Jet Propulsion A Simple Guide to the Aerodynamics and Thermodynamic Design and Performance of Jet Engines

Introduction

This chapter sets out the background to the new airliner which is to form the basis of the first part of this book. The aircraft, to be called the New Efficient Aircraft (NEA), will be a large wide-body aircraft designed to give low fuel burn, in anticipation of the likely rise of fuel price and pressure to reduce CO2 emissions. The aircraft will have two engines.

The costs and risks of a new aircraft or engine project are huge, but the profits might be large too. Some background is first discussed concerning the history and business of jet propelled aircraft and the impact of concerns for the environment. In explaining the requirements some of the units of measurement used are discussed. Design calculations in a company are likely to assume that the aircraft flies in the International Standard Atmosphere (or something very similar) and this assumption will be adopted throughout this book. The standard atmosphere is introduced and discussed towards the end of the chapter.

Some background

The age of jet travel really got started when the Boeing 707 entered service in 1958. By the time this aircraft was initiated, Boeing had already acquired considerable experience of large multi-engine jet aircraft, bombers and tankers, so it was in a strong position to make good design choices. The 707 was conceived as a long-range aircraft, which in those days meant it was capable of flying across the Atlantic non-stop with a full load of passengers, typically 110 in a two-class cabin. The range with maximum payload was only 2800 nautical miles (nm), but the shortest distance between London and New York is 2991 nm and going west there are normally headwinds that increase the effective distance. Such flights would therefore operate with less than the maximum payload, which would mean less than maximum freight on board, if all seats were taken.

The Boeing 707 had four engines and very much set the trend for aircraft which followed it. The fuselage was circular for most of its length, the wings were swept and the turbojet (no bypass flow) engines were mounted on pylons to hang under and forward of the wing. Hanging the engines under the wing has many advantages, in particular their significant weight is close to where the lift is generated, which makes the structure lighter.