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InnovMetric Software


Keeping Everything In Check

PolyWorks cuts symmetry and alignment check time by 75% on Bombardier jets

Published: Thursday, May 16, 2013 - 09:43

As your flight approaches the airport, the hydraulics sound from landing gear lowering provides reassurance. But as the plane touches down, an unexpected jolt and passengers’ squeals dash your calm. The plane’s forceful impact with the ground has resulted in what’s commonly referred to as a “hard landing,” and it’s considered to be a frequent incident. Every pilot will experience at least one hard landing during the course of his career.

Whether due to meteorological conditions, mechanical problems, being overweight, or pilot error, a hard landing can vary in seriousness from mild passenger discomfort to extensive damage to the aircraft. When a hard landing occurs, the airplane must be taken out of service and checked for structural damage before it’s allowed to fly again. At Bombardier Aerospace, this is where the ground support equipment team comes in.

The world’s third-largest civil aircraft manufacturer, Bombardier Aerospace designs, manufactures, and supports innovative aviation products for the business, commercial, specialized, and amphibious aircraft markets. Dedicated to setting new standards of customer care and aircraft availability, Bombardier offers a comprehensive range of support and services to its customers. Within its customer support group is the Canadair Regional Jet (CRJ) ground support equipment team, which consists of experts committed to resolving technical issues to keep the aircraft flying.

The CRJ ground support equipment group focuses on the commercial aircraft division, and lately on Bombardier’s CRJ NextGen series of regional jets. When an incident occurs where an airplane requires a symmetry and alignment check to analyze its structural engineering—for example, from being hit by a baggage transporter or a jet bridge, or after undergoing a hard landing—a notification is sent to the CRJ ground support equipment group, and the in-service engineering team is dispatched, on short notice, to any location worldwide.

“Knowing that a grounded plane can sum up to $100K/day in lost revenue, the CRJ ground support equipment team is dedicated to working around the clock, and across the globe, to return aircraft to service as fast as possible,” says Benoit Roby, CRJ ground support equipment coordinator at Bombardier.

Once the In-Service Engineering team is on location, it will perform a diagnostic to determine whether the incident has caused any deviations or damage to the components or to the structure of the airplane that may affect its airworthiness limitation. This diagnostic is done by inspecting the airplane, which includes performing a symmetry and alignment check to expose damage that might otherwise go unnoticed. Then, after inspection, if the aircraft is out of specification, maintenance is performed. When completed, a final symmetry and alignment check is done to ensure that the airplane is airworthy.

Symmetry and alignment check

A symmetry and alignment check is a dimensional verification of the aircraft’s airframe to determine whether its wings and tail are symmetrical to its longitudinal axis. The symmetry check includes inspection of fuselage vertical deviations, horizontal stabilizer dihedral, engine vertical deviations, engine horizontal alignment angle, fuselage horizontal deviations, wing and horizontal stabilizer alignment, vertical stabilizer alignment, wing incidence and twist check, landing gear check, and the symmetry of the winglets. The alignment check of the aircraft’s structure means that the position relationship of each major component must be inspected; this includes inspection of the wing group, tail group, and fuselage group.

Figure 1: Typical aircraft setup for the alignment and symmetry check

Prior to the check, specific conditions must be respected to ensure the precision of the measurements, namely, the aircraft should be inside a closed hangar where air currents or sunlight will not interfere with the alignment readings; the motors should not have operated within the past four hours; all of the fuel tanks should be drained; and the aircraft must be in a neutral or level position (i.e., mounted on jacks with its weight evenly spread out).

The challenge: the traditional method

Traditionally, the symmetry and alignment check has been performed by using the plumb bob and datum plane method. This involves taking manual measurements using plumb bobs, precision optical levels, transit rulers, tape, and numerous geometrical accessories that make up the symmetry and alignment kit. However, each kit is aircraft-model specific, meaning that when it’s in use, its accessibility is limited. Also, the traditional method requires two technicians and, in the best-case scenario, takes between 12–14 hours to complete.

To perform the check, target points are taken based on the symmetry screws located on the airplane as datum points. The plumb bob line is then dropped to the floor and manually measured. Due to the extraordinary size of the airplane, obtaining the measurements is both time-consuming and physically demanding on the technicians. Reporting is done manually, so two technicians must be present: one to take the measures, and one to record the results.

Figure 2: Taking measurements manually requires time and patience to ensure perfection.

The physical size of the symmetry and alignment kit used in the traditional method poses another set of challenges. Because the kit comes in an oversized crate, simply ensuring that the shipment follows the mobile team being dispatched to an international location is a feat. Additional costs, delays, and customs issues are common occurrences. These complications have, on occasion, resulted in team members being forced to wait for the kit upon their arrival, making their time unaccountable during the wait. Also, shipping the kit back to the initial destination poses another set of problems because the equipment is packed by another crew, meaning there’s the risk of damaging or misplacing tools.

