The problem of the aircraft noise is certainly one of the factors that affect not only at the planning of a new airports or expanding of the existing airports, but also at the aviation industry as a whole. In order to mitigate this problem, a series of a different measures are undertaken today, whose effects are finally evaluated by the application of an appropriate indices and the aircraft noise metrics. In this paper, a brief chronological review of the aircraft noise metrics development is shown, as well as their classification according to the different criteria. The analysis of the certain aircraft noise metrics, with the close attention to their interconnections, is accomplished. Additionally for the nowadays frequently used metrics and their advantages and limitations, special attention was given. An overview of the supplemental aircraft noise metrics, which are now proposed and as such can be accepted by the general public, is given. Key words: aircraft, noise, metrics

Purpose The purpose of this paper is to present novel recursive expressions for modelling the replacement costs of aircraft engine life-limited parts during shop visits to assist engine operators in both evaluating their decisions regarding the applied life-limited parts management strategies and tracking the replacement costs consistently throughout the life of the engine. Design/methodology/approach The replacement costs of aircraft engine life-limited parts are modelled analytically in this research, which strives to quantify the costs of used and unused lives of the replaced parts, incurred during engine shop visit events. Inputs for this model include the list price of life-limited parts, the replacement decisions made on all previous shop visits and the number of cycles the engine has operated at different thrust ratings on all previous operating intervals. Findings The average annual escalation rate of life-limited parts list prices was shown to range from 5% to 7%. The presented model is not only suitable for calculating the costs of used and unused lives of life-limited parts during past engine shop visit events but also for application in the life-limited parts replacement cost forecasting and optimisation models. Originality/value Uniquely derived recursive expressions represent the final result of the developed model which, to the authors’ knowledge, had not been studied elsewhere in the academic literature. The analysis of aircraft engine life-limited part list prices carried out to account for the average annual escalation rate enables the prediction of replacement costs during subsequent shop visits.

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Purpose The paper aims to investigate the compatibility of manned-aircraft airborne collision avoidance systems (ACAS) for use on unmanned aerial vehicles (UAV). Design/methodology/approach The paper uses the Fault Tree method for defining ACAS model adapted for the UAV operations, with the aim of showing the presence of certain factors that configure in such ACAS system, and whose failure can lead to an adverse event – mid-air collision. Findings Based on the effectiveness analysis of ACAS solution adapted for the UAV operations, for given inputs, it can be concluded that the probability of ACAS failure is on the order of 10–4, as well as that in the case of autonomous ACAS solution for the UAV, the probability is reduced to 10–5. The most influential factors for the failure of the UAV’s ACAS are as follows: technical implications on the UAV, human factor, sensor error, communication and C2 link issue. Practical implications The established model could be used both in the UAV’s ACAS design and application phases, with the aim of assessing the effectiveness of the adopted solution. The model outputs not only highlight the critical points of the system but also provide the basis for defining the Target Level of Safety (TLOS) for the UAV operations. Originality/value The developed model can be expected to speed up the design and adoption process of ACAS solutions for the UAVs. Also, the paper presents one of the first attempts to quantify TLOS for the UAV operations in the context of collision avoidance systems.

The purpose of this paper is to examine the pressure drop caused by placing an airfoil at different angles of attack in the straight part of the rectangular air duct, as the first step of investigating the possibility of using a staggered cascade of airfoils for gradual deflection of the airflow in radial elbows of an air supply system used in industrial boilers. The initial problem was approached by using the commercial CFD code based on the Finite Volume Method (FVM) to numerically simulate a 2D incompressible turbulent flow and by conducting direct experimental measurements in the wind tunnel. The results of CFD simulations have been compared to experimentally measured data for two considered cases of inlet velocities and five different angles of attack. Numerical solutions show an adequate level of agreement with experimental measurements. The obtained results indicate the possibility of using a staggered cascade of airfoils for gradual deflection of the airflow.