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The concept of Mechanical Resonance is fundamental when we speak about engineering, especially in the field of structures and mechanics. It's a phenomenon regarding the dynamic behaviour of a system (whatever you can think about).  What do we mean by "dynamic behaviour"? Simply, dynamic is what moves, the contrary of static, that is, standing, not moving. From a mathematical and physical point of view, a dynamic phenomenon changes during time, i.e, is described by equations in which time is a variable; instead, a static phenomenon doesn’t depend on time, is described by equations in which time doesn’t appear as a variable. If we take some pictures of a static phenomenon during the time, the pictures are all the same, nothing changed during the time. In reality, every system, although it seems to be static, it moves. Let consider, for example, a house: from a macroscopic point of view, a house is static, but in reality, its structure is continuously subjected to

Introduction to airplane accident  Airplane accidents have guided aviation to improve airplanes over time. The analysis of these catastrophic events revealed weaknesses in airplanes design and gave a better understanding of the phenomenona that can lead to airplane accident. For this reason, each airplane accident had a key role in regulamentations (FFAR) updates and design choices, to make the probability of an airplane accident extremely remote. In this article, I will present one of the most famous airplane accident with an incredible lucky end. The luckiest airplane accident: Boeing 737, Aloha Airlines 243 The Boeing 737 of Aloha Airlines 243 flight, 28 April 1988 is the most famous airplane accident in the history of Aeronautics. The accident happened at an altitude of 7300m An entire part of the fuselage was lost due to a crack propagated from fatigue loads (cyclic loads) generated by pressurization cycles, the so-called GAG (Ground-Air-Ground) cycles. The fracture was born