ESDU 84040 gives graphs from which quick first approximations can be obtained to the landing field lengths for all types of "conventional-landing" civil-transport aeroplanes. The estimation method assumes the use of typical civil-transport-certification style landing manoeuvres from the screen on to a hard, level, dry runway. The data are applicable over a wide range of ambient conditions and the effect of non-still-air conditions can be taken into account. The method is intended for use in initial or project design work but may also be of use in checking results of more detailed estimation methods. It is based on an analysis of landing data obtained from aeroplane flight manuals and the use of true ground speed at the screen and mean "brakes-on" deceleration as correlating parameters. A practical worked example illustrates the use of the data, and a table is included summarising landing field length factors from current civil certification requirements.