A simulated payload apparatus (SPA) for testing in a flight motion system (FMS), which has a body for mounting in the FMS, and which simulates an actual payload during the FMS test. The SPA may include a plurality of adjustable weights that are mountable on and/or removable from the body to vary the mass and/or center of gravity of the SPA. The SPA may include an adjustable bracket for interfacing with a motion drive of the FMS, in which the bracket is positionable along the body to vary the moment of inertia of the SPA. The SPA may include an onboard electronic measurement device that is configured to measure a motion characteristic of the SPA and/or communicate information about the measured motion characteristic in real-time during the FMS test. The SPA may include a laser alignment for aligning the SPA relative to test equipment of the FMS.