Aerospace Engineering Commons^™

Convergence And Robustness Issues In Computational Fluids, Xiaoqiang Zeng

Doctoral Dissertations

The present research develops two methods to improve the convergence and robustness of CFL algorithm, the triple time method and error- limited time step ramping method.

A general formulation of the triple time scheme is developed by introducing three pseudo time-marching steps to control three preconditionings for artificial dissipation, non-linear equation iteration convergence and linear equation iteration convergence separately. It is proven that the triple time method can be degenerated to the single time method and the multiple DDLGS iteration method at special cases.

Stability analysis is used to choose the optimum combination of three preconditionings from the steady preconditioning, …

Wind Tunnel Investigation Of The Static Stability And Control Effectiveness Of A Rotary Tail In A Portable Uav, Jose R. Rivera Parga

Theses and Dissertations

The Air Force Research Lab, Munitions Directorate, Flight Vehicles Integration Branch (AFRL/MNAV) developed a man-portable, carbon-fiber matrix UAV with a flexible rectangular wing of 24" span and 6" chord, 18.2" length. There is a need for the development of smaller and lighter UAV's to perform certain missions. The objective of this experimental study was to determine the behavior and the aerodynamic characteristics of rotary tails. The bird-inspired rotary tail mechanism studied enabled control of two degrees of freedom and was configured to provide elevator deflection and rotation. Its effects on the static stability and control effectiveness were measured using the …

Computational Aerodynamic Analysis Of Converging Free Jets, George Wayman Hatcher

Masters Theses

The aerodynamics of converging free jets was studied to determine the characteristics of the flow field involved in the manufacture of meltblown fibers. The two-dimensional computational fluid dynamic analysis was validated through comparison to boundary layer theory. The converging jet geometry consisted of two symmetric rectangular channels 30º from the axis of symmetry, 0.013 inches wide, converging toward a free expansion region at standard atmospheric conditions. The two channels were 0.015 inches apart at the exit, and the perpendicular wall region between them was flush with the upper and lower plate faces of the meltblowing die. Upstream boundary conditions of …

Development Of F/A-18 Spin Departure Demonstration Procedure With Departure Resistant Flight Control Computer Version 10.7, David J. Park

Masters Theses

The purpose of this study was to evaluate the capability to demonstrate F/A-18 Hornet departure characteristics, mainly the spin, with Flight Control Computer (FCC) Operation Flight Program (OFP) Version 10.7 (v10.7). Version 10.7 was released to the Navy and Marine Corps F/A-18A/B/C/D fleet in 2003. Version 10.7 was developed based on the existing FCC OFP (v10.5.1) to minimize out-of-control flight or departure related mishaps. Version 10.7 was only a software upgrade and no hardware change to the existing F/A-18 was made. Version 10.7 was remarkable since most of the known F/A-18 departure prone flight envelopes were rendered departure free by …

Analysis Of Pilot Performance Using Precision Visual Flight Rules, Thomas Morrissey

Masters Theses

Precision Visual Flight Rules (PVFR) seeks to allow helicopter pilots to fly predetermined routes in high density traffic areas with greater precision by using a Global Positioning System (GPS). An analysis of the cross-track error during the PVFR developmental testing is presented. The primary objective is to determine the dominant factors which effect pilot performance using this higher standard of precision. Factors which are investigated include: total flight time, recent helicopter flight time, pilot ratings, and experience with the particular aircraft and GPS model. A conclusion is presented on which factors need to be addressed before opening up PVFR routes …

Flightlines, Vol. 12, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

The Effects Of Gender And Regional Dialect On Performance In Aviation Communication, Erin E. Mccollum

Master's Theses - Daytona Beach

The purpose of this study was to analyze the performance effects of gender and regional dialect on air traffic control statement recall. Sixty-one student volunteers participated in the experiment. Thirty-one participants held a pilot’s license and 30 participants had no flight experience. Each participant listened to one CD with 60 ATC statements each representing a male and female voice and New England, Southern, and General American dialect. Participants were asked to recall exactly what they heard. If the participant could not understand what they heard, they requested a repeat. The participant’s performance was recorded to CD and analyzed. Demographic questionnaires …