Roby and his team reached the point where they needed to simplify their symmetry and alignment process with a portable system common to all airplanes. “Transport of the traditional symmetry and alignment kit had considerable drawbacks, which led us to consider using a 3D scanning solution,” says Roby. “Yet we were looking for a solution that would not affect the input or the output of our reporting system. After selecting the portable 3D hardware, I turned to our tooling services measurement specialists, and they highly recommended PolyWorks.”

The goal of the CRJ ground service equipment team was to eliminate equipment, save time, and make the measurement instruments as simple as possible because not all technicians are metrology specialists.

The solution: 3D metrology method

Roby’s team opted for the portable Leica Absolute Tracker AT401 and the 1.5-in. corner-cube reflector combined with InnovMetric’s PolyWorks Inspector software. The selected 3D metrology method provides a universal solution that is compatible with all aircraft, making limited accessibility to the tools a thing of the past. “The new solution is universal, portable, and fits right in a carry-on,” says Roby. “This is a huge plus since we don’t even have to check in the equipment for air travel.”

Add to the equipment a laptop and a homemade stand onto which the laser tracker is mounted, and the symmetry and alignment kit is complete—greatly simplifying transport logistics.

Figure 3: Portable Leica Absolute Tracker AT401 and the 1.5-in. corner-cube reflector combined with InnovMetric’s PolyWorks Inspector software.

Sometimes the previously mentioned best conditions for performing the symmetry and alignment check can’t always be respected. With the flexibility and robustness that this solution now provides, some of the preparation steps can be eliminated, reducing logistic constraints. Yet the most noteworthy benefit is the major time savings: A symmetry and alignment check can now be completed with only one technician in six hours—and Roby even estimates that they will be able to do it in four hours.

“The ROI benefit of this solution is straightforward: What once took two men and 12 hours to perform can now be completed with one man in six hours—which amounts to huge savings,” says Roby. The previous method often encountered delays during transport, and the CRJ ground support equipment team was not able to set a flat service rate. With the 3D metrology method the team can estimate the costs—a significant plus because within an organization like Bombardier, being able to plan operations costs is key.

The application

With PolyWorks, the entire symmetry and alignment procedure is simplified. The technician arrives on location, sets up his equipment, and identifies the target points on the airplane. Once this is done, he begins measuring using the corner-cube reflector, and PolyWorks does the rest. Operations such as determining the axis, moving the device, pairing, and adjusting to match are performed in PolyWorks. As each measure is taken, the data are instantly accessible in PolyWorks, and it’s automatically updated throughout the report.

Figure 4: Data of the measures taken with the corner-cube reflector is immediately available in PolyWorks’ Inspector.

PolyWorks reduces human error. “I have confidence in PolyWorks,” says Roby. “If a mistake occurs during the process, it’s immediately pinpointed.” After measurement of the target points is complete, the technician instantly gets real-time deviations with respect to nominal points from the CATIA CAD model in PolyWorks. Roby finds the interoperability of the software intuitive. In fact, the ease with which PolyWorks handles the model imported from the CAD software, as well as the facility to generate reports, were the key factors that influenced Roby’s buying decision.


By using PolyWorks, it’s now easier to generate reports. The results are exported to Excel, and the standard report format in place remains untouched. “Due to the fact that we must adhere to the strictest international standards, we needed a solution that would not affect our model file,” says Roby. “PolyWorks is easy to understand and use, plus it complies with our standards.”

Because reports can now be done in real time, PolyWorks offers the reporting flexibility that the in-service engineering team needs in the field. Moreover, the PolyWorks technical support group closely collaborated with Roby’s team to create reports that adapted to their needs. The result: Reports are optimized, yet there’s no effect on the report model because the input and the output are exactly the same.


PolyWorks was initially purchased to assist the CRJ ground support equipment team with its symmetry and alignment check, and it has proved that it can do more. “PolyWorks offers the versatility that we need,” says Roby. “We purchased this product for one purpose, and we’ve started to use it for our mapping needs.” By integrating PolyWorks into its inspection process, Bombardier reduced by 75 percent its symmetry and alignment check time, and with this in mind, the company is in the process of evaluating PolyWorks for the symmetry checks of amphibious aircraft.

Figure 5: The entire symmetry and alignment check process has been simplified.

Damage assessment is and always will be essential to aircraft repair. Fortunately, there are proven solutions assisting inspection crews in getting the structurally damaged aircraft back in the air as fast as possible, reducing downtime, saving money, and contributing to safer air travel.


About The Author

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InnovMetric Software

Founded in 1994 and headquartered in Quebec, QC, Canada, with subsidiaries worldwide, InnovMetric Software Inc. is the leading provider of universal 3D metrology software solutions. The world’s largest industrial manufacturing organizations (Toyota, General Motors, Volkswagen, Honda, BWM, Daimler, Ford, Rolls-Royce, Pratt & Whitney, Boeing, Embraer, Bombardier, Apple, and many more) trust InnovMetric’s PolyWorks software and associated technical services to maximize the benefits of 3D measurement technologies for their engineering and manufacturing applications. Including its subsidiaries and joint ventures, InnovMetric Software has more than 250 employees across 10 countries: Canada, United States, Mexico, Brazil, France, Benelux, India, Thailand, China, and Japan.