Engineering Commons^™

Flight Testing Amateur-Built Helicopters, Jeffrey Scott Bender

Masters Theses

Test-flight procedures for the amateur-built helicopter are presented. Test methods were acquired from acceptable practices for flight testing Normal Category Rotorcraft, Amateur-Built Aircraft and Ultralights. These acceptable practices were modified to overcome the challenges faced by the amateur-built helicopter test pilot. These challenges include limited in-flight instrumentation. A significant modification of procedures was to establish a methodology of flight testing using collective control stick position as an indicator of power during performance testing. Additionally, this procedure provides a method structured to overcome limited instrumentation during testing of stability and control. In-flight test data of a United States Army OH-58 was …

Effects Of Foreign Object Damage From Small Hard Particles On The High-Cycle Fatigue Life Of Ti-6a1-4v, Joseph L. Hamrick Ii

Theses and Dissertations

Thin rectangular samples of Ti-6Al-4V were damaged by four methods to represent foreign object damage found in turbine engine blades: 1) impact with 2 mm and 5 mm diameter glass spheres at 305 m/s, 2) impact with 2 mm and 4 mm diameter steel spheres at 305 m/s, 3) quasi-static displacement controlled indentation using steel chisels with 1 mm, 2 mm and 5 mm diameter tips and 4) shearing notches with a 2 mm diameter chisel point under a quasi-static loading condition. Finite element analysis was used to study the relationship between the stress state created by the plastic damage …

Reverse Engineering Of Foreign Missiles Via Genetic Algorithm, Jon D. Wollam

Theses and Dissertations

One mission of the National Air Intelligence Center (NAIC) is the reverse engineering of foreign missile weapon systems from incomplete observational data. In the past, intuition and repeated runs of a missile performance model were required to converge to a solution compatible with observed flight characteristics. This approach can be cumbersome and time consuming, as well as being subject to undesirable influences from the analyst's preconceptions and biases. An alternative approach has been created to apply genetic algorithm (GA) techniques to allow automation of the process, wider exploration of the design space, and more optimal solutions matching the observational data. …

Feasibility Study Of An Integrated Safety Seat For Infants And Children Under The Age Of Two Traveling In Commercial Aircraft, Muneer A. Bakhsh

Master's Theses - Daytona Beach

The purpose of this study was to investigate the feasibility of integrated safety seat for children and infants onboard commercial aircraft. The researcher collected and analyzed data on the subject of safety seats for children and infants onboard commercial aircraft. The 115 participants for this study were randomly selected from the population of parents boarding commercial aircraft with infants and/or children. The research method used was descriptive and also compared the integrated safety seats for infants and children in automobiles to commercial aircraft. The survey examined whether or not parents were interested and willing to pay for an integrated safety …

An Intermittent-Combustion General Aviation Aircraft Engine Exhaust Noise Prediction Algorithm, Hiroko Tada

Master's Theses - Daytona Beach

From an environmental point of view, the reduction of aircraft noise has become an important factor recently. There are two factors that make airplane noise: propeller noise and engine noise. This report puts emphasis on only the engine noise in order to begin understanding what airplane engine exhaust noise is. At first, the engine exhaust noise is comprehended using the Dobrzynski's engine noise theory. Next, a discussion about an Embry-Riddle Aeronautical University (ERAU) engine system, engine exhaust system configurations, and microphone setting standards that show the ERAU engine system exhaust noise data. Finally, an Intermittent-Combustion (IC) General Aviation (GA) aircraft …

Space-Available Transportation: An Analysis Of The Cost Of Providing 'Free' Travel, Frank J. Long

Theses and Dissertations

The purpose of this study is to estimate the costs borne by the government for providing space-available travel to eligible uniformed services personnel and their dependents. As the primary provider of the space-available privilege, it is important that the Air Force have an estimate of the burden that the administration of that privilege places on the budget. In January 1993, the Air Force discontinued its 15-year-old practice of charging a fee for space-available travel aboard AMC-owned or controlled aircraft. The fee had been set at $10 in 1978 and was collected to recover a portion of the costs associated with …

