Re: longest flight?

From:         Alan Wong <Alan.Wong@anu.edu.au>
Organization: Australian National University
Date:         08 Oct 96 13:00:08 
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I wrote:
>>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?

kls@ohare.Chicago.COM (Karl Swartz) wrote:
>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.

Having had a look at the ETOPS no-go areas, I can now answer my own questions.
The north pole and far northern Asia are off-limits. Current routes that go
or have great circle routes near the north pole include Europe to Japan/Korea
and Hong Kong to Chicago/Toronto. Routes between major centres that go near the
north pole are likely to be very long and deviations to the south will not be
a large penalty. In the case of Hong Kong to Chicago/Toronto, China is also
off limits, thus making the actual route further to the south (in addition to
the more southerly route to take advantage of the jetstream on the eastbound
sector).

>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.

Mmmm. This will also depend on how the aircraft is configured. For instance,
Qantas 767s were (probably still) not allowed to fly to Europe from Asia over
Afghanistan because their emergency oxygen packs were too small. If the plane
lost cabin pressure over Afghanistan, there wasn't enough oxygen to last till
the plane cleared the mountains. (Source: Australian Aviation) Other 767s such
as Lauda and Lufthansa/Condor had no such problems.

I do not think there are many other areas besides the Himalayas that poses major
problems. There are certainly high mountains elsewhere, but they tend to be a
narrow band (eg Alps, Andes) allowing stricken aircraft to quickly evade them.
The Rockies, on the other hand, are fairly broad, but many aircraft do cross
it.

>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.

As I mentioned before, China is also virtually off-limits except for a few
corridors.

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

Unfortunately, the only sectors currently flown are Johannesburg to Perth
and Melbourne, both of which are heavily penalised under 180 min ETOPS.
Similarly for other southern hemisphere trans-continental routes such as
Auckland to Buenos Aires and Johannesburg/Cape Town to Rio/Sao Paulo/Buenos
Aires. This will have implications for airlines such as Qantas, Air New
Zealand and South African Airways when purchasing aircraft eg A340 vs 777X.

Alan.