Lockheed Hercules C-130H Qualification/Evaluation Manual page 10

When power is advanced, the aircraft yaws LEFT and RIGHT RUDDER must be applied to keep
the aircraft in trim.
The C-130 experiences a marked reduction of directional stability at low dynamic pressures, high
power settings, and at elevated side slip angles. This reduction in directional stability is
manifested to the pilot as a low rudder force gradient (small rudder forces produce large side slip
angles). There are several contributors to this reduction in directional stability, one of which is
the normal force produced by the propellers when the propeller is at an angle to the oncoming
flow:
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