Basically, you may not operate outside the limitations of the aircraft and/or extrapolate beyond the performance limits of your aircraft's performance charts
As an example of the problem I cite the Cessna 404 manual. The take off charts only go to 40°C, but the climb charts (both dual and single engine) go to 50°C, and the sea level cruise performance only goes to 35°C.
If 40C is the max for take off, why the 50C climb?
What CASA are saying now is that 35C then becomes the limiting factor in operations. Which we know is bollox.
This is the CASA solution (not published in the meeting minutes),
Unless a safety concern exists, it is not CASA's responsibility to compel OEMs, TC/STC holders, etc to amend information included in the AFM. If there is operational need for data beyond the ranges included in the AFMs, an operator may explore if extending those ranges is possible by contacting the OEM, relevant design organisations, etc. If this results in a change to the AFM, then that change will be approved as discussed above. Any cost of such change to the AFM will likely fall on the operator initiating the change.
The above is signed by a Rob Walker, CASA Stakeholder Engagement Group Manager. What is his background?
Personally, for the take off I would work the problem hence,
OAT 50°C @ sea level = 4,000 DA = 1,000 PA @ 40°C, since DA is what influences performance. I would be interested in
djpil and
JT comments.