Papers by Author: Fairuz Izzuddin Romli

Abstract: Aircraft redesign process normally does not start from scratch and requires a well-defined reference baseline design as the starting point for redesign changes. In general, the baseline design is often chosen based on the closeness of its existing performance capability to the driving requirement. This practice essentially presumes that such condition guarantees a minimum amount of required redesign changes, hence the least development risk. However, it is argued here in this study that such notion can be misleading because risk also depends on the type and the extent of the changes. Instead, it is believed that the existing baseline design architecture is an important element that will influence its suitability for the redesign task at hand. Through a sample aircraft redesign case study, the possible effects of existing design architecture on the redesign process is demonstrated and highlighted.

Abstract: Conventional aircraft designs have been highly successful within commercial passengers transport markets for a very long time, as evident from current fleet of many airlines. However, with the anticipated stricter environmental regulations to be imposed on future flight operations by the related governing bodies, the relevance of conventional aircraft designs to remain competitive has been questioned. On the other hand, some research ventures have been made to pursue revolutionary designs like blended wing body (BWB). This study aims to preliminarily assess the comparison of expected future emission performance between conventional aircraft design and blended wing body design. It addresses the ongoing debate on whether conventional aircraft designs can be expected to be able to cope with impending stricter environmental regulations and/or whether the venture into revolutionary designs is really necessary. Analyses done are largely based on the historical trends of conventional aircraft designs with regards to the lift-to-drag ratio and fuel consumption parameters. As for the blended wing body, its projected emissions performance is based on published data in the literature. The outcome from these analyses solidifies the belief that conventional aircraft designs will face tougher chances to remain operational under new environmental regulations and the search for revolutionary design with better aerodynamic efficiency such as blended wing body is becoming rather necessary.

Abstract: Flight delays have become a big problem for current air transportation system, especially in busy domestic markets like those in the United States. This situation is predicted to worsen in the future with progressive increase in the air traffic demands. Since on-time performance has become a main competitive element for market success, many airlines resort to the flight padding practice as a means to improve their ranking. In brief, flight padding time is the additional time incorporated into the flight schedule to compensate for predicted delays. This study explores flight padding practices by identifying the factors that can influence the decision-making process for the required amount of pad time to be added for a particular flight route. Examples of ATL-JFK and ATL-SFO flight routes have been used to demonstrate the results of this study. All in all, it is shown that the flight padding practice is widely-used by airlines and scheduling factors such as departure time and month of flight have high influences in dictating the amount of the required pad time.

Abstract: System maintenance is necessary to prolong the operational life of a system. There are four types of maintenance policies which are corrective, preventive, scheduled and predictive (conditioning based maintenance). However, this paper focuses on preventive maintenance and corrective maintenance policies. In general, the goal of preventive maintenance is to retain the system at its good operating conditions before the occurrence of any failure while corrective maintenance is done as a result of the system’s operating failure. This paper investigates the effects of maintenance activities for Engine Indication and Flight Instruments subsystems of the avionics system of a general aircraft. The simulation of the maintenance process is done using Monte Carlo and Discrete Event simulation methods for different preventive maintenance interval (PMI).

Abstract: A study on the effect of allocating a square blockage in front of a rotating cylinder is presented. The aim of the study is to determine the optimum design of the blockage to enhance the lift generating performance of the rotating cylinder. A numerical simulation is carried out to investigate the effect of different sizes of blockage towards the lift generating performance of the rotating cylinder. The simulation adopted a fully turbulent flow, having Reynolds number of 600. The cylinder is spinning at 5000 RPM. The validation of the simulation RANS code FLUENT is done through comparison with the published results from past studies. In general, the results suggest that the lift generating performance of the rotating cylinder will be improved by placing a blockage in front of it.

Abstract: The approach to problems of wall interference in wind tunnel testing is generally based on the so-called classical method, which covers the wall interference experienced by a simple small model or the neo-classical method that contains some improvements as such that it can be applied to larger models. Both methods are analytical techniques offering solutions of the subsonic potential equation of the wall interference flow field. Since an accurate description of wind tunnel test data is only possible if the wall interference phenomena are fully understood, uncounted subsequent efforts have been spent by many researchers to improve the limitation of the classical methods by applying new techniques and advanced methods. However, the problem of wall interference has remained a lasting concern to aerodynamicists and it continues to be a field of active research until the present. The main objective of this paper is to present an improved classical method of the wall interference assessment in rectangular subsonic wind tunnel with solid-walls.

Abstract: Change Ranking of Product Subsystems (CROPS) is a computer program that is designed to act as a decision-making aid for designers during early stages of their product redesign process. It generates a ranking of all subsystems within the existing product design architecture based on their estimated redesign risk. This information assists designers in selecting the right existing subsystems to be initially changed to satisfy the driving requirements, which have to be quickly decided. In this program, evaluation of redesign risk captures both direct and indirect change effects that potentially result from the modification of each subsystem. Designers are provided with a relative reference as to how risky and extensive it is to change one subsystem over the others, which can be useful when they have options to pick between several subsystems to modify for the same redesign requirement.

Abstract: Product redesign is hardly a straightforward process, especially for complex products. The existence of intricate interrelationships between different components of product design architecture makes it more susceptible to change propagation phenomenon. In this case, redesign risk is not easy to predict since the change effects are being propagated to other components from the initiating change component. Because of this condition, choosing the right initiating change component is essential to control redesign process risks, apart from being able to successfully satisfy the product requirements. With this notion, this paper proposes a method that systematically ranks all components of an existing product design based on their estimated redesign risk. By having this information, designers can make a better redesign planning. The demonstration of this method is presented through an example aircraft redesign case study.

Abstract: Known as “coir”, the fibrous husk of the coconut fruit has potential for integration as a constituent in impact-resisting aerospace materials. As a preliminary study, kinetic energy absorption of this natural fiber is studied prior to further testing, for instance; a non-ballistic surface impacted at high velocity by a small mass is the equivalent mock-up to runway debris. The purpose of this study is to find the relationship between the thickness of the fiber with the kinetic energy absorption. Fabricated fiber panels measuring 10×10×t cm with various thickness are subjected to mild steel projectiles launched by a light gas gun at a constant pressure. The velocity of the projectiles is set to be consistent with the velocity range of typical transport-category aircraft. The impact response of the panels aids in predicting the required amendments where plies of coir sheets are increased to which perforation is impossible. The relationship established from the experimental results is then used to predict the amount of layers required for total translational kinetic energy absorption.