Active Local Volume Displacement Cancellation Of A Vibrating Baffled Beam, Marcellin Zahui

Dissertations

An active noise control apparatus is developed. The device reduces the sound radiated from a vibrating clamped beam. The attenuation of the sound field is obtained through minimization of local volume displacements of the vibrating beam. Two single-input/single-output cancellation devices are used. Each device employs a motion sensor and an acoustic actuator. The actuator is a loudspeaker equipped with a pressure sensor to detect its volume displacement. The motion sensor signal is related to the local volume displacement of the structure which is then reduced by a loudspeaker driven with an equal but opposing volume displacement. The volume displacement sensors …

Designed Reduction Of Radiated Noise Characteristics From Two-Bladed General Aviation Propellers, Chandra K. Stich

Master's Theses - Daytona Beach

In recent years increased public awareness has made the reduction of environmental noise pollution a top priority for the aviation industry. Utilizing current technology, this study examines the reduction of noise generated by two bladed general aviation propellers, through design. The Aircraft Noise Prediction Program - Propeller Analysis System (ANOPP-PAS) is used to predict the noise and performance characteristics for an industry typical reference propeller as well as for the final quiet and efficient design.

This investigation is based on the use of a 200 hp engine rotating a 76 inch propeller. Typically, such a propeller would be rotated at …

Large Amplitude Pitching Of Supermaneuver Delta Wings Including Flow Control, Yahia A. Abdelhamid

Mechanical & Aerospace Engineering Theses & Dissertations

The unsteady, three-dimensional Navier-Stokes equations are solved to simulate and study the aerodynamic response of a delta wing undergoing large amplitude pitching motion up to 90° angle of attack. The primary model under consideration consists of a 76° swept, sharp-edged delta wing of zero thickness, initially at zero angle of attack. The freestream Mach number and Reynolds number are 0.3 and 0.45 × 106, respectively. The governing equations are solved time-accurately using the implicit, upwind, Roe flux-difference splitting, finite-volume scheme. Both laminar and turbulent flow solutions are investigated. In the laminar flow solutions, validation of the computational results is carried …

Jet Stability And Noise Computations Using Direct Numerical Simulation, Farouk Owis

Mechanical & Aerospace Engineering Theses & Dissertations

The computations of axisymmetric jet noise with symmetric disturbances are investigated using the direct numerical simulation of the unsteady compressible Navier-Stokes equations. High order accurate numerical schemes are employed for the solution of the governing equations. The investigation shows that MacCormack schemes with operator splitting and minimum dispersion error can be used to predict noise radiated from subsonic and supersonic jets with low and high Reynolds numbers. In addition, different kinds of nonreflecting boundary conditions are used at the inflow and outflow boundaries. These boundary conditions include characteristic boundary conditions, buffer domain technique and perfectly matching layer method. The results …

Flow Separation Prevention On A Turbine Blade In Cascade At Low Reynolds Number, James P. Lake

Theses and Dissertations

The problem of flow separation from a low pressure turbine blade was investigated. The operating conditions under which the separation occurred were documented through measurement of surface pressure coefficients, boundary layer velocity and turbulence profiles, total pressure loss coefficient and wake velocity momentum deficit. Three different means for reducing the losses associated with the flow separation were also investigated. A boundary layer trip, dimples, and V-grooves were studied as passive means requiring no additional energy to reduce the separation losses. The boundary layer trip was only successful for an inlet and axial chord Reynolds number of 50k with a reduction …

Closely Supervised Reactive Control Of An Uninhabited Aerial Vehicle, Roy G. Glassco

