and interpreting drawings,” Kret explained, “and sometimes more than five hours.”

Until now work instructions have been stacks of a dozen to 50 B-sized 2D drawings plus text descriptions for each task. The mechanics on the shop floor had to:

  • Interpret paper documents,

  • Leave assigned tasks to search for missing information, and

  • Wait while mechanical engineers and liaison engineers sorted through the paper themselves.

“The standard work instruction was always 'install per view,’” Kret pointed out. “The manufacturing engineer laid out the task in 2D CAD drawings, even though most of the info is in 3D formats. This forced the shop floor mechanics to interpret what the blueprint was showing, which added time and confusion—and ultimately rework.”

He explained that “a mechanic might have 50 views but inevitably a critical one was not provided. Something the mechanic needed to see was partly blocked, even in the most relevant drawing, or the mechanic needed to see behind or beneath something else that no drawing showed.” Not surprisingly, errors occurred.

“With MBIs, we are able to move the designers’ intentions in the engineering drawing into the hands of the mechanics,” said Boeing Phantom Works engineer Keith Mason, a specialist in work instructions. “We can cut two to three hours of interpretation out of the liaison engineer’s workday.” Boeing’s manufacturing R&D unit, Phantom Works is based in St. Louis, MO, as is IDS. Kret and his team are based in Long Beach, CA.

Models, software, wireless

The MBI solution to the shop-floor paper problem includes:

  • Graphics for each specific task based on digital models of the nose and cockpit of each C-130.

  • Hyperlinks to the text-based instructions and processes, of which Boeing has thousands. “By incorporating all the process specs, the mechanics never have to run to the tech library,” said Kret. “A mechanic can now start a task within minutes,” with knowledge of model based instruction.

  • Integration to the Boeing IDS manufacturing execution system (MES) called I-GOLD, an acronym for “Integrated Government OnLine Data.” In addition to sequencing and scheduling operations, I-GOLD manages the buy-off process for each task.

The software prevents editing the geometry that comes into MBIs. Allowing edits risks changing engineering intent and the consequent loss of vital configuration control. “It is a strength that you can manipulate the geometry—hide, unhide, rotate and so on—and reuse the engineering data, but it cannot be changed in the MBI,” Kret says.

“Delmia gives the shop floor engineers access to all the tools and capabilities that the design engineers have,” Kret pointed out, citing profound progress on MBI-type capabilities in the software in the past two years.

For example, the relevant Boeing specifications now can be attached with hyperlinks to the mechanics’ instructions, for reference right from the shop floor. Also, prior to MBIs, tools such as drill guides and templates and their blueprints were not integrated. The mechanics had to figure it out. “Soon we will have even more robust hyperlinks that will take the mechanic not just to the specification’s front page, but right to the page that is needed.

Instant MBI acceptance

The success of the C-130 MBIs is reflected in two anecdotes from the debut at Boeing San Antonio facility:

  • One mechanic who was lent a Tablet PC with access to the MBIs “would not give it back to us at the end of the day,” Kret said. “I worked right alongside the mechanics for half a day, and then they were on their own,” said Kelly Merryman. “At the end of the first day, we asked the first mechanic who used the MBIs what he thought of them on a scale of one to five. His answer was, 'eight.’” Kret pointed out this underscored the nearly instant acceptance of MBIs on the shop floor.

  • A tool-crib attendant was unaware of MBIs until a mechanic lent her his Tablet PC. She found it extremely helpful in finding the tool because she had a graphic. “The MBI had a picture of the tool and its identifying number, and the attendant found it in five minutes, instead of the usual hour or more,” Merryman said. “Using MBIs is very intuitive,” Kret pointed out. Other identifiable results include simplifying hand-offs between mechanics, such as when additional help is called in, and helping mechanics orient themselves to tasks and positions inside the aircraft. In addition, MBIs incorporate shop floor “tribal knowledge,” that is how tasks are actually performed.

  • Capabilities within Delmia detect any engineering update relevant to an MBI, and then automatically flag it. This solves the problem of updating drawings and tracking revisions that occur after information has moved to the shop floor as work instructions. In this way, MBIs address the perennial problem of out-of-synch revisions on the shop floor.

  • Capturing non-conformances and discrepancies as they occur. This is done automatically with an “iCapture” button Phantom Works engineers added to the main MBI screen. Kret and his team expect this to minimize future version control and configuration management challenges.

“On the shop floor, this is an important advantage,” Kret explained. “For the first time, MBIs give mechanics the capability of identifying a discrepancy. Until now, the mechanic had to go get an inspector and the inspector would write it up. Now the mechanic can snapshot the discrepancy and add it to the model.” He continued, “right away the engineer can very clearly see what the problem is, and he doesn’t have to do any interpretation. Depending on the significance of the problem, a disposition can be made on that same info.”

The idea for this came from an engineer who saw one of Kret’s early MBI presentations on the C-130 program. “MBIs,” Kret pointed out, “let the engineers and mechanics step through each task and process, so only a few simulations were needed for the C-130s,” he added. The simulations were done to validate fundamental concepts, demonstrate best practices, and clarify complex tasks.

Faster learning

The most dramatic MBI benefit to Boeing is the future possibility of cutting the C-130 AMP’s allotted six-month turn-around time, Kret noted. This is in spite of all the learning-curve issues related to differences between the as-designed and as-received and the huge number of C-130 variants.

“The 12:1 ROI is just the beginning,” Kret said, even though the learning curve gains can’t be fully measured until more aircraft have been modified. Additional ROI metrics being calculated are cycle time, level of support manpower, and quality control. Kret calculated a 17% ROI in engineering, just from using the Delmia tools. That is in addition to the 40% productivity gained with the second C-130.

“The engineering productivity gain is based on catching problems before a design goes out to the shop floor,” Kret added. One reason for the delay in metrics is the rapid scale-up in the use MBIs. From a handful of tasks on the first aircraft, 28 have been identified for the second, and between 200 and 300 for the third C-130 and those that follow.

MBI implementation on C-130 AMP won a coveted Acquisition Excellence award from the Warner Robins Air Logistics Center in Robins Air Force Base, GA, and a Silver Eagle award from Boeing’s Global Mobility Systems. The Silver Eagle is for process improvement, teamwork, meeting all quality specifications plus on-time delivery.

Jack Thornton is a freelance technology writer. Contact him at

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