Modern Trends in Aircraft Hydraulic Systems - Case Study Example

Modern Trends in Aircraft Hydraulic Systems Name Name of Institution Modern Trends in Aircraft Hydraulic Systems Introduction The performance capabilities of aircrafts increased tremendously in the latter stages of the 20th Century. The increase in performance meant that aircrafts required even more force to ensure acceptable levels of control. It is an accepted fact that pilots often make split-second decisions, and the aircraft has to respond to these quick decisions as fast as possible. The need for a quick response is evident in both commercial and military aircraft. Hydraulic systems were introduced into the high-performance aircrafts to reduce the effort that pilots needed to exert. These systems can be operated by computers that follow control laws or by direct input from the pilots. This paper will examine some of the latest developments in aircraft hydraulic systems. The emphasis will be on some of the recently released commercial aircraft as they have to meet challenges like carrying the highest number of passengers while saving fuel costs and other operational costs. These challenges impact control, meaning that these aircraft have to adopt new types of hydraulic systems. Hydraulic System in the Airbus A380 The Airbus A380 is an airplane that holds the record for being the largest operating passenger plane. Given that the lengthy lifespan of commercial aircraft, the A380 can be considered to be a modern trend-setting aircraft. The size of the aircraft means that it has to be powered by a number of innovative technologies. According to Adams (2001), the A380 has a wingspan of approximately 262 feet, a width that is comparable to the length of a football field. The plane also has a twin deck design that can carry more than 600 passengers depending on an airline’s configuration. These factors have a drastic bearing on control as the airplane’s take-off and landing weights exceed most of the other commercial aircraft. Therefore, the pilots have to move huge surfaces, with the aircraft’s vertical stabilizer alone having the same surface area as the entire wing of the Airbus A320 aircraft (Adams 2001). Airbus considered implementing the traditional hydraulic system on the A380, but these plans were set aside for a new hydraulic system that combined electric and hydraulic flight control (Adams, 2001). In order to understand the reason behind the need to embrace a new design, it is important to establish some of the disadvantages of the hydraulic system that is used in older planes. To begin with, passenger airplanes developed in the 1970s utilized a 3,000-psi system as the system could handle the lower weights of the aircrafts. The weakness in a 3000-psi system is that it requires considerably larger components that will increase the total weight of the aircraft. For instance, the diameter of the lines would have had to be larger in order to prevent pressure loss in such a large aircraft. Weight is a critical factor in aviation as it has an impact on fuel efficiency and, therefore, the profitability of airlines. If the Airbus A380 utilized such a system, it would have added to its already considerable weight. Therefore, the designers of the aircraft had to adopt an alternative hydraulic system that would have sufficient power to move large flight surfaces while being lighter than the typical 3000-psi systems. The solution that Airbus developed was a dual architecture system. The architecture included four separate flight control systems with two of them being powered by electricity and the rest being powered hydraulically (‘A380 Pushes 5000 psi,’ 2002). The reason for the dual architecture was to prepare for scenarios where any combination of the independent systems failed. The pilot would retain control of the aircraft in such a scenario, and this level of preparedness was unequaled at the time of its implementation. A significant feature of the hydraulically controlled system in this architecture is the fact that it was powered by a 5000-psi system. This system had been reserved for military aircraft, and even the supersonic Concorde was limited to a 4000-psi hydraulic system (‘A380 Pushes 5000 psi,’ 2002). Figure 1: Hydraulic system pressures for commercial and military aircraft The use of higher pressure at 5000 psi allows sufficient power to be conveyed with smaller hydraulic components and piping. It is estimated that this feature alone reduces the weight of an aircraft by about 3,300 pounds or one and a half metric tons (Adams, 2001). The designers of the plane also experimented with the existing hydraulic fluids to confirm that they would not degrade under the higher operating pressures (‘A380 Pushes 5000 psi,’ 2002). Another design challenge was the material selection as the aluminum used in 3000 psi systems could not withstand the added pressure. Eaton, the manufacturer of the A380’s hydraulic system, used steel or titanium to handle the higher pressures (‘A380 Pushes 5000 psi,’ 2002). In addition to the above features, the hydraulic pumps employed by the Airbus A380 had two unique features. The first was a very low pressure and noise pulsation. It is noted that the pressure in the system could vary from 4900 to 5100 psi as a result of normal pulsations. These variations increase fatigue and reduce reliability leading to Airbus’ decision to seek a pump with ±1% pulsation that allowed pressure variation from 4950 to 5050 psi (‘A380 Pushes 5000 psi,’ 