OK, I stand corrected. :-)  The point was a triple engine failure due to
the same maintenance error repeated three times.  This is the key flaw
in the triple redundancy approach if you don't stagger your maintenance
on the three units.

Bill Freeman

Mark wrote>
The introduction of ETOPS (Extended Twin Ops - Allowing twins to fly up to
207mins from an Alternate) has had a huge effect on airline safety. Due to
the concerns Bill mentioned, ETOPS certification requires that an Airline
prove that their maintenance program is set up to avoid dual maintenance on
critical systems during a single ground time. If it can't be avoided, the
work must be performed by independant crews, it this can't be done, the
aircraft will be downgraded to Non-ETOPS for the next flight.

The effect of this has been so positive on safety that most 3+ engine long
haul operators adopted this principle for their aircraft, although it is not
strictly required. The next version of the 777 (LR - Long Range up to 18
hour commercial flights) will mark the move beyond ETOPs to LROPs. This will
remove the artificial limits (like 180 mins from an airfield) to be replaced
by aircraft limits. eg an A/C may have a 5:20 limit on oil quanitiy under
MAXCON thrust. They are looking at the next improvements to maintenance
safety.

Then again, who wants to fly for 18 hours? Imagine Sydney-Rio via the south
pole. About 7 hours with no alternate after you pass Christchurch.
Wrathall Mark 

 
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