[bongodriver]

Originally Posted by klem

OK, well the calculations take place in the script so its not a problem but I'll run those "2%" estimates alongside them just for the hell of it. Hopefully find time this coming weekend.

btw I'm assuming those old A&AEE TAS charts used density altitude as well otherwise the whole measurement process is pointless. They do say 'on a standard day'.

The data in flight manuals is almost certainly always going to be based on standard conditions (ISA) it basically sets the benchmark.
when conditions are exactly ISA then assume density and pressure altitude are the same, density altitude increases with deviations from ISA in the positive temparature range and likewise reduces in colder temps.

bottom line is when you test in actual conditions then assume the density altitude and compare against the charted data.