A Compact Tracker with Unrestricted Portability

3D-Model-of-Boeing-737

Pilatus, one of Europe’s oldest aircraft manufacturers, chose the API Tracker 3 for its tooling and quality control. The tracker’s portability and ability to compare connect with Pilatus’s CAD system. The single laser tracker helped check the soundness of more than 100 planes in one year.

Pilatus Flugzeugwerke AG, founded in 1939, is the leading manufacturer of single-engine turboprop aircraft and the only Swiss company to develop and construct aircraft and training systems and sell them on every continent. The company also opened a new chapter in terms of quality control 70 years after the company was founded and in the year in which the largest volume of orders in the company’s history had been achieved to date; in future, portable, laser-based measuring systems will guarantee that manufacturing tolerances are observed.

The highest demands in terms of quality apply globally within the aviation sector. A task that already represents a challenge within series aircraft manufacturing becomes a work of art in itself within customized aircraft manufacturing: guaranteeing the quality of Pilatus aircraft. As thousands of individual parts are involved that have to fit together perfectly, the complexity of quality control within production increases, as all of the parts and the modules produced from them must undergo an entire and extremely precise quality control check. In particular, observing the accuracy of fit within the current partial series manufacturing plays a vital role within Pilatus; the customers’ individual challenging requests in terms of production can only be taken into consideration and tested with this production process.

Since the beginning of 2009 an API laser tracker has played a major part in the company’s ability to implement these customer requests and still produce effectively and with high-precision. The ultra-precise but nevertheless portable measuring system does not just guarantee the proverbial Swiss quality in terms of jig and gauge construction.

The jig construction: where everything comes together

As is also the case with other international aircraft manufacturers, Pilatus manufactures the parts of an aircraft, such as the body, cockpit or wings, at different sites. The measuring points are already defined when they are constructed enabling the jigs for the parts assembly to be checked at a later stage to guarantee their accuracy for assembling. Measuring these points guarantees that the jig corresponds with the CAD data. On the basis of these reference points, an aircraft wing, for example, which is made up of thousands of individual parts, can be assembled precisely and be checked at crucial points to ensure that it corresponds with the CAD data.

A laser tracker demonstrates its unique ability with these measurements, namely to be able to measure large parts quickly and, above all, to measure objects with high-precision. With measuring distances of up to 60 metres it is also suitable for the body and wing assemblies for large aircraft. Thanks to the flexible assembly and set-up options on the API laser tracker, even areas that are difficult to access can be effectively measured. In terms of measurement, this represents significant additional expenditure. Without the new laser-based measuring technology, Pilatus was only able to make an actual adjustment to these versions with the CAD data with CMM or extremely expensive Theodolite measuring systems. As soon as the laser beam lands on the reflective mirror of the measuring sphere, the XYZ position of the reflector is calculated and displayed. A laser tracker realizes the measuring point deviations from the CAD model in real time – a prerequisite for assembling in an efficient and dimensionally accurate manner.

However, the size of a jig itself does not always create problems for manufacturing; often its complexity is also a metrological challenge, as is illustrated in the following example of a jig for the construction of a cockpit. Pilatus can only guarantee that the completed cockpit corresponds exactly to the specification on the construction plans due to the large number of measuring points on the jig.

This jig also has tooling holes (drill holes) that accommodate the tooling balls for the laser reflector (SMR) on the tracker. The toolings balls are magnetic and even allow overhead assembly. The measuring process can be initiated by remote control and, in this way, these measurements can be carried out by one person. Each measuring cycle only requires marginally more time than the few seconds required for the sensor to reach the measuring point. As a result, measuring efforts are significantly reduced – measurements that previously required days, can now be completed within a few hours.

Saving time means saving money

Drilling holes is not generally considered a challenge or even a time-critical task outside of the oil industry. However, in aircraft construction it is of vital importance. Not just that certainly a six-digit number of drill holes comes together when constructing an aircraft; their exact positioning is crucial as the drill holes accommodate the rivets that fasten the aluminium shell of the aircraft to the hull (stringers and ribs). In the past, the drill holes could only be made once the outer skin was fitted onto the hull – the exact position of the drill holes was only determined at this point. This manufacturing process was extremely time-consuming and complicated – and it had to be completed moving from the interior to the exterior. Laser measuring technology now allows another incredibly time-saving procedure: using a laser tracker each coordinate can be transferred from the CAD system to the jig. This means that even during the manufacture of the outer skin, all hole positions can be drilled precisely on CNC machines. As Pilatus manufactures a wide range of the most diverse types of aircraft – from the PC 12 NG, which is suitable as a business and touring aircraft as well as for special missions, such as air surveillance and search and rescue flights (during the earthquake catastrophe in Haiti 25 PC-12 were used), right up to the PC-21 training aircraft, a single-engine turboprop aircraft for training military pilots – the efficient and time-saving manufacture of different versions is of particular interest.

