ABSTRACT Consideration of the environmental impact of aircraft has become critical in commercial aviation. The continued growth of air traffic has caused increasing demands to reduce aircraft emissions, imposing new constraints on the design and development of future airplane concepts. In this paper, an aircraft design optimisation framework is used to design aircraft that minimise specific envi- ronmental metrics. Multidisciplinary design optimisation is used to optimise aircraft by simultaneously considering airframe, engine and mission. The environmental metrics considered in this investigation are CO 2 emissions — which are proportional to fuel burn — and landing- takeoff NO x emissions. The results are compared to those of an aircraft with minimum direct operating cost. The design variables considered in the optimisation problems include aircraft geom- etry, engine parameters, and cruise settings. An augmented Lagrangian particle swarm optimiser and a genetic algorithm are used to solve the single objective and multi-objective optimisation problems, respectively. 1.0 INTRODUCTION Aviation has become a major mode of transportation, accounting for more than 10% of the world’s passenger miles traveled (1) . According to the Intergovernmental Panel on Climate Change, it is pre- dicted that civil air transport will continue to grow at a rate of 5% per year (2) . The continued growth in air traffic has caused increasing environmental concerns. Demands by the public, environ- mentalists, and governments to reduce aircraft environmental impact, have imposed new constraints on the design and development of future aircraft concepts (3) . Some current technological THE AERONAUTICAL JOURNAL JANUARY 2012 VOLUME 116 NO 1175 1 Aircraft conceptual design for optimal environmental performance R. P. Henderson Institute for Aerospace Studies University of Toronto Ontario, Canada J. R. R. A. Martins jrram@umich.edu Department of Aerospace Engineering, University of Michigan Michigan, USA R. E. Perez Department of Mechanical and Aerospace Engineering Royal Military College of Canada, Kingston Ontario, Canada Paper No. 3712. Manuscript received 4 April 2011, revised version received 26 June 2011, accepted 10 July 2011.