John, thanks for your comments and thoughtful observation, which stirred more thoughts. '
Did my post represent what I intended', I think so.
However, as much as I detest trivial debate about words and meanings, in this context, what is the difference between 'presumptions' - your choice, and my use of 'assumptions'. *
Considering a scenario from an earlier post; - always use a wet V1, which might to some minds infer that there will be an 'additional' safety margin, but probably not as much as envisaged by the differences in speeds (call for perf engineer).
Thence 'presumption' represents an engineering, regulatory, management, view. A technical judgement before the event, credited with greater certainty in specific - as designed /calculated, operations.
Conversely crews relate to assumptions. Some held before an event - bias, erroneous knowledge - belief that requirements are understood; others from a real time evaluation of the situation as presented to them.
The latter may not have the same certainty as prior presumption, more often much less certainty. A wet V1 on a dry runway, or a wet V1 on a wet runway, but how wet; what is presumed vs what is assumed.
The gap between the two is a view of airmanship. **
Yet from OP#1, the difference could be that management's (we know best) after-the-event judgement, with FDR analysis, is biased by the presumption that crews will behave as in the calculated performance, rules, regulations, and trained for situations.
Whereas the crew have to assume that their assessment of the situation at the time is appropriate, and act accordingly - airmanship; there is no right or wrong,
no guarantees, only probabilities and historical interpretation; either to learn from (assumptions) or chastise crews (presumptions).
I prefer to start with the crew making a reasonable judgement because they were there, at the time; so learn from them.
*
The words assume and presume both mean that you take something for granted as being true, but the difference is based on how certain you are.
Assume is typically used in situations where someone takes something as the truth with a very low level of certainty or with no proof at all.
Presume usually involves a higher level of certainty and is used in situations where someone makes an educated guess based on reasonable proof or evidence.
Assumption is a noun related to the verb assume, and refers to the act of taking for granted or supposing something. Likewise, presumption is a noun related to the verb presume, and refers to a belief on reasonable grounds or probable evidence.
Presume and assume are often used interchangeably and have similar meanings. When you’re trying to decide which word to use, think about the level of certainty involved and whether it’s a guess with no proof (an assumption) or a guess with reasonable evidence (a presumption). Assume vs Presume
**
My view of Airmanship in this post.
Do we presume or assume that the glass is half full, or half empty.