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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.

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.

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.

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.

The modern helicopters are designed with maximum serviceability and long life expectancy to ensure minimum life cycle cost. The purpose of this paper is to present a framework to incorporate the customer requirements on reliability and maintainability (R&M) parameters into the design and development phase of a contemporary helicopter, and to discuss the way to capture operational data to establish and improve the R&M parameters to reduce life cycle cost.

From the analysis, it is established that the reliability and maintainability cost is the major contributor to the life cost. The significant reliability and maintainability parameters which influence R&M cost are identified from analysis. The operational and design data of a contemporary helicopter are collected, compiled and analyzed to establish and improve the reliability and maintainability parameters.

The process depicted in the paper is followed for a contemporary helicopter and substantial amount of life cycle cost reduction is observed with improvement of R&M parameters.

The benefits of this methodology not only reduce life cycle cost but also improve the availability/serviceability through less failure and less time for scheduled maintenance. The methodologies also provide the reliability trends indicating potential area for design improvement.

The proposed approach assists asset managers to reduce the life cycle costs through improvement of R&M parameters.

It's been nearly 20 years since the introduction of commercial jet powered aircraft. The powerplants which made these aircraft possible have proven to be extremely reliable. “Prolonging Engine Service Life” became a natural economic objective of the airlines, and the initial practice of overhauling engines at specified intervals gradually evolved into the current on‐condition maintenance concept designed to minimise operating costs. While these practices and extensive parts repair activities resulted in major economies, the resultant extended operation of hardware has in many cases caused more frequent engine removals and often ultimately more extensive parts replacement. In addition, engine fuel consumption has been compromised to varying degrees.

Maintenance on gas turbine engines results from failures in one or more of the engine's major subsections. Maintenance and support costs can be reduced if the capability exists to isolate the failures down to the lowest possible component in the engine. The modular engine maintenance concept has recently been evolved to facilitate this cost reduction. The important considerations as well as the benefits of this concept are discussed. Considerations included are: design, failure modes and isolation techniques, and implementation. The Air Force F100‐PW‐100 engine maintenance concept is used for discussion purposes.

Maintenance is constantly challenged to increase productivity by maximizing up‐time and reliability while at the same time reducing maintenance expenditure and investment. Traditional reliability models are based on detailed statistical analysis of individual component failures. For complex machinery, especially involving many rotable parts, such analyses are difficult and time‐consuming. This paper aims to propose an alternative method for estimating and improving reliability.

The methodology is based on simulating the up‐time of the machine or process as a series of critical modules. Each module is characterized by an empirically derived failure distribution. The simulation model consists of a number of stages including operational up‐time, maintenance down‐time and a user‐interface allowing maintenance and replacement decisions.

Initial analysis performed on aircraft gas‐turbine data yielded an optimal combination of modules out of a pool of multiple spares, resulting in an increased machine up‐time of 16 percent.

The benefits of this methodology are that it is capable of providing reliability trends and forecasts in a short time frame and is based on available data. In addition, it takes into account the rotable nature of many components by tracking the life and service history of individual parts and allowing the user to simulate different combinations of rotables and operating scenarios. Importantly, as more data become available or as greater accuracy is demanded, the model or database can be updated or expanded, thereby approaching the results obtainable by pure statistical reliability analysis.

The model presented provides senior maintenance managers with a decision tool that optimizes the life cycle maintenance cost of complex machinery in a short time frame by taking into account the rotable nature of modules.

ANYONE ENGAGED in aircraft engineering who has visited the Air Canada maintenance base at Montreal to observe the layout, equipment and operating system will have bound to come away greatly impressed with the facilities and efficiency of the plant. In the writer's opinion it is one of the most advanced airline maintenance bases in the world.

Audits of long‐term insurers are complex, high‐risk engagements. The auditor’s consideration of materiality has a direct impact on the quality of such audits. So far, however, no research has been published on the application of materiality in audits of long‐term insurers. This study examines various aspects of planning materiality in the audits of listed South African long‐term insurers on the basis of responses to a questionnaire, taking into account issues identified from the literature reviewed. A number of recommendations are made on the basis of the findings. Largely on the basis of the results of this study, the South African Institute of Chartered Accountants has commissioned a project to revise existing guidance for auditors.