AleniaAermacchi increases testing productivity with LMS Test.Lab

Integrated LMS Test.Lab environment deployed for broad range of trainer aircraft testing assignments

In the competitive aviation industry, where test execution is under pressure and highly accurate testing is taken for granted, AleniaAermacchi realized a significant increase in test operation productivity since it upgraded to LMS Test.Lab in 2004. AleniaAermacchi engineers use LMS Test.Lab for developing trainer aircraft that combine superior maneuverability and controllability with low cost of ownership. The integration of multiple test applications into LMS Test.Lab helps them efficiently run any kind of structural, modal, operational modal or environmental test assignment. In this way, Aermacchi is able to tackle operational in-flight tests on a highly advanced M346 trainer prototype just as easily as executing vibration tests on avionics instruments for the smaller SF-260 aircraft.

Covering the complete pilot training syllabus

For more than half a century, designing and manufacturing trainer aircraft has represented the core activity of AleniaAermacchi. The continuous evolution of aircraft frequently redefines training objectives, and consequently, the search for new trainer aircraft featuring the required capability. Today, the company offers a comprehensive range of trainer aircraft that covers every phase of the pilot training syllabus. The smallest aircraft in its portfolio is the AleniaAermacchi SF-260, which is designed to screen student pilot candidates in the most effective way. This aircraft features the flight characteristics and performance levels necessary to cover the entire primary phase of training.

At the high end of its aircraft offering, AleniaAermacchi is currently finalizing the M-346. This aircraft is the company's first advanced new-generation jet trainer specifically designed to meet 21st century flying training requirements. Altogether, AleniaAermacchi's trainer aircraft business, with integrated support and fleet management services inclusive, accounts for about 50% of the turnover of the company. In 2003, AleniaAermacchi also became part of the Finmeccanica group, which is Italy's leading high-tech company operating in the design and manufacture of aircraft, helicopters, space infrastructures and defense electronics as well as in transport, energy and information technology.

High test workload and diverse testing scope

Reliability is key for trainer aircraft that require high lift power and excellent maneuverability to successfully tackle the extreme flight conditions of territorial missions or aerobatic endeavors. In the development process of such aircraft, AleniaAermacchi focuses testing efforts on the verification of full-aircraft performance and the way internal aircraft systems and components operate. The complicated relationship between structural strength, control system operation, aero engine power and aerodynamic performance translates into a significant testing workload and a diverse spectrum of tests. AleniaAermacchi's testing assignments span operational in-flight tests as well as specific tests concerning engine and systems operation, structural strength assessment, such as loads measurement, bird impact, fire resistance and environmental qualification.

To more efficiently perform multiple test applications, AleniaAermacchi decided in 2004 to upgrade to the LMS Test. Lab software platform for structural, modal and environmental testing. Edoardo Porrini, test engineer working at AleniaAermacchi's main plant in Venegono, Italy, comments, "Today, AleniaAermacchi runs vibration control, spectral acquisition and (operational) modal analysis on LMS Test.Lab, and plans to upgrade time data processing at a later time. We particularly value LMS systems for providing accurate measurement acquisition and delivering reliable result processing. In addition, the process- centric workbooks featured in LMS Test.Lab accelerate our test campaign procedures and further increase data consistency. The productivity boost realized in this way helps a great deal in tackling our huge testing workload within the limi

Operational in-flight tests performed on M346 prototype

An example of a cuttingedge application is the preliminary in-flight test program executed on the first prototype of AleniaAermacchi's brand new high-end M346 trainer aircraft. In this high-channel-count test, approximately 900 critical signals in the flying aircraft were transferred to data acquisition systems on the ground using telemetry. A number of these channels were acquired using an LMS SCADAS 310 front-end and served as input for dedicated dynamic investigations, such as buffet and flutter. The latter, in particular, represents a potentially catastrophic aerodynamic instability that can lead to aircraft loss, involving a coupling between two natural vibration modes (resonance frequencies). During initial test flights of the first M346 aircraft, LMS Test. Lab enabled AleniaAermacchi engineers to perform a real-time spectral analysis monitoring of the aircraft, by continuously displaying 16 channels of choice for the safe conduct of the flights.

The M346 has been designed according to modern aerodynamic concepts utilizing vortex lift to enhance maneuverability and maintain controllability under extreme flight circumstances. M346's thrust-to-weight ratio, superior flight performance and latest-generation mission avionics make it a powerful aircraft with remarkable potential. A reprogrammable flight control system enables AleniaAermacchi engineers to effectuate different degrees of piloting difficulty as well as to simulate the handling characteristics of different operational aircraft. These capabilities illustrate the importance of operational in-flight tests in increasing the aircraft performance envelope and monitoring flutter and other undesirable phenomena, Porrini indicates. "During different maneuvers, LMS Test. Lab provided reliable insight regarding structural modes that involve fuselage, wing, aileron and tail bending and torsion. This enabled us to monitor specific resonance frequencies and their respective tendency to shift towards so-called 'alarm frequency ranges'."

Successfully completing customer-specific tests

On the much smaller SF-260 primary trainer aircraft, AleniaAermacchi recently performed a customization project that involved the installation of a g-meter and two other instruments in the aircraft's cockpit. These additional instruments are integrated in a secondary instrument panel, which is mounted on top of the existing instrument panel by means of a dedicated bracket. An important constraint introduced by the g-meter manufacturer is that correct g-meter operation is only guaranteed as long as local vibrations remain under a specified maximum level. To verify local vibrations on the instrument panel, AleniaAermacchi engineers ran an aircraft ground test to measure dynamic vibration responses during a complete engine runup cycle. They conducted this test by applying LMS Test.Lab Spectral Acquisition and investigating the recorded time data afterwards. The purpose of this test was to assess the impact of the rotating propeller blades by identifying the frequency (bands) in which propeller blade motion amplifies the vibration excitation of the engine.

As the measurement results of this initial test indicated insufficient bracket damping characteristics, AleniaAermacchi engineers updated the design of the bracket. They shifted the front to the rear, and enlarged the size of the bracket clamp. To make sure that the resonance frequency of the bracket would not coincide with the identified frequency (bands), a number of sine shaker tests were performed on different configurations of the modified design (different materials, with/ without damper, etc.)

The M-346 in flight.

In the design validation stage, the secondary instrument panel, with the additional instruments and the updated bracket design, were installed in aircraft in preparation of new engine ground tests. Engineers also analyzed the final design through a modal impact test and performed shaker tests to verify g-meter operation in between the tests and afterwards. "In the different steps of this customization project, we performed measurements using a variety of LMS Test.Lab applications," Porrini comments. "AleniaAermacchi engineers described the acquisition, analysis and postprocessing operation of each of these application procedures as being fast, intuitive and precise."

Doubling the productivity of structural testing

As a leading manufacturer of trainer and air support aircrafts, AleniaAermacchi is systematically challenged to integrate technological advances, achieve increased performance and deliver top economic value. In today's competitive setting in aviation markets, top engineering skills and market-leading engineering solutions are key in developing new successful aircraft.

Porrini concludes, "To maintain our competitive edge, we systematically innovate aircraft design and increase the performance of the development process. In this regard, the deployment of LMS Test.Lab is important, as it further enhances test reliability and measurement efficiency. In addition, the LMS Test.Lab platform, which incorporates multiple test applications, enables our engineers to perform modal, operational modal, spectral or environmental investigation with increased efficiency. The doubled productivity, as reported by our testing teams in recent test assignments, confirms that we succeeded in accelerating test execution considerably."