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Technical Paper

Math Modeling of Airfoil Geometry

New and powerful methods of characterizing existing and new airfoil geometries with mathematical equations are presented. The methods are applicable to a wide range of airfoil shapes representing traditional, cusped, reflexed, flat-bottom, laminar, transonic, and supersonic designs. With the emphasis on low-speed airfoils, several existing airfoils are first closely matched with the math-modeling methods. Then, to support the design of new airfoil geometries, a new interpretation of Theodorsen's potential flow method is outlined for the calculation and presentation of surface velocity in inviscid flow. Also, a vector approach is introduced for the calculation of pitching moment. Finally, new math-modeled airfoils are proposed for conventional and unique aircraft configurations.
Technical Paper

Drivmatic Retrofit

Fuselage panels for the Boeing 747 aircraft have been assembled at the Northrop Commercial Aircraft Division Alameda (D2) facility since the mid 1960's. The assembly work has been accomplished using Gemcor CNC Drivmatic systems. These systems have performed reliably since their initial installation in the late 1960's, but have recently begun to show their age. In 1992, the decision was made to establish a project that would direct the retrofit of these systems to state-of-the-practice condition. This paper will discuss the planning, scheduling and specification development for that project.
Technical Paper

Thermal Benefits of Advanced Integrated Fuel System Using JP-8+100 Fuel

One of the thrusts of the Advanced Integrated Fuel System (AIFS) initiative, sponsored by the Fuels Branch of the Aero and Propulsion Power Directorate at Wright Laboratories (WL/POSF) with partial funding from the United States Navy, is to realize the potential improvements in aircraft thermal management systems due to the 100 degrees F increase in fuel heat sink capacity of JP-8+100 fuel. This paper summarizes the conceptual design and top-level trade studies conducted by Northrop Grumman Corporation (NGC) under an AIFS contract. These studies examined the air vehicle-level payoffs of JP-8+100 fuel applied to the (1) F/A-18C/D (representing an existing fleet aircraft), (2) F/A-18E/F (representing an aircraft currently under development), and (3) a more-electric aircraft/subsystem integration technology (MEA/SUIT) configured version of an F/A-18 (representing a future aircraft). The objectives and approaches of these studies are presented.
Technical Paper

An Overview of Electrically Powered Control Actuation Health Management

As More Electric Aircraft design becomes the preferred system concept for several aerospace platforms, the electro-mechanical actuator (EMA) is emerging as a solution of choice for the primary flight control actuation system. This paper will give a brief history of electric actuation for flight systems, diagnosis and prognosis demonstrations and current state of health management research. AFRL and NASA working with industry and academic partners have been developing health management technologies that will help prevent the occurrence of some inherent EMA failure modes. Advanced fault diagnostics and failure prognostics were applied to the critical failure modes identified in the Failure Mode, Effects, and Criticality Analysis (FMECA). Modeling and simulation of EMA with degraded components were developed to support the design and evaluation of physics-based algorithms. Test data were generated using EMA hardware to validate high-fidelity EMA and physics-of-failure models.
Technical Paper

Potential Technology to Unclog Hot Day Operational Limit

Fuel has been a popular choice for thermal system designers to use for absorbing aircraft accessory heat load due to its consumable nature. However, the shortcoming of using fuel as a heat sink is the dependency of environmental conditions. This deficiency has plagued the current United States Air Force fleet operation especially performing ground hold and low altitude attack mission during hot days. A Northrop Grumman led industrial team, commissioned by AFRL Power directorate through the INVENT program, has vigorously explored potential technologies to assist air force to enhance the mission capability. The results show various promising technologies not only can extend the hot day operational limit but also can potentially have an unrestricted capability. This paper describes the results from the study performed by Northrop Grumman for an advanced unmanned air vehicle (AUAV) for potential technologies and discusses the modeling approach in support of the analytical process.
Technical Paper

A Method of Shared Regenerative Power Management

The characteristics of large electrical loads encountered in the modern More Electric Aircraft (MEA) require regenerative power processing in order to preserve the power quality within acceptable transient and steady state limits. In an MEA with large active loads and pulsed power demands, it is necessary to employ an architecture that safely and effectively processes regenerative energy resulting from the dynamic loads. For instance, the electrical flight control actuation presents one of the largest regenerative power sources encountered by the generation system. Typical approach is to dissipate this energy through resistors of the power electronics which increases the size and penalizes the aircraft.
Technical Paper

Meeting Challenges of Key Characteristics (KC) Measurements in Aerospace Manufacturing

The objective of this paper is to discuss challenges involved in the measurement of key characteristics in an integrated aircraft assembly line environment. The measurement process is complicated by the fact that each workstation may have different fixture configurations that pose limitations on accessibility, optimum positioning of the measurement device, and accurate transfer of data into aircraft coordinates. The project objective is to develop and implement an optimum metrology system that meets program requirements to reduce both the cost of quality and product cycle time through increased measurement efficiency, “as-built” feature characterization, assembly guidance, “real-time” control, data analysis, and report generation.
Journal Article

Power & Thermal Systems Integration Techniques for High Performance Jet Aircraft

The high electrical power demand and heat rejection characteristics of a high energy laser pose new challenges to airframe power and thermal system designers. Typically, the power demand requires additional power storage devices and electrical generator upsizing which will adversely impact the engine performance and installation envelope. The thermal system is complicated by an already limited onboard heat sink, resulting in a bulkier system. Utilizing conventional approaches, the aircraft will suffer from additional weight, less available installation volume, and lower overall performance. This paper presents a potential integrated power and thermal system with attributes to minimize aircraft penalty. The system is a collection of various integration techniques that will be discussed individually for potential standalone application.
Journal Article

Applied Accurate Robotic Drilling for Aircraft Fuselage

Once limited by insufficient accuracy, the off-the-shelf industrial robot has been enhanced via the integration of secondary encoders at the output of each of its axes. This in turn with a solid mechanical platform and enhanced kinematic model enable on-part accuracies of less than +/−0.25mm. Continued development of this enabling technology has been demonstrated on representative surfaces of an aircraft fuselage. Positional accuracy and process capability was validated in multiple orientations both in upper surface (spindle down) and lower surface (spindle up) configurations. A second opposing accurate robotic drilling system and full-scale fuselage mockup were integrated to simulate doubled throughput and to demonstrate the feasibility of maintaining high on-part accuracy with a dual spindle cell.
Journal Article

A Hybrid Economy Bleed, Electric Drive Adaptive Power and Thermal Management System for More Electric Aircraft

Minimizing energy use on more electric aircraft (MEA) requires examining in detail the important decision of whether and when to use engine bleed air, ram air, electric, hydraulic, or other sources of power. Further, due to the large variance in mission segments, it is unlikely that a single energy source is the most efficient over an entire mission. Thus, hybrid combinations of sources must be considered. An important system in an advanced MEA is the adaptive power and thermal management system (APTMS), which is designed to provide main engine start, auxiliary and emergency power, and vehicle thermal management including environmental cooling. Additionally, peak and regenerative power management capabilities can be achieved with appropriate control. The APTMS is intended to be adaptive, adjusting its operation in order to serve its function in the most efficient and least costly way to the aircraft as a whole.