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Experimental Flight Test Management. Optimization procedures and flight test techniques
Language: English This thesis is written in English
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Pierluigi De Paolis, Università degli Studi di Napoli - Federico II, 2016
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Approaching to flight test is paramount to keep clear in mind that accurate test management is the cornerstone between failure and success. Flight testing remains an essential element of sound air vehicle development. The current emphasis on expanding the use of M&S has been promulgated with the intention that it can help to reduce flight test time and cost, enhance test safety, and increase testing efficiency.
The “predict-test-validate” (a.k.a. ”model-test-model”) paradigm is held forth as the most efficient combination of these development tools. In this paradigm the initial modelling and simulation guides the planning and conduct of flight testing, with incremental test results then used to enhance the accuracy and/or fidelity of the simulation before the process is repeated. The cycle would be repeated many times during the course of the test program, especially in an effort to avoid the "fly-fix-fly" paradigm that commonly proves inefficient and trying to avoid future operational shortfalls.
Although much of the technical leadership in the NATO aerospace industry and Italian Defence Department insist that M&S is not intended to replace flight testing, there remains concern among flight test practitioners that the result will be an overreliance on simulation. This has a potential for neglecting invaluable empirical test data verifying system performance. In addition, detrimental and potentially hazardous system characteristics may not be uncovered, and overall assessment of vehicle worthiness vis-a-vis its mission will suffer. Appreciation for a sound balancing of flight testing with simulation must be promulgated. In addition, a methodology appears to be needed to help insure this sound balance.
The term M&S is taken to include:
- Digital models and computer simulations using those models;
- Mathematical analytical tools such as Computational Fluid Dynamics;
- Simulated flight testing such as in wind tunnels and engine altitude test chambers;
- Hardware-in-the-loop simulations;
- Pilot-in-the-loop simulations, with and without hardware-in-the-loop;
- In-flight simulation;
- Other large-scale ground tests.
Each of these initially employ simplified system representations that become more complex as the systems engineering process defines the system during the course of development and as test data becomes available to improve model and simulation fidelity and accuracy. Present initiatives are expanding the application of verification and validation of M&S resources to ensure that they function as intended and suitably represent real-world behaviour. Flight testing itself can be considered a simulation if the test article is an experimental system or early prototype, if some internal or external system functions are contrived, and if test conditions do not truly match actual in-service scenarios (such as simulated combat). OT&E flight test relies heavily on constructive simulation and PITL tactical simulations. All this has become more popular as simulation capabilities have increased and flight test budgets and schedules have decreased.
However, the flight environment, with systems interacting and with a pilot (perhaps) in control, is not a simulation. Flight test remains the most dynamic and credible medium for collecting actual system performance data.
Test management holistic concept is much more, taking into account also the relevant phase of actual test preparation, test matrix identification (totality of test points to be performed), coordination, FTTs set-up, generation of new validation techniques and reporting, of course.
The purpose of this thesis work is to show how an accurate test management based on alternative geometry acquisition processes, test matrix generation algorithms, M&S, new FTTs and validation procedures can be used effectively and efficiently to support flight testing. In particular, in order to reduce the scope of the subject activity the focus is kept on a specific branch of the test field known as Store Integration and Safe Separation; the approach could be expanded to other branches of flight test, but customization would be required.
The question becomes how much flight testing can really be replaced by simulation before jeopardizing the safety of flight and increasing the cost of simulation prohibitively to make it worthwhile. Simulation is not a panacea for all test problems, but a valuable tool that must be used cautiously and wisely in the course of a test program, the key word is “balance” and its maidservants are “optimization, synchronization and coordination”.