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The University of Southampton

SESA2025 Mechanics of Flight

Module Overview

This module further develops the fundamental concepts underpinning aircraft flight, stability, and control. The focus is initially on capturing the aerodynamic behaviour of lifting and control surfaces within simple mathematical models leading to simple 3-DOF equations of motion for a rigid aircraft. Ideas of equilibrium and trim are captured by determining the steady control inputs needed to fly simple steady trajectories, including feasibility, conditional static stability, and drag optimality. These concepts are extended into three-dimensions using ideas of motion as a geometric transformation leading to the full 6-DOF dynamical systems, state space formulation, and flight simulators; linearization about a steady trajectory leads to linear state space models, characteristic motions and dynamic stability, response to gusts, stability augmentation, and linear control. The lectures are complemented by two formative coursework with relevance to the taught material.

Aims and Objectives

Learning Outcomes

Knowledge and Understanding

Having successfully completed this module, you will be able to demonstrate knowledge and understanding of:

  • Aerodynamic and control forces acting on aircraft, including high-lift devices, origins of drag. [SM1(m),EA1(m),P1(m)]
  • Aircraft equilibrium, control/trim inputs required for steady trajectories, static stability, optimality. [SM1(m),EA1(m),P1(m)]
  • Description of motion in three-dimensions, Euler angles and rates, full 6-DOF equations for rigid symmetrical aircraft, state space formulation, solution in the time domain and flight simulation. [SM1(m),EA1(m),P1(m)]
  • Linearised state space equations for small disturbances about a steady trajectory, aerodynamic derivatives, longitudinal and lateral characteristic motions, eigenmodes, dynamic stability. [SM1(m),SM6(m),EA1(m),EA3(m),P1(m)]
  • Control inputs for steady sideslip, coordinated turns. Linear response to control inputs and wind gusts. Simple state feedback and autopilots. [SM1(m),SM3(m),SM4(m),SM6(m),EA1(m),EA3(m),EA6(m),P1(m),P6(m)]
Subject Specific Intellectual and Research Skills

Having successfully completed this module you will be able to:

  • Perform simple calculations of aircraft trim, lift and drag, static stability. [SM3(m)]
  • Perform simple calculations and computations of aircraft characteristic motions in both timedomain and in terms of eigenmodes [EA2(m),G1(m),P6(m)]
  • Analyse aircraft lift/drag/moment data. [EA6(m),P6(m)]
Transferable and Generic Skills

Having successfully completed this module you will be able to:

  • Study and learn independently. [P4(m),G2(m)]
  • Demonstrate study and time management skills. [G2(m)]
  • Solve problems systematically. [SM3(m),EA1(m),EA3(m),G1(m)]
Subject Specific Practical Skills

Having successfully completed this module you will be able to:

  • Study and learn both independently. [P4(m),G2(m)]
  • Demonstrate study and time management skills. [G2(m)]
  • Solve problems. [SM3(m),EA1(m),EA3(m),G1(m)]
  • Appreciate some of the technical issues associated with aerospace vehicle design. [D1(m),D2(m)]


Introduction Aerodynamic forces and moments: Nomenclature, aircraft axes, lifting and control surfaces, high-lift devices, aerodynamic derivatives, aerodynamic centre, induced flow and downwash, aerodynamic derivatives and neutral point for complete aircraft. Thrust, drag, stall, compressibility effects, wing sweep, trim tabs. Aircraft equilibrium and static stability: Control and trim inputs for steady equilibrium level flight, steady climb, manoeuvring with constant acceleration. Stick-fixed and stick-free static stability, static margins, lateral static stability. Effects of high-lift devices, optimal trim configurations and minimum drag. Aircraft motion in three-dimensions: Motion as geometric transformation, aircraft body and Earth axes, rotation matrices, Euler angles, Euler rates and angular velocity, transformation of vector quantities, inertial time derivative, gravitation effects. Estimation of orientation from inertial sensors, autopilots. Full 6-DOF equations for a rigid aircraft, state space formulation. Solution in the time domain, flight simulators. • Small disturbance equations Linearization about steady equilibrium flight, wind axes, stability and control derivatives, matrix representation, eigenvalues and eigenvectors of characteristic motions, dynamic stability, linear state space formulations, decoupling of longitudinal and lateral motions for symmetric aircraft. Longitudinal dynamic stability: Wind axes and aerodynamic derivatives, gravitational effects. Stick-fixed dynamic stability, Routh–Hurwitz criterion, eigenvalues and eigenvectors of characteristic motions. Phugoid and short period oscillations. Reduced order models and longitudinal approximations. Handling qualities. Lateral dynamic stability: Eigenvalues and eigenvectors of characteristic motions. Dutch roll, spiral mode and roll subsidence. Reduced order models. Handling qualities. State space formulation for response and control applications. Estimation of lateral aerodynamic derivatives. Reduced order models and lateral approximations. Steady sideslip and correctly-banked turn. Control and Response: Control inputs to achieve a given trajectory, stability augmentation and state feedback, autopilots and flight control. Response to wind gusts. Revision and Example lectures. Coursework feedback sessions.

Learning and Teaching

Teaching and learning methods

Teaching methods : lectures supplemented by coursework feedback sessions. Learning activities include directed reading and problem solving.

Independent Study118
Total study time150





MethodPercentage contribution
Continuous Assessment 30%
Final Assessment  70%


MethodPercentage contribution
Set Task 100%


MethodPercentage contribution
Set Task 100%

Repeat Information

Repeat type: Internal & External

Linked modules

Pre-requisites: SESA1015 and SESA2022

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