alf5071h,
I feel you've distilled most of what's important in your recent post. This accident is a real wake-up call for those who do or might have to land on 'limiting' runways... which is
all of us.
When you're "close to the edge" in performance terms, virtually everything you need to do becomes a "single point of failure" scenario, with limited or no chance of recovery due to time and workload constraints. In the case under discussion (wet, slippery, MEL items, CRM issues), everything has to go right for a successful outcome: landing not in TDZ = G/A or crash; RWY state worse than advertised = G/A or crash; groundspeed too high = G/A or crash; spoilers not deployed = G/A or crash; autobrakes not engaged = G/A or crash; engine(s) not at idle = G/A or crash, etc. By the time a critical failure has been recognised, you'll probably be outside the normal operating envelope and into the "hope this works and we get away with it" area. How many landings around the globe, every month, fall into the "got away with it" category?
It doesn't take much to turn an assured landing in an assured accident, when you're operating with low margins. Maybe more emphasis needs to be put on "rejected landings" in these sort of cases? After all, if you're on an instrument let down with a DH of 500' and the cloud is BKN @ 400', OVC @ 500', you shouldn't be suprised if it ends up as a missed approach. In my last sim detail we practiced rejected landings as part of the lesson plan and very useful it was, IMHO.
Statistically, there are variations in all the parameters involved with landing an aircraft and bringing it to a halt and these create a probability distribution for the actual stopping distance. On a non-limiting, dry runway you can be well up in the percentiles yet be perfectly safe. Also, there is plenty of time to recognise a gross error, such as lack of braking or an extremely long float. For cases like the one under discussion, small changes in external factors (let alone internal ones) can put you off the end before you know it; it can be a subtle combination too: wind not as advertised, runway braking coefficient lower, slightly prolonged flare, delay in reverser operation... it all adds up to a potential disaster but as you were
expecting things to be a bit more marginal than normal operations, it becomes difficult/impossible to spot something that takes you "over the edge".
I'm reminded of the overrun accident @ Chicago and many others. It doesn't have to be a short runway - you can go off the end of 3,000m in the wrong conditions - but there is so little time to recognise & correct the situation when tarmac is at a premium...
