Upgrade of Loss-of-Lubricantion Operation Capability for EC145T2 (BK117 D-2) Main Gearbox

EC145T2 (BK117 D-2) program is now under way by Kawasaki Heavy Industries (KHI) and Eurocopter Deutschland. In this program, the main gearbox (MGB) was upgraded by KHI to increase the power rating and improve the loss-of-lubrication (dry-run) operation capability to conform to the current Federal Aviation Regulation (FAR) requirement that requires 30 min safe operation. The modification of the MGB was minimized to maintain the high reliability of the current BK117 C-2 MGB and avoid any additional cost. The temperature distribution of the MGB under dry-run condition was estimated on the bases of KHI experiences of several dry-run tests and the characteristics of this MGB. The dry-run operation capability was upgraded by the modification of the bearing and gear design under the estimated condition without using additional devices, such as an emergency lubrication system or oil traps in the housing. The new design was verified by the preliminary company test and the type certification (TC) test to demonstrate the capability of 30 min level flight followed by landing after lubrication system failure. A 37 min 57 s dry-run operation was successfully completed in the preliminary test and 51 min 13 s dry-run operation was successfully completed in the TC test. The measured temperatures of bearings and gears were close to the estimated values. Through this program, the design modification method for dry-run operation capability was established. In this paper, the design policy and the result of the dry-run test are described.