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The search for ever-lower emission technology for future generations of aircraft engines is actively progressing on both sides of the Atlantic. Tucked away on a modest-size stand at this year’s Farnborough International Airshow was a highly varied collection of unconventional engine technology displays – a clear indication of radical innovation already being investigated as a part of Ultimate, the European Horizon 2020 research and innovation project.

In part two of a two-part series, Richard Gardner discusses various aerospace propulsion innovations and continued work by aerospace engineers and scientists to advance aircraft engine technologies to increase efficiency and lower emissions.

Aircraft potable (drinking) water systems haven’t changed significantly in the last half-century. These systems consist of cylindrical water tanks pressurized by bleed air from the jet engines, with insulated stainless steel distribution lines. What has changed recently is the increase in the possibility of aircraft picking up contaminated drinking water at foreign and domestic stops. Customer awareness of these problems has also changed - to the point where having reliable drinking water is now a competitive issue among airlines. Old style potable water systems that are used on modern aircraft are high maintenance and exacerbate the growth of microbes because the water is static much of the time. The integrity of some pressurized water tanks are also a concern after years of use. Cost-effective mechanical and biological solutions exist that can significantly reduce the amount of chemicals added and provide good potable water.

The characteristics of turbines for turbojet and space power plant applications are compared on the basis of power requirement trends, working fluids, materials, and system requirements. The differences in Brayton and Rankine cycles, the requirements of the cycles imposed on turbines, and typical losses inherent in present low power space turbines are discussed. A comparison is made of representative present and future turbines for turbojet and space power applications. Future large space turbines will parallel the performance and design techniques of high performance gas turbines. Some of the design techniques of steam turbines can also be used because of experience with wet vapor and long endurance. The future goals and problem areas of turbojet and space turbines are shown.

This paper attempts to assess the benefits of a unique distributed propulsion concept, known as the Multi-Gas Generator Fan (MGGF) system, over conventional turbofan engines on civilian vertical takeoff and landing (VTOL) applications. The MGGF-based system has shown the potential to address the fundamental technical challenge in designing a VTOL aircraft: the significant mismatch between the power requirements at lift-off/hover and cruise. Vehicle-level performance and sizing studies were implemented using the Grumman Design 698 tilt-nacelle V/STOL aircraft as a notional personal air vehicle (PAV), subjected to hypothetical single engine failure (SEF) emergency landing requirements and PAV mission requirements.

Due to ongoing efforts by the aviation industry, much has been learned over the last several years regarding jet engine power loss and compressor damage events caused by the ingestion of high concentrations of ice crystal particles into the core flow path. Boeing has created and maintained a database of such ice crystal icing (ICI) events to aid in analysis and further study of this phenomenon. This article provides a general update on statistics derived from the Boeing event database, and provides more details on specific event clusters of interest. A series of three flight campaigns have, over the past five years, collected in-situ data in deep convective clouds that will be used for the assessment of the new FAA CFR Part 33 ice crystal environmental envelope Appendix D, and the equivalent EASA CS-25 Appendix P.

The AiResearch TFE731-2 Turbofan Engine Control system was created out of a recognition of engine and aircraft operating requirements in which a free weighting of candidate control components and logic was made. From this free design iteration process, which considered both conventional and advanced concepts of control, the control described in this paper has evolved and has fulfilled the in-flight operating requirements of the engine.

The contribution that aged hardware makes to performance deterioration is of interest to operators of JT3D turbofan powered aircraft since a significant percentage of these engines have exceeded 20,000 hr of operation. Recent studies involving numerous engine disassemblies, rebuild, and test cell runs reveal the most significant effects of aged hardware are the loss in high and/or low compressor stall margin; and, that a large number of parts must be replaced to realize a significant improvement in fuel consumption, with the exception of the reduction that can be obtained by controlling turbine seal clearances.

This Aerospace Information Report (AIR) is a general overview of typical airborne vibration monitoring (AVM) systems with an emphasis on system hardware design considerations. It describes AVM systems currently in use. The purpose of this AIR is to provide information and guidance for the selection, installation, and use of AVM systems and their elements. This AIR is not intended as a legal document but only as a technical guide.

