The aim of the HELMGOP II project was to investigate the performance of a mist lubrication system using commercially available thioether lubricant (MCS-293TM) on a helicopter main gearbox as compared to a conventional oil jet lubrication system.
In order to achieve this, experimental investigations were performed involving loss of oil on a representative helicopter main gearbox on a complete test rig with a high-speed input drive and a passive dynamometer to power the MGB and to subject it the necessary loading conditions for the lubrication tests. A mist lubrication system capable of delivering a controlled flow rate of the thioether lubricant and pressurised air had been designed and built for the experiment which provided adequate lubrication to the MGB gears and bearings with minimal impact to the original lubrication system.
While some positive effects of the thioether lubrication were confirmed, there were some difficulties to demonstrate the overall goal of emergency lubrication due to the inability of the thioether mist to penetrate the high speed input bearing because of windage. A follow-up project Helicopter Main Gearbox Health (MGH) will aim at overcoming this hurdle.