An experimental study on airplane ground performance on a grass runway

• A new method for airplane performance measurement on grass airfield. • Development of new measuring devices: IMUMETER for takeoff and landing distances and a portable wheel tester for braking action and rolling resistance. • Year-round measurement of soil moisture and cone index on five different grass airfields. • Ground performance measurement by means of flight tests. • A preliminary model for airfield performance. The article presents experimental research of airfield performance of an airplane on grass airfields. A new testing methodology was developed and two new measuring devices were designed and developed: a portable wheel tester for measuring wheel rolling resistance and IMUMETER device for measuring take-off and landing distances. Year-long tests were carried out on soil parameters that determine the traction performance of the aircraft landing gear wheel: soil moisture content and soil penetration resistance. The studies were carried out at 5 different airfields with grass runway located in south-eastern Poland and course of soil penetration resistance and moisture content variability during the year for the studied airfields was determined. Based on these results, relationships between soil moisture and penetration resistance were developed. The influence of soil type upon penetration resistance was discussed. Aircraft performance tests were carried out on two grass airfields. Take-off and landing roll distances were measured together with green vegetation unit mass. The test results showed that both the penetration resistance and the mass of green vegetation influenced the airfield performance, with the influence of vegetation being stronger than of soil. The rolling resistance of aircraft landing gear wheels was tested using two methods: dynamometric tow test and with the use of a portable wheel tester. The test results were used to develop a preliminary airfield performance model, which takes into account soil penetration resistance, soil moisture and the unit mass of green vegetation on the runway. Verification flight tests were performed and based on their results it was concluded that the proposed new model describes the performance well, but at high humidity, the results of ground roll distance are overestimated.