More factors:
* Headwinds are only taken onto account for 50%, tailwinds for 150%
* For dry runways, no Thrust Reverser is used for aborting Take-off during certification
* Normal landing figures on dry runways are 166% of the test pilots results, on wet runways I think it is 115%
* Be aware though... Non-Normal landing figures are the ACTUAL numbers without any safety factors... So it wouldn't be very wise to land on a runway which is JUST long enough according to the books when you are coming in with only half the flaps you would normally have..
These figures were floating around in my head, so I stand to be corrected...
FT