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Technical Paper

ProRAPP: A Computer Program for Propeller/Rotor Noise Prediction

The current emphasis on environment protection by reducing noise pollution has led to stricter noise standards for general aviation aircraft. As a result, there is a growing demand for a computational tool to predict the noise during the design process. A computer program, called ProRAPP, has been developed for the prediction of noise generated by propeller/rotor blades. The acoustic pressure is calculated using a form of Ffowcs Williams-Hawkings equation which is suitable for numerical implementation. For noise predictions, the observer can either move with the propeller/rotor hub or it can be fixed to the ground. Experimental data from both wind tunnel and flight tests are used to validate the numerical results.
Technical Paper

Studies of Light-Twin Wing-Body Interference

The results of an analytical study of aerodynamic interference effects for a light twin aircraft are presented. The data presented concentrates on the influence of a wing on a body (the fuselage). Wind tunnel comparisons of three fillets are included, with corresponding computational analysis. Results indicate that potential flow analysis is useful to guide the design of intersection fairings, but experimental tuning is still required. While the study specifically addresses a light twin aircraft, the methods are applicable to a wide variety of aircraft.
Technical Paper

Determination of the Operational Environment of the Propeller Blades on Beech 1900D Aircraft

Data obtained from digital flight data recorders are used to assess the actual operational environment of propellers on a fleet of Beech 1900D aircraft in commuter role. Information is given on various aerodynamic parameters as well as those pertaining to engine and propeller usage. The takeoff rotation has been identified as the most demanding phase of flight in terms of unsteady loads exerted on the propeller blades. Special attention is paid to ground operations.
Technical Paper

Common Firewall Approach to Aviation Architecture

While most industries have already adopted the use of IP networks to exploit the many advantages of network connectivity, the aircraft industry still has not significantly deployed networked devices in the aircraft. Security and reliability are two main concerns that have slowed the transition to this technology. The ability for Air Traffic Control to send digital communications to aircraft could significantly improve the aircraft safety by improving the speed and efficiency of communications. In addition, if devices could offload flight data to servers on the ground for analysis, the accuracy and efficiency of maintenance and other decisions impacting the aircraft could significantly improve. The purpose of this research is to propose an IP-based LAN architecture for the aircraft which provides a scalable solution without jeopardizing flight safety.
Technical Paper

Spy Blimps Revisited: A Performance Comparison between Two Competing Approaches

While operational airships globally number in the low dozens, interest in buoyant or semi-buoyant platforms continues to arouse imaginations of commercial and military planners and developers alike. The airship-as-advertisement business model is the only model that has proven sustainable on any scale since the crash of the initially successful LZ-128 Hindenburg effectively ended regular passenger and cargo transport by airship, and the 1962 termination of the US Naval airship program terminated regular large-scale surveillance from airships. Efforts in the US and Japan during the 2000's to have a self-sustaining sight-seeing business model using the modern semi-rigid Zeppelin NT both failed. In theory, the buoyant nature of airships provides compelling endurance and cost-per-ton-mile capability which fills a niche arguably not currently occupied by other modes of transportation.
Technical Paper

As9100 Registration Difficulties and Organizational Benefits: A Supplier Satisfaction Survey

A supplier satisfaction survey was developed and administered to 129 Aircraft suppliers who are AS9100 registered. The primary objective of the survey was to assess organizational benefits, attributed to the AS9100 standard, and registration process difficulties. Survey results from 49 responses indicated that the primary reason for seeking AS9100 registration was customer requirement, followed by improving production and service. Further analysis indicated that the top three difficulties were evaluating effectiveness of employee training, obtaining and analyzing data on customer feedback and satisfaction, and monitoring and measuring processes. The top three reported benefits, improved quality awareness among employees, an increase in employee training, and improved internal communication, respectively, were all non-financial in nature.
Technical Paper

Wiring Assessment of Aging Commuter Class Aircraft

The reliability and maintenance of electrical wiring and electrical components in aging aircraft have become areas of concern for the aviation industry. Numerous investigations have been conducted on the aging aspects of wiring and systems of large transport and military airplanes, with funding primarily from the FAA (Federal Aviation Administration), Air Force, and NASA. However, because of the large number of smaller general aviation aircraft in service, a need for examining the condition of wiring, electrical components and maintenance procedures for smaller aircraft exists. The Aging Aircraft Research Laboratory at the National Institute for Aviation Research (NIAR), Wichita State University, has conducted a comprehensive teardown evaluation of three high time commuter class airplanes. This teardown included assessment of aircraft wiring, electrical systems and circuit breakers through general and intrusive visual inspections and laboratory tests.
Technical Paper

Parametric Investigation of Ice Shedding from a Business Jet Aircraft

Ice particles shed from aircraft surfaces are a safety concern because they can damage aft-mounted engines and other aircraft components. Ice shedding is a random and complex phenomenon. The randomness of the ice fragment geometry, size, orientation and shed location in addition to potential particle breakup during flight poses considerable simulation challenges. Current ice shedding analysis tools have limited capabilities due to the lack of experimental aerodynamic coefficients for the forces and moments acting on the ice fragment. A methodology for simulating the shedding of large ice particles from aircraft surfaces was developed at Wichita State University. This methodology combines experimental aerodynamic characteristics of ice fragments, computational fluid dynamics, trajectory analysis and the Monte Carlo method to provide probability maps of shed particle footprints at desired locations.
Technical Paper

