Big John wrote:

I've see a number of individuals who drank from wake up to the time
their eyes closed for sleep at night.

They were able to pass any and all tests of ANY kind (memory, verbal,
body activity, etc) given to them other than a breathalizer (sp) which
only measures a approximation of alcohol in the body, not any
impairment. The powers that be, assume impairment with an arbitrary
level measured.

How do you know this individual was not one whose body assimilated
alcohol in a manner that did not effect normal activities by any
measure (test)? Were the results of any impairment tests published?

The tolerance of long-term users of alcohol is somewhat of a myth.
Alcoholics certainly are able to appear to "hold" their liquor by not
having the same loss of motor skills and reaction times as casual users,
but those measures are not the complete story. Alcohol affects many
things, such as depth perception, night vision, the ability to do
multitasking, judgment, concentration, and so on. Many of these more
complex, but less obvious abilities are affected by the same amount
whether or not the person has gained a tolerance for alcohol. There are
precisely the skills that are necessary for safe flight.

Long term alcohol use does create a tolerance, which manifests itself
mostly in the area of motor skills. It takes a higher blood alcohol
content for an alcoholic to reach the same level of "impairment' as a
casual drinker, as measured by motor skill and reaction time testing.
However, while motor skills might be less affected, most research
suggests that alcohol equally affects those with an alcohol tolerance
and those without. Judgment and the ability to do several things at the
same time are prominent on those lists.

Alcoholics are the most dangerous, since they think they are not
affected, and other people don't notice the effects as quickly. However,
they do have many of the same physical reactions to alcohol,
particularly those which are critical to safety. These can include a
lowered ability to judge distances, to track other objects and determine
points of path intersection, some loss of night vision, and reduced
ability to absorb external information.

In particular, testing has been performed on simulators, and it has been
found that while a pilot with a tolerance for alcohol might be able to
fly a routine flight with an elevated blood alcohol level with no
noticeable problems, things change when his workload increases. The
alcoholic pilot tends to concentrate on the mechanics of flying to the
exclusion of all else, just as much as a casual drinker. This results
in a tendency to overcontrol, lapses in judgment, and a tendency to
block out more and more external information, such as inputs from
peripheral vision, radio communications, non-essential gauges, and so
on. In short, they focus, and lose the ability to absorb and evaluate
information. Imagine what happens in IMC with a partial panel failure,
or a fuel problem while trying to stabilize for landing.

Because alcohol has similar effects on all people for the more complex
tasks, the impairment levels are not arbitrary, and long term alcohol
use does not give people immunity from its effects.