Re: B777 range

Date:         19 Dec 96 03:06:34 
From:         matt@firstsol.com (matt weber)
Organization: 1st Solutions Inc.
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In article <airliners.1996.2791@ohare.Chicago.COM>, Chuanga@cris.com says...
> Two possible routes
>for the ultra-long-range aircraft mentioned in the report were
>Dallas-Hong Kong and Singapore-Los Angeles.  I guess it's fairly
>obviously which two airlines are most interested in the aircraft.
>(However, based on other reports, it seems to me that Singapore Airlines
>was more interested in the B777-100X.)

An analysis indicates that neither route (SIN-LAX or HKG-DFW) is like to be
reachable  non-stop in the other direction, i.e LAX-SIN or DFW-HKG. LAX-SIN is
about 7300nm via the great circle. The reality is that it is hard to fly it
that way, so the real distance is probably more like 7600nm. DFW-HKG is a
little better, but the problem in flying a perfect great circle route are
worse. You probably end up with abou 7200nm of so. The analysis however
neglects two important issues.

1 ) Both routes would fly much of the trip head long into the jet stream for
much of the flight. Anyone who doesn't realize how much of a problem that is
should take a look at the flight times for HKG-LAX versus LAX-HKG. One if
flown against the wind, the other flown with the wind. LAX-HKG is 3 hours
longer, and probably is very very close to ultimate endurance on a 747-400.
LAX-SIN would fly over almost exactly the same route, only has more than
1000nm further to go. That suggests the 777 needs an ultimate endurance of
more than 17 hours to make the trip in the winter. The situation from DFW is
better, but not a lot better. In the summer months the prevailing wind
situation is better, but you trade that problem for another problem.

Range is under standard conditions, and in still air. In the winter, it is
anything but still air. In the summer, it tends to be a good deal warmer than
standard conditions at both LAX and DFW. I don't know about CX, but QF 8,
which flies LAX-SYD operates with serious payload restrictions, and generally
summer tempertures at LAX knock about 10,000kg off the maximum takeoff weight
for QF8.I suspect it would knock a similar amount off MGTOW on a 777. On a 777
that is probably about 90 minutes worth of fuel.

Airlines routinely limit payload to extend the range, the problem is I am not
sure you can limit the payload enough to allow these flights to operate with
any load at all. I note that UA seems to have quietly stopped the ORD-HKG
non-stop service I suspect the winter wind conditions pushed the flight times
out past what the aircraft could do. When it did operate, I believe a poster
to this newsgroup indicated it was being restricted to 265 or 285 passengers
(more than 100 empty seats). I have a feeling it carries almost no freight. I
know that when QF operated 747-SP's on the LAX-SYD run, which was very close
to ultimate endurance on the aircraft, the average freight lift out of LAX was
100kg! Even  today QF 8 usually carries only 3500kg of freight.

The improved range 777 would be able to make the HKG-JFK run fairly easily.
The wind situation tends not be as bad for as much of the flight, and the
trip is about 500nm shorter than LAX-SIN. Also JFK probably isn't as warm as
often as LAX or DFW, so you can operate at higher weight more of the time.

I have no doubt that both SQ and CX are interested in the aircraft, I just
doubt they are for the routes suggested.

My opinions and experiences anyway.