Volcanic ash and damages on aeroplanes
Volcanic ash are small magma particles, of less than 2mm in diameter, which are emitted into the atmosphere, cooled and consolidated, during an eruption. They are composed mainly of silicates and therefore are extremely abrasive.
Why they are dangerous. Volcanic ash are particularly insidious due to the difficulty to be seen. In fact, in case of cloud cover, dark night, or simply when dilute (eg at a certain distance from the point of emission), they are hardly distinguishable from the normal atmospheric clouds. In addition, normal radars used for air navigation are not able to locate them because of their small size.
Damages to airplanes. A plane that passes through an area affected by the presence of volcanic ash, even in very small quantities, is subject to abrasion of its surface, and in particular the cockpit. This could result in opacification of the glass and, consequently, it would reduce to zero visibility from the driver.
Moreover, volcanic ash - melting at a lower temperature than the normal operating temperature of the jet engine - in contact with the turbines, can melt and weld on their surfaces, causing occlusion of ventilation holes and disrupting the smooth operation of engines, and - worst case scenario - may determine the most serious cases imprisonment.
Le ceneri e i gas vulcanici possono inoltre interferire con l’elettronica di bordo causando malfunzionamento degli strumenti di navigazione e producendo forte odore di zolfo all’interno del velivolo.
Misure di prevenzione. Negli anni ’90 vennero istituiti 9 Volcanic Ash Advisory Centre-VAAC con il compito di fornire informazioni agli enti gestori del traffico aereo di ogni Stato sulla presenza e dispersione delle ceneri vulcaniche in atmosfera in tutto il mondo.