In order to extend the fatigue life of an aging fleet of aircraft, a.fu2l scale air frame fatigue testudis conducted on a representative airframe in the laboratory. For simulating the service loadsudon the airframe, a spectrum load sequence has to be derived from the flight parametersudrecorded in the flight data recording (FDR) system. The data recorded on a magnetic tape isudtransferred to digital format through an interface along with other parameters that are enteredudby the pilot, such as weight of aircraft, stores carried, type of sortie, etc. The recorded data hasudto be "cleaned up" to eliminate electronic disturbance, tape related problems and intern7ittentuddata points.udThe noise elimination is solely dependent on experience one has developed after looking at theudvarious continuous parameters like Fuel Remainder, Vertical Acceleration (g,), Indicated AirudSpeed, Mach Number, Barometric Altitude, etc. The permissible minimum and maximum variations within a second, for each of the parameters form the basis for the elimination ofudnoisy data points. The FDR data has an advantage of recording all the parametersudsynchronously at an equal interval of one second. Hence the vectors of g, and fuel remainderudtogether with take off weight, as recorded by the pilot, can be used to obtain loads taking intoudaccount fuel consumption and the stores carried during the sortie.udA computer code has been developed for filtering spurious amplitudes/ excursions due to noiseudrecorded on the tape. The 'gv' is the acceleration normal to flight direction, while 'g,' and 'g,'udare longitudinal and lateral accelerations; data from a large number of FDR files are thenudarranged randomly, flight by flight, from which number of exceedings of various 'g' levels wereudcounted to arrive at a 'g' -exceedance curve that is representative of the service load history forudthe fighter aircraft. Finally, a representative spectrum load sequence was derived throughudanalysis of all these flight parameters, for full scale fatigue testing in the laboratory.ud(Full paper not available)ud
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