What are "secondary precessional forces" that apply to boomerangs in flight?
The aerodynamic forces on the boomerang are roughly like the springs that limit the (primary) precession of a rate gyroscope.  These forces introduce a secondary torque, which in turn produces the secondary precession in question, which is needed to tilt aka &quot;lay over&quot; the boomerang.  (My physics is rusty; the physics SE may be more fruitful.)