This AIR is a general overview of typical airborne vibration monitoring (AVM) systems with an emphasis on system hardware design considerations. It describes AVM Systems currently in use.

This Aerospace Recommended Practice (ARP) is a general overview of typical airborne engine vibration monitoring (EVM) systems applicable to fixed or rotary wing aircraft applications, with an emphasis on system design considerations. It describes EVM systems currently in use and future trends in EVM development. The broader scope of Health and Usage Monitoring Systems, (HUMS) is covered in SAE documents AS5391, AS5392, AS5393, AS5394, AS5395, AIR4174. This ARP also contains the essential elements of AS8054 which remain relevant and which have not been incorporated into Original Equipment Manufacturers (OEM) specifications.

This Aerospace Information Report (AIR) is a general overview of typical airborne engine vibration monitoring (EVM) systems applicable to fixed or rotary wing aircraft applications, with an emphasis on system design considerations. It describes EVM systems currently in use and future trends in EVM development. The broader scope of Health and Usage Monitoring Systems, (HUMS ) is covered in SAE documents AS5391, AS5392, AS5393, AS5394, AS5395, AIR4174.

This SAE Aerospace Information Report (AIR) is a general overview of typical airborne engine vibration monitoring (EVM) systems with an emphasis on system design considerations. It describes EVM systems currently in use and future trends in EVM development.

This report proposes a new high efficiency “fuselage fan” concept of aircraft propulsion for subsonic airplanes also noted as “fusefan” (FF). The fusefan concept consists of one or two rings of swept blades rotating around the fuselage. This variable pitch fan has an important advantage in comparison with currently used turbofan engines: it dramatically increases the cross-sectional bypass area of the propulsion system by 3-5 times. As shown in the paper this propeller has an efficiency in cruise flight of 9-16% more than the current turbofan propulsion system. It also provides a large increase in static thrust (40-75%), which in turn decreases takeoff distance about 30-45%, and has a clean wing aerodynamically due to the absence of nacelles. An analysis of the benefits of the fuselage fan compared with the Advanced Turboprop Propeller (ATP) and propfan “Unducted Fan” (UDF) shows that for equal disk loading the “fuselage fan” has the following advantages: 1.

Jet engine malfunctions can be detected by acoustic and vibration measurement. A means of detecting engine malfunctions, or functional variations, with a high confidence level is being investigated using digital computer techniques. Operation of the analyzer is based on subjecting incoming “real time” data to predetermined tests and categorizing the data based on these tests. Using this method, several different types of possible malfunctions could be checked at one time in less than 10 sec. Acoustic and vibration designdata, required to form the malfunction decision rule, were tape recorded in test programs of actual known malfunctions in jet engines. Both normal engine data and malfunction data with several degrees of failure were used to establish each predicted-malfunction detection mode. This paper presents the status of this activity.

Laboratory, component, and engine tests have been conducted by the General Electric Co. to evaluate the various lubricant properties important to the J79 jet engine. Such properties as elastomer volume swell, oxidation-corrosion, coking characteristics, and lubricity were evaluated. The effects of these various properties on engine performance and how the laboratory results relate to the component results and engine test results are discussed.

This Recommended Practice covers a means of determining the performance acceptability of new production or overhauled starters that will be used for cranking turbine engines and is intended for use where torque measuring equipment is not available or desirable. This method determines acceptability of the overall performance of the starter on a flywheel test stand, rather than the performance at specific speed conditions. It allows a slight variation of output torque outside specified limits, as long as the overall performance is up to standard.

This Aerospace Information Report (AIR) addresses the subject of aircraft inlet-swirl distortion. A structured methodology for characterizing steady-state swirl distortion in terms of swirl descriptors and for correlating the swirl descriptors with loss in stability pressure ratio is presented. The methodology is to be considered in conjunction with other SAE inlet distortion methodologies. In particular, the combined effects of swirl and total-pressure distortion on stability margin are considered. However, dynamic swirl, i.e., time-variant swirl, is not considered. The implementation of the swirl assessment methodology is shown through both computational and experimental examples. Different types of swirl distortion encountered in various engine installations and operations are described, and case studies which highlight the impact of swirl on engine stability are provided. Supplemental material is included in the appendices.