Theses and Dissertations

Closely Supervised Reactive Control is an alternative control method for uninhabited aerial vehicles that incorporates some of the benefits of both manual and autonomous operations. Utilizing an onboard camera, an operator can control a UAV by manually choosing desired targets. The flight path of the uninhabited vehicle is determined autonomously from the camera gimbal angles. The operator of the payload (i.e. camera), has close supervision of the aircraft. The aircraft, using an onboard computer, is given autonomous control to alter flight path to fly towards a target and at a specified range, loiter over the target. In the basic mode …

Wind Tunnel Investigation Of Joined Wing Configurations, Jennifer Corneille

Theses and Dissertations

The Air Force Research Laboratory's Munitions Directorate is looking to extend the range of its small smart bomb. One proposed idea is to retrofit the bombs with a wing kit, particularly a joined wing configuration. A typical joined wing configuration is one where the wings are positioned in such a way that they form a diamond in both plan and front views. The purpose of this study is to conduct low speed wind tunnel testing of the joined wing configuration to help determine if the joined wing is more beneficial than a single wing configuration. Configurations with differing sweep angles …

Solving An Inverse Control Problem Using Predictive Methods, Chad J. Davis

Theses and Dissertations

Model Predictive Control is the class of control methods that optimizes a specified performance index in order to minimize the weighted future output deviations from a setpoint trajectory. This thesis applies MPC in the inverse sense -- known aircraft outputs are applied in the performance index as setpoints in an attempt to determine what control histories caused those outputs. Using this method, aircraft mishap investigators could then have a means of determining what the control surface deflections were throughout an incident since Flight Data Recorder data does not include control surface deflections. The actual Flight Data Recorder data from aircraft …

Close Formation Flight Control, Andrew W. Proud

Theses and Dissertations

In this research the close formation flight control problem is addressed. The formation consists of a lead and wing aircraft, where the wing flies in close formation with the lead, such that the lead's vortices produce aerodynamic coupling effects, and a reduction in the formation's drag is achieved. A controller, i.e., a formation-hold autopilot for the wing aircraft, is designed such that the formation's geometry is maintained in the face of lead aircraft maneuvers. In the formation flight control system, the wing and lead aircraft dynamics are coupled due to kinematic effects, and, in the case of close formations, additional …

Optimization Of A Vortex Generator Configuration For A 1/4-Scale Piper Cherokee Wing, Kerri A. Raykowski

Master's Theses - Daytona Beach

Several sets of wind tunnel tests were performed to determine an optimum vortex generator configuration for a 1/4-scale model of the Piper Cherokee wing. Several variables were incorporated into this experiment in an effort to determine their influence on vortex generator performance enhancement (or degradation). Vane type vortex generators were used with 3 different leading edge sweeps: zero (rectangular planform), 20, and 45 degrees. Three different vortex generator heights were tested (0.05”, 0.1”, and 0.2”) to find the optimal vortex generator height relative to the local boundary layer thickness. The vortex generator angle of incidence relative to the freestream was …

Reduction Of Helmet Buffeting In Open Cockpit, Single Seat Race Cars, Mark Vallon

Master's Theses - Daytona Beach

At speeds approaching 240 mph, drivers of open cockpit race cars frequently experience large aerodynamic forces which act on the helmet. These forces, specifically the aerodynamic buffeting of the helmet, reach levels which are very fatiguing and distracting to the driver, and are therefore unacceptable. Little investigation has been done in this area, because normal wind tunnel tests do not isolate the helmet from the rest of the car. During this project, measurements of aerodynamic forces acting on a helmet inside a race car cockpit were made to determine the cause of the buffeting, and to determine possible improvements.

