Overview and Definitions — Page 18, Lesson 24

We're starting fresh with the Overview and Definitions chapter of your Principles of Flight course. This is the foundation—the symbol list that every formula in the entire syllabus will build on. I want you to treat this like learning a new language, because that's exactly what it is. Every symbol here is a word, and every formula is a sentence. Let me walk you through the list of symbols first. These are the standard notations used throughout these notes. I have to be upfront: there is no universal defining standard for these symbols across all aviation textbooks. Other books might use some of these same symbols with different definitions. So the ones I'm giving you now are the widely accepted ones that conform to the Learning Objectives for your ATPL exams. Starting with the Latin symbols. Lowercase 'a' is the speed of sound. 'AC' is the aerodynamic centre. 'AR' is aspect ratio. Lowercase 'b' is span. 'C' is Centigrade. Lowercase 'c' is chord length. 'CD' is the drag coefficient. 'CG' is centre of gravity. 'CP' is centre of pressure. 'CL' is the lift coefficient. 'CM' is the pitching moment coefficient. 'D' is drag. 'Di' is induced drag. 'F' is force. Lowercase 'g' is acceleration due to gravity—and note, it's also used for load factor in some contexts. 'K' is Kelvin. 'L' is lift. 'L/D' is the lift to drag ratio. 'M' is Mach number. Lowercase 'm' is mass. Lowercase 'n' is load factor. Lowercase 'p' is pressure. 'Q' or lowercase 'q' is dynamic pressure. 'S' is area, specifically wing area. 'T' is temperature. 't/c' is the thickness-chord ratio. 'V' is free stream speed, which is your TAS—true airspeed. 'VS' is stall speed. And 'W' is weight. Now the Greek symbols, and these are just as important. Alpha, α, is angle of attack. Beta, β, is sideslip angle. Gamma, γ, is angle of climb or descent. Delta, Δ, means increment in—a change in a quantity. Mu, μ, is Mach angle. Rho, ρ, is density. Sigma, σ, is relative density. And phi, φ, is angle of bank. There's a note about gamma I want you to pay attention to. The Greek symbol γ has been used in these notes to denote angle of climb and descent. But the Learning Objectives use θ, theta, for the same thing. There's evidence that an exam question uses γ for angle of climb and descent. So the notes have been amended to use γ, but you should consider either γ or θ to indicate angle of climb and descent. Don't let that catch you out in the exam. Finally, the 'Others' section. The symbol ∝ means proportional to. And the symbol that looks like a dot over an equals sign means is approximately equal to. Now, let's move to the self-assessment questions. This is where we put these definitions to work. We have two aircraft, and I want you to keep the data straight. Aircraft (1): mass 2000 kilograms, engine thrust 4000 newtons, V1 speed 65 knots, take-off run to reach V1 is 750 metres, and the time taken to reach V1 is 30 seconds. Aircraft (2): mass 2000 kilograms, engine thrust 8000 newtons, V1 speed 130 knots, take-off run to reach V1 is 1500 metres, and the time taken to reach V1 is 40 seconds. We're also given that 1 nautical mile equals 6080 feet, and 1 metre equals 3.28 feet. At V1, both aircraft experience an engine failure and take-off is abandoned. The questions walk you through the fundamental physics. Part (a) asks how much work was done to aircraft (1) getting to V1. Part (b) asks how much power was used. Parts (c) and (d) repeat that for aircraft (2). Then we move to momentum: part (e) asks how much momentum aircraft (1) possesses at V1, part (f) for aircraft (2), and part (g) asks how many times greater the momentum of aircraft (2) is. Then kinetic energy: part (h) for aircraft (1), part (i) for aircraft (2), part (j) how many times greater the kinetic energy of aircraft (2) is. Part (k) asks you to state the mass and velocity relationship of both aircraft and compare to their momentum and kinetic energy. Part (l) asks which has the greater effect on kinetic energy, mass or velocity. And part (m) asks what must be done with the kinetic energy so the aircraft can be brought to a stop. These are the book's practice questions—let's try them one at a time.