Applied Mechanics and Materials Vol. 225

Abstract: Malaysia had in the past sent two remote sensing satellites to orbit by collaborating with foreign space companies to build homegrown capacities for space technology development. At the educational institutions, a pico-satellite development program would be an ideal first step to establish such capacity as students could gain the experience and know-how through the complete cycle of designing, building and testing a satellite. As it is now, some of their overseas counterparts have already succeeded in running CubeSat programs due to strong support from kit manufacturers and their national space agencies. However, the cost to purchase such kits could be discouraging and National Space Agency (ANGKASA) recognises the needs to initiate some designs that could be used or referred to for further development or expansion. In this paper, a hardware design of On-Board Data Handling (OBDH) board using PIC Microcontroller is presented. OBDH is a main subsystem which controls all subsystems in the satellite. It provides a series of important services like command, telemetry, data communication, data acquisition, process, storage and management. The PIC Microcontroller made by Microchip Corporation is chosen as it is widely used by the industry and academia in Malaysia. The 16-bit PIC24 microcontroller has been recognized as a suitable part due to its performance, memory, peripherals, cost effective solutions as well as availability. The method used in designing the OBDH in this pico-satellite is first based on a main mission to investigate ionospheric effect on GPS signal transmission. Other considerations taken are that the parts used should be of commercial off the shelf product and having its own development board for ease of testing. The expected result would be the successful arrangement of all required parts in limited pico-satellite’s size and the accomplishment in achieving the satellite’s missions through simulation.

Abstract: One of the necessary parts of CubeSat’s design is the thermal analysis. It will provide the operating temperatures and their distribution for all devices inside the CubeSat. For decision, which temperature standard can be used for components it is necessary to know the maximum and the minimum value of the temperature. In virtue of these results the position of the all devices must be also optimized. Some methods of the thermal control are also proposed. Contrary to most subsystems the thermal subsystem is not independent of the others. All elements in the spacecraft have an influence on the thermal housekeeping by either emitting or absorbing energy or both respectively. The objective of thermal subsystem is to ensure that the spacecraft operate within the spacecraft operating temperature range. There are two types of thermal control technique; passive and active. Due to the size and power constraint of CubeSat, passive thermal control will be more suitable but analysis must be done in order to know that passive control is sufficient. The FEA methodology would be utilized in order to determine the spacecraft operating temperature within the range. To accomplish this, MSC Nastran Patran software will be used as the FEA modeling tool. The MD Patran will act as preprocessing tool whereas MD Nastran will act as post processing tool. If the simulated thermal range is deviates, temperature sensors and heaters will be mounted on the CubeSat to monitor the deviation. Alternatively, mounting Kapton tape onto the CubeSat structure and laying gold coating would be another method to maintain the desired temperature range. The design of the thermal system shall be based on passive methods. This approach is vital to avoid power consumption in cases where it would not be necessary. As conclusion the thermal subsystem is designed to operate the spacecraft throughout its mission phases without any failure.

Abstract: Accurate life prediction of aircraft engine components is very critical because it has a direct impact on aircraft safety and on operators’ profits. The engine bleed air system valves have considerably high failure rates when the engines are operated in desert conditions because of sand particles erosion and blockage. In this work, an Artificial Neural Network (ANN) model for the prediction of failure rate of the most important of these valves in Boeing 737 engines is developed and validated. A previously developed feed-forward back-propagation algorithm is implemented to train the ANN. The effects of changing the number of neurons in the input layer, the number of neurons in the hidden layer, the rate of learning, and the momentum constant are investigated. The model results are validated using comparisons with actual valves failure data from a local operator in Saudi Arabia, as well as comparisons with classical Weibull model results.