Tests …

Tip Vortex And Crenulation Effects In A Compressor Cascade With Moving Endwall, Barry W. St Germain

Theses and Dissertations

The effects of changing Reynolds number and flow coefficients on the velocity and pressure flow fields within a linear cascade with moving endwall were investigated in this experimental thesis. All flow field measurements were taken at a constant compressor blade tip gap clearance of 1.0 % chord and endwall speed of 318.6 ft/s (97.1 m/s), with flow coefficients of 0.40, 0.52, 0.62 and 0.72. All data acquisition occurred in a plane 23 % chord downstream of the trailing edge plane of the linear cascade. Hotwire probes determined the complete passage, three-dimensional fowled behind both crenulated and regular blade geometries. Vector …

Whole Spacecraft Vibration Isolation, Gregory G. Karahalis

Theses and Dissertations

The Department of Defense identified launch vibration isolation as a major research interest. Reducing the loads a satellite experiences during launch will greatly enhance the reliability, lifetime, and payload to structure ratio. DoD satellite programs stand to benefit significantly from advances in vibration isolation technology.

Effects Of Pressure Gradients On Turbulent Boundary Layer Flow Over A Flat Plate With Riblets, Franklin L. Dement Jr.

Theses and Dissertations

The Air Force Institute of Technology Boundary Layer Research Facility test section was modified to create controlled non-zero streamwise pressure gradients. The capability of the modified facility to reproduce theoretical laminar boundary layer velocity profiles and to create a self-preserving flow with an adverse streamwise pressure gradient was verified with three-dimensional laser Doppler anemometry. The effects of streamwise adverse and favorable pressure gradients on turbulent boundary layer flow characteristics (velocity profiles, turbulence and skin friction) and vortex formation over a flat plate with riblets at low speed (U = 5 mIs) were studied. Normal and spanwise velocity profiles for both …

Robust Eigenstructure Assignment Using Positive Definite Output Feedback Control, Adam G. Harris

Theses and Dissertations

This research investigates a method of eigenstructure assignment for the classes of controllers known as positive definite output feedback control. The research began with a closed loop system with output feedback control that utilizes a collocated actuator-sensor pair. It is shown that this system is robust because it is globally stable for positive definite feedback. Analytical analysis is then completed to determine gains that minimize a cost function that is the error between the desired and achievable (assuming positive definite output feedback) eigenstructure. Examples are given at the end of the thesis to validate the computer code and theory results.

Design And Analysis Of On-Orbit Servicing Architectures For The Global Positioning System Constellation, Gregg A. Leisman, Adam D. Wallen

Theses and Dissertations

Satellites are the only major Air Force systems with no maintenance, routine repair, or upgrade capability. The result is expensive satellites and a heavy reliance on access to space. At the same time, satellite design is maturing and reducing the cost to produce satellites with longer design lives. This works against the ability to keep the technology on satellites current without frequent replacement of those satellites. The Global Positioning System Joint Program Office realizes that it must change its mode of operations to quickly meet new requirements while minimizing cost. The possibility of using robotic servicing architectures to solve these …

A Statistical Analysis Of Space Structure Mode Localization, Amy M. Cox

Theses and Dissertations

Cyclic structures, such as antenna arrays, multi-bay trusses, and compressor blades, are significantly impacted by slight changes to system periodicity. Manufacturing errors of 5% or less can result in drastic changes to a structure's modal behavior. This change in modal behavior is significant, since it may result in the focusing of modal energy to individual substructures of the system. Poor modal identification can result in poorly designed control systems, resulting in shape control and pointing issues for space antennae. Additionally, modal energy localization may damage individual system components due to unanticipated levels of cyclic loading, leading to high cycle fatigue.

Progressive Failure Analysis Of Composite Panels, Stephen M. Spottswood

Theses and Dissertations

The objective of this research was to determine the physical response, including material failure, of a curved composite panel designed to resist transverse loading. The cause of the material failure, in the form of delamination, fiber and/or matrix failure, was determined through various criterion based on non-linear movement using a finite element analysis technique. Data generated both with and without the addition of progressive failure criteria, was compared with previously published experimental data, noting where the theory diverges from the experimental results. The inclusion of various failure criterion, to include maximum stress, Lee, and Hashin, provided a more realistic representation …

