Search

The intense usage of Swiss military airplanes has a significant impact on fatigue life. The Swiss design life based on the OEM design goal is reduced. As a result, special program has to be implemented to ensure the structural integrity over the aircrafts’ lifespan. An important task was to perform a full scale fatigue test that reflects the Swiss usage spectrum. The life of the Swiss military airplanes could thus be extended to meet the economic life goals – using fatigue tests – by more than 10 years for the Venom De Haviland DH-112 and the Mirage III. Today former military planes like the Pilatus P3 (trainer), Venom, Vampire, Hunter and Mirage III are civil registered. During operations in military service, these planes had strict requirements regarding inspection, maintenance and life time. In civil aviation however, there are no such regulations for these planes and their maintenance and operation is only superficially regulated. The Pilatus P-3 (military trainer in service from 1958 till 1990) was originally built for a design life time of 2'500 flight hours and 10'000 flight cycles. As the aircraft started to reach 2'500 hours in military service, the limit was increased to 3'000 flight hours and 12'000 flight cycles. Although most of the Pilatus P-3 airplanes still in service today have already reached 3’000 flight hours by now, they are still flying around and have been doing so since 1995 as civil airplanes. An initial assessment already demonstrated that the wing of the P-3 required further some strengthening in 1959/60. This part of the wing is still considered to be critical based on the current review. Following the current risk assessment which was based on ICAO standard, recommendations were made to fly the P-3 till 5’000 flight hours with no constraints but beyond 5’000 flight hours further engineering investigation (damage tolerance analysis) and inspections are definitely needed. The P-3 has real potential for longer usage in civil conditions as the result of the less severe usage compared to the conservative original design spectrum from Pilatus.

Early airplanes were designed using purely static conditions and mainly tested only based on simple wing tests. But despite the significant advances in design, manufacturing and testing capabilities, structural failures may still occur. Thus, new concepts are required to ensure safe operations over the lifetime of an airframe. To this end, the International Committee on Aeronautical Fatigue and Structural Integrity (ICAF) was established in 1951 in response to growing concerns over fatigue issues in metal aircraft structures. A conference and symposium are organized biannually by one of the 14 member states to foster contacts among the scientific community engaged in aircraft structural integrity. In 1958 Juerg Branger developed a concept for a fatigue simulator at the Federal Swiss Aircraft Factory (F+W). The Pilatus P3 trainer became the first airplane to be tested in Emmen, Switzerland to demonstrate the safety of the airframe over a lifetime of 2’500 FH. This first test demonstrated the importance of full-scale fatigue tests to ensure the structural integrity of the airframe. As a result of the tests, a redesign of the spar was undertaken on the entire fleet of the Swiss Air Force. Due to the intense usage of the fighters deployed by the Swiss Air Force, further full-scale fatigue tests were undertaken on the Venom, the Mirage III, and also on the F/A-18. All tests yielded some unusual and unexpected results, despite the significant advances achieved in fatigue prediction technologies. As the complexity of the materials used in modern aircraft design increases, such as titanium and composites, more and more analysis is being taken over by highly sophisticated software and test procedures. Furthermore, composite structures necessitate test criteria that are very different to those used for metals; while hybrid structures are even more complex. The wing rib problems experienced by the Airbus 380 clearly demonstrate the challenges of modern structures in fatigue certification. Even more advanced structures, such as the ones used on the Boeing 787 and the Airbus 350, will provide further challenges and insights. Future tests for structural integrity will have to include more operational impacts such as ground handling incidents and environmental influences. Structural integrity is still an important means to ensure safe operations in aviation for all types of airplanes, including unmanned air vehicles.

The fluctuation theorem characterizes the distribution of the dissipation in nonequilibrium systems and proves that the average dissipation will be positive. For a large system with no external source of fluctuation, fluctuations in properties will become unobservable and details of the fluctuation theorem are unable to be explored. In this letter, we consider such a situation and show how a fluctuation theorem can be obtained for a small open subsystem within the large system. We find that a correction term has to be added to the large system fluctuation theorem due to correlation of the subsystem with the surroundings. Its analytic expression can be derived provided some general assumptions are fulfilled, and its relevance it checked using numerical simulations., 5 pages, 5 figures; revised and supplementary material included

Air Vehicle: Advanced Structure & Aerodynamics, Electrical Plane Air Traffic Management: Virtual Controller, Virtual Tower, Full Automation, Single Sky Airport Infrastructure: CO2 neutral from home to airport, higher efficiency

The Swiss review summarizes fatigue work in Switzerland. It includes main contributions from the Zurich University of Applied Sciences (ZHAW), RUAG Switzerland Ltd. (RUAG Aviation), CFS Engineering. This document forms a chapter of the ICAF conference minutes published by the conference host nation. The format of the review reflects ICAF requirements.

International audience; We investigate energy exchanges through scales occurring when a surface wave reflects on a harmonically oscillating wall. We first experimentally evidence the creation of Doppler-shifted waves and measure their height as a function of the oscillation amplitude. Then, we theoretically compute the amplitudes of these new waves in the gravity regime. Both results show that even without bulk non-linearities, oscillating paddles in a fluid container lead to a complex wave energy spectrum competing with the one predicted by wave turbulence. To exemplify this point, we characterize a simple one-dimensional model consisting of a linear wave equation in an oscillating cavity with distinct injection and dissipation mechanisms. It displays features usually associated with non-linearities, as self-similarity in a spectral domain (the so-called inertial range), appearance of energy at larger and/or lower scales than the forcing one and creation of shock waves.

In some recent papers, the use of random forces has been related to a systematic breakdown of the fluctuation theorem. In the framework of nonequilibrium molecular dynamics, we provide a derivation of this theorem for systems driven by both deterministic and stochastic forces. It turns out that it is still valid and describes the total dissipation, explicitly the sum of two dimensionless works for which fluctuation relations may fail. We numerically study their range of validity, comment on experimental results, and point out in which limit a noise can be neglected.

National audience

PURPOSE We report a patient with chronic Sweet syndrome (SS) treated by anti-Tumor Necrosis Factor (TNF) therapy, who presented with a severe bilateral chemosis. METHODS Case report. RESULTS Conjunctival biopsy revealed an ocular localization of SS. CONCLUSIONS SS is a rare disorder that usually affects middle-age women. It is characterized by an acute febrile neutrophilic dermatosis. To our knowledge, this is the first documented case of an ocular localization in SS and the first report of a severe bilateral chemosis as ocular manifestation.

International audience