Scoring Tests of Aircraft Transmission Lubricants at High Speeds and High Temperatures

Abstract : Aircraft engines always contain gears that have to be lubricated under conditions of high speeds and extremely high temperatures. In this field of application scoring damage can be likely to occur. In Europe and partly also in the USA the scoring load capacity of gear oils is expressed in terms of PZG Scoring Load Stage. The FZG Gear Test Rig is described. The normal test procedure A/8.3/90 as standardized in DIN 51 354 using A-type gears at a pitch line velocity of v = 8.3 m/s and a starting oil temperature of 90 C is presented. A modified procedure at double speed and increased oil temperature A/ 16.6/140 is discussed. The scoring load capacity of aircraft transmission lubricants is worldwide expressed in Ryder Gear Test results. Because of high costs and problems with the availability of test gears a modified PZG Ryder Test was developed. The method is presented and comparative results of typical aircraft engine oils in the FZG, the FZG-Ryder and the original Ryder Gear Test are shown. From this experience it becomes obvious that alternative test methods for the evaluation of scoring load capacity of aircraft transmisssion lubricants can be available in the near future.