2002). Eaton met this requirement by using an attenuator that was built into the system as well as an 11-piston rotating group (‘A380 Pushes 5000 psi,’ 2002). The second unique feature was the presence of a disengagement clutch that had not been implemented in other commercial aircraft. The clutch facilitated the disconnection of any malfunctioning pumps in flight or when the plane is on the ground. It protects the rest of the hydraulic system from contamination and allows airlines to avoid accommodating passengers as a result of a single malfunction (‘A380 Pushes 5000 psi,’ 2002). As stated, the hydraulic system in the A380 combined hydraulic and electrically powered systems. The electrical section utilizes a circuit that powers electro-hydrostatic actuators. These are non-conventional features, and they act as a backup system (‘A380 Pushes 5000 psi,’ 2002). The use of the electrical systems indicates the presence of a trend towards what is referred to as power-by-wire flight systems. Airbus is experimenting with this system and success will allow future aircrafts to have flight surface that are exclusively controlled by electrical power. This would eliminate the complex hydraulic systems and aircrafts will be able to carry more passengers or cargo as a result of the reduction in weight (Adams, 2001). Figure 2: Airbus A380 Hydraulic System showing the four independent systems Hydraulic System in the Boeing 787 Dreamliner According to Babej (2014), the Boeing 787 is the direct competitor of the A380, but it assumes that the airline industry would move towards more direct flights between cities. The large A380 was designed with the view that passengers will continue to embrace the hub and spoke system. It is arguable that the future of commercial aviation will be determined by which of these two planes will be more successful. The 787 uses innovative technology in all aspects of its designed. For instance, it has very efficient engines, and it is made from lightweight composite materials (Babej, 2014). The plane’s hydraulic system also has a number of new features that are bound to be adopted by other commercial aircraft. Figure 3: Boeing 787 Hydraulic System Architecture (Dodt, 2011). The Boeing 787 uses an architecture that appears to be similar to the traditional architecture where there are three separate systems. These are the right, center and left systems, and they regulate control actuators, nose gear steering, flaps, thrust reversers, and landing gear actuation (Boeing, 2007). The right and left systems are driven by pumps that are situated on the engine gearbox. An electric-motor-driven hydraulic pump provides additional power when demanded (Boeing, 2007). The design of the left and right systems is similar to traditional aircraft. The central system is the one that exhibits significant differences in the way it is powered. In the traditional design, it was powered by a 3000 psi pump to meet demands during takeoff and landing. The central system was the powered by a smaller electric-driven hydraulic pump for the rest of the flight. The 787 uses a different design for the central system as it is powered by two 5000 psi hydraulic pumps. One of them runs for the duration of the flight while the other comes in to meet peak demands. Like the Airbus A380, the 787 benefits from a reduction in weight because the 5000 psi system requires smaller components. The Airbus A350 has been designed to compete with the 787, and it also features a 5000 psi system (Airbus, 2015). Conclusion As stated, the capabilities of commercial aircrafts have increased considerably. This research paper has examined two of the trend-setting modern aircrafts that are bound to determine the future of aviation. In both cases, there has been a switch from 3000 psi hydraulic systems to the 5000 hydraulic system. The benefits of the switch have included reduced weight, improved redundancy, and easier maintenance. The later inclusion of the 5000 psi system on the A350 shows that more aircraft will shift towards hydraulic systems that are powered by higher pressure. The only differences will be in the design of backup systems as the Airbus relies on four independent systems while the Boeing utilizes three independent systems. An additional trend is the move towards more electric flight control systems that might eventually replace the heavy and complex all-hydraulic control systems. References A380 pushes 5000 psi into realm of the common man. (2002). Hydraulics & Pneumatics. Retrieved May 5 2015 http://hydraulicspneumatics.com/200/TechZone/HydraulicPumpsM/Article/False/6497/TechZone-HydraulicPumpsM Adams, C. (2001). A380: ‘More Electric’ Aircraft. Avionics Today. Retrieved May 4 2015 www.aviationtoday.com/av/commercial/A380-More-Electric-Aircraft_12874.html#.VUcXOJOKv_g Airbus S.A.S. (2015). A350 XWB: Technology. Airbus. Retrieved May 5, 2015 http://www.airbus.com/aircraftfamilies/passengeraircraft/a350xwbfamily/technology-and-innovation/s Babej, M.E. (2014). Airbus A380 vs. Boeing 787 Revisited. Forbes. Retrieved May 5 2015 http://www.forbes.com/sites/marcbabej/2014/12/11/airbus-a380-vs-boeing-787-revisited/ Dodt, T. (2011). Introducing the 787. ISASI. Retrieved May 5, 2015 http://www.isasi.org/Documents/library/technical-papers/2011/Introducing-787.pdf The Boeing Company. (2007). 787 No-Bleed Systems: Saving Fuel and Enhancing Operational Efficiencies. Boeing. Retrieved May 5 2015 http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/article_02_3.html Read More