I just spotted a Boeing 777. These planes are big. Unbelievably big. So big that if you really know how big a 777 was, your brain would try to suffocate itself.
Sorry. I saw the HGTTG movie recently. Back to the topic at hand.
Anyway, the B777. The interesting thing about the 77—apart from its enormous size—is the fact that it is currently the only two-engined plane in the world to carry a transpacific certification. You can see in the photo below that ETOPS is written on the 777's Section 41*.
In the simplest sense, ETOPS is a certification to fly transpacific flights. Now, I'm unsure who has the authority to approve aircraft for flight over international waters but I suspect that the FAA has their grimy little hands all over it. It could also be the insurance companies, but I'm really not sure.
Prior to the certification of the 777, the only aircraft "approved" (whatever that means) to fly across the Pacific were the A340, DC-10, L-1011, and of course the ubiquitous 747. I'm unsure of the 707 and older models (the DC-8, the piston-engined Constellation, etc.)
All of these aircraft has at least three main engines. Primarily, people get jumpy about this sort of thing for safety reasons: an aircraft is better able to perform if it loses an engine if it has more engines to begin with.
The logic breaks down, however, when we learn that the DC-10 and L-1011 (and possibly the 747, although I'm unsure) are unable to operate with more than one failed engine. Thus, we don't gains a redundancy advantage and we may presume that, because the 777 is a newer airplane, it has more reliable engines.
ETOPS is evaluated in terms of time-to-fly once a failure occurs. Presently, the 73 is rated for 120 minutes (I believe) of single-engine flight, and I've heard that they are applying for a 180 minute certification. This allows them to fly routes where they will be, at any given time, no more than 120 minutes from a suitable landing strip. Of course, increasing this envelope increases the number of locations that a 73 can fly to.
It is my understanding that the 777 gained its ETOPS cert by demonstrating single-engine flight for over 6 hours. I think.
Damned impressive, if you ask me.
* Section 41 is the Boeing internal designation for the nose and cockpit assembly. This system is used—modified only slightly—on the 767 and 777. I remember hearing that the 737 and 757 share a similar component. See the photograph below—there is a ring around the cockpit just a few feet back from the windows. This is the Section 41 separation.
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