title: Increasing flight safety
Creators: name: Behbahani-pour, Mohammed Javad
Publisher: name: University of Glasgow
Year: 2024

description: Aviation accidents continue to horrify some people till this day, yet aviation safety has been the highest priority for the industry for the past decade, and according to the Civil Aviation Authority flying is often said to be the safest form of passenger travel in terms of fatalities per distance travelled as compared to rail and car accidents. In order to help safety, it is important to understand areas where human errors are and to design new technology and adopting new procedures in order to prevent or reduce risk of aircraft accidents and or incidents.

This research aims to increase flight safety on large transport aeroplanes by examining fuel tank explosions, fire, fuel leakage, and fuel contamination (water) and providing alternative solutions. One of the factors involved in increasing flight safety is to minimise the risk of fuel tank explosions on large transport aeroplanes. Fire and fuel leakages can result in fuel tank explosions. Fire in the vicinity of the fuel tank can heat the fuel and increase its temperature to the auto ignition point, at which fuel burns without any source of ignition, thus resulting in fuel tank explosion. Fuel leaking from the tanks can be ignited by different sources with catastrophic consequences; therefore, it is important to detect any fuel leakage before the departure of the aircraft. Currently, fuel leak detection systems are not installed on commercial aircraft to detect fuel tank leakage. The approach proposed in this thesis requires the fuel vent ports on the wings to be replaced with fuel vent valves, which can be controlled to be in an open or closed position. The fuel vent valve will be closed when certain conditions are fulfilled; the fuel ullage area is then pressurised to 4psi and the rate of change in the pressure drop is measured over a period. Several experiments have been conducted and the results show that a continuous fuel leak of one litre per minute can be detected. Further experiments show that, if the fuel tank is pressurised to higher pressures, a fuel leak could be detected sooner.

In all commercial and non-commercial aircraft, there is no fire-extinguishing system in the avionics bay. All navigation and communication computers are located on the racks and cooled by either ambient or air-conditioned air. Each computer contains several circuit boards, which, in cases of overheating, can burn and increase the risk of fire igniting the surrounding components and structure, thus jeopardising flight safety. It is therefore important to provide fire-extinguishing system capabilities in the aircraft avionics compartment. The approach proposed in this thesis is to extract nitrogen from the ambient air using an air separator module, then route the nitrogen to the avionics bay racks, where it can extinguish any fire. The temperature of the nitrogen is controlled at around 25°C to prevent thermal shock effects on the circuit boards before the nitrogen is injected into the avionics compartment. A series of experiments were conducted, aimed at gathering data using dry nitrogen under different pressure values to extinguish different sizes of fire. The analysis of the experiments showed that increasing nitrogen pressure resulted in faster extinguishing of a flame. This is because nitrogen under pressure quickly decreases the oxygen concentration available for combustion. Nitrogen is ideal for extinguishing a fire on an electrical system because it is noncorrosive and does not cause a short circuit. There have been different cases of aircraft accidents due to water contamination in aviation fuel. Since large transport aeroplanes fly at very high altitudes, where the ambient temperature can reach –60°C, water freezes at this point, causing blockages in the fuel pipelines, fuel filters, booster pumps, etc., which can result in engine thrust reduction and/or engine shutdown. Microbiological contamination of the fuel can result in fuel tank structure corrosion, which, in turn, can lead to a fuel leak. In addition, biological contamination in the fuel can cause other technical problems such as fuel quantity indication malfunction and fuel filter clogging. Therefore, it is important to eliminate or reduce the presence of water and microbial growth in the fuel. This thesis aims to increase flight safety by minimising the effects of water and biological contamination in the jet fuel inside fuel tanks on large transport aeroplanes. The proposed methodology is that water contamination is eliminated by extracting water from the fuel using a water/fuel separator, and microbial contamination is eliminated using ultrasonic technology. Several experiments were performed by taking fuel samples checked for the presence of microbes, then subjecting them to ultrasonic. The fuel sample was in a stainless-steel container where it was subjected to the ultrasonic waves externally. The experimental results showed that ultrasonics can heat the fuel and destroy the microorganisms effectively. In addition to the experiments presented, several Simulink simulations have been created to demonstrate the proposed algorithms.