Intermittent fault detection on an experimental aircraft fuel rig: Reduce the No Fault Found rate

Abstract

Abstract-In the context of aircraft engineering and maintenance, No Fault Found (NFF) is a chain of events that develops from a pilot experiencing a system malfunction with postflight maintenance failing to reproduce the reported symptoms. Without any repair being undertaken, the malfunction may be experienced again on subsequent flights. This present significant cost impacts to the industry that includes financial, reduced operational achievement, airworthiness challenges and potential flight safety issues. One of the major causes identified for NFF occurrence within electronic, mechanical and hydraulic products are faults that are intermittent in nature. This makes it difficult to use systematic fault detection techniques effectively, as system are subject to unknown disturbances and model uncertainties. The philosophy behind this criterion is that the designed model-based Fault Detection (FD) observer should be robust to disturbances but sensitive to intermittent faults where the occupance of intermittent faults can be alarmed by the use of an adaptive threshold. The aim of this paper is to demonstrate the development of such methodologies and to examine its performance in a real-world test bed. The test bed consists of an aircraft fuel system simulation rig which simulates by hardware the components of an aircraft fuel system.

Feed-forward observer-based intermittent fault detection

“…Hence, the intermittent fault acts an ever-increasing dispute in the maintenance of electronic, mechanical and hydraulic equipment. An ample fraction of breakdowns associated to the intermittent faults will test well and will be classified as ''No Fault Found'' (NFF) [1][2][3].…”

Intelligent Fault Diagnosis of an Aircraft Fuel System Using Machine Learning—A Literature Review

“…The latter is beginning to be used to replace previous maintenance methods to reduce costs and the number of failures [8]. CBM is sensitive to incipient failures, but another challenge is the possibility of intermittent failures (No Fault Find, NFF) in the fuel system [9]. The good news is that health management systems, previously not being considered at the design phase, are now beginning to receive attention [10].…”