Educating Graduate Engineers on Safety through Flight Testing

October 9, 2019October 14, 2019 admin flight test flight test instrumentation, flight test safety, Lorenzo Trainelli, Politecnico di Milano

Dr. Lorenzo Trainelli

The Flight Testing graduate course at the Politecnico di Milano University (PoliMI) is an elective taken in the second (last) year of the Master of Science in Aeronautical Engineering.  The aim of the course is to provide fundamental concepts and skills on the Flight Test process, principles, techniques, operational organization, and practical execution.  The university first offered the course in 2005, part of the radical change in the Italian academic framework related to the “Bologna process” (a major initiative bringing more coherence to the Higher Education system across Europe).  This brought the opportunity to review the Aeronautical Engineering curriculum and introduce several new elements, both theoretical and applied.

For the first few years, the course was entrusted to professionals from the industry:  The lectures were given by Paolo Chimetto, then Flight Test & Experimental Flight Line Manager of the AleniaAermacchi M346 program (now CTO – Head, Ground & Flight Validation and Verification, Leonardo Aircraft); and the labs were charged to Giovanni Bonaita, a senior FTE and CVE with a long experience in both fixed- and rotary-wing at SIAI Marchetti, AleniaAermacchi, and AgustaWestland.  Their experience gave the course a markedly job-oriented flavor and stimulated the possibility of offering the students a practical flight test activity. This was readily accomplished in 2006 by holding a flight test campaign using an instrumented ultralight two-seater and was done yearly ever since [1,2].

The current teacher, Lorenzo Trainelli, PhD, is an associate professor in Flight Mechanics and Aircraft Design at the Department of Aerospace Science and Technology, PoliMI. He teamed with Chimetto and Bonaita from the very start, looking after the organization and execution of the flight test campaign, while learning the basics of the art from the two industry experts.  Trainelli’s partner in crime is Alberto Rolando, adjunct professor of Aircraft Instrumentation and Navigation Aids at PoliMI and designer/developer of the Mnemosine system, a modular, minimally intrusive Flight Test Instrumentation (FTI) suite dedicated to small aircraft [3].  This system, undergoing continuous upgrade and expansion, is capable of retrieving over 40 time-stamped flight parameters and successfully supported the type certification of two Italian LSA models in 2010 and 2018 according to German and other European regulations [4,5].  The Mnemosine FTI is always installed on the test airplane for the duration of the annual educational campaign, providing a wealth of data for technical analysis (above).

In performing the campaign, which typically includes 20 to 30 flight missions, each student is called to act as the responsible Flight Test Engineer (FTE) for a test mission [6].  Therefore, he plans the activity, producing a FT Planning Document ahead of the test. Then he performs the test flying alongside an expert instructor pilot, and finally, the FTE carries out the data analysis, presenting his/her findings in a FT Report.  Further collateral tasks include the preparation of FTI calibration reports, weight and balance reports, and debriefing sheets.  The teacher reviews and assess all this documentation, acting as FT manager, in cooperation with all other functions involved: FTI, airplane manufacturer, pilot, and airfield operator.

An important part of the planning work is related to flight safety. Indeed, a section of the FT Planning Document is entitled “Safety Considerations” and includes a Test Hazard Analysis (THA).  For the first time outside the university campus facilities, the students are asked to be part of a safety management process by analyzing in first person the possible risks connected to their specific flight tasks.  These tasks include performance and flying qualities, stalls, climbs, glides, level accelerations/decelerations, longitudinal and lateral-directional static and dynamic stability. The execution follows the applicable FT discipline and techniques, as found in the CS-23 Flight Test Guide, MIL-STDs, recommended practices, and other applicable references.

The THA includes the identification of the hazards, the assessment of the risks involved, the proposal of mitigating procedures, and the issuance of related recommendations. Typically, a Hazard Analysis Risk Management Matrix, complete with Hazard Severity category and Hazard Likelihood level, is required.  An example of safety considerations applicable to the test topics of interest is represented by the case of stall testing. Here, among other issues, the inherent loss of altitude is identified as a possible hazard, as it may cause proximity to ground and possible conflict with other traffic. Mitigation by assigning higher altitudes conflicts with the very low ceiling allowed to ultralight aviation in the test range (either 1,000 or 2,000 ft AGL), so this typically results in performing the stall tests at or about the maximum altitude permitted and not over the airfield whenever other aircraft may interfere.

This example highlights the need for the student to consider simultaneous–and possibly competing–aircraft limitations, airspace limitations, and other elements such as weather, airfield conditions, schedule, etc..  Notwithstanding the basic character of the tests and the fact that the test vehicle is already well known and shall be operated in its safe envelope by a pilot having much experience on that specific model, the students are encouraged to look at safety management in a proactive way.

Sometimes, either the analysis of the FT Planning Document or the discussion in the pre-flight briefing, clearly point out a limited safety consciousness, which is all too natural for the students, having previously been engaged mainly in theoretical studies, with perhaps a few experiences of running experimental activities in a university lab under close tutorship by faculty and technicians.  Therefore, even if relatively limited in scope, the safety analysis required in the planning phase and application during the FT campaign is considered an important contribution to the wealth of experience gained by the course students and a valuable introduction to future professional assignments in experimental activities.

Dr. Lorenzo Trainelli

Endnotes

1. Trainelli L., “Politecnico di Milano Flight Test Exercise at Italian Naval Aviation Test and Evaluation Center”, Flight Test News, Society of Flight Test Engineers, 49 (6), 2018.

2. Trainelli L., “Politecnico di Milano Educational Flight Test Campaign”, Flight Test News, Society of Flight Test Engineers, 49 (10), 2018.

3. Rolando A., Rossi F., Castelletti T., Reghenzani F., “Mnemosine Mark-V: the Fifth Generation of an Ultra Light Machine-Dedicated FTI System”, 27th Annual Society of Flight Test Engineers European Chapter Symposium, Nuremberg, Germany, May 10-12, 2016. (http://www.sfte-ec.org/node/946)

4. Trainelli L., Rolando A., “Reliable and Cost-effective Flight Testing of Ultralight Aircraft”, Journal of Aircraft, 48 (4): 1342-1350 (2011). (http:/dx.doi.org/10.2514/1.C031277)

5. Trainelli L., Rolando A., Gadarco T., Terzaghi V., Riccobono M., “Flight Testing of a New Ultralight Airplane for LTF-UL Certification”, 27th Annual Society of Flight Test Engineers European Chapter Symposium, Nuremberg, Germany, May 10-12, 2016. (http://www.sfte-ec.org/node/948)

6. Trainelli L., Rolando A., Bonaita G., Chimetto P., “Experiences in Academic Flight Testing Education”, Aircraft Engineering and Aerospace Technology, 86 (1): 56-66 (2014). (http:/dx.doi.org/10.1108/AEAT-10-2012-0178)