Strength of Stiffened Panels with Multiple Site Damage

Multiple site damage (MSD) on aging aircraft accumulates from fatigue loading over a period of time. For ductile materials such as 2024-T3 aluminum, MSD may lower the strength below that which is predicted by conventional fracture mechanics. An analytical model referred to as the linkup (or plastic zone touch) model has previously been used to describe this phenomenon. However, the linkup model has been shown to produce inaccurate results for many configurations. This paper describes several modifications of the linkup model developed from empirical analyses. These modified linkup models have been shown to produce accurate results over a wide range of configurations for both unstiffened and stiffened flat 2024-T3 panels with MSD at open holes. These modified models are easy to use and give quick and accurate results over a large range of parameters.
Technical Paper

The Application of Neural Networks for Spin Avoidance and Recovery

This paper presents a method by which artificial neural networks can be trained and used to identify a possible spin entry, differentiate between an incipient spin and a stabilized spin, and predict required recovery controls. These were then implemented into a simulation and tested using data from actual flight tests conducted by NASA Langley Research Center, to verify that artificial neural networks can successfully be used for this application. The spin avoidance and recovery system functioned properly. In addition, a weighting system was developed to predict possible spin characteristics of aircraft, depending on the relative magnitude of the three principal moments of inertia.
Technical Paper

Hole Quality Assurance by Optimization of Drilling Parameters for Carbon Fiber Composite Material

Composites are finding more and more applications in the aircraft industry. Drilling good quality holes is a major challenge for the manufacturing industry. The major factors which have an effect on hole quality are cutting parameters like speed and feedrate, machine rigidity, tool material, workpiece material, and tool geometry. The hole quality was studied by measuring the hole diameter and visually observing other parameters like shape and fiber breakout. Force analysis indicates that thrust increases with an increase in feedrate. Speed does not seem to have a very significant effect on thrust. The tool geometry plays a very important role in fiber pullout.
Technical Paper

Implementation of Automatic Airspace Avoidance in an Advanced Flight Control System

An algorithm is developed and validated for automatic avoidance of restricted airspaces. This method is devised specifically for implementation with an advanced flight control system designed for general aviation application. The algorithm presented here implements two inputs to the aircraft; the bank angle, and the airspeed, while the control system always ensures coordinated maneuvers. Unlike collision avoidance systems, the current method is not designed to serve in an advisory role, but to assume complete control of the aircraft if necessary. It is demonstrated that in order to implement this technique, the aircraft must be assigned an immediate domain whose size would have to depend on the aircraft performance and flight conditions. The strategy is designed such that as the domain surrounding the aircraft approaches that of the restricted airspace, aircraft control would switch gradually away from the pilot and to the controller, which would initiate an evasive maneuver.
Technical Paper

High Speed Drilling of Al-2024-T3 Alloy

The competitive market has forced the industry to develop methodologies to reduce lead-time of the products without sacrificing quality. One of the major metal removal operations in the aerospace industries is drilling. Over 100,000 holes are made for a small single engine aircraft. Naturally, demand for faster production rate results in the demand for high-speed drilling. But the cost of hole-making operations becomes a significant portion of the total manufacturing cost. This paper discusses the high speed drilling of Al-2024-T3 alloy, the effect of feed and speed on hole quality features like oversize, roundness error, burr height and surface roughness.
Technical Paper

Tail Icing Effects on the Aerodynamic Performance of a Business Jet Aircraft

Experimental studies were conducted to investigate the effect of tailplane icing on the aerodynamic characteristics of 15%-scale business jet aircraft. The simulated ice shapes selected for the experimental investigation included 9-min and 22.5-min smooth and rough LEWICE ice shapes and spoiler ice shapes. The height of the spoilers was sized to match the horns of the LEWICE shapes on the suction side of the horizontal tail. Tests were also conducted to investigate aerodynamic performance degradation due to ice roughness which was simulated with sandpaper. Six component force and moment measurements, elevator hinge moments, surface pressures, and boundary layer velocity profiles were obtained for a range of test conditions. Test conditions included AOA sweeps for Reynolds number in the range of 0.7 based on tail mean aerodynamic chord and elevator deflections in the range of -15 to +15 degrees.
Technical Paper

Response of an Advanced Flight Control System to Microburst Encounters

An envelope protection scheme is proposed for responding to a microburst. This approach is based on limiting the allowable maximum inertial deceleration of the aircraft when flying at low airspeeds. This technique is shown in simulations to be very effective at preventing stall and resulting in minimal loss of altitude. It is speculated that the same scheme can also protect an aircraft in the event of other forms of windshear encounters, such as making a sudden turn to downwind.
Journal Article

Operational Loads Monitoring of a Fleet of Beech 1900D Aircraft

Presented here are analyses and statistical summaries of data collected from 11,299 flight operations recorded on 6 BE-1900D aircraft during routine commuter service over a period of three years. Basic flight parameters such as airspeed, altitude, flight duration, etc. are shown in a form that allows easy comparison with the manufacturer's design criteria. Lateral ground loads are presented for ground operations. Primary emphasis is placed on aircraft usage and flight loads. Maneuver and gust loads are presented for different flight phases and for different altitude bands. In addition, derived gust velocities and various coincident flight events are shown and compared with published operational limits.