Abstract
Aim: Presentation of problems related to impact (bird) tests and research instruments enabling true reconstruction of real collision conditions. Identification of characteristic structural and configuration differences between impact systems used for different test objects, types of reconstructed collisions and the scale of the analysed phenomenon.
Introduction: A collision of a fast moving aircraft with a foreign body poses a major threat to the safety of civil and military aircrafts. In order to fully understand the processes that take place at the time of collision, the Foreign Object Damage (FOD) phenomenon has to be empirically investigated in laboratory conditions, and proper research methods need to be applied. Due to the specific character of these tests, the application of specialised research instruments enabling true reconstruction of real conditions and precise data recording, is required. The structure and the parameters of a test system depend on the type of the event reconstructed and the energy of impact. In the article the author analyses different impact systems used for scientific and industrial tests conducted in aviation research laboratories.
Methodology: The paper presents an analysis of problems related to the execution of bird tests and discusses the methods for the acceleration of objects thrown, the test stands enabling proper exposure of the tested structure to the influence of the foreign body, and the structure of the foreign body reflecting the shape and the size of a real bird. Additionally, the article presents the issues related to propellant devices enabling acceleration of a foreign body to the required impact velocity. Among them, solutions in the area of pneumatic guns are shown and their advantages and disadvantages are described. The paper also presents the structure of trigger mechanisms and their influence on the energy performance of the propellant system. The author characterises muzzles for the separation of the thrown object from the elements of the sabot, which enables the acceleration of the projectile in the barrel of the pneumatic gun. The examples of sabots for small and big calibre guns with different energy performance are also given.
Conclusions: The analysis indicates that the basic problems in impact tests concern the acceleration of projectiles used. For that purpose, pneumatic guns are most commonly applied. Majority of test systems used so far enable reconstruction of collisions taking place at low altitudes, where the most common cause for aircraft structure damage are small birds flying individually or in flocks. Due to growing flight safety demands, the development of impact tests aimed at true reconstruction of conditions at high altitudes, where collisions with bigger and heavier birds takes place, is therefore a must.
Keywords: flight safety, aircrafts, birds, collisions, pneumatic gun
Type of article: review article