Traditional means of dynamically balancing propellers -- adding counterweights -- allows for proper balance at one specific operating condition and for a limited amount of time since the propeller blade angle and aerodynamic loads change during flight. The negative effects of propeller imbalance vary from passenger discomfort to fatigue of on-board equipment. The effects of wear on the system also degrade balance over time. Significant costs are expended keeping vibration under control or simply monitoring its effects so as to predict potential failures. In comparison, the IPBS continuously repositions balance weights as needed during flight operation. The result is propeller balance maintained at the lowest possible level during the entire flight and reduced Direct Operating Costs.
A four-hour flight test was conducted in 2004 with sponsorship and oversight from the USAF Air Mobility Battlelab and engineering support from the Robins Air Force Base C-130 System Program Office (330th ASG). The demonstration began with the installation of an IPBS on a 54H60-91 Hamilton Sundstrand propeller system. Several typical flight profiles were conducted with the support of the 339th Flight Test Squadron of Warner Robins Air Force Base, Ga. Although vibration levels varied throughout the power spectrum on the 54H60-91 propeller, once activated, the IPBS proved it could maintain vibration levels at approximately 10 to 20 times less than any condition between thrust reverse (-6,000 inches-pounds torque) and maximum power (18,600- inches-pounds torque). Throughout this operating range, the required balance corrections varied in both amplitude and in angular position. In addition, the performance of the IPBS was unaffected by ambient air temperature from ground to 20,000-feet. The data gathered demonstrated that the IPBS is capable of performing required corrections automatically and reliably, with no additional workload for the flight crew.
According to Meyer, the tests demonstrated that the EM-IPBS concept is a robust in-flight system for turboprop aircraft that should produce significant operations and support savings, realized by eliminating the lengthy maintenance actions required to periodically balance propellers per the requirements. The reduced maintenance also will increase readiness by returning aircraft to the operational squadron earlier. Further, the large reduction in propeller vibration should provide a significant decrease in the maintenance cost of engine, gearbox and airframe mounted equipment. The high level of predictive maintenance afforded by IPBS also can be used to provide Prognostic Health Management (PHM) and diagnostics information to maintenance crews. Since the system results in less fatigue for both on-engine and on-board equipment, as well as lower failure rates, Direct Operating Costs (DOCs) are reduced.
With headquarters in Cary, N.C., and sales in excess of $630-MM, LORD Corporation is a privately-held company that designs, manufactures and markets devices and systems to manage mechanical motion and control noise and vibration; formulates, produces and sells general purpose and specialty adhesives and coatings; and develops products and systems utilizing magnetically responsive technologies. With manufacturing in nine countries and offices in more than 15 major business centers, LORD Corporation employs more than 2,400 worldwide. Visit www.lord.com for more information.