Consul,
Are you not refering to the despatch element of ldr, ie 1.67 etc etc. The Boeing PI is unfactored and JAR1.50 does not require factoring for perf calculations for actual conditions as found. Now if they despatched with figures outside the ones you mentioned and had no alternate in limits thats a different story. Some operators require PI to be factored but Jar 1.50 reads that it doesnt and as such many dont including my company.Boeing recommend that if a runway is wet to use advisory info and good braking colummns resulting in an actual landing distance. Jar then is happy if the commander is satified that sufficient lda is there. It all Starts at Jar 1.50, and I would appreciate your feed back, or indeed anyone elses with a specialityty in perf vis a vis jar. Microsoft performance data is not welcome.