DreamLand #576 “I don't really feel the conditions pose a risk, the aircraft could have easily stopped had they not been in the wrong configuration and floated down 50% of the runway, all these overrun accidents have a lot in common.”
Common features: misassessed the situation, or with a reasonable assessment, chose an inappropriate course of action.
In order to avoid repeating the common features in similar circumstances we need to know why these features applied in this accident.
There appears to an industry habit of accepting excessive tailwinds. History has clearly demonstrated the increased risk. Control factors at 10kts tail were applied by requiring specific flight tests and operational approval for any higher speeds; these usually limit operations to specific circumstances and rarity of use. Furthermore, authorities might prohibit tailwind / contaminated (flooded) runway combination as risk reduction.
Another habit is accepting dispatch landing distances without reassessing the conditions. Some operations might place too much ‘implied’ authority with dispatchers; thus crews do not check for changes or particularly any implications of change, e.g. wet/good at dispatch could quickly deteriorate to wet/poor in heavy rain. Is the dispatch landing distance the same? How ‘wet’ is wet, and how much deviation requires using contaminated/flooded landing performance.
Further habits include reliance on reverse thrust. This provides an everyday standard for judging deceleration and stopping distance, but certification and dispatch distances, those with safety margins applied to counter the risks in operation, do not consider reverse.
Even if the actual landing distance suggested that the aircraft could land in the conditions, it did not have a safety margin consistent with the conditions and configuration - thus there was no safety margin. The factored landing distances, as used for dispatch, appear to give a reasonable margin of safety in operation and thus should be used in a pre-landing assessment of distance required.
“The aircraft could have easily landed on this runway …” #578.
The report gives the actual landing distance required as between 7500 and 8100ft depending on the wind speed used (note 11). These values applied to the wet/good runway report at dispatch (F30) and thus may not have been realistic in the actual conditions. Boeing ‘actual’ landing distances (QRH) use thrust reverse, thus a late or non-selection could result in an overrun, as could a landing beyond the assumed 1000ft touchdown position. These distances are at the runway limit, and in no way equate to only 60% of the distance available; certainly not easy, not safe.
So common features; lack of, or poor knowledge of landing performance, the variability in runway conditions, the significant increase in risk with tailwind / wet runway, habit, and the required margin of safety – safety is minimizing unnecessary risk.
This accident not only had unnecessary risk, it was an unnecessary accident.