"Greg D. Moore \(Strider\)" wrote:

Of course it doesn't work that way in practice.

Person 1 looks and says, "hmm, looks good, besides, if I'm wrong, #2 will
catch it."
Person 2 looks and says, "well I'm in a hurry, I'm sure #1 caught anything,
besides, that's why #3 is there."
Person 3 looks and says, "well, I don't want to be the guy that calls out #1
and #2 for being wrong, so I won't say anything. I'm sure if this was
really a problem, they'd have caught it."

Adding people like this does not necessarily make things any safer and in
fact can make things less safe.

What's the cause and effect here? Having too many people, or poor
implementation/allocation of responsibility, or poor training and
supervision?

The way to properly due this is to focus on failsafe procedures. For one,
an interlock that doesn't permit the clock to go past X time unless the door
is registered as closed (and I'd be surprised if they don't have this).

On submarines we have a switch that operates a remote display in the
control room indicating whether or not a hatch is shut - but when
shutting the hatch we still had people verify the hatch shut and
locked. The indicator was used to verify that conditions had not
changed, but eyeballs and hands (two pairs of each) were used to
establish that condition.

The people are mostly a feel-good measure.

And insurance against instrumentation failure.

Nine time out of ten the switch on the hatch I was usually associated
with shutting after a period inport was non functional because it had
been bumped or damaged as the hatch in question was the main access
and loading path into and out of the submarine.

And even after the care taken while shutting the hatch, and the care
taken to verify its condition on shutting - when we went deep we
regularly (as in every five minutes or so) verfied the hatch remained
shut and not leaking for the entire time we were deep.

When our asses were on the line, if possible we didn't trust
instrumention, and if *required* to trust instrumentation we had two
completely seperate instruments wherever possible/practical. We had
three different instruments for measuring depth - two on seperate
power circuits, and the third was mechanical.

Think about when you fly. The flight attendants are told to check the doors.
They don't have all 3 or 5 or whatever check every door. And for the main
loading door, they have a procedure to make sure the door is locked and the
slide enabled.

When's the last time you heard of a door on an airliner not being sealed
properly?

I suspect that if on takeoff an airliner was committed irrevocably to
a course where minor door failure was extremely dangerous, even if an
abort was laid on, and the door absolutely had to perform for as much
as two weeks... They just _might_ treat them differently.

That they have had decades of experience and millions of operational
cycles might also have something to do with it.

D.
--
Touch-twice life. Eat. Drink. Laugh.

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL