The problem is there is obviously a limit to operation temperature wise. The FAA can state there must be a limit, but in a civil court you will be questioned on whether or not your decision to fly created a liability that was not covered by the manufacturer
The Chieftain flight manual offers absolutely no advice on what the operational temperature limit is. The normal take off chart only goes to 35°C and the single engine climb to 37°C, yet the performance section preamble says for single engine climb at 38°C (100°F) increase climb speed from 106 to 110 kts, if you encounter 38°C at altitude then logic says the ground temp is higher than 38°C.
The 100°F is mentioned because of FAR 23.1043(b) — Cooling tests
Maximum ambient atmospheric temperature. A maximum ambient atmospheric temperature corresponding to sea level conditions of at least 100 degrees F must be established. The assumed temperature lapse rate is 3.6 degrees F per thousand feet of altitude above sea level until a temperature of −69.7 degrees F is reached, above which altitude the temperature is considered constant at −69.7 degrees F.
As Cessna says, the performance charts represent what the FAR 23 aircraft was tested to, they are not limits, and calculation with respect to density altitude, if conditions of pressure altitude and temperature are not charted, is acceptable.
