A. Pérez de la Serna, S. Parra Adán, E. Gómez Viñas, H. Climent Máñez

DOI Number: N/A

Conference number: IFASD-2017-153

Landing is one of the most critical phases in the aircraft operation, as most of the accidents occur during this manoeuvre. National Transportation Safety Bureau (NTSB) statistics show that more than 40% of aircraft accidents occur during landing manoeuvres, and most of them use to imply a substantial damage for the aircraft and/or the crew/passengers. During landing, the vertical velocity of an airplane is quickly reduced to zero when the wheels strike the ground. This process is accomplished by a transfer of energy from kinetic energy of the sinking airplane to internal energy in the shock absorption system, where it is dissipated. The vertical velocity of the airplane is brought to zero within a fraction of a second, and hence the forces applied to the structure through shock strut change from zero to a maximum also in a fraction of a second. This rapid change in velocity, or equally in application of force, excites the lower vibration modes of the structure. Therefore, the structural dynamic characteristics of the structure must be taken into account. Nevertheless, flight test have proved that the assessment of the severity of a landing impact needs to be based not only on sink rate, but also in lift/weight ratio at landing (load factor). According to this fact, there are two scenarios that can make landing manoeuvre particularly critical and severe: — Hard landing: event in which an aircraft has a controlled landing with a large sink rate — Rebound landing: event in which the aircraft touches the ground normally, but goes back to the air for 2-3 seconds and then falls again over the ground. This second impact uses to happen with the spoilers deployed and so, with an important decrease of wing lift, making load factor during the second impact around 0.5-0.7g. This paper presents the continuation of the works performed at Airbus DS Military Transport Aircraft Aeroelasticity and Structural Dynamics department in the last years [1-4]. It will show the methodology to calculate both hard landing and rebound landing, and how these simulations are compared with Flight Test data. It will also prove that sink rate is not the unique relevant parameter in order to assess landing severity.

Read the full paper here

In Categories: 1.Events, Dynamic loads, IFASD 2017
Email
Print
LinkedIn
The paper above was part of  proceedings of a CEAS event and as such the author has signed a publication agreement to have their paper published in the repository. In the case this paper is found somewhere else CEAS always links to the other source.  CEAS takes great care in making the correct content available to the reader. If any mistakes are found  in the listings please contact us directly at papers@aerospacerepository.org and we will correct the listing promptly.  CEAS cannot be held liable either for mistakes in editorial or technical aspects, nor for omissions, nor for the correctness of the content. In particular, CEAS does not guarantee completeness or correctness of information contained in external websites which can be accessed via links from CEAS’s websites. Despite accurate research on the content of such linked external websites, CEAS cannot be held liable for their content. Only the content providers of such external sites are liable for their content. Should you notice any mistake in technical or editorial aspects of the CEAS site, please do not hesitate to inform us.