Re: longest flight?

From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
Date:         25 Sep 96 13:40:12 
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>This opens up an interesting topic. What are the major routes (either
>currently possible or likely to be possible in the not too distant future)
>that cannot be flown with 180 minute ETOPS? The ones that come to my mind
>are flights over southern hemisphere oceans ie flights linking Australia,
>Africa and South America. Tahiti to Los Angeles seems to be one and possibly
>Europe to southern South America. In contrast, I believe that all intra
>northern hemisphere routes can be done by 180 minute ETOPS. Any comments and
>corrections?

My great circle mapper (http://www.chicago.com/airliners/gc.html) can
now plot ETOPS go/no-go areas, though the data is not complete so
there may be a few holes that are in fact flyable.

Some northern hemisphere routes aren't flyable, even with a 180 minute
rule-time, if you stick with the shortest route.  Um ... try MIA-BKK.
(Perhaps not a highly probably route, but it illustrates the point.)
It goes right over the pole, and up there, you're not near any sort of
alternate.  Large expanses of northern Asia are also off-limits.

Another factor in the northern hemisphere is mountains.  As a Qantas
pilot recently reminded me, lack of airports isn't the only reason for
no-go areas.  The Himilayas pose a problem for a twin with one engine
out.  They're also a problem for *any* airliner that loses cabin
pressure since descending to an altitude with breathable air would
require you fly underground.

Now think about Delhi to Northern Europe (LHR, FRA, CDG, for example).
I heard that Afghanistan may become off-limits for US carriers, which
requires only a modest diversion to the north, but that takes you into
the mountains.  Diverting to the south is longer, but it takes you
over Iranian airspace, which surely is off-limits for many carriers.

Ok, that's wandering away from the ETOPS issue.  In looking for some
really long routes that weren't too far-fetched, I noticed HKG-SCL and
HKG-EZE.  (SCL = Santiago, Chile; EZE is Buenos Aires, Argentina)  SCL
is a bit longer, but EZE is almost entirely in non-ETOPS (even 180
minute) territory the whole way.  Someone suggested LIM-BKK which is
considerably further, but it looks to be easy for ETOPS.  At these
distances, you may be close enough to opposite sides of the planet for
nearly any route to be close to the great circle, allowing you to pick
one that allows ETOPS -- assuming a twin would have the range.

Europe to South America is not a problem.  In fact, most of Europe to
the eastern part of South America (including Rio and Buenos Aires) can
be done with 120 minute ETOPS with little or no penalty.  There's a
hole in the Atlantic that poses a problem for routes like LHR-CCS
(Carracas, Venezuela) but it all but disappears with a 180 minute
rule-time.

Australia to Africa is mostly ok -- only the southerly points get bit
by a lack of suitable island alternates in the southern Indian Ocean.

--
Karl Swartz	|Home	kls@chicago.com
		|Work	kls@netapp.com
		|WWW	http://www.chicago.com/~kls/
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills