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uilt into the control system and automatically engages when LCO is detected. The F-16 is
perhaps the most notorious LCO prone fighter aircraft.
LCO Representative Case: F16
The thin, flexible wing supersonic F-16 fighter routinely encounters a range of LCO
mechanisms (4-11Hz) for its wide variety of store configurations. 14 The F-16 wing is a cropped
delta planform blended with the fuselage and is composed of a NACA 64A-204 airfoil with a
wingspan of 32 ft, 8 in. The wing aspect ratio is 3.2 and has a leading-edge sweep angle of 40
deg. It possesses nine external store stations, as shown in Figure 2-1: a pair of wingtip missile
stations; a pair of underwing missile stations; a pair of generally air to ground stations; a pair of
stations just outboard of the fuselage, generally used to carry fuel tanks; and a centerline station.
The centerline station is considered not to have a significant effect on the aeroelastic
characteristics of the F-16. For a given takeoff configuration, thousands of downloads may be
possible.
For the F-16, wing-store flutter usually takes the form of LCO instead of classical flutter,
which is normally divergent and catastrophic. Aerodynamic and stiffness non-linearities limit the
amplitude and prevent divergence. Note that the non-linearities do not cause the LCO, instead
they serve to inhibit divergent flutter by limiting its amplitude. The F-16 has two primary LCO
mechanisms. Others exist but apply only to store loadings peculiar to certain countries.
The first type of LCO mechanism consists of configurations containing heavy stores and
AIM-9 missiles. The most significant mechanism is heavy stores with high pitch inertia at
stations 3/7 and AIM-9’s on the wingtips. Generally, the characteristics of these mechanisms are
only antisymmetric and occur around 5Hz. The driving LCO mode is a result of a coupling of the
wingtip AIM-9 pitch mode and the heavy store pitch mode. The presence of other stores affects
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