Not sure about rubbish, but a while back an NTSB report into a PA-31 crash highlighted a major factor being that the aircraft was operating outside the performance data envelope. It was back from the 80s or 90s, so haven't got the time to dredge it up. The NTSB seemed to be saying that the performance chart limits were also the environmental limits for operation and the aircraft should not have been there. Goes back to the rule you can interpolate between lines, but not extrapolate beyond them. I think Piper covers up to ISA +20 and stops there, which means around 35C at SL is the max temp for operation. While they are now based in Florida, the original plant and testing was in Pennsylvania, where ISA +20 is not common, so fits.
PS the short of it was that the commuter Navajo could not maintain altitude while well within the loading envelope and crashed en-route on a very hot day in the mid-west. Pretty sure litigation was being aimed at Piper who may have made a statement that the charts are the limits and operating outside of the charted lines was not endorsed by the manufacturer.
I mean you could say it's not a hard limitation as such, but similar to oil grade in your engine. Run the wrong SAE grade of oil intentionally the engine will damage and fail, you could be held responsible for what is damaged. If you are running 10W-30 oil its max recommended ambient is 30-35c, is it safe to operate above that, probably for short duration. If it's 10W-40 it gets up to 40C but not recommended above that. Avgrades W080/W100 are basically similar to SAE-10W-30 with W100 maxing out at 30C recommended.
Last edited by 43Inches; 24th Jan 2023 at 23:14.