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The F-4 Phantom II was the United States' primary air superiority fighter aircraft during the Vietnam War. This airplane epitomized American airpower doctrine during the early Cold War, which diminished the role of air-to-air combat and the air superiority mission. As a result, the F-4 struggled against the Soviet MiG fighters used by the North Vietnamese Air Force. By the end of the Rolling Thunder bombing campaign in 1968, the Phantom traded kills with MiGs at a nearly one-to-one ratio, the worst air combat performance in American history. The aircraft also regularly failed to protect American bombing formations from MiG attacks. A bombing halt from 1968 to 1972 provided a chance for American planners to evaluate their performance and make changes. The Navy began training pilots specifically for air combat, creating the Navy Fighter Weapons School known as "Top Gun" for this purpose. The Air Force instead focused on technological innovation and upgrades to their equipment. The resumption of bombing and air combat in the 1972 Linebacker campaigns proved that the Navy's training practices were effective, while the Air Force's technology changes were not, with kill ratios becoming worse. However, the last three months of the campaign introduced an American ground radar system that proved more effective than Top Gun in improving air-to-air combat performance. By the end of the Vietnam War, the Air Force and Navy overcame the inherent problems with the Phantom, which were mostly of their own making.

Thesis (M. of Military Art and Science)--U.S. Army Command and General Staff College, 2007. / The original document contains color images. Title from title page of PDF document (viewed on May 27, 2008). Includes bibliographic references.

An accurate estimate of the gasturbine inlet air temperature is essential to the stability of the engine since its control depends on it. Most supersonic military aircrafts have a design with the engine integrated in the fuselage which requires a rather long inlet duct from the inlet opening to the engine face. Such duct can affect the temperature measurement because of the heat flow between the inlet air and the duct skin. This is especially true when the temperature sensor is mounted close to the duct skin, which is the case for most engines. This master thesis project therefore revolved around developing a method to better estimate the engine inlet temperature and to compensate for the disturbances which a temperature sensor near the duct skin can be exposed to. A grey box model of the system was developed based on heat transfer equations between different components in the inlet, as well as predictions of temperature changes based on a temperature model of the atmosphere and thermodynamic laws. The unknown parameters of the grey box model were estimated using flight data and tuned to minimize the mean square of the prediction error. The numerical optimization of the parameters was performed using the Matlab implementations of the BFGS and SQP algorithms. An extended Kalman filter based on the model was also implemented. The two models were then evaluated in terms of how much the mean squared error was reduced compared to just using the sensor measurement to estimate the inlet air temperature. It was also analyzed how much the models reduced the prediction errors. A cross-correlation analysis was also done to see how well the model utilized the input signals. The results show that the engine inlet temperature can be estimated with good accuracy. The two models were shown to reduce the mean square of the prediction error by between 84 % and 89 % if you compare with just using the temperature sensor to estimate the temperature. The model which utilized the Kalman filtering was shown to perform slightly better than the other model. The relevance of different subcomponents of the model were investigated in order to see if the model could be simplified and maintain similar accuracy. Some investigations were also done with the relationship between different temperatures of the inlet to further understand the flow patterns of the inlet and to perhaps improve the model even more in the future. / En korrekt uppskattning av lufttemperaturen vid inloppet till turbofläktmotorer är väsentlig för stabil motorfunktion eftersom den direkt påverkar motorregleringen. För militära flygplan där motorn är integrerad i flygplansskrovet krävs ofta en relativt lång luftkanal för att leda luften till motorn. En sådan kanal kan påverka temperaturmätningen på grund av det värmeutbyte som sker mellan luften i kanalen och kanalväggen, speciellt då temperaturgivaren placeras nära kanalväggen eftersom den då kan påverkas av temperaturgränsskiktet nära kanalväggen. Det här examensarbetet handlade därför om att utveckla en metod för att bättre skatta temperaturen i motorinloppet och kompensera för de störningar som en temperaturgivare nära kanalväggen kan utsättas för. En fysikalisk model av systemet togs fram baserat på värmeöverföringen mellan olika komponenter i luftintagskanalen, samt ett sätt att förutse temperaturändringar baserat på en generell temperaturmodell för atmosfären och termodynamiska lagar. Många parametrar i den fysikaliska modellen av systemet var dock okända så dessa skattades baserat på flygdata. Parametrarna anpassades till modellen på ett sådant sätt att den genomsnittliga kvadraten av modellens skattningsfel minimerades. Den numeriska optimeringen av parametrarna utfördes med hjälp av Matlabs implementation av BFGS- och SQP-algoritmerna. Ett utökat kalmanfilter baserat på modellen implementerades också. De två modellerna utvärderades i termer av hur mycket de reducerade kvadraten av skattningsfelet och jämfördes med att endast använda temperaturmätningarna för att skatta temperaturen. Det undersöktes även hur mycket skattningsfelen reducerades. Korskorrelationen mellan skattningsfelet och insignalerna undersöktes även för att se om modellen hade utnyttjat insignalerna på ett bra sätt. Resultaten visar att det går att skatta temperaturen i motorinloppet med god noggrannhet. De två modellerna visade sig reducera den genomsnittliga kvadraten av skattningsfelet med mellan 84 % och 89 % om man jämför med att bara använda temperaturgivaren för att skatta temperaturen. Den modell som utnyttjade kalmanfiltrering visade sig ge något bättre resultat än den andra modellen. Olika delmodellers relevans undersöktes för att se om modellen kunde förenklas utan att modellens noggrannhet äventyrades. Några tester utfördes även för att undersöka förhållandet mellan olika temperaturer i intaget. Detta för att få en bättre förståelse för strömningen i intaget och resultatet skulle eventuellt kunna användas för att förbättra modellen ytterligare i framtiden.

