Mr AirNz From New Zealand, joined Feb 2002, 867 posts, RR: 1
Reply 3, posted (12 years 4 days 18 hours ago) and read 819 times:
Etops, aka Extended Twin Range Operations is where a twin engine aircraft is permited to fly over vast distances (eg oceans) as long as it stays close enough to certain airports. This is so if it suffers an engine failure it can land at one of these airports. For example, an aircraft certified for 180 minutes etops can fly anywhere as long as it stays within 180 minutes of one of these suitable airports. To get etops certification, each airline must meet certain maintenance requirements etc.
Rick767 From United Kingdom, joined Jan 2000, 2662 posts, RR: 51
Reply 6, posted (12 years 4 days 17 hours ago) and read 799 times:
ETOPS does not have to be 180 minutes of course. Any extension of the standard 60 minute rule for twin engined aircraft is classified as ETOPS (e.g. 120 / 138 minutes). 180 minutes is the most popular these days, but our 757ER aircraft are only 138 minute certified whilst our 763s are 180 minute.
The 763s also used to be 138 minute many moons ago.
As VirginFlyer correctly states, the time requirement is based on the single-engine cruise speed (so 180 minutes = 3 hours at the single engine cruise speed). For the 757/767 this equates to 1,200nm in still air.
Also worth noting that if on a non-ETOPS route you must stay within 60 minutes of an adequate airfield, but on an ETOPS route you must be within the time limit of a suitable airfield. There is a subtle difference between the two, based on the weather and availability of approach aids etc..
I used to love the smell of Jet-A in the morning...
VirginFlyer From New Zealand, joined Sep 2000, 4575 posts, RR: 40
Reply 8, posted (12 years 4 days ago) and read 713 times:
QANTASpower - might I suggest this website: http://gc.kls2.com/. It will calculate great circle distance, and plot the route on a map, between any two points in the world (well, almost any two - it has difficulty of course with antipodean points). Just as an aside in case you don't know, great circle is the shortest distance between any two points on the globe - effectively what it is is if you were to take you two points, and then put an 'equator' that went right around the earth, that would be the great circle path.
Anyway, the other useful feature of that site is that it will show you what areas are 'off-limits' for ETOPS operations for the various applicable time rules. Of course, as different aircraft cruise at deifferent speeds, it isn't 100% accurate, but it gives a good idea. According to the mapper, the great circle route for SYD-LAX is doable under 180 minute ETOPS or greater. Of course, airlines don't just fly along the great circle route - prevailing winds and such are also taken into account. But again, it gives a good general idea.
Hope this is useful
"So powerful is the light of unity that it can illuminate the whole earth." - Bahá'u'lláh