2193. Accuracy in Weighing Aircraft: Second and Third Order Effects and Techniques for Their Corrections
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Paper
Abstract
The first order effect of the application of an aircraft’s mass to a load cell is to generate an output voltage shift proportional to the mass. Second order effects influencing this output include the geometrical nonlinearities from integrating the stress-strain effect on a spring element. Other second order influences include temperature vs. span, altitude and latitude vs. the mass/weight ratio, and the angle of the platform surface. Vibration and wind effects could also be considered second order influences. Third order effects include material nonlinearities, hysteresis, creep, and residual side loads. This paper will discuss the genesis of these various effects and the correction techniques that are established along with some possible solutions for the future. Present fully electronic strain gage load cell aircraft scales are capable of weighing aircraft to an accuracy of about 0.1% or 1000 ppm. Without compensation for effects due to such things as latitude, altitude, and wing lift this error grows to 1%. With advanced calibration techniques and mathematical tracking of second and third order effects the error in aircraft should be reducible to about 100 ppm.
