Aircraft engines pressurization

During the late 1980s two air tragedies resulted from very similar common cause failures. In both cases (a Japan Air Lines Boeing 747 and a United Airlines DC-10), hydraulic control was lost when the redundant hydraulic systems (seven in the 747 and three in the DC-10) were disabled by loss of hydraulic fluid when the hydraulic lines in the rudder of the aircraft were severed. Only one hydraulic system in either aircraft would have been sufficient to maintain control of the aircraft. The only location on either aircraft where all the hydraulic lines were in close proximity was in the rudder. Even though the trigger event was different for each aircraft (aft pressure bulkhead failure and sudden depressurization in the 747 and an engine explosion in the DC-10), both aircraft crashed due to common cause failure of redundant hydraulic control systems. 

U.S. Environmental Protection Agency regulations for commercial, jet, and turbine-powered aircraft (3) are based on engine size (thrust) and pressure ratio (compressor outlet/compressor inlet) for the time in each mode of a standardized takeoff and landing cycle. Once the aircraft exceeds an altitude of 914 m, no regulations apply. 

By far, the largest application of the axial compressor is the aircraft jet engine. The second most common usage is the land-based gas turbine, either the aircraft derivative or generic designed type. In last place of the applications comes the process axial compressor. All principles of operation are exactly the same. About the most obvious difference is that the gas turbine compressor is a higher pressure ratio machine and therefore has more stages. 

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