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Safety by Design
Published in David O'Hare, Introduction to Safety Science, 2022
The main development in task analysis was that of hierarchical task analysis (HTA) formulated in the 1970s.11 Influenced by the then-current theories on problem-solving, planning and goal-directed behaviour, HTA consists of establishing a task hierarchy from an overall goal down through a series of sub-goals. HTA fits well within an overall systems perspective which was becoming established with the increasingly complex and sophisticated technological developments in aviation, manufacturing, power generation and others. For example, the goal of starting the engines on a jet aircraft can be described as consisting of three sub-goals and their associated actions. The first two sub-goals are to provide power and fuel (as in an automobile) with the addition of a third sub-goal requiring a pressurised air source to start the fan blades turning. Providing power is achieved by turning on the main battery and then starting the auxiliary power unit (APU), a small jet engine situated in the rear of the aircraft. Once running, the APU provides the power to provide the pressurised air needed. To start turning the blades, the air supply to the cabin is temporarily switched off and the air diverted to the engine. Fuel has to be loaded on board and is then provided to the engine by turning on the fuel pumps.
Power supplies
Published in David Wyatt, Mike Tooley, Aircraft Electrical and Electronic Systems, 2018
An APU is a relatively small gas turbine engine, typically located in the tail cone of the aircraft. The APU is a two-stage centrifugal compressor with a single turbine. Bleed air is tapped from the compressor and connected into the aircraft's air distribution system. Once started (see Chapter 10) the APU runs at constant speed, i.e. there is no throttle control. The APU shuts down automatically in the event of malfunction.
Engine performance
Published in Mohammad H. Sadraey, Aircraft Performance, 2017
The gas turbine engine can be used in several configurations: turbojet engine, turbofan engine, turboprop engine, and turboshaft engine. Small gas turbine engines called auxiliary power unit (APU) have also been developed to supply transport aircraft with electric power. In general, the specific fuel consumptions (SFCs) of jet engines are higher than those of engines.
Three-objective optimization of aircraft secondary power system rotor dynamics
Published in Mechanics Based Design of Structures and Machines, 2022
Joseph Shibu K., K. Shankar, Ch. Kanna Babu, Girish K. Degaonkar
The secondary power system discussed here is a gas turbine engine-based one, which comprises of an auxiliary power unit (APU) and an air starter unit. APU provides stand-alone power to the main engine subsystems and air to the air starter for starting the main engine. The arrival of the stronger secondary power systems is attributed to powerful engines and their ever increasing demand for secondary power for subsystems. The same trend is followed by many modern military aircraft and has made increasing use of auxiliary power to enhance both the handling merits and airborne effectiveness. The design of secondary power systems has gained significant importance over the years. The design of the APU rotor system for secondary power system’s in-flight operating requirement of emergency landing in case of main engine failure is a difficult task as it may adversely affect the continuous operation on ground. Hence, a multi-objective problem is formed where the unbalance response at critical speed, response during maneuvering, and shaft weight of rotor system are optimized simultaneously. Studies on these objectives have shown that they are conflicting in nature. The optimization of manuevering aircraft rotor system with three objectives is a novel work.
Assessment of Augmented Reality Technology’s Impact on Speed of Learning and Task Performance in Aeronautical Engineering Technology Education
Published in The International Journal of Aerospace Psychology, 2021
Kristoffer B. Borgen, Timothy D. Ropp, William T. Weldon
To ensure relevance and transfer to both the learning and real-world aviation operational environments, researchers selected a checklist procedure for starting the aircraft’s APU. The APU is a self-contained gas turbine engine used on many large aircraft. It is operated by maintenance and flight crews to provide pneumatic bleed air and electrical power for the airplane during ground operations or during certain emergency flight conditions. Most APU starting procedures consist of required checklist tasks which must be accomplished in a specific sequence in order to safely start the APU. Successfully navigating and performing this multi-step task requires locating and manipulating multiple switches and reading and monitoring system status information on various multi-function display screens, and continuous team communication.