who reckons the beaver would meet the flight requirements of FAR23 (let's say at amendment 45)?
Once certificated, an aircraft does not have to retrospectively satisfy any new certification standards that are promulgated. Therefore, the Beaver would only have to meet the standards required at the time of its initial certification. There are, therefore, many aircraft flying which do not meet current certification standards.
One aspect of stalling requirements for part 23 certification that needs to be taken into account is that stall tests are flown wings level and with 30 deg AoB in both directions, and all are flown with idle power and 75% max continuous power. Stalling characteristics at higher power settings and greater bank angles/normal accelerations are not tested and, therefore, some aircraft may demonstrate adverse stalling characteristics at high power and high g and still be certificated.
#78 provides a link to a Beaver Flight Manual in which, on page 36 of Section IV, it gives values for stall speeds at different bank angles/normal accelerations. There are two interesting points about this data. First, does it relate to aircraft with wheels, skis or floats? I would expect a difference between, say, wheels and floats due to the floats reducing overall directional and longitudinal static stability (resulting from surface area forward of the c.g). Secondly, Vs@>1g = Vs@1g x sq rt(load factor). From the Manual, Vs@1g = 60 mph and Vs@2g = 105 mph. Theoretically, Vs@2g should be 84 mph. Can any Beaver operators explain this discrepancy? It is not uncommon for accelerated stall speeds to be lower than theoretical (usually due to Reynolds' number effects) but I have never before come across an aircraft where they are greater.
Please note that my comments above are not a comment on the accident but points of interest resulting from other posts on this thread.