CFI,
It's hard to teach and old dog new tricks.
This is a glaring example of what two ICAO audits and the recent FAA audits found, CASA's lack of internal training and standardization, and a lack of solid advisory material --- and the industry knowledge level is not too flash, either!!!
The legal position is clear and simple --- you are legally bound by the AFM, but culturally and individually far too many FOIs ( and there is no shortage of individuals in industry agreeing with them) that are, quite simply, years out of date.
In one instance, we have had to get a "strongly worded letter" from the US Type Certificate holder for the Metro, a CASA FOI was demanding "stall demonstrations" with the stall and attitude warning system/stick pusher deactivated. As a subsequent accident in Scandinavia has illustrated, and we have always known, the stall demonstration demanded by the CASA FOI would have almost certainly resulted in the loss of the aircraft and crew ---- and was strictly prohibited by the AFM ---- a fact the FOI refused to recognize.
Sadly, the C&T pilot who refused to accede to the direction of said FOI (he didn't wish to commit suicide) has effectively committed professional suicide ---- as so often happens with CASA, you can win the battle, but lose the war.
Can I suggest you take it up with the the Office of the Director, he doesn't believe his troops are doing anything but a great job.
Tootle pip!!
PS: It is so long since I have used a "Black Book", I don't remember where the 15% come in?
If you have un-factored AFM/POH data, it need careful though as to factors. For landing, in my opinion, 15% is cutting it too fine for most of us who are not test pilots, how about 50% plus.
After all, for FAR 25 aircraft ( and some FAR 23) the demonstrated landing field length is 60% of the length published in the AFM/POH.