 The recent incident involving a missing aircraft is an alarming signal regarding the design and safety of aircrafts. In this issue, Prof. Alan Lau Kin-tak, Associate Dean (Industrial Relations) of the Faculty of Engineering, shared with us some knowledge about aircraft design, flying regulations, safety and monitoring systems to analyze the root cause of problems and incidents from a scientific perspective.
What are the fundamental principles in designing an aircraft?
There are four basic forces — gravity, lift, thrust and drag, that make an airplane fly. Any changes of these forces can affect the speed or direction of the aircraft. In general, aircraft flies up to 30,000 feet from the ground which is equivalent to the height of Mount Everest. Some birds also fly up to that height and thus creating risks for aircraft flight. The higher the aircraft flies, the more changes will occur in its surroundings. For example, temperature drops to negative degrees and becomes static until tropopause is reached; air pressure drops until stratosphere is reached; and density of air continues to fall.
Aircraft interior is of paramount importance in aircraft design. Air pressure, temperature, oxygen and humidity levels inside the aircraft have to be maintained at the levels as 8,000 feet above ground in which human being and aircraft structure can withstand. Also, aircraft flight principles are very much related to airfoil design and operation so as to satisfy for lifting requirements at different stages including takeoff, climbing, cruising, descending and landing. Aircraft design requires a naturally stable system so that it will revert to stable flight conditions in the absence of operating commands.
In general, what are the causes of aviation incidents?
Aviation incidents are generally caused by weather-related or mechanical-related pilot errors, other human errors, adverse weather conditions, mechanical failures, sabotages and other causes. From 1950 to 2010, around 50% of aviation incidents and accidents were caused by pilot errors. The most common pilot errors include tail-strike and emergency landing without extending the wheels etc. Others were caused by mechanical or engine failures including flying in single-engine, external crash, oil leakage, turbine oil overheat, low oil pressure, emergency landing, hydraulic brake failure, metal corrosion, hard landing, repairing problems etc. With regard to human errors, various factors are taken into consideration — conditions in runway, maintenance and repairing quality, pilot quality and attitude, as well as accuracy of instructions given by control towers.
What is “black box” installed in an aircraft?
The ‘black box’ installed in the aircraft serves as a flight data recorder that can withstand an impact of 3,400 times of the force of gravity, record for 17 to 25 hours, contain a battery that can last up to 30 days, transmit from a depth of 6,000 metres under the sea, withstand high temperature up to 1,000 degree Celsius, and emit 37.5 Hz of ultra-sound per second. However, to protect the recorded data, no instant communication system is installed in the black box. The data can only be retrieved for investigation if the black box is found after the incidents. Hence, locating the black box is of utmost importance in finding out the causes of aviation incidents as all flight data and conversations in the cockpit are recorded in the black box.
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