[QUOTE=Earl Boebert;179304]I’m not a professional mariner, but I did read the report. It is based on a thing called the SAFTE/FAST model, a computer program that according to the people who sell it (it’s a commercial product)is based on first principles of brain chemistry and has been experimentally validated. You plug in a person’s sleep history and the model tells you how degraded their performance is in terms of equivalent blood alcohol level – the assumption being that being fatigued is like being drunk.
So if you believe the model, you believe the conclusion. If you don’t, you don’t. A lot of people believe in SAFTE/FAST, IMHO because it seems to be the only game in town. A lot of people don’t completely trust it, because the “validation” of the model has taken place in a laboratory setting and is not related to real-world accident/incident data. In other words, it should be possible to look at a bunch of accidents and near-misses and compare the theoretical impairment of crew given by the model against the actual impairment demonstrated by a casualty. This examination doesn’t seem to have happened.
(I put the word “validation” in quotes because I’ve done a lot of work with predictive mathematical models and believe firmly that they are never validated, only invalidated. You can have 1000 runs that correlate with observed data and that history tells you nothing about 1001st. Been there, done that, took the lumps :-))
Bottom line: lots of theory and hand-waving, little or no use of real-world data on impairment.
And they may have done inadequate research on existing literature:
from the report, Section 3.5:
“There is another important element to consider when examining why the recommendation in CEMS to change to a schedule that allows 7 to 8 hours of consecutive sleep was not implemented: there is no scientific evidence to suggest that a schedule that allows 7 to 8 hours of uninterrupted sleep is better than one that allows for 7- to 8-hours of sleep in more than one episode. [U]For example, to the best of the research team’s knowledge, there are no data that directly compare a rectangular [/U][U]two-watch schedule of 7:5:5:7 or 8:4:4:8 with the square watch 6:6:6:6,[/U] which is the primary schedule used by the majority (70%) of the companies surveyed as part of this report.”
[FONT=TimesNewRomanPS]"Results. The mean modeled cognitive effectiveness for all watches within each system were 96%, 96%, 89% and 66% for the 1-in-3 straight eights, 1-in-3 straight fours, 1-in-2 (8-4-4-8) and the current CF 1-in-2 (6-6-6-6), respectively. "
This report found the 8:4:4:8 better than straight sixes. But in all fairness, it was for submariners, and, well… they were Canadian… Also done with FAST. Odd they didn’t note it.
There’s so much literature out there, I imagine anyone could find what they want, especially when they couch the terms in a fashion that identifies ‘acceptable’ vice ‘optimal’ performance.