In article , vince
writes
The truth, for both aircraft and the V 22 is somewher between these
extremes.
The Boeing 777 for example is rated to fly for three hours and about
1300 miles on one engine.

That's more to do with the reliability of the chosen engine, after one
fails the chances of the other failing is statistically small to make it
improbable (as far as the regulations are concerned). The reliability
required when ERTOPS started (Extended Range Twin Engined Operations)
was something like less than one engine shutdown (on the engine type)
per 100,000 flight hours (that was when it was 120 minutes instead of
180).

All twins should fly on one engine after a fashion, for conventional
flight this is not too big a problem. The trade off is smaller because
you can trade climb performance, altitude and airspeed (to an extent)
for the extra power needed, so you don't need twice the power needed for
take-off to fly.

The V-22 IIRC is supposed to be able to land vertically on one engine,
and take off empty in an emergency on one engine. I'm not sure this
has been demonstrated yet.

The scenario I'm thinking of is a heavily laden V-22 leaving a carrier
with an engine failure occurring during transition. With very little
height or forward speed to play with (and the possible need to return to
the carrier for safe [vertical?] landing), it needs enough power to
maintain height on a single engine (by definition equal to its weight).

This scenario is significant because this is where many Harrier losses
occur (a problem that will always exist with fixed wing VSTOL aircraft
due to the envelope they operate in when hovering). There is no other
way to save the aircraft other than brute force vertical thrust.

The only way round it may be to take-off with a low fuel load and refuel
immediately, but that takes away some of the efficiency advantages the
V-22 claims.

--
John