Re: Boeing considering ultra-long range 747-200X

Date:         15 Nov 97 16:24:42 
From:         "P. Wezeman" <pwezeman@blue.weeg.uiowa.edu>
Organization: The University of Iowa
References:   1
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On 5 Nov 1997, Karl Swartz wrote:
> Flight International, in the current issue, reports that Boeing is
> evaluating airline interest in an ultra-long range 747 based on the
> 747-400F and seating 355-380 passengers in typical configurations.
> Range would be 9,200 statute miles (14,800 km) compared to 8,380 mi
> (13,480 km) for the 747-400.
>
> The 747-200X moniker suggests that the proposal would use the small
> upper deck of the 747-400F (same size as the 747-100/200) with the
> airframe weight reduction allowing the increased range.  (According
> to www.boeing.com, the MGTOW and fuel capacity of the 747-400F is the
> same as the passenger version, so the freighter airframe doesn't seem
> to offer any benefit in that regard.  What happened to the freighter
> having a stronger wing that boosted it from 875,000 lbs to 920,000 lbs
> MGTOW?)

   This seems practical. According to "Jane's All the World's Aircraft",
the 747-400F has a maximum unfueled weight of 610,000 lb., which is with
250,000 lb. payload. With this payload, the range at maximum gross takeoff
weight (875,000 lb.) is 5,063 miles. Assuming that it would reach this
distance with 45 minutes of fuel, say 15,000 lb., the weight at the end
of the flight if 625,000 lb., for a ratio of initial mass to final mass
of 875/625 or 1.40. Using Breguet's equation for range, which states that,
other things being equal, range is proportional to the natural logarithm
of the mass ratio, to fly 9,200 miles would require a mass ratio of about
1.84. Taking off with 875,000 lb., the weight at 9,200 miles would
be about 475,000 lb. Subtracting 360,000 lb. for the empty weight of
the plane, and 15,000 lb. for a 45 minute fuel reserve, this leaves
100,000 lb. payload, which should be enough for 380 passengers, although
this would also have to include the seats, overhead baggage racks, cabin
attendants, service carts, and anything else needed which is not part of
the empty weight of a freighter.
   It has been claimed that the 747-400 has less aerodynamic drag than
the 747-400F, as the longer upper deck gives the 747-400 better
area ruling. If this is correct, they might get slightly better
performance by shortening the 747-400 at both ends to accommodate the
reduced number of passengers. Compared with putting seats in the 747-400F
this would obviously be a lot more expensive, but the work would be
essentially the same as they did earlier in developing the 747SP.

                        Peter Wezeman, anti-social Darwinist

                             "Carpe Cyprinidae"