Space Maneuver Vehicle Orbital Mission Planner: Development Of Application And Analysis Of On-Demand Maneuvering Ability, Shon P. Williams

Theses and Dissertations

The USAF has developed the Space Maneuver Vehicle (SMV) to fulfill the requirement for flexibility, rapid response, and on-demand maneuverability of space assets. This reusable satellite merges the efficiency and readiness of aircraft-like operations with the capability of global coverage from space. Designed to provide over 10,500 fps of velocity change (or delta-v) while in orbit, the SMV out-maneuvers existing satellites by up to 100 times. This thesis helps transition the SMV to the operational area by demonstrating their responsiveness to varied mission taskings. The SMV Orbital Mission Planner allows the operator to place any number of SMVs in orbit …

Fatigue Response Of Repaired Thick Aluminum Panels With Bondline Flaws, David S. Conley

Theses and Dissertations

his research investigated the fatigue response of precracked 558 x 177.8 x 6.35 mm (22.0 x 7.0 x 0.25 in) 2024-T351 aluminum panels repaired with single-sided partially bonded, unidirectional, eighteen ply boron/epoxy reinforcements. Disbonds were introduced into the bondline of each repair during the adhesion process using teflon inserts. Five different disbond configurations, with varying disbond locations and sizes, were tested. Each repaired panel was subjected to constant amplitude cyclic fatigue loading with a maximum stress of 120MPa. Results from the different configurations were compared against one another and against repaired panels with no debonds to assess the effect of …

Toward Development Of An Integrated Aerospace Power Doctrine, Toby G. Doran

Theses and Dissertations

This thesis discusses the state of the Air Force, decision making factors in the making of military doctrine, the definition of doctrine, Air Force doctrines today, new ways to develop doctrine, including models and hypothesis-research-analysis loops, space doctrine, control of space, space superiority and a call for aerospace power doctrine.

A Nonlinear Pre-Filter To Prevent Departure And/Or Pilot-Induced Oscillations (Pio) Due To Actuator Rate Limiting, Michael J. Chapa

Theses and Dissertations

Closed loop instability caused by excess phase lag induced by actuator rate limiting has been suspected in many aircraft departures from controlled flight and pilot-induced oscillations (PIO). As part of the joint Air Force Institute of Technology Test Pilot School (AFITITPS) program, a nonlinear rate limiter pre-filter (RLPF) was developed to minimize the phase lag induced by rate limiting. RLFF performance was evaluated inside the feedback path, but primary emphasis was on the pilot command path. Closed loop computer and motion-based flight simulation were conducted to prepare for the flight test. The HAVE FILTER flight test project was flown using …

Simsat: A Satellite System Simulator And Experimental Test Bed For Air Force Research, James E. Colebank, R. Dan Jones, Randall D. Pollak, Donald M. Mannebach, George R. Nagy

Theses and Dissertations

SIMSAT (the SIMulation SATellite) is an AFIT-sponsored program to develop a laboratory-based physical satellite simulator. SIMSAT supports experimentation in areas of attitude control, precision pointing, and vibration suppression. SIMSAT development began with the purchase of a three-axis gas bearing which simulates a torque-free space environment. SIMSAT subsystems provide power, attitude control, telemetry, and structural support to experimental payloads. Project challenges included integration of attitude control software/hardware, high-output power storage devices, remote communications, high-frequency data collection, structural design, and computer display outputs.

Space Launch Operations And The Lean Aerospace Initiative, Troy L. Endicott

Theses and Dissertations

This study analyzes current expendable launch procedures and identifies truly lean, value-added steps in launch operation enterprises as they relate to the Lean Aerospace Initiative (LAI). LAI and the concepts of lean thinning are discussed and followed by a review of current and future launch system requirements and their opportunities for lean practices. The study also discusses in detail current Delta II expendable launch processing operations and presents results in a case study that show how lean principles have helped the Delta II launch team drastically reduce on-pad time, restructure its testing philosophy, and streamline its operations flow. Many of …