Adaptive Synchronization Of Chaos For Secure Communication, Manish Pantha

Master's Theses - Daytona Beach

The purpose of this thesis is to study the use of adaptive synchronization of chaos for secure communication. Several non-linear models were studied, the one-dimensional logistic map, two-dimensional coupled logistic map, three dimensional Lorenz systems with and without time delay. Numerical simulation using MATLAB was conducted. The Lorenz system with time delay was studied numerically as well as by testing an analog circuit and comparisons was made between them. It has been pointed out in many research papers that for low-dimensional chaotic processes, once intercepted, the information can be readily extracted, so the interest has been directed to higher dimensional …

On The Equilibrium States Predicted By Second Moment Models In Rotating, Stably Stratified Homogeneous Shear Flow, Minsuk Ji, Paul A. Durbin

Paul A. Durbin

The structural equilibrium behavior of the general linear second-moment closure model in a stably stratified, spanwise rotating homogeneous shear flow is considered with the aid of bifurcation analysis. A closed form equilibrium solution for the anisotropy tensor aij, dispersion tensor Kij, dimensionless scalar variance q2/k (S/Sθ)2, and the ratio of mean to turbulent time scale ε/Sk is found. The variable of particular interest to bifurcation analysis, ε/Sk is shown as a function of the parameters characterizing the body forces: Ω/S (the ratio of the rotation rate to the mean shear rate) for rotation and Rig (the gradient Richardson number) for …

Analytical Solution For Low-Thrust Minimum Time Control Of A Satellite Formation, John Sang-Pil Seo

Theses and Dissertations

Satellite formations or distributed satellite systems provide advantages not feasible with single satellites. Efficient operation of this platform requires the use of optimal control of the entire satellite formation. While the optimal control theory is well established, only a very simple dynamical system affords an analytical solution. Any practical optimal control problem solves the resulting two-point boundary value (TPBV) problem numerically. The relative satellite dynamics using Hill's coordinate system and approximations made by Clohessy and Wiltshire, combined with body-fixed thruster control, result in a linearized dynamic system. This dissertation provides the analysis for the minimum time satellite formation control by …

Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman

Theses and Dissertations

There is a growing interest in understanding how uncertainties in flight conditions and structural parameters affect the character of a limit cycle oscillation (LCO) response, leading to failure of an aeroelastic system. Uncertainty quantification of a stochastic system (parametric uncertainty) with stochastic inputs (initial condition uncertainty) has traditionally been analyzed with Monte Carlo simulations (MCS). Probability density functions (PDF) of the LCO response are obtained from the MCS to estimate the probability of failure. A candidate approach to efficiently estimate the PDF of an LCO response is the stochastic projection method. The objective of this research is to extend the …

An Analysis Of The Conventional Wire Maintenance Methods And Transition Wire Integrity Programs Utilized In The Aviation Industry., Susan Jeruto Kiptinness

Electronic Theses and Dissertations

Aging aircraft wiring poses a significant threat to both commercial and military aircraft. Recent air disasters involving aging aircraft wiring have made it clear that aging wiring can be catastrophic. Aging of an electrical wiring system can result in loss of critical functions of equipment or loss of information regarding equipment operation. Either result can lead to an electrical failure causing smoke and fire, consequently being a danger to public health and aircraft safety.

