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As the cost and complexity of modern aircraft systems increases, emphasis has been placed on model-based design as a means for reducing development cost and optimizing performance. To facilitate this, an appropriate modeling environment is required that allows developers to rapidly explore a wider design space than can cost effectively be considered through hardware construction and testing. This wide design space can then yield solutions that are far more energy efficient than previous generation designs. In addition, non-intuitive cross-coupled subsystem behavior can also be explored to ensure integrated system stability prior to hardware fabrication and testing. In recent years, optimization of control strategies between coupled subsystems has necessitated the understanding of the integrated system dynamics.

As technology for both military and civilian aviation systems mature into a new era, techniques to test and evaluate these systems have become of great interest. To achieve a general understanding as well as save time and cost, the use of computer modeling and simulation for component, subsystem or integrated system testing has become a central part of technology development programs. However, the evolving complexity of the systems being modeled leads to a tremendous increase in the complexity of the developed models. To gain confidence in these models there is a need to evaluate the risk in using those models for decision making. Statistical model validation techniques are used to assess the risk of using a given model in decision making exercises. In this paper, we formulate a transient model validation challenge problem for an air cycle machine (ACM) and present a hardware test bench used to generate experimental data relevant to the model.

Aircraft power demands continue to increase with the increase in electrical subsystems. These subsystems directly affect the behavior of the power and propulsion systems and can no longer be neglected or assumed linear in system analyses. The complex models designed to integrate new capabilities have a high computational cost. Hardware-in-the-loop (HIL) is being used to investigate aircraft power systems by using a combination of hardware and simulations. This paper considers three different real-time simulators in the same HIL configuration. A representative electrical power system is removed from a turbine engine simulation and is replaced with the appropriate hardware attached to a 350 horsepower drive stand. Variables are passed between the hardware and the simulation in real-time to update model parameters and to synchronize the hardware with the model.

Aircraft power demands continue to increase with the increase in electrical subsystems. These subsystems directly affect the behavior of the power and propulsion systems and can no longer be neglected or assumed linear in system analyses. The complex models designed to integrate new capabilities have a high computational cost. This paper investigates the possibility of using a hardware-in-the-loop (HIL) analysis with real time integration. A representative electrical power system is removed from a turbine engine model simulation and replaced with the appropriate hardware attached to a 350 horsepower drive stand. In order to update the model to proper operating conditions, variables are passed between the hardware and the computer model. Using this method, a significant reduction in runtime is seen, and the turbine engine model is usable in a real time environment. Scaling is also investigated for simulations to be performed that exceed the operating parameters of the drive stand.

The interdependency between propulsion, power, and thermal subsystems on military aircraft such as the F-35 Joint Strike Fighter (JSF) and F-22 Raptor continues to increase as advanced war-fighting capabilities including solid-state radars, electronic attack, electric actuation, and Directed Energy Weaponry (DEW) expand to meet Air Force needs. Novel analysis and testing methodologies are required to predict these interdependencies and address adverse interactions prior to costly hardware prototyping. As a result, the Air Force Research Laboratory (AFRL) has established a dynamic hardware-in-the-loop (HIL) test-bed wherein transient simulations can be integrated through advanced real-time simulation with prototype hardware for integrated system studies and analysis. This paper details a test-bed configuration where a dynamic simulation of an aircraft turbine engine is utilized to control a dual-head electric drive stand.

The detrimental effects of prolonged sitting during long-duration flights include deep vein thrombosis, pressure sores, and decreased awareness and performance. However, the cushion is often the only component of the ejection seat system that can be modified to mitigate these effects. This study investigated the long-duration effects of sitting in four ejection seat cushions over eight hours. Subjective comfort survey data and cognitive performance data were gathered along with comparative objective data, including seated pressures, muscular fatigue levels, and lower extremity oxygen saturation. Peak seated pressures ranged from 1.22–3.22 psi. Oxygen saturation in the lower extremities decreased over the eight hours. Cognitive performance increased over time regardless of cushion with the exception of the dynamic cushion, which induced a decrease in performance for females.

Operator fatigue and time-of-day induced variations in cognitive effectiveness can lead to lapses in attention, slowed reactions, and impaired reasoning and decision-making that has been shown to contribute to accidents, incidents and errors in a host of industrial and military settings. During the past three years, the US Air Force has sponsored the development of a model of human fatigue and circadian variation and a scheduling tool based upon the model that will be used to minimize aircrew fatigue. The initial test version of the tool has passed review by the operational wings of the AF and a final operational product is in advanced development and validation. The software was developed by SAIC and NTI and is called the Fatigue Avoidance Scheduling Tool (FAST™). This fatigue forecasting system is being developed and tested by NTI under a small business innovative research (SBIR) grant from the US Air Force, now in the third year of a three-year program.

Side-facing seats are present in a variety of aircraft. During impact, these seats load the occupants in a different manner than typical forward-facing seats, namely the occupants are exposed to a lateral impact. In order to minimize injury during a crash, it is necessary for the occupants to prepare themselves and be situated in a position for maximum protection. In an effort to understand occupant initial position in a side-facing seat, a 3-D rigid-body model was developed of a side-facing seat configuration with three occupants, using the Articulated Total Body (ATB) program. The occupants were seated side-by-side in webbed troop-style seats, and each occupant was restrained by a lap belt. Three different initial occupant positions were studied, and each of the three occupants in a given simulation were seated in the same position. A 10 G lateral pulse with an approximate duration of 200 ms was applied to the vehicle.

The Air Force Research Laboratory Deployment and Sustainment Division (AFRL/HES), in coordination with Arthur D. Little, Inc., has undertaken a system-of-systems approach to defining and designing aerospace ground equipment (AGE). This method is usually used to take advantage of the open architecture nature of ne and developing electronics through modular design. This paper discusses how we applied it across the electronic, mechanical, and structural aspects of AGE to research and develop a new concept to meet the burgeoning needs of the 21st century Air Force.