Abstract: For meeting requirements of staying in the stratosphere for a long time period more than one year and less of maintenance, the power and propulsion system of the stratospheric airship is required to have high reliability. In this regard, reliability design is a key procedure in the design phase of the power and propulsion system of stratospheric airship. This paper focuses on the quantitative analysis of the reliability for the power and propulsion system of the stratospheric airship. Firstly, the reliability of the solar cell array and the fuel cell of power system are discussed respectively. Then, different topologies of the power system are discussed and compared. The reliability of the propulsion system is also analyzed in different configurations. The reliability of the basic combination of the power and propulsion system is discussed. For improving reliability, a new type of combination for the power and propulsion system is proposed. Reliability models of proposed combination are created through simplification. The ZhiYuan-1 is used as a demonstration problem to show the capability of this reliability-improved method. The result shows that the reliability of ZhiYuan-1 power and propulsion system increases by 12.8%.

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: This paper addresses the current scenario of air traffic over Malaysian airspace and its impact on existing routes and capacity. In dealing with the increase of capacity, ICAO has embarked on implementing several new measures that would accommodate more aircrafts and the same time maintaining the highest level of safety. Those measures are outlined in ICAO’s Doc 9574 and 9937. Instead of introducing more routes, which up to one point could reach its maximum saturation point, ICAO has introduced Reduced Vertical Separation Minima (RVSM). RVSM increases the number of aircraft that can be accommodated on the given route. The Malaysian airspace is strategically located in the middle of the Westbound and Eastbound routes over the Asia Pacific region. This is an added advantage for the installation the Height Monitoring Unit for RVSM performance of aircraft. Generally, almost all of the aircraft overflying Malaysian airspace are already at their optimum flight levels. This paper uses the trend for year 2010 and 2011 data provided by the Department of Civil Aviation of Malaysia in the analysis. The paper analyses the current scenario of air traffic safety over Malaysian airspace and identifies suggestions to develop a system that could extract information from ADS-B for height monitoring purposes.

Abstract: This paper attempts to utilise aircraft maintenance historical data and information for future aircraft design from the perspective of maintanability. Aircraft feedback information contains various types of information that could be used for future improvement rather than just the failure elements. The study shows that the aircraft maintenance related feedback information systems analyses were very useful for deciding maintainability effectiveness; these include planning, organising maintenance and design improvement. There is no doubt that historical data information has the ability to contribute with an important role in design activities. The results also show that maintainability is an importance measure that can be used as a guideline for managing efforts made for the improvement of aircraft components.

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: Bolted joints of aircraft lug assembly play an important role in connecting the wing and fuselage of an aircraft structure. Generally, the bolted joints get loosened because they are frequently exposed to the dynamic loads induced when an aircraft is in service. For this reason, it is important to monitor the condition of the bolted joints to avoid any critical defect that will lead to any risk in human life. However, it is difficult to conduct the bolted joints’ loosening inspection by an operator. In past few decades, optical fiber based sensor has been widely used due to its advancement over a conventional piezoelectric (PZT) sensor, especially due to its small size and light weight. With regard to this, a loosening monitoring of bolted joints using optical fiber bending sensor for aircraft lug assembly is proposed in this paper. The lug assembly specimen, which consists of a stainless steel lug, CFRP/Nomex honeycomb sandwich panel, carbon-steel bolt, nut and washer, and the monitoring system, which consists of a single mode fiber with ten optical fiber bending sensor nodes and an Optical Time-domain Reflectometer (OTDR) were used to determine the bolt loosening at every 1 degree interval.

Abstract: A normal aircraft flight includes taxi, takeoff, climb, cruise, descent, precision approach and finally landing. This study focuses on landing where the aircraft returns to the ground safely. In low visibility conditions, when pilots are unable to see the runway, the aircraft can always be diverted to another airport. However, low visibility can also affect all airports in the vicinity, forcing aircrafts to land in low visibility conditions depending on Instrument Flight Rules (IFR). Many countries have employed the landing systems because of inaccuracy, unreliability and dependency of Visual Flight Rules (VFR). In this paper, aircraft landing systems accuracies and limitations will be studied and compared for the purpose of assessing the best possible system currently available that can be achieved and implemented.