Helicopters characteristically exhibit large amplitude vibration at low frequencies, often caused by the main rotor-induced shears and moments. To reduce these vibrations, the rotor is designed to minimize the induced shears and moments, and the fuselage is designed to be free of resonance at the frequencies of these rotor-induced inputs. Also, many helicopters employ vibration mitigation devices.
Under the sponsorship of Eustis Directorate, Kaman Aerospace has conducted experimental and analytical studies of the Dynamic Antiresonant Vibration Isolator (DAVI), an inertially coupled isolation device which permits a high degree of isolation at discrete low frequencies without sacrifice of elastic stiffness.
The principles upon which the DAVI is based and laboratory test results are presented to show the independence of DAVI isolation from the weight of the isolated item. The application of the DAVI to crew seat isolation is also discussed. A summary of the work done on the application of the DAVI to helicopter rotor isolation, including results of analysis and testing, is presented.