Originally Posted by
RAT 5
Having said that, an over run is not caused by touching down in the correct place a couple of knots too fast; it is more likely caused by touching down too far, even at the correct speed, and then being too tardy with braking. Given all the buffers built into the calculations an over-run has to be either very different wind conditions than expected or gross mishandling; and that includes too fast or too long, usually both.
Gerard van Es at the NLR-ATSI (Netherlands Air Transport Safety Institute) has studied runway overruns;
on their site, there's more than you'll probably care to read on
runway excursions. From
his numbers, the "long landing" is a factor twice as often as "speed too high". Of course a landing can suffer from both. I'm attaching a slide from
his 2013 presentation below. Van Es seems to believe that a lot of runway overruns could be avoided if pilots did more go-arounds on unstabilized approaches and these "long flares".
I have no idea what considerations went into the setting of the touchdown standards, but I'd guess that putting the touchdown zone safely behind the threshold means the flare occurs over tarmac: maybe over soft ground, pilots would come out of the flare higher since they'd be afraid of hitting the dirt, and then "float" longer? and the extra 5 knots on the air speeds might be a safety allowance for sudden wind variations?
To get back to the original topic of this thread: the NLR-ATSI
runway excursions page also has links to statistics on overruns/veeroffs for select years that show the aircraft type, and they're sortable. Sort first by aircraft type, then by phase and occurrence, and the incidents are easily countable:
in 2013, the B737 had 10 landing overruns (and 3 veeroffs), while the A320 had 10 landing veeroffs (and 2 overruns). In previous years, the A320 had a lot less veer-offs, but the B737 overruns had comparable numbers, so the premise of this discussion seems correct.
I have been searching for figures on worldwide departures by aircraft type, but couldn't find any; fleet sizes are not that different, but departure numbers can still vary considerably if a type flies more short sectors. Does it seem plausible that the B737 would have 5 times as many departures as the A320?