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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.

A highly modified F/A-18 aircraft is being used to demonstrate that aeroelastic wing twist can be used to roll a high performance aircraft. A production F/A-18A/B/C/D aircraft uses a combination of aileron deflection, differential horizontal tail deflection and differential leading edge flap deflection to roll the aircraft at various Mach numbers and altitudes. The Active Aeroelastic Wing program is demonstrating that aeroelastic wing twist can be used in lieu of the horizontal tail to provide autonomous roll control at high dynamic pressures. Aerodynamic and loads data have been gathered from the Phase I AAW flight test program. Now control laws have been developed to exploit aeroelastic wing twist and provide autonomous flight control of the AAW aircraft during Phase II. Wing control surfaces are being deflected in non-standard ways to create aeroelastic wing twist and develop the required rolling moments without use of the horizontal tail.

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.

Two compact intercoolers are designed for the Rotax 914 aircraft engine to increase engine power and avoid engine knock. A study is performed to investigate the effects of unsteady airflow on intercooler performance. Both intercoolers use air-to-liquid cross flow heat exchangers with staggered fins. The intercoolers are first tested by connecting the four air outlets of the intercooler to a common restricted exit creating a constant back pressure which allows for steady airflow. The intercoolers are then tested by connecting the four air outlets to a 2.4 liter, 4 cylinder engine head and varying the engine speed from 6000 to 1200 RPM corresponding to decreasing flow steadiness. The test is performed under average flight conditions with air entering the intercooler at 180°F and about 5 psig. Results from the experiment indicate that airflow unsteadiness has a significant effect on the intercooler's performance.

Due to the instabilities that may occur in power systems with regulated loads such as those used in military aircraft, ships, and terrestrial vehicles, many analysis techniques and design methodologies have been developed to ensure stable operation for expected operating conditions. However, many of these techniques are difficult to apply to complex systems and do not guarantee large-displacement stability following major disturbances such as faults, regenerative operation, large pulsed loads, and/or the loss of generating capacity. In this paper, a design paradigm is set forth guaranteeing large-displacement stability of a power system containing a significant penetration of regulated (constant-power) loads for any value of load power up to and including the steady-state rating of the source. Initial investigations are performed using an idealized model of a dc-source to determine the minimum requirements that ensure large-displacement stability.