Introduction To Aircraft Flight Mechanics: Perf...
EAS 4010 - Flight Performance Mechanics Credits: 3Prerequisites: EGN 3321 - Dynamics and EGN 3331 - Strength of Materials Course Description: This course is an introductory course into aircraft flight mechanics. Topics include introduction to airfoil theory, aircraft performance measures, wing design, lift/drag on wing performance, and an introduction to jet propulsion systems.
Introduction to aircraft flight mechanics: perf...
Aerodynamics and Aircraft Performance, 3rd edition is a college undergraduate-level introduction to aircraft aerodynamics and performance. This text is designed for a course in Aircraft Performance that is taught before the students have had any course in fluid mechanics, fluid dynamics, or aerodynamics. The text is meant to provide the essential information from these types of courses that is needed for teaching basic subsonic aircraft performance, and it is assumed that the students will learn the full story of aerodynamics in other, later courses. The text assumes that the students will have had a university level Physics sequence in which they will have been introduced to the most fundamental concepts of statics, dynamics, fluid mechanics, and basic conservation laws that are needed to understand the coverage that follows. It is also assumed that students will have completed first year university level calculus sequence plus a course in multi-variable calculus. Separate courses in engineering statics and dynamics are helpful but not necessary. Any student who takes a course using this text after completing courses in aerodynamics or fluid dynamics should find the chapters of this book covering those subjects an interesting review of the material.
Aircraft flight mechanics are relevant to fixed wing (gliders, aeroplanes) and rotary wing (helicopters) aircraft. An aeroplane (airplane in US usage), is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
A heavier-than-air craft (aircraft) can only fly if a series of aerodynamic forces come to bear. In regard to fixed wing aircraft, the fuselage of the craft holds up the wings before takeoff. At the instant of takeoff, the reverse happens and the wings support the plane in flight.
In flight a powered aircraft can be considered as being acted on by four forces: lift, weight, thrust, and drag. Thrust is the force generated by the engine (whether that engine be a jet engine, a propeller, or -- in exotic cases such as the X-15 -- a rocket) and acts in a forward direction for the purpose of overcoming drag. Lift acts perpendicular to the vector representing the aircraft's velocity relative to the atmosphere. Drag acts parallel to the aircraft's velocity vector, but in the opposite direction because drag resists motion through the air. Weight acts through the aircraft's centre of gravity, towards the centre of the Earth.
In straight climbing flight, lift is less than weight. At first, this seems incorrect because if an aircraft is climbing it seems lift must exceed weight. When an aircraft is climbing at constant speed it is its thrust that enables it to climb and gain extra potential energy. Lift acts perpendicular to the vector representing the velocity of the aircraft relative to the atmosphere, so lift is unable to alter the aircraft's potential energy or kinetic energy. This can be seen by considering an aerobatic aircraft in straight vertical flight (one that is climbing straight upwards or descending straight downwards). Vertical flight requires no lift. When flying straight upwards the aircraft can reach zero airspeed before falling earthwards; the wing is generating no lift and so does not stall. In straight, climbing flight at constant airspeed, thrust exceeds drag.
In straight descending flight, lift is less than weight. In addition, if the aircraft is not accelerating, thrust is less than drag. In turning flight, lift exceeds weight and produces a load factor greater than one, determined by the aircraft's angle of bank.
Dr. Morris specializes in aircraft flight path and accident reconstruction using recorded radar data, flight data recorder data, Global Positioning System (GPS) data, and aircraft performance. His expertise includes flight dynamics and aircraft performance analyses, flight simulation, automatic control systems, aircraft stability and control, aerodynamics (including Computational Fluid Dynamics, or CFD), thermodynamics, space-based navigation systems, and aerospace education. He has also performed numerous aircraft icing analyses to support both accident investigation and certification. Dr. Morris has repeatedly taught the University of Kansas course "Aircraft Icing: Meteorology, Protective System, Instrumentation and Certification" and is a past Chairman of the Society of Automotive Engineers (SAE) Aircraft Icing Technology Committee. He is also an Associate Fellow of the American Institute of Aeronautics and Astronautics (AIAA) and has served on both the AIAA Atmospheric Flight Mechanics Technical Committee and the AIAA Applied Aerodynamics Technical Committee.
So how does this all work with MATLAB and Simulink? Well first, let's talk about the iterative design process for designing aircraft flight control. First, you need to design the dynamic model. So how do you do that? You'll start by determining the geometry of your vehicle, determining the aerodynamic characteristics of the vehicle based on that geometry-- this can be done through a number of different methods including wind tunnel testing. You'll create a simulation to verify that design, and once you have a simulation, you can design the flight control laws based on that model.
As an aircraft flight control designer, you may have to iterate through this process several times before you achieve your desired results, and while you're iterating through this design there are additional steps that you may also be working on such as creating a hardware in the loop simulation, building hardware and software such as the actual vehicle to do flight testing and then analyzing and visualizing those results from the flight test. Today, we'll focus on the top four highlighted blocks, but there are tools available to help you throughout this entire design process.
So you see, it's a wing, body, tail design. You can see the air foils that are input into the DATCOM system. And again, that three view of the aircraft. So like I said before, I won't cover how DATCOM works, but I will show you what the output looks like. And when we look here, you see the output isn't very useful in MATLAB. It's a text file. It's got all the information I need, but not in a very useful format. So what I'm going to use is the DATCOM Import tool with the Aerospace Toolbox. And we can see the line I run here. DATCOM Import on that output file from the DATCOM. And it processes the data. And if I take a look at that data, we can see now I've got a structure of all my aerodynamic coefficients for my flight conditions that I defined in my DATCOM file.
And that's pretty much it for the model. So I've shown you how to model the dynamic system. Now, let's talk about how to design the flight control for two modes of flight. This is equally as complex as what I just showed, but I think I've got a good way to show you how you can use our automatic PID tuners to quickly design a flight control system, or any type of control system for that matter, based on what your design workflow is. As I mentioned twice before, I'm going to design two different control loops that I can change between using state flow that will allow me to visualize this change and simplify my control logic design process. First, I'll be designing the altitude tracking air path where I'll feedback altitude in the outer loop to allow the aircraft to pitch and control altitude while maintaining airspeed. The second is the max thrust climb air path where I can send a maximum throttle command to the engine and then pitch up and down to achieve the desired airspeed for fast step altitude changes.
OK, so that's state flow. It's a little bit different than Simulink. I hope it wasn't too complicated for you. Again, I'm taking questions at the end. So please, if you have any questions about this stuff I'll be answering them for you. So ask away. So I don't want anything to scare you away, think, oh, this is too complicated, because it's really great, helpful tool if you're doing this type of control design. OK, so we're back here. So I've shown you how I'm going to toggle between those two modes. Let me zoom all the way in to the very inside of the loop here. In aircraft design, at least the way I learned it, is you tune your controllers loop by loop. First I'll tune the pitch rate loop and then the z acceleration loop and then the flight path loop.
So to wrap this up, I've showed you how to model your dynamic aircraft system in Simulink, including the aerodynamics and the environment. I've shown you how you can use Simulink control design and state flow for complex flight controller design, and how to automatically tune gains with the PID tuner. So you can tune gains for systems that use proportional feedback loops, proportional integral, or PID control loops. Any combination can be tuned with the PID tuner. And I've shown you how you could visualize your results in 3D using the FlightGear interface from the Aerospace Blockset.
When no two flights are the same, you need a solution that is up to the challenge. APG and RocketRoute provide flight planning, runway analysis and aircraft performance services to military agencies in many parts of the world. 041b061a72