Comment by Aloisius
1 year ago
Six 9s would be half a minute of downtime per year.
I don't see how that is possible given the maintenance required for these planes. Even the simple A checks ground a plane for hours every couple hundred flights while D checks take months to complete every 6-10 years.
Edit: minute not hour
> I don't see how that is possible given the maintenance required for these planes
You normally only count unplanned downtime in those stats for aircraft.
By my math, six 9's is 30 seconds, not 30 minutes?
(1 - 0.999999) * (60 * 24 * 365)
EDIT: This chart agrees: https://en.wikipedia.org/wiki/High_availability#Percentage_c...
You are correct. Forgot what my units were in bc.
The six 9s are probably meant as catastrophic failure rate, not downtime.
It counts any event where the plane has an unplanned event including unscheduled maintenance, unplanned flight deviations, and of course catastrophic failures.