Course Introduction#

What is Flight Mechanics?#

Without going back to basics too much, a definition of what Flight Mechanics is can be garnered from the definitions of each word:

flight - the action or process of flying through the air

—Oxford English Dictionary

So Flight is relatively easy to understand. Mechanics, when not referring to people who fix machinery is defined as

mechanics - the branch of mathematics dealing with motion and forces producing motion

—Oxford English Dictionary

Flight Mechanics allows us to construct a mathematical model of an aircraft to analyse and predict flight characteristics. Generally, a model is a simpler representation of a system that has sufficient fidelity to represent the parameters of interest - so we are not concerned with, say, turbulence modeling in this course as this is a higher order parameter when understanding aircraft performance, stability, and control.

Within the field of mechanics, we define kinematics as the study of motion, without reference to the forces causing it - problems involving the kinematic equations (\(s,u,v,a,t\) equations…\(v=u+a\cdot t\), ). This allows us to solve some problems in aircraft flight involving aircraft performance (given an aircraft’s position, speed, and acceleration, we can determine basic distance parameters).

To gain further insight, we need to understand the forces that cause motion - this is the field of kinetics. The forces of interest for this course are, lift, drag, thrust, and weight - with which you should be familiar from MMAE 312, Aerodynamics of Aerospace Vehicles.

Course Structure#

This is a large course, comprising five interrelated modules:

  • Understanding how speed is measured on an aircraft using a pitot-static

  • Defining and converting between Indicated, Calibrated, Equivalent, True Airspeed, and Groundspeed

  • Defining relationships between basic forces and motion in steady, level flight, with aircraft represented by a point mass.

  • Range calculations.

  • Understanding aircraft loading in accelerated flight.

  • Earth, Stability, Wind, Body Axes systems

  • Aerodynamic Angles

  • Euler Angles

  • Reference frames, and relative motion

  • Newton’s Second law as applied for aircraft forces and moments

  • Defining trimmed conditions

  • Utilising relationships between control surface deflections, and forces around the aircraft CG.

  • Using the small perturbation theory to linearise the aircraft nonlinear differential equations of motion.

  • Developing transfer functions to relate control input and state/non-state variables.

  • Understanding the difference between aircraft states (e.g., \(u\)) and other variables (e.g.., \(\beta\))

  • Stability definitions for first order and second order systems.

  • Laplace transforms, characteristic equation.

  • Longitudinal EOM dynamics; short-period (pitch) mode, phugoid mode.

  • Lateral/Directional EOM dynamics; spiral mode, roll mode, Dutch roll mode.

  • Predicting the dynamic stability of fixed wing aircraft.

  • Reduced order models for modes.

Each of these could be an entire course on its own, so we will not be able to cover the entirety of each subject, but we will develop an understanding of sufficient detail to answer questions on a range of topics in each subject.