Fighter pilots operate in environments where an erroneous decision may have fatal consequences. A tactical decision support system (TDSS) could aid the pilots to analyze the situation and make correct decisions. The TDSS can, for instance, highlight important information and suggest suitable actions. The aim of this thesis is to provide a situation analysis model of combat survival that can be utilized in a TDSS. The first part of this thesis describes an analysis of what the model needs to describe and how it can be used. It is concluded that the model should evaluate the outcome of different actions with respect to combat survival. This evaluation can guide the pilot’s decision making, so that actions leading to dangerous situations are avoided. The analysis also highlights the need of handling uncertainties, both measurement precision uncertainty regarding the locations and capabilities of the threats (enemies) and inference uncertainties regarding the prediction of how the threats will act. Finally, arguments for focusing the rest of the work on a single fighter aircraft and threats located on the ground are presented. The second part of the thesis suggests a model, which describes the survivability, i.e., the probability that the aircraft can fly a route without being hit by fire from ground-based threats. Thus, the model represents the inference uncertainty, since it describes the probability of survival. The model’s characteristics are discussed, e.g., that the model is implementable and can be adapted to describe different kinds of ground-based threats. Uncertainty in terms of measurement precision influences the estimate of the survivability. Two different ways of representing this is discussed: calculating the worst case scenario or describing the input as random variables and the resulting survivability as a random variable with a probability distribution. Monte Carlo simulations are used for estimating the distribution for survivability in a few illustrative scenarios, where the input is represented as random variables. The simulations show that when the uncertainty in input is large, the survivability distribution may be both multimodal and mixed. Two uncertainty measures are investigated that condense the information in the distributions into a single value: standard deviation and entropy. The simulations show that both of these measures reflect the uncertainty. Furthermore, the simulations indicate that the uncertainty measures can be used for sensor management, since they point out which information that is the most valuable to gather in order to decrease the uncertainty in the survivability. Finally, directions for future work are suggested. A number of TDSS functions that can be developed based on the model are discussed e.g., warnings, countermeasure management, route-planning and sensor management. The design of these functions could require extending the threat model to incorporate airborne threats and the effects of countermeasures. Further investigations regarding the uncertainty in the model are also suggested.

