It used a pair of Watson angle and rate sensors and appropriately scaled gains to reduce both pitch and roll motion. Measured pitch and roll angles and rates were used in real time to actuate one pair of fins near the stern at properly scaled rates, and with scaled frequency response characteristics. When reoutfitting was complete, the model was shipped to Bethesda, MD for radio-controlled seakeeping tests. It is one of the few facilities in the world suitable for testing a free-running model of the Regency's size and speed at all headings, in accurately simulated sea states. The test program consisted primarily of 33 runs with the active control system functioning at a full-scale speed of 37 knots at 5 headings in a simulated seaway with a 3.5 m significant wave height and a modal period of 6.0 sec.
Modal period is the period of maximum wave energy.
Multiple runs were made at each heading to improve the statistical reliability of the data. Most of these runs were at a beam heading. Two fixed fin runs were also carried out in the same 5.0 m beam seas. The accompanying Figure shows the stages of data acquisition and transmission from the free-running model to the data analysis computer located alongside the MASK tank. Eight channels of analog signals from the sensors on the model were digitized using the transmitter's A-D card, and then were multiplexed and transmitted to the shore based receiver via the radio telemetry link.