I have studied landing overruns for a long time now. I also worked on the
European Action Plan for the Prevention of Runway Excursions. Like many other occurrences, overruns are caused by more than just one factor. An important issue I found was that pilots often do not know what the basic assumptions are that have been made by the manufacturer for a landing. The (inflight) landing performance data that a pilot has for its aircraft arebased on a number of assumptions which involves the pilot. First of all it is assumed that you land with a certain speed and touch the runway at a certain distance from the threshold. Many manufacturers use a fixed distance for this airborne distance (this is going to change in the near future following the TALPA ARC).Then it is assumed that you lower the nose without any delay. Next if you had decided that you wanted to use reverse thrust it is again assumed in the performance data that you select this a certain time after touchdown. The same is true formanual braking. Finally it is assumed that the ground spoilers are deployed (if you have these installed of course). Any deviation from these assumptions will eat away any margin you had on the available runway. Indeed most landing overruns are related tolarge deviations from the performance assumptions: long landings and late use of stopping devices. For instance delaying the thrust reverser selection could result that you go into ground idle. When selecting reverse thrust in this modeit would take twice as much time to get maximum reverse than when you are inflight idle. On a slippery runway this could mean that you go off the end ofthe runway. Information about the assumptions made in landing performance data is not always easy to find. The FCOM and FCTM often have little quantified information (typically it will state things like “prompt”, “without delay”,etc.). I believe that we can help reducing the overrun threat by informingpilots about the assumptions made in landing performance data and by giving pilots more understanding of what the consequences are of deviating from these assumptions. Of course when you deviate from an assumed action it will not automatically mean that you will always overrun the runway.