We tackle the problem of identifying the structural dynamics of the twin tails of the F-15 fighter plane. The objective is to first investigate and identify the different possible attractors that coexist for the same operating parameters. Second is to develop a model that simulates the experimentally determined dynamics. Third is to suppress the high-amplitude vibrations of the tails due to either principal parametric or external excitations. To understand the dynamical characteristics of the twin-tails, the model is excited parametrically. For the same excitation amplitude and frequency, five different responses are observed depending on the initial conditions. The coexisting five responses are the result of the nonlinearities. After the experimental identification of the system, we develop a model to capture the dynamics realized in the experiment. We devise a nonlinear control law based on cubic velocity feedback to suppress the response of the model to a principal parametric excitation. The performance of the control law is studied by comparing the open- and closed-loop responses of the system. Furthermore, we conduct experiments to verify the theoretical analysis. The theoretical and experimental findings indicate that the control law not only leads to effective vibration suppression, but also to effective bifurcation control. We investigate the design of a neural-network-based adaptive control system for active vibration suppression of the model when subjected to a parametric excitation. First, an emulator neural network was trained to represent the structure and thus used to predict the future responses of the model. Second, a neurocontroller is developed to determine the necessary control action. The computer-simulation studies show great promise for artificial neural networks to control the model vibrations caused by parametric excitations. We investigate the use of four different control strategies to suppress high-amplitude responses of the F-15 fighter to a primary resonance excitation. The control strategies are linear velocity feedback, nonlinear velocity feedback, positive position feedback, and saturation-based control. For each case, we conduct bifurcation analyses for the open- and closed-loop responses of the system and investigate theoretically the performance of the different control strategies. We also calculate the instantaneous power requirements of each control law. The experimental results agree with the theoretical findings. / Ph. D.

This thesis presents a simulation study on the thermal performance of the fuel systemin a fighter aircraft. The main objective is to investigate the potential utilization of thefuel system as a heat sink and explore various operational aspects that can enhance itsperformance. To achieve this, the study focuses on analyzing the impact of tank emptyingsequences, fuel types, and the implementation of bypass recirculation under low thrustconditions.The fuel system is modeled using the Modelica language-based tool, Modelon Impact,which enables a thorough and detailed examination of its thermal behavior. A functionalmodel of the fuel system has been successfully built in this modeling tool. The investiga-tion of the three operational aspects has been divided into two heat sink studies. Heat sinkstudy 1 examines the tank emptying sequences, with three different sequences being inves-tigated. The simulation results did not demonstrate any clear and significant benefits fromusing different emptying sequences. However, emptying the fuselage tank first showedslightly better behavior compared to the sequence that involved emptying the wing tanksfirst. Heat sink study 2 focuses on the implementation of bypass recirculation of the fuelback to the tanks. The primary objective of heat sink study 2 is to maintain the feed linetemperature close to the threshold determined by the fuel type in order to . The simulationresults revealed significant improvements in the heat sink capacity of the system, reachingup to 168%.

