Acquiring Tail Load Spectra from In-Flight Measurements

摘要

In order to obtain fatigue-load spectra for the design of aircraft tailstructures a number of (usually simplifying) assumptions are made in order to account for the effects of: (1) external disturbances (gusts, turbulence), (2) control inputs (elevator, rudder, tail plane trim); and (3) aircraft response behavior. The derived spectra cannot easily be verified, at least not with measured data, since service-load measurement programs that have been conducted in the past were mainly concentrated on measuring and registration of vertical accelerations of the aircraft at the center of gravity. These accelerations are a good measure of main-wing loads, but the correlation with tail loads is usually poor, in general the relation between aicraft tail loads and aircraft motion parameters is insufficient for the derivation of tail loads and tail load spectra. Therefore the best and most direct way to obtain aircraft tail loads is by measurement using calibrated strain gages. To this purpose a measurement program has been started in the Netherlands in order to validate the procedures that are currently used for the determination of tail load spectra and to improve the statistical knowledge of gusts and manoevuers, with respect to tail loads. In this measurement program tail loads are obtained from a commercially operated Fokker 100 aircraft in service with a Dutch airline company (KLM).