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Old 27th Aug 2011, 23:24
  #96 (permalink)  
john_tullamarine
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SOPs are a two-edged sword.

They are sound and desirable to follow on the very great majority of occasions due to the probabilistic nature of our activities.

However, there are few, if any, guarantees in flying.

If/when the ducks are lined up against your interests ... on the rare occasion it may be more sensible to ignore the rule and do something different.

However, these rare exceptions ought not to be generalised into some sort of rule-based behaviour.

Two takeoff instances which come to mind -

(a) post V1 with multiple systems failure which will preclude safe flight .. for instance, I wouldn't envy a pilot with a combined engine failure and total hydraulic loss.

(b) low speed schedule with an uncontrollable yaw post V1 OEI again probably due to a systems failure

While noting that the certification paradigm safeguards against such things - in general - if we find ourselves on the wrong end tail of the distribution curve .. it was a day that we ought to have stayed in bed .. and it is then that the Captain gets to earn his/her salary in a few seconds. No necessary guarantees in many instances that the fallback gameplan will work. However, if it has a significantly higher probability of success, it has to be adopted if the main plan clearly has gone irrecoverably awry.

It is for this sort of reasoning that this type of thread is important. It makes the reader think about things ahead of potentially being confronted with something similar.

I did not wish to present it as a suggested mode of operation but as an exception.

Precisely.
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