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Fig. 3.16. The C-130 Hercules demonstrating fuselage upsweep. (Photo courtesy of
Paul Burke.)

wing spars (the internal beam supporting the wing) can carry Many did not believe the Wright
through the lower fuselage below the passenger deck, resulting brothers had flown in 1903.
in a continuous spar structure. This allows the wing to be fully Until their demonstration in
cantilevered (supported by one end) with no need for external France in 1908, the French
bracing. Most commercial transports since the DC-3 have called them the “Wright liars.”
chosen this approach. Because the fuselage is positioned higher
than for a high-wing airplane, there is less need for fuselage
upsweep. The primary disadvantage is the requirement for long landing
gear to provide ground clearance for engines.

COWLING SAVES THE BOEING 737

The Boeing 737 was initially designed with turbojet engines
(see Chapter 5).To improve efficiency the move was made
to turbofans engines, which have a bigger diameter.The
Boeing 737 had been designed close to the ground since
the small-diameter turbojets did not need much clearance.
Boeing had difficulties retrofitting the Boeing 737 with
turbofans engines with so little clearance.The result is an
unusual cowling design (see Figure 3.17) that is flat near
the bottom.The insert in the picture is of the old engine
for comparison. Creating this innovative cowling saved the
Boeing 737, which has now become the most popular
commercial jet airplane in history.