Matthew Greaves

Diagnostics of a Defective Bearing Within a Planetary Gearbox with Vibration and Acoustic Emission

Whilst vibration analysis of planetary gearbox faults is relatively well established, the application of Acoustic Emissions (AE) to this field is still in its infancy. For planetary-type gearboxes it is more challenging to diagnose bearing faults due to the dynamically changing transmission paths which contribute to masking the vibration signature of interest. The present study is aimed at developing a series of signal processing procedures to reduce the effect of background noise whilst extracting the fault feature from AE and vibration signatures. Three signal processing techniques including an adaptive filter, spectral kurtosis and envelope analysis, were applied to AE and vibration data acquired from a simplified planetary gearbox test rig with a seeded bearing defect. The results show that AE identified the defect earlier than vibration analysis irrespective of the tortuous transmission path.

The Investigation Human-Computer Interaction on Multiple Remote Tower Operations

The aim of current research is to develop an effective human-computer interaction framework for multiple remote tower operations. Five subject-matter experts familiar with multiple remote tower operations and human performance participated in current research. The Hierarchical Task Analysis (HTA) method is used to break down activities, scenarios, and tasks into single separate operations. The step by step breakdown of multiple remote tower operations included ATCO’s operational behaviors involving human-computer interaction such as interaction with EFS, OTW, RDP, and IDP during task performance were noted. Designing and managing human-computer interactions require an understanding of the principles of cognitive systems, allocation of functions and team adaptation between human operators and computer interactions. It is a holistic approach which considers distributed cognition coordination to rapidly changing situations. The human-centred design of multiple remote tower operations shall be based on a strategic, collaborative and automated concept of operations, as the associated high performance of remote tower systems in conflict detection and resolution has the potential to increase both airspace efficiency and the safety of aviation. The focus is on the human performance associated with new technology in the RTC and the supported tools used by an Air Traffic Control Officer, to ensure that these are used safely and efficiently to control aircraft both remotely and for multiple airports. The advanced technology did provide sufficient technical supports to one ATCO performing a task originally designed to be performed by several ATCOs, however, the application of this new technology also induced huge workload on the single ATCO.

Bearing signal separation enhancement with application to a helicopter transmission system

AbstractBearing vibration signal separation is essential for fault detection of gearboxes, especially where the vibration is nonstationary, susceptible to background noise, and subjected to an ardu...

The evaluation of pilot’s situational awareness during mode changes on flight mode annunciators

Current research investigates automation feedback design compared with a potential design solution that may increase pilot’s situation awareness of the Flight Mode Annunciators (FMAs) to reduce pilot workload and improve human-automation coordination. The research tools include an Eye Tracker and B747 flight simulator. This research evaluated two types of FMAs; a proposed glareshield mounted FMAs against the baseline FMA design mounted on the Primary Flight Display using an objective eye tracker. There are 19 participants including professional and private pilots and aerospace engineers. The results suggest that proposed glareshield design is the better design compared with the baseline design which demonstrated larger mean pupil sizes related to the higher workload. A design solution was proposed that moved the FMAs to a MCP position, taking into account EASA and FAA design guidance, as well as several design principles including positioning to increase salience and the proximity compatibility principle. The results of the experiment found that FMAs on the MCP could increase pilot SA and reduced the mean fixation duration compared to the PFD position. Although the study used a small sample size, it demonstrates the value of further research to evaluate the proposed design.

Planetary bearing defect detection in a commercial helicopter main gearbox with vibration and acoustic emission

Helicopter gearboxes significantly differ from other transmission types and exhibit unique behaviours that reduce the effectiveness of traditional fault diagnostics methods. In addition, due to lack of redundancy, helicopter transmission failure can lead to catastrophic accidents. Bearing faults in helicopter gearboxes are difficult to discriminate due to the low signal-to-noise ratio in the presence of gear vibration. In addition, the vibration response from the planet gear bearings must be transmitted via a time-varying path through the ring gear to externally mounted accelerometers, which cause yet further bearing vibration signal suppression. This research programme has resulted in the successful proof of concept of a broadband wireless transmission sensor that incorporates power scavenging while operating within a helicopter gearbox. In addition, this article investigates the application of signal separation techniques in detection of bearing faults within the epicyclic module of a large helicopter (CS-29) main gearbox using vibration and acoustic emissions. It compares their effectiveness for various operating conditions. Three signal processing techniques, including an adaptive filter, spectral kurtosis and envelope analysis, were combined for this investigation. In addition, this research discusses the feasibility of using acoustic emission for helicopter gearbox monitoring.

The Evaluation of Pilot’s First Fixation and Response Time to Different Design of Alerting Messages

Current research investigates the limitation of current cockpit design for Crew Alerting System (CAS) and Quick Reference Handbook (QRH), and proposes a potential design solution that might enhance crew performance. Using eye tracking device, an experiment was conducted based on Flight Simulator Software. Objective eye movement data as long as subjective feedback from participants were collected to evaluate the design. 24 participants experienced 4 scenarios with both traditional design and integrated design. Results demonstrated that participants never made error in locating the instructions by integrated design. It is due to the obvious fact that the instructions of integrated design will present itself, hence decrease the chance of executing the wrong NNC by eliminating the degree of choices. On the other hand, 75% of the participants experienced at least one error in finding the correct instruction, which is probably due to the limitation of QRH itself due to options too close in formatting which causes clicking the wrong page accidently. Furthermore, a trend was identified by eye movement patterns for longer fixation duration, smaller saccade amplitude, and less time fixated on instruction area occur in integrated design. Current research found that integrated design of CAS and QRH is superior in acquiring accurate solutions for emergent situations and processing the information presented compared with traditional design.

Helicopter gearbox bearing fault detection using separation techniques and envelope analysis

The main gearbox (MGB) is a crucial part of a helicopter. MGB bearings suffer intensively from stress and friction during flights hence concerns for their health condition and detecting potential defects become critical for the sake of operation safety and system reliability. In this study, bearing defects were seeded in the second epicyclic stage bearing of a commercial Class A helicopter MGB. Vibration and tachometer signals were recorded simultaneously for the purpose of fault diagnosis. The tests were carried out at different power and speed conditions for various seeded bearing defects. This paper presents a comparison of signal processing techniques employed to identify the presence of the defects masked by strong background noise generated from an operation helicopter MGB.

Polarimetric Imaging for Air Accident Investigation

We report a trial wherein a simple 4 CCD visible-band Polarimetric Imaging (PI) camera was fielded against aircraft debris distributed across an arid terrain, a littoral region and a small number of maritime debris targets A debris field realistically simulating an aircrash and a debris grid of aircraft remains were observed from an air platform flying in dry and sunny conditions. We report PI utility in support of air accident investigation by an enhanced ability to successfully locate small targets within the scene via the use of colour enhanced and decorrelated intensity PI products. Our results indicate that handheld PI capability may represent an effective low cost, upgrade and augmentation option for existing and future imaging systems that would support air accident investigators and assist in the cueing of more sophisticated assets and/or analyst attention.