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Fault-tolerance in commercial aircraft applications is typically achieved by redundancy. In such redundant systems the primary component is checked before the start of a flight to see if it operates correctly. The aircraft will not take off unless the primary is functioning. Airplane manufacturers must certify the airplane systems to be safe for flight. One means of safety certification is by safety analysis which shows that the probability of failure in a typical flight is bounded. The probability bound requirement for a system is based on the criticality of system failure. Usually backup components are checked at intervals that span multiple flights. The first backup may be checked more frequently than the second or higher levels. This leads to flights where the system may have latent faults in the backup components. The probability of failure in such cases varies from flight to flight due to the different exposure times for components in the system.

Recent work has shown that when an aircraft encounters ambient ice-supersaturated conditions (where contrails may form and persist), it may be possible to avoid contrail formation by shifting cruise altitude up or down 2000 feet. If an aircraft's cruise altitude is shifted from the optimal profile during a portion of the mission, fuel consumption increases. Because on average approximately 20% of distance flown by commercial airliners is through ice-supersaturated regions, this study quantifies the fuel burn penalties for the notional scenario of flying the same fraction of cruise at altitude displacements of +2000, -2000, and -4000 ft. Present aircraft performance data was used to generate accurate fuel burn penalty estimates. This study finds that the net penalties for existing aircraft to fly contrail avoidance shifts vary between 0.2% and 0.7% increase in block fuel consumption.

Aircraft thermal management (ATM) is increasingly important to the design and operation of commercial and military aircraft due to rising heat loads from expanded electronic functionality, electric systems architectures, and the greater temperature sensitivity of composite materials compared to metallic structures. It also impacts engine fuel consumption associated with removing waste heat from an aircraft. More recently the advent of more electric architectures on aircraft, such as the Boeing 787, has led to increased interest in the development of more efficient ATM architectures by the commercial airplane manufacturers. The ten papers contained in this book describe aircraft thermal management system architectures designed to minimize airplane performance impacts which could be applied to commercial or military aircraft.

The simultaneous operation of all systems generating, moving, or removing heat on an aircraft is simulated using integrated analysis which is called Integrated Energy System Analysis (IESA) for this book. Its purpose is to understand, optimize, and validate more efficient system architectures for removing or harvesting the increasing amounts of waste heat generated in commercial and military aircraft. In the commercial aircraft industry IESA is driven by the desire to minimize airplane operating costs associated with increased system weight, power consumption, drag, and lost revenue as cargo space is devoted to expanded cooling systems. In military aircraft thermal IESA is also considered to be a key enabler for the successful implementation of the next generation jet fighter weapons systems and countermeasures. This book contains a selection of papers relevant to aircraft thermal management IESA published by SAE International.