Fighter pilots operate high-performing powerful aircraft, equipped with complex sensor systems, in a dynamic and hostile environment. The pilots need to have control over their own aircraft as well as the developing situation surrounding them. Moreover, the fighter pilot rarely is on a mission by himself, but collaborates with teammates to achieve the goals jointly. This collaboration between fighter aircraft cannot take place without technology in the form of a tactical support system (TSS) that aids the pilots with information retrieval and decision-making. A TSS in a fighter aircraft fuses data from different sources and organizes the information in order to assist the pilot in building situation awareness and support in the decision-making during missions. The capabilities of the aircraft and its sensors, as well as the design of the TSS will directly affect how the pilots can perform the missions. The technology and the design at the same time enable and constrain the possible acting space, such that the tactics and plans for the missions will be a consequence of these factors. Hence, the design and development of such a complex system requires deep knowledge about the users and understanding of how they will operate the system. High usability is among the requirements for such a specialized and advanced system as the TSS, and in order to achieve this there is a need to understand the circumstances the system will be used in. Due to the complex nature of the military operations and the difficulties to access the domain for others than pilots, it is challenging for designers of the TSSs to obtain this needed knowledge. Therefore, this thesis aims at investigating the nature of the operations, as well as the practice of user participation in the domain, in order to increase the designers’ knowledge and give guidance to how users should participate in the development of the systems.  Several methods that aim to design efficient and usable systems are available. User-centered design is a holistic philosophy that prescribes that the interests and needs of the users should be in focus through the whole development process in order to achieve better systems. At the core of user-centered design is to increase the knowledge about the users and their needs. This thesis applies two perspectives, which both contributes to fulfill the goal of user-centered design of the TSSs by obtaining more knowledge about the users. The two perspectives are: a better understanding of how the users/pilots utilize the TSS to perform teamwork during missions, and an insight into how the users/pilots participate during the development process of the TSSs.  The teamwork perspective is motivated by the fact that fighter pilots perform a majority of their missions collaborating in teams. Their teamwork is depending on technology since the pilots are separated from each other in their fighter airplanes. Understanding this teamwork is hence a key to understanding the users in this domain. This thesis investigates the nature of teamwork between fighter pilots based on a theoretical teamwork model, the  “Big Five” of effective teamwork proposed by Salas, Sims, and Burke (2005). The “Big Five” model contains eight elements that Salas et al. identified as necessary for effective teamwork: adaptability, backup behavior, closed-loop communication, shared mental models, mutual performance monitoring, team orientation, mutual trust, and team leadership. The user-participation perspective is based on the notion that involving the users in different stages through the development process will benefit the results. However, user participation can take many different forms. The users can have different roles during the process, and the impact their opinions will have on the product can vary. This thesis investigates user participation and the roles the users, i.e. pilots, have in the development process of fighter aircraft of TSSs and cockpit interfaces.  These two perspectives are each assigned an aim in the investigation. For the first aim, Increase the knowledge about how fighter pilots collaborate in teams during missions with the current systems, ten fighter pilots were interviewed about their views on teamwork. The teamwork elements of the “Big Five” model are explored and described for the military fighter context. With this knowledge, a task performance cycle is proposed which shows were in the cycle of a mission each teamwork element is most important. Finally, a modified teamwork model adapted for mission performance for fighter pilots is suggested. For the second aim, Increase the knowledge about how pilots can and should participate in the design process of fighter aircraft interfaces, a study on how pilots participate in the design work of cockpit interfaces is conducted. The inquiry is based on a questionnaire, which was distributed to designers of fighter cockpit interfaces. The results indicate that the designers think the pilots have and should have many different roles in the design process. The designers wish to be able to observe pilots at work to a greater extent and to obtain more information and ideas from them. They also think that pilots should be more involved as examiners and testers. However, pilots should not be designers or decision-makers regarding design, according to the majority of respondents.  The presented contributions of the team-related research in this thesis are a deeper understanding and rich descriptions of how fighter pilots perform missions from a teamwork perspective. The teamwork elements are examined, and their relations and their importance during mission performance are described. For example, it was found that the abilities to monitor each other, to adapt, and to communicate were the most important factors for effective teamwork during a mission. For the investigation of how designers of pilot interfaces work with user representatives in the design process, the contribution is a description of the different roles the users can have during the development process in this domain. The results are primarily intended to inform designers of tactical support systems and cockpit interfaces. However, other domains where team members are distributed, and are highly dependent on technology for their teamwork, should benefit from the findings. / NFFP6 VINNOVA

A decomposition methodology based on the concept of "thermoeconomic isolation" applied to the synthesis/design and operational optimization of an advanced tactical fighter aircraft is the focus of this research. Conceptual, time, and physical decomposition were used to solve the system-level as well as unit-level optimization problems. The total system was decomposed into five sub-systems as follows: propulsion sub-system (PS), environmental control sub-system (ECS), fuel loop sub-system (FLS), vapor compressor and PAO loops sub-system (VC/PAOS), and airframe sub-system (AFS) of which the AFS is a non-energy based sub-system. Configurational optimization was applied. Thus, a number of different configurations for each sub-system were considered. The most promising set of candidate configurations, based on both an energy integration analysis and aerodynamic performance, were developed and detailed thermodynamic, geometric, physical, and aerodynamic models at both design and off-design were formulated and implemented. A decomposition strategy called Iterative Local-Global Optimization (ILGO) developed by Muñoz and von Spakovsky was then applied to the synthesis/design and operational optimization of the advanced tactical fighter aircraft. This decomposition strategy is the first to successfully closely approach the theoretical condition of "thermoeconomic isolation" when applied to highly complex, highly dynamic non-linear systems. This contrasts with past attempts to approach this condition, all of which were applied to very simple systems under very special and restricted conditions such as those requiring linearity in the models and strictly local decision variables. This is a major advance in decomposition and has now been successfully applied to a number of highly complex and dynamic transportation and stationary systems. This thesis work presents the detailed results from one such application, which additionally considers a non-energy based sub-system (AFS). / Master of Science