Conventional maintenance practices do not effectively manage aging wiring problems. More proactive methods are needed so that aircraft wiring failures can be anticipated and wiring systems …

Modeling And Simulation Research And Instruction At The U.S. Air Force Academy, Russell M. Cummings, Scott A. Morton, Keith Bergeron

Aerospace Engineering

Modeling and simulation has become a driving force within the engineering and science communities as the cost of, and time for, experimentation continues to rise. Some areas of study, such as chemistry and biology, may not even have the ability to fully evaluate certain processes experimentally, making modeling and simulation even more important. The situation has led many areas of research to the necessity of modeling and simulating various processes using computers. In addition, the rise in computational capabilities (the supercomputers of a decade ago are outmoded by the PC clusters of today), has led to a paradigm shift from …

How They Flew: Modern Flight Test Of Pioneering Wright Aircraft, Klas Walace Ohman

Masters Theses

The first controlled and sustained powered flight was arguably the single most important transformational world event of the 20^th century. This accomplishment just over 100 years ago on the isolated, cold and windy Outer Banks of North Carolina was nothing short of miraculous. What enabled two bicycle mechanics from Dayton, Ohio to succeed where many others had tried and failed is also most incredible. However, unlike some other technical advancements, primarily either the Wrights or those interviewing them tell this story - with little independent verification. It is precisely for this reason that re-tracing the steps of these pioneers …

Aircraft Turbulence Detection And Display From The Professional Pilot’S Perspective, Leslie Owen Kagey

Masters Theses

The purpose of this study was to investigate the detection and display of weather avoidance information to commercial airline, business aircraft, and general aviation aircraft cockpits from the perspective of the professional pilot.

A flight campaign was conducted over a period of three years. Convective weather detection was attempted utilizing an experimental airborne weather radar installed on NASA’s Airborne Research Integrated Experiments Systems (ARIES) Boeing 757. Additionally ground-based Next Generation Radar (NEXRAD) information and textual data was linked to the aircraft for correlation. It was determined after encountering several heavy turbulence events that radar detection and conventional displays alone were …

The Most Important Aviation System: The Human Team And Decision Making In The Modern Cockpit, John Cody Allee

Masters Theses

The most critical aviation system is the human operator in the cockpit of modern aircraft. Regardless of the advancements in microelectronics and automated decision-making apparatus, the human will still remain ultimately responsible for the safety of those in the air and on the ground. Humans, however, are not entirely predictable or consistent when functioning in this capacity. The relationship between crewmembers becomes a critical aspect of this system, and this paper focuses on methods to improve both individual and especially crew decision-making in aviation. Concepts and structure from the Navy’s Crew Resource Management program are used as the background for …

A Model For The Application Of Test And Evaluation Concepts By The Air Element Of The Canadian Forces During The Materiel Acquisition And Support Lifecycle, Troy M. Crosby

Masters Theses

Recent experience has proven that the Test and Evaluation (T&E) terms and responsibilities described in Department of National Defence and Canadian Forces policies and orders – particularly those related to the Category flight test system – are poorly understood and frequently in conflict with contemporary approaches to Materiel Acquisition & Support. As a result, financial and airworthiness authorities may not be recognizing the benefits inherent to the timely application of T&E by the Air element of the Canadian Forces during the Materiel Acquisition & Support lifecycle. At the same time, the on-going inconsistent application of T&E is resulting in frustration …

Integration Of The Join Direct Attack Munition On The F-14b Tomcat, Paul J. Filardi

Masters Theses

Leading up to and including most of the Vietnam War, the U.S. military’s air-to-ground weapons consisted mainly of unguided freefall bombs. Their accuracy was limited and therefore required multiple aircraft to attack the same target, sometimes over and over again. The costs were high in effort, aircraft and lives. In May 1972, a flight of F-4 Phantom aircraft employed new weapons, called laser-guided bombs, against a seemingly indestructible bridge. When the smoke cleared, the bridge that had taken seven years and almost 900 dedicated attack flights was destroyed and the age of smart weapons had begun.

During the 1990’s the …

The Influence Of Organization Culture On Aviation Safety – A Case Study Of A United States Navy Fa-18 Landing Mishap, Peter J. Kind

Masters Theses

Aviation safety has improved dramatically in the last 50 years as evidenced by declining mishap rates. Improvements in aviation safety have come about primarily through work on two fronts; mechanical improvements (aircraft and its support systems) and human improvements (human interface, training and process interaction). Safety improvements on the hardware side of aviation have come relatively quickly and continuously, paralleling advances in engineering and science. Today’s aircraft have become extremely reliable machines with redundancy built into every system.

