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. If you extrapolate data to consider flying at 50C when the chart ends at 35C you are basically taking on the liability if something goes wrong. That is in Pipers view anyway. It may also be the case with Cessna, in that they can say, 'yes, that will probably work' but unless there is paperwork that says how to and that its endorsed by the manufacturer you will probably be on your own in court vs the families of the injured.
The case I was referring to was post accident, Piper says it considers the lines the tested limits, or more precisely the end of their liability. Somebody else could measure lines further out and take on that liability if they so wish, so it's not a limitation for the aircraft in general. So I take in the case of the Cessna operator, Cessna says in theory your working is sound, however if you then crashed they will just point to the AFM charts and say we don't endorse flying beyond the lines and they had come up with their own methods to extrapolate data. There is a big difference between an OEM saying yes that will work, we don't see anything wrong with your idea and providing written support that it is approved.
I can think of several instances where engineering fixes were applied to a certain manufacturers aircraft when it had issues under approval from them that it was possible. When it came to claim a defect unrelated under warranty the said manufacturer disowned the aircraft and said it had too many modifications now to be considered for cover.
The big question to always ask the original manufacturers are 'is this an approved method where I will be covered in an accident' and 'will I still be covered by warranty if I do this'. If you don't ask these specific questions you will just get, 'yeah looks OK to me, fill ya boots'. There is a difference between capability and legal liability. Remembering that the OEM will not want any responsibility for an accident.
And in short the question will be asked at what point would extrapolating data not be ok, there is obviously a limit somewhere. Cessna and Piper will probably always fall back on that they designed the aircraft for normal environmental conditions, 50C would be beyond that for sure. I know a lot of transport aircraft that have 50C as the environmental limit, they can still perform well at that temp, just a lot of other things are not countered for, which is not specified as why that's the limit. I've operated turbine aircraft in the high 40C region, but had specific data for the performance, they performed fine for the charted performance limits.
So the question is, is it legal to fly using extrapolated data, yes (in a grey area), will you be safe in a court of law if you have an accident where persons or property are damaged, probably not.
Comes back to the old car adage of driving to the conditions. You can be driving below the speed limit, but if you take a wet corner and slide off the road you were not driving to the conditions. Your passengers will claim compensation under your name and so on, luckily in Australia its CTP and liability Insurance.
Last edited by 43Inches; 1st Feb 2023 at 21:35.