Search Results

This set is comprised of two titles, Aircraft Thermal Management: Systems Architectures and Aircraft Thermal Management: Integrated Energy Systems Analysis both edited by Mark Ahlers.

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.

Historically the manufacturing of aircraft fuselages with capacities of 100+ passengers requires large panels and assemblies to be integrated through processes of manipulating them into proper alignment to one another, and then fastening the panels and assemblies together. The manipulating and alignment processes typically incorporate large handling devices and cranes to move the large panels and monolithic tools or measurement alignment systems to precisely align the aircraft components. After the individual panels and assemblies are properly aligned, they can be fastened together. Normally, the fastening process is performed manually with the aid of fastener location templates. There are problems with these processes. They require high capital investments for tooling and facilities; up to two shifts (16 hours) to complete the loading, indexing, and fastening operations; and depend on a highly skilled and knowledgeable work force to minimize discrepancies.

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.

The objectives of this work are to search for a structure-borne sound power measurement method that can be consistently deployed among different test facilities, and to investigate how test results can be compared at different test stands. A series of experimental tests are conducted to compare selected test methods by measuring structure-borne power transmitted from simulated mechanical sources to a supporting plate through single contact and multiple contacts, respectively. The frequency range of interest in these tests is a broad range from 100Hz to 10 kHz. Test methods under this experimental study include the cross-spectral method, the mobility method and the reverberant plate method. In addition, simplified mobility methods based on ideal sources and the synthesized force are also examined. Advantages and limitations of each test methods are discussed from a practical industrial standpoint.

A process is implemented to propagate uncertainties inherent to the Statistical Energy Analysis (SEA) modeling practice to variance in predictions. A Monte Carlo based approach is scripted for the VA-One environment to account for uncertainties in gross parameters of SEA model subsystems. The variance module of the commercial software is used to estimate possible variations in local modal properties. A first-order expansion solution is applied to integrate uncertainties in the power inputs of the system. The impact of each type of source is assessed in computing overall variance in predictions. The process is applied to analysis of in-flight interior cabin noise predictions using a simplified aft fuselage section SEA model.

The significant problem of engine power-loss and damage associated with ice crystal icing (ICI) was first formally recognized by the industry in a 2006 publication [1]. Engine events described by the study included: engine surge, stall, flameout, rollback, and compressor damage; which were triggered by the ingestion of ice crystals in high concentrations generated by deep, moist convection. Since 2003, when ICI engine events were first identified, Boeing has carefully analyzed event conditions documenting detailed pilot reports and compiling weather analyses into a database. The database provides valuable information to characterize environments associated with engine events. It provides boundary conditions, exposure times, and severity to researchers investigating the ICI phenomenon. Ultimately, this research will aid in the development of engine tests and ICI detection/avoidance devices or techniques.

CFD now stands alongside the wind tunnel in terms of importance to aerodynamic design. Its usage by engineering designers involves many thousands of runs per year, and the rate is increasing. For the simpler aerodynamic flows where viscous effects are modest, CFD has become the dominant tool for aerodynamic design. The primary role of the wind tunnel for such flows is for validation of a design and for determination of aerodynamic characteristics over the broad flight envelope. For more complex flows that are dominated by strong viscous effects, CFD is beginning to make a contribution. It is thought by many that the principle challenge for the future is to develop better computers and algorithms in order to better address the computation of complex flows over complex airplane geometries. But recent experiences involving the application of CFD to the design of the new Boeing 777 airplane has taught us that the challenge for the future is really much broader.