Date: 15 Nov 97 16:24:42 From: "P. Wezeman" <email@example.com> 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"