43 inch,
Sure, whilst ever the hot section is producing hot air, it could be argued that in some respect the engine has the ability to produce a small amount of power, what does the TQ gauge tell you ?.
If the aircraft was stationary on the ground with the engine operating at FI, what power is the engine producing, in terms of TQ ?, so does it make the amount produced relevant, I do not think so, great to have but probably not even indicating on the TQ gauge.
So, unless the propeller is ceased in fine pitch, how does one have this massive amount of "windmilling" drag if the engine has actually failed and the prop will start feathering on its own ?.
What I think many here are thinking about is the FI position, engine still producing high oil pressure, prop lever still selecting high rpm and the oil making the fine pitch happen, yet engine not actually scheduling enough fuel to produce positive TQ, this produces high drag (common training scenario, we've all seen it, but would it happen in real life ?).
A ceased prop in fine'ish pitch will produce high drag.
For example, jump into a CSU single engine piston, climb to 10,000ft, pull the mixture, set the glide, once estabilshed write down the FPM, pull the pitch lever into the coarse position ( pull pitch lever out ), check the FPM.
I did this in a lightly loaded C207, first reading was 1480FPM, the second was 690FPM. Whilst the single engine prop operates differently this indicates what a small pitch change will do to a glide/drag produced.