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CH04_Anderson 7/25/01 8:57 AM Page 105

Stability and Control 105

horizontal stabilizer and trim tabs maintain pitch stability and it is the
elevator that controls the pitch.

Flying Wings
Today there are examples of airplanes that have no horizontal stabi-
lizers, such as the B-2 bomber shown in Figure 4.4. How can that be?
It would seem impossible for the airplane to compensate for any shift
in loading. If the B-2 copilot decides to move to the aft cabin, will the
B-2 flip? This is the tricky part of designing a flying wing. In
John Northrop was a talented
this case control surfaces on the trailing edge of the wing
engineer who worked for both
move up or down in unison, like an elevator, which moves the
Lockheed and Douglas. Northrop
center of lift forward or aft, depending on the location of the
was a strong advocate of flying
center of gravity. These control surfaces both balance and sta-
wings. He started his own
bilize the airplane.
company to develop the flying
Figure 4.5 shows a picture of the Northrop YB-49 Flying
wing with the first model, a
Wing, which flew in the late 1940s. In the picture one can see
piston-powered version of the
the two control surfaces, both in the down position, allowing
YB-49 (Figure 4.5).
them to act as elevators and flaps.

Fig. 4.4. B-2 bomber.