Originally Posted by
beardy
IF it's a software problem AND it's the same software on both engines I would have expected that to impinge on ETOPs certification since the risk of the second engine doing the same thing is higher than if it were a mechanical (as opposed to design) fault. ETOPs is defined by acceptable risk of the other engine failing within a set time period and whilst demonstrated failure rate is a very good metric it should not, IMHO, be considered in isolation.
when put that way it is so logical, i do hope certifying bodies used same logic. long time since I did a long flight over water, and always preferred 4 to 2, having read your post that preference will remain in place.