Happy landings

The requests of passengers within commercial aviation cannot always be observed when it comes to training military pilots: even normal flight operations undergo severe stresses and even with the Pilatus training aircraft, there have been occurrences of them being manhandled by their pilots. The PC-21 type of aircraft, designed for basic, advanced and mission training, deal with these incidents without any complaints. In cases of real hardship, this can lead to stresses and strains or distortion to the structure of the aircraft; the appropriate evidence from the inspections that are officially required for such cases was difficult to establish up until now. Pilatus also took new approaches in this respect supported by the new laser measuring technology.

All of the aircraft of this type have over hundreds of measuring points, spread over the entire body of the aircraft, measured precisely during the assembly and also available in the CAD data set. With the help of a laser tracker, it is now possible to measure the position of these points after a specific incident on the aircraft and to compare this with the original structure of the aircraft in the CAD data set. Advantages for the customers: combined with the unprecedented performance characteristics and features that this type of aircraft has, these preventative maintenance and quality control measures significantly contribute to the comparatively low life cycle costs for this trainer.

Dynamic measurements are possible

The engineers at Pilatus have already envisaged other fields of application for the laser measuring system: its ability to measure in real time also enables it to carry out a stress test during a movement sequence. In doing so, the measuring system has the ability to record a 3600 range and in verticals it is a respectable +800 to – 600. Even the measuring set-up itself is implemented quickly with the Swiss aircraft manufacturer’s impressive variety of models, whereby setting up close to or even under the aircraft poses no problem. The tracker head is only 36 cm high and it weighs only 8.5 kg. If nothing else, the compactness of the whole system facilitates the measuring of complex jigs with large dimensions, of which there are a large number at Pilatus.

Better is the enemy of good

If Beat Mathis, Head of Tooling at Pilatus, is asked about the criteria and reasons for using laser measuring technology, it will soon become clear that customers are the priority for the Swiss aircraft manufacturers and, therefore, they are interested in constantly further developing the high quality products and making them even more efficient. Even when, as was the case during their success in 2009, over 100 aircraft were produced and delivered; at Pilatus no series products leave the production line, on the contrary: the company reacts extremely flexibly to all enquiries concerning special requests from its customers – who, for this reason, come from all corners of the world to Stans in Switzerland and brought the company its best operating results in its history in 2009.

Beat Mathis: “Before we made our decision we had a detailed look at the options that laser-based measuring systems offered and drew up a shortlist. All systems successfully completed the tasks in hand and the test measurements without any problems in terms of measuring accuracy. We were impressed with API’s professional software integration and the connection to our CAD systems. We were also confident with the speed of the data transfer and the ability of the system to deal with large data files. Last but not least: the laser tracker from API was by a long way the most compact device in the test. As we often have to measure in inaccessible places and are travelling throughout the world with the tracker, we attached great importance to the unrestricted portability of the whole system. Taking everything into consideration, the decision was then very easy for us!”

Pilatus is already developing a new aircraft today. This much can be revealed: following the PC-21 military trainer, it will be another aircraft for the commercial sector. And, as is customary with the Swiss aircraft manufacturer, it will definitely adopt a deserved leading position within its specific market sector.

 

Pilatus Flugzeugwerke AG, founded in 1939, is the leading global manufacturer of single-engine turboprop aircraft and the only Swiss company to develop and build and aircraft and training systems and sell them on every continent. The company, with its headquarters in Stans, is one of the largest employers in Central Switzerland with over 1200 employees. Other independent subsidiaries in Broomfield (USA), Adelaide (Australia) as well as Altenrhein (Switzerland) belong to the Pilatus Group. The company was certified by the Swiss Association for Quality and Management Systems (SQS) in accordance with the EN/AS 9100:2003 requirements. Class and type rating training for pilots and mechanics correspond to the JAR-FCL requirements and are recognised by the Federal Office for Civil Aviation. Pilatus is supported globally by 40 independent sales and service centres.