Why do you think that the certification rules require the optimum and best landing distance the factory test pilots can do during the certification test flights to be factored by 1.67.
Landing is the
least accurate form of flying we can undertake, unlike take off which can the most accurate. There are so many variables during the most stabilised approach that it is possible to suggest that most landings are randomly variable within a strict set of parameters. The greaser is as much a function of
good luck as it is for high level of skill.
That extra 67% might a number that mathematicians, statisticians and scientists might recognise as being the result of a standard deviation calculation which reveals how spread out numbers are from the average, calculated by taking the square root of the arithmetic average of the squares of the deviations from the mean in a frequency distribution.
That is by forcing the issue you might be able to do better than the factory test pilot or pilot of average ability but you may well go "out to the other end" on the average. Being the conservative lot we are we assume the worst case in a statistical sense to calculate our required landing distance, i.e. the best we can do under the best conditions with a 67% fudge factor just in case.
If we were to
require a gauranteed landing at say a 95% probability we might see runway lengths doubled.
Expedience suggests that the averagely proficient pilot doing the right thing according to the AFM should be able to meet the landing distance required most of the time, at least enough to be "routine".
So why do we get twitched up when every one of the factors involved in what should be a succesful landing gets pushed up the "long" end of the list and the HIALS at the other end are hove into a closer view than is healthy.??
We do what is prudent, we accept that we didn't get it "right enough"
this time and go round, from wherever that becomes apparent.
It only becomes a problem when it becomes a habit.
I'm not suggesting for a minute that we do the "oh well, thats fate routine" but if we have not developed any nasty habits then, we also need to accept that sometimes sh!t just happens and not expect to get done over here or anywhere else for it.