Unfortunately, while the overall aviation mishap rate has declined, the percentage of accidents attributed to “human error” has steadily increased. Strides in …

The Results Of The T-45 Main Landing Gear Uplock Investigation And The Effect That Organization Structure Had On Them, Christina Marie Stack

Masters Theses

The T-45, a military jet trainer aircraft for the Navy, recently experienced two cases of an uncommanded main landing gear extension during high airspeed and high g conditions. These events resulted in an investigation to understand the cause. The initial response to the mishaps was to limit the fleet to lower airspeeds since both mishaps occurred at high speeds. This limitation was not extensively restrictive for fleet operations; however, it was limiting for acceptance flights and functional check flights of aircraft. During the investigations, two different mechanical problems were discovered in the main landing gear uplock mechanism. This mechanism is …

Modeling Launch Vehicle Success Using Artificial Neural Networks, Jennifer A. Schuck

Master's Theses - Daytona Beach

Expendable launch vehicles in the United States currently have a reliability of 92%. The failures that do occur cost millions of dollars in spacecraft replacement, lost revenue, and other expenses. These costs are passed on in higher insurance rates and launch vehicle price. If the launch outcome of the launch vehicles could be better predicted, the overall cost of launching payloads into space would decrease. This study used artificial neural networks to model the overall launch outcome of a launch vehicle so that the results of a launch could be predicted. Two neural network architectures--MLP and fuzzy ARTMAP--were trained on …

Aeroelastic Analysis Of A Flexible Membrane Wing, Isaac Nguri Wanjohi

Master's Theses - Daytona Beach

The focus of this research proposal is the investigation of the aeroelastic effects of a flexible lift augmentation system (LAS) wing. This research involves characterization of the forced vibration response of a wing appendage used to augment short field take off and landing (STOL) operations.

Although flutter theory is now well understood, the LAS presents the complications of a highly deformable airfoil shape as well as larger structural damping values compared to metal wings.

The proposed research will involve derivation of the equations of motion aided by experimental data from nodal excitation of the wing; stiffness and rigidity modeling from …

Pilot Performance And Eye Movement Activity With Varying Levels Of Display Integration In A Synthetic Vision Cockpit, Julie Michele Stark

Psychology Theses & Dissertations

The primary goal of the present study was to investigate the effects of display integration in a simulated commercial aircraft cockpit equipped with a synthetic vision display. Combinations of display integration level (low/high), display view (synthetic vision view/traditional display), and workload (low/high) were presented to each participant. Sixteen commercial pilots flew multiple approaches under IMC conditions in a moderate fidelity fixed-base part-task simulator. Pilot performance data, visual activity, mental workload, and self-report situation awareness were measured.

Congruent with the Proximity Compatibility Principle, the more integrated display facilitated superior performance on integrative tasks (lateral and vertical path maintenance), whereas a less …

Stability Analysis Of Jump-Linear Systems Driven By Finite-State Machines With Markovian Inputs, Sudarshan S. Patilkulkarni

Electrical & Computer Engineering Theses & Dissertations

A control system with a fault recovery mechanism in the feedback loop and with faults occurring in a non-deterministic manner can be modeled as a class of hybrid systems, i.e., a dynamical system switched by a finite-state machine or an automaton. When the plant and controller are linear, such a system can be modeled as a jump-linear system driven by a finite-state machine with a random input process. Such fault recovery mechanisms are found in flight control systems and distributed control systems with communication networks. In these critical applications, closed-loop stability of the system in the presence of fault recoveries …

Uncertainty Propagation And Robust Design In Cfd Using Sensitivity Derivatives, Michele M. Putko

Mechanical & Aerospace Engineering Theses & Dissertations

This study investigates and demonstrates a methodology for uncertainty propagation and robust design in Computational Fluid Dynamics (CFD). Efficient calculation of both first- and second-order sensitivity derivatives is requisite in the proposed methodology. In this study, first- and second-order sensitivity derivatives of code output with respect to code input are obtained through an efficient incremental iterative approach.

