Page 80 - Understanding Flight

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Wings 67

Fig. 3.8. The X-29 with its forward-swept wing. (Photo courtesy of NASA.)

DC-8 in Figure 3.9. There are several advantages to tapering a wing.
One reason to taper a wing is to adjust the load along the wing’s
span. The designer wants to distribute the wing loading such that it
is reduced at the wingtip. A high tip loading will put a large bending
load on the wing. This means that the entire wing structure has to be
built stronger, and thus heavier, to handle the load. If you hang a
swing from the end of a tree branch, the branch will bend consider-
ably. Thus, we know from experience to hang the swing closer to the
trunk of the tree. A rectangular wing will have a large tip loading and
so will require a stronger structure. A tapered wing reduces tip load-
ing and thus results in a lighter wing structure.
The primary disadvantage of a tapered wing is that it is more
On June 13, 1979, a human-
difficult to build. Most small, inexpensive aircraft use at least
powered airplane, the
part constant-chord wings. The wing of the Cessna 172, shown
Gossamer Albatross, crossed
in Figure 3.10, is a good example of a part constant-chord wing.
the English Channel. On July
A well-known example of a constant-chord wing is the 1960s
7, 1981, the solar-powered
line of Piper airplanes called the Cherokee, shown in Figure 3.11.
Solar Challenger crossed the
These early Cherokees had a wing that was dubbed the
English Channel.
“Hershey Bar” wing since it looked like a Hershey chocolate bar.