22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-5.3.3

IN-FLIGHT THRUST DETERMINATION BY LOAD MEASUREMENT ON THE ENGINE MOUNTING SYSTEM

H. Muhammad, Muhardi, W. Kuntjoro, B.E. Sritjahjono
Department of Aeronautics and Astronautics, Institute of Technology Bandung, Indonesia

Keywords: in-flight thrust measurement, engine mounting system, drag, performance

In-flight thrust measurement is of much interest as it allows, in principle, to verify the specified engine and propeller performance as well as to quantify the drag of the aircraft. Classical methods rely on well known techniques to determine propeller thrust in steady straight flight conditions, using data from the engine and propeller manufacturers. For the aircraft manufacturer the disadvantage of having to rely on data from the engine and propeller manufacturers is that any aircraft performance shortfall becomes identical to a larger than predicted airframe drag and consequently the sole responsibility of the airframe manufacturers. This paper describes an alternative method of the in-flight thrust measurement, which does not require data from engine and propeller manufacturers and consequently would allow an independent assessment of thrust and drag. In principle, the thrust of the propeller is transferred to the airframe through the engine mounting system. By measuring the loads on this engine mounting system, the thrust of the propeller can be obtained. A flight test program to determine the propeller thrust using small piston-prop PZL- 104 Wilga-Nurtanio ‘Gelatik’ laboratory aircraft of the Department of Aeronautics and Astronautics, Institute of Technology Bandung, has been performed. Eight strain gauges were installed on the structure of engine mounting system of this aircraft. The propeller thrust obtained from the flight test program will be presented and discussed in this paper. Comparison with other test results using other methods to derive propeller thrust will be also given.

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