In the Cessna 404 manual take off and landing tabulated data only goes to 40°C, however climb data, both dual and single engine, goes to 50°C.
How can we say 40 is the operational limit because the take off chart only goes that high, but climb data goes to 50?
I would have thought a prudent pilot would work backwards from the climb charts. Ensure s/he could reach the required gradient at temps between 40 and 50, and then from the take off chart determine the distance from a density altitude calculation.
All the Cessna manuals I've seen have a preamble to the performance section which says,
Demonstrated Operating Temperature
Satisfactory engine cooling has been demonstrated for this airplane with an outside air temperature 23°C above standard. This is not to be considered as a operating limitation. Reference should be made to Section 2 for engine operating limitations.
Notably the preamble also says the performance information allows planning with reasonable accuracy, not exact, as the preamble again says, it assumes "
using average pilot technique (however you quantify that)
with an airplane and engines in good condition". I don't see how using DA when temp is 40< to extract T/O data transgresses any rule, regulation etc The climb charts would suggest that 50°C is the practical limit, because that's as far as the chart goes. Why else have the climb charts go to 50 if take off is limited to 40? Inversion? Where do you source that data?