Originally Posted by LOKE
What did the computer tell the pilot? Given the conditions – was he capable – of stopping only on the surface provided? Or was he capable of stopping on the surface provided, plus all of the above mentioned additives – which means that he should have been able to stop in about 50% of the runway available?
You are asking a bunch of different questions in your post. I am not familiar yet with all details of the report, but I did read the preliminary safety recommendation (January 2006) and commented on it in Risks:
http://catless.ncl.ac.uk/Risks/24.16.html#subj9.1
Some of your questions are already answered by that, as follows.
The computer was calculating stopping distance based on immediate deployment of reversers. Stopping distances as calculated in the operations manual do not take into account reverser deployment. So there is a mismatch of information there which was not explicitly stated as the pilots were using the tool. Also, the "WET-FAIR" runway-conditions parameter that the pilots entered into the calculation obviously did not accurately represent the actual state of the runway with regard to available friction.
With these two assumptions, one mistaken and one not fulfilled during the landing, the calculation said the aircraft would stop with 560 feet of runway remaining.
The NTSB pointed out that had the reverse-thrust "credit" not been used, the calculation would have indicated that they did not have enough distance available to land, with either runway condition of "FAIR" or especially of "POOR", which it was.
That all does not have to do with regulations. That has to do with a calculating tool using assumptions which do not match the pertaining conditions (including delayed reverse thrust). One is going to have problems there no matter what the regs say.
PBL