Guided procedure for the Zonal Safety Analysis in aircraft preliminary design

Due to limited internal volume, often a high density of equipment installations is present on board an aircraft. For this reason, in case of a device failure, every component installed in close proximity could be damaged, causing a catastrophic domino effect. This paper presents a guided procedure for the Zonal Safety Analysis (ZSA) performed during the airplane conceptual design. This methodology allows aerospace engineers to carry out a devices installation on the aircraft taking into account the possible interactions among them in case of failure. In the Zonal Safety Analysis methodology, each equipment is characterized by a risk score, evaluating various types of accidents, for example mechanical breaks, electric damages, explosions. Considering every installed device and the possible spread of damages, a global risk score is obtained, which should be minimized in order to obtain a safer project as possible. In order to allow the engineer to conduct a Zonal Safety Analysis, a computer-aided software based on the ZSA methodology has been realized and presented in this paper. Thanks to a Graphical User Interface (GUI), many trade-off studies can be rapidly carried out and the safest solution can be designed. First, the tool requires the user to define the bays in which the aircraft is partitioned. Then, for each zone, the engineer selects all the equipment (e.g. avionic devices, electric generators, actuators, pumps) to be installed. These components and relative risk scores are included in a database compiled within the tool. Once every equipment has been selected, the risk level of every zone is evaluated, taking into account the possible interactions among all the close systems. Finally, the tool estimates the global risk score. All the results are shown to the user by means of tables and graphs. The engineer should comply the necessary changes (e.g. varying components location) in order to obtain a better design from a safety point of view. In the final part of the paper, a test case of the Zonal Safety Analysis methodology applied to an Unmanned Aerial Vehicle is presented. The obtained results are reported and discussed. This example demonstrates that the realized software can be useful to conduct a preliminary design a safer airplane.