Re: Fracturing the Pacific

Date:         27 Aug 97 03:57:54 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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M Carling wrote:
>Thomas Holland <innot@frankfurt.netsurf.de> wrote:
>> jimcam@arctic.ca wrote:
>>
>> > With 3 hours ETOPS you can take a 767 anywhere
>> > through the Arctic.
>>
>> Unless some airports are unavailable due to weather (not unlikely).
>
>Exactly. The questions are: 1) how many days each year will enough suitable
>airports be available to permit crossing the Arctic without unacceptable
>detours, and 2) given however many days per year that is, can a carrier make
>money on the route, given the cost of an added stop on the days when bad
>weather requires it. This is quite speculative, and there is plenty of room
>for disagreement.

It's only speculative in the absence of the facts, which shouldn't be
*that* difficult to obtain.  Given the number of days per year, you
can calculate the rest.  An early paper on ETOPS (V. W. Attwooll, "The
Extended Range Operation of Twin-Engined Public Transport Aircraft,"
Journal of Navigation, vol. 38 no. 3, pp. 423-430, 1985) goes through
this exact exercise with the North Atlantic.

In that paper, they also talk about the future availability of the
alternates:

    One obvious requirement of an alternate airport is that it shall
    not be low weather minima when it is needed.  As shown above, the
    planned route must be decided on the assumption of the
    availability of certain alternates.  Alternates nominated at the
    flight planning stage must have a high degree of expectation of
    being open if required.  One proposed method of achieving this is
    to require that the forecase weather at nominated alternates shall
    equal or exceed that required for single-engined landing
    multiplied by a suitable factor.  This factor is intended to allow
    for deterioration and forecase error over the interval of a 3 to 7
    hours between the flight planning time and the time the alternate
    might actually be needed.  In ICAO studies the factor was taken as
    three.  This rule has implications for the economics of operation
    (frequency of flight cancellations).  These are discussed below.

The paper then goes on to include the following tables:

Table 3. Frequency (%) of airfield conditions falling below
         required minima, including factor

                ----- factor -----
                1.5     2.0    3.0

Keflavik         3       5     10
Sondrestrom      5       8     13
Narssarssuaq    39      50    >50

Table 4. Frequency (%) of flight cancellations due to the
         unavailability of alternates

             Essential                 ----- factor -----
Rule-Time    Alternates                1.5     2.0    3.0

60 minutes   Prestwick, Keflavik,      30      40     53
             Sondrestrom, Frobisher,
	     Goose
90 minutes   Keflavik                   8      13     22
120 minutes  Keflavik                   3       5     10

(The paper further notes that Reykjavik and Akureyri airports, while
not as suitable, could substitute for Keflavik in a pinch, and that
Akureyri has substantially different weather patterns.)

The same analysis can be done for the various Arctic routes.  There
didn't seem to be much speculation or room for disagreement in 1985,
so I don't see why there should be now except for the frequency of
airport unavailability.  Your entire premise seems to be that the
various Russian airports are unavailable *far* more often than Sondre
Stromfjord (which I'd expect to have pretty nasty weather at times).
Absent any facts to substantiate that, I find the argument singularly
unpersuasive.

--
Karl Swartz	|Home	kls@chicago.com
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