Hello John,
As I said in my previous post, the statement that the TOD must not be more than 1.25 x TORA is incorrect. The correct statement on page 19 of the CAP 698 is the TOD x 1.25 must not exceed the TORA. this leaves a 20% safety margin.
The correct versions of these factors (on page 19) are not the inventions of the examiners, but come straight from the regulations JAR OPS(1), 1.530. Class B aircraft take-off.
You are correct that this means that the maximum TOD is only 80% of the TORA, (and of the TODA and ASDA with no stopway or clearway).
They are also (some of) the factors that the students are expected to use when they move on to the CPL flying.
I had always assumed that the factors specified in FAR are more or less the same. Are they not?