An approximate statistical moment method for uncertainty propagation is first demonstrated on a quasi one-dimensional (1-D) Euler CFD code. This method is then extended to a two-dimensional (2-D) subsonic inviscid model airfoil problem. In each application, given statistically independent, random, normally distributed input …

Aerodynamic Analysis Of Lattice Grid Fins In Transonic Flow, Karl S. Orthner

Theses and Dissertations

Lattice grid fins have been studied for missile tail control for several years. A lattice grid fin can be described as an unconventional missile control surface comprised of an outer frame supported by an inner lattice grid of lifting surfaces. This unconventional fin design offers favorable lift characteristics at high angle of attack as well as almost zero hinge moments allowing the use of small and light actuators. In addition, they promise good storability for potential tube-launched and internal carriage dispenser-launched applications. The drawback for the lattice grid fins is the high drag and potentially poor radar cross section performance …

Detached Eddy Simulation Analysis Of Pak-B Low Pressure Turbine Blade, Kyle Malone

Theses and Dissertations

Two cases were computationally investigated using the detached eddy simulation (DES) turbulence model: an unmodified Pak-B blade and a Pak-B blade with a dimple located at 65% of axial chord. Both cases were created so that they simulated an infinite span with an infinite number of dimples. The cases were run for an inlet Reynolds number of 25,000. The computed results were used to resolve the location of separation and reattachment, visualize the streamlines for the dimpled case, build velocity magnitude contour and vector plots, and map the thickness of the boundary layer. The results were then compared to previous …

Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Brian H. Harrington

Theses and Dissertations

The effect of magnetogasdynamic (MGD) interactions on flow acceleration and thrust in a scramjet accelerator/nozzle are examined numerically at a free-stream flight condition of Mach 8. The parameters of conductivity pattern and load factor are varied in both inviscid and viscous flow regimes with the intent of increasing axial force exerted on the flow through a scramjet accelerator. The numerical code solves the Navier-Stokes equations with additional source terms for the MGD forces and energy interactions. An accelerating Lorentz force is applied to the flow resulting from a constant magnetic field and an electric field produced by two continuous side …

Fretting Fatigue Behavior Of Shot-Peened Titanium Alloy Tl-6al-4v Under Seawater Conditions, William Y. Allen

Theses and Dissertations

The fretting fatigue behavior of the shot-peened titanium alloy, Ti-6Al-4V, was investigated under a corrosive environment of synthetic seawater. Fretting fatigue tests were performed over a wide stress range to determine the effect of seawater at high and low cycle fatigue regimes. The results from this study showed: (1) seawater significantly reduces the fretting fatigue life of shot-peened Ti-6Al-4V at both high and low cycle fatigue relative to its counterpart in ambient laboratory conditions, (2) shot peening increases the fretting fatigue life of Ti-6Al-4V when tested under dry and seawater conditions relative to its counterpart of unpeened Ti-6Al-4V, (3) surface …

Cold Flow Testing Of A Modified Subscale Model Exhaust System For A Space Based Laser, David B. Jarrett

Theses and Dissertations

The aim of this research was a continued study of gas-dynamic phenomena that occurred in a set of stacked nozzles as reported by Captains Ian Bautista in 2003 and Scott Bergren in 2002. The arrangement of the stacked nozzles was a modified version of a 1/5th scale-model of one quadrant of the conceptual Space Based Laser Integrated Flight Experiment (SBL IFX) gas dynamic laser. Rather than cylindrical rings of nozzles, the stacked nozzles were flat and able to be rotated about a vector normal to the nozzle exits. This set of stacked flat nozzles was installed on a blow-down/vacuum wind …