The “Multifunctional Lightweight Design for Variably Configurable Monuments” (MICHEL) project ran from 1 September 2018 to 30 June 2021 under the fifth national civil aviation research programme. The consortium comprised Lufthansa Technik AG (LHT), Diehl Comfort Modules, the Technical University of Hamburg (TU HH), the Hamburg University of Applied Sciences (HAW), and other partners. LHT led the development of a predictive health‑maintenance (PHM) concept for line‑replaceable units (LRUs) and contributed to the design of a modular measurement‑and‑transmission kit. Diehl focused on the SkyPax 2.0 concept for monument reconfiguration, while TU HH pursued the detailed engineering of the measurement module. The project was funded by the German Federal Ministry of Economic Affairs and Climate Action (BMWK).

The technical core of the report is the PHM concept for LRUs. LHT’s work package AP 2.2 produced a comprehensive maintenance workflow that starts with in‑flight fault detection of an LRU, continues through spare‑part procurement, and ends with installation. The concept was illustrated with a coffee‑machine example and was built on data gathered from cabin crew, maintenance technicians, and engineering staff. Fault scenarios were derived from historical LRU failure reports, and the focus was placed on individual LRUs rather than entire monuments because monuments are less failure‑prone.

Central to the PHM approach is a measurement‑and‑transmission module that can be attached to any LRU insert, such as a steam oven or a coffee machine. The module measures electrical current as a first indicator of functional status, but the design allows extension to pressure, temperature, or humidity sensors. To keep the data stream manageable, the module stores measurements temporarily and applies a filtering rule: only values that deviate from a predefined standard are transmitted. When an LRU operates normally, the module remains silent, thereby reducing bandwidth consumption. Each insert is uniquely addressed, so the aircraft server can identify the source of each message. The module’s firmware runs on an STM32 microcontroller, uses an analog‑to‑digital converter, and communicates wirelessly via protocols such as MQTT or CoAP. Data are encoded in CBOR and compressed with the Lempel‑Ziv‑Welch algorithm to minimise payload size.

The PHM workflow comprises four stages: signal generation, temporary storage, onboard forwarding, and ground‑station reception. Trend detection algorithms analyse the incoming data to identify gradual degradation. Once a trend crosses a threshold, the system evaluates the severity and generates a notification that is sent to a ground station. The report presents a signal‑and‑process chain diagram that maps these stages and shows how the module integrates with the aircraft’s existing avionics infrastructure.

A functional prototype of the measurement module was built as a “breadboard” assembly, where components were connected by wires rather than soldered. This prototype was tested in a cabin mock‑up at LHT’s facility in ZAL, confirming that the wireless link and filtering logic work as intended. Parallel to the hardware tests, the specification was refined to meet aviation‑industry standards, incorporating requirements for electromagnetic compatibility, temperature tolerance, and mechanical robustness.

The demonstration phase (work package AP 2.3) involved assembling a modular kit that could be installed on various LRUs. TU HH led the detailed design, while Diehl supplied mechanical integration expertise. The kit was validated in a controlled environment, showing that the module can be deployed without interfering with the LRU’s normal operation. The final report outlines future work, including expanding the sensor suite, integrating the module into a full aircraft health‑monitoring system, and conducting flight‑test validation.

In summary, the MICHEL project delivered a viable PHM concept for LRUs, a low‑power, low‑bandwidth measurement module, and a demonstration of modular integration. The collaboration among LHT, Diehl, TU HH, and HAW combined expertise in avionics, mechanical design, and systems engineering, enabling the project to progress from concept to prototype within the three‑year funding period.