error_401. I disagree; IMHO many commercial aviation professionals misuse the term ‘buffet boundary’, and without good technical description few really understand what it is, or what it might mean when applied to a modern commercial aircraft.
Similarly, knowledge of the margins between normal / abnormal operations and a hazardous situation is weak, or again misunderstood to an extent that it may bias the choice of action in an upset / stall / overspeed encounter.
If an aircraft encounters a stall condition at high altitude then the protection devices will still work; the recovery procedure should be followed.
In the event of overspeed encountering buffet, the aircraft response will depend on type, but within the expected range of upset conditions the aircraft will still respond to the controls. The certification requirements and flight test evaluations should define the safety margins to an extent that commercial pilots should not fear such situations.
Of course this does not exclude the possibility of encountering something completely unexpected (by regulation or otherwise). My own unfortunate experience included encountering a gust at medium altitude which resulted in a control limited climb – full forward stick and still going up (overflying a lenticular cloud). Subsequent investigation showed that this was at the limit of certification expectation.
My lesson learnt was to maintain the appropriate control input and wait, the situation slowly corrected.
What pilots must consider, is that in these situations, although the encounters are sudden, they are dynamic, something will change; aircraft speed, control effectiveness, or the effect of the atmosphere (upset condition).
There is significant risk in assuming that the aircraft has entered some mythical no-fly area or that the controls have failed. In just a few seconds things will change, the important aspect is to identify the change, reassess the situation and ensure that the control input is correct.
Do not over react as this may induce a real upset. Dispel all thoughts of altitude bust, caution and warnings, structural failure, etc; control your thinking.
Rule 1, fly the aircraft.