Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - HADES (HADES - Optical Hot Air Leak DEtection System)

Teaser

Light carbon structures are increasingly used in modern aircrafts for reducing weight and thus fuel consumption. The carbon materials are more sensitive to overheating than metals. Hot air ducts are used to conduct air heated by engine exhaust to the cabin heating system. At...

Summary

Light carbon structures are increasingly used in modern aircrafts for reducing weight and thus fuel consumption. The carbon materials are more sensitive to overheating than metals. Hot air ducts are used to conduct air heated by engine exhaust to the cabin heating system. At several locations, those hot air ducts are installed within or in close proximity to the carbon structures. Therefore, reliable and precise hot air leak detection is an essential safety feature of modern aircrafts. The proposed activity aims at developing an innovative, powerful and reliable fibre-optic technology for an aircraft hot air leak detection system and validating it in a representative aircraft environment. State-of-the-art electrical hot air leak detection systems detect and localize leaks in aircraft hot air ducts by analyzing electric shortcuts. However, the response of such systems just indicates that the critical temperature is exceeded. It is impossible to vary the threshold setting along the cable and false alarms due to stray signals are common. Localization of leaks is difficult, and the sensor cables are irreversibly damaged by exceeding the critical temperature. Based on our deep understanding of using fibre-optic sensing systems in harsh and safety-critical environments, NKT Photonics GmbH - LIOS Sensing will select the optimum fibre-optic technology for hot air leak detection in aircrafts, which overcomes the limitations of the electrical systems, complies with the requirements of the tender and fulfils the other essential requirements of aircraft applications. LIOS will demonstrate the technology’s capabilities, using a proof-of-concept system in the NKT Photonics GmbH - LIOS Sensing laboratories. After testing, the demonstrator will be re-design to bring it closer to TRL6, a demonstration within an aircraft environment. The re-designed demonstrator will be installed at the facilities of the topic manager and tested in collaboration with the topic manager.

Work performed

During the reporting period, a detailed baseline study was executed by NKT Photonics. The main focus was to execute a broad screening of fibre optic technologies. Each technology is reviewed in detail, described and analyzed in regard of complexity, performance, feasibility, development risk. After reviewing, a decision matrix was generated in cooperation with the Topic Manager. Based on this decision matrix and the requirements matrix, the most suitable technology for the addressed problem (hot air leak detection with high spatial resolution in the order of cm) was selected.
Since the environmental requirements for aerospace applications are higher demanding than for the typical fibre optic sensing applications, the availability of components which are matching or are close to the requirements had a strong impact on the chosen technology. Thus, an extensive overview of components and modules was conducted in parallel to the baseline technology study. The specification/requirement matrix is divided into 2 separated phases. First phase is describing the general functionality of the system (POC1). The setup of this POC1 is executed in the first half of the project, POC2 will be part of the project\'s second half.
The POC1 components were selected according to the baseline study results, the specification matrix and availability. The identified components were laid out in detail and acquired. Afterwards, the test-rig was set-up and all parts and modules were tested and brought up.
In addition, a test plan was elaborated, and a temperature test-unit, the so-called environmental box, was developed, laid out and built up. The test plan validates all necessary requirements for the first phase.

Final results

Expected result of this project is a functional demonstrator showing a superior spatial resolution of at least 2.5cm. The technology is based on a fibre optic Fibre Bragg Grating (FBG) design, which can read more than 1000 FBGs. The time for scanning those FBGs and their data processing and alarming will be levered to a whole new level of few seconds. We are also developing to achieve a temperature accuracy of at least +/-2°C over the whole measurement distance.
This approach is able to set new standards for distributed monitoring and security standards. Localizing a defect, such as a hot air leak in a light carbon structures, that fast and accurate can decrease the probability of consecutive faults and the down time for maintenance and repair works. This can lead to a safer and cheaper operation of aircrafts.
In addition, this technology can be used in a broader industry, where the precise spatial resolution is of importance, such as the process industry.

Website & more info

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