From CS 25 AMC.
CS 25.251(e) states that probable inadvertent excursions beyond the buffet onset boundary may not result in unsafe conditions.
It also requires that the envelopes of load factor, speed, altitude and weight must provide a sufficient range of speeds and load factors for normal operations.
An acceptable means of compliance with the requirement is to establish the maximum altitude at which it is possible to achieve a positive normal acceleration increment of 0·3 g without exceeding the buffet onset boundary.
Does this mean that at the buffet boundary (1.3 g), there should not be a stall warning, thus this defines the margin between stall speed and buffet boundary?
Also, is there an operational maximum altitude based on ATC climb requirement – 300ft/min?
Thus in a civil aircraft there should not be a ‘corner’ point, but even if a limit was reached it should be safe to exceed the buffet boundary by a small amount.