Engine health management

Rolls Royce uses Engine Health Management (EHM) to track the health of thousands of engines operating worldwide, using onboard sensors and live satellite feeds.

A corporate EHM team covers all the business sectors which enables the Group to develop technologies and best practice. In the Civil market for example, the Trent family of engines is supported by a comprehensive Rolls-Royce EHM capability operated in conjunction with Controls and Data Services (CDS), a Rolls-Royce company, and accessible as appropriate by the airlines involved.

EHM is a pro-active technique for predicting when something might go wrong and averting a potential threat before it has a chance to develop into a real problem. EHM covers the assessment of an engine’s state of health in real time or post-flight and how the data is used reflects the nature of the relevant service contracts. Essentially, EHM is about making more informed decisions regarding operating an engine fleet through acting on the best information available.

The evolution of EHM and the revolution in its use has significantly reduced costs by preventing or delaying maintenance, as well as flagging potentially costly technical problems. New assets will incorporate EHM capability, and techniques will, where possible, be retro-fitted to existing equipment.

Broader engineering disciplines can benefit from the data that is collected. As operational profiles of technical performance are revealed in ever more detail – from individual components to whole engines – so engineers can develop more thorough and cost-effective maintenance schedules, and designers can feed higher reliability features into the engine products of the future.

EHM uses a range of sensors strategically positioned throughout the engine to record key technical parameters several times each flight. The EHM sensors in aero engines monitor numerous critical engine characteristics such as temperatures, pressures, speeds, flows and vibration levels to ensure they are within known tolerances and to highlight when they are not. In the most extreme cases air crew could be contacted, but far more often the action will lie with the operator’s own maintenance personnel or a Rolls-Royce service representative in the field to manage a special service inspection.

The Trent engine can be fitted permanently with about 25 sensors. The figure below shows the typical parameters measured for EHM.

Many of these are multi-purpose as they are used to control the engine and provide indication of engine operation to the pilot as well as being used by the EHM system. These are selected to make the system as flexible as possible.

The main engine parameters – shaft speeds and turbine gas temperature (TGT) – are used to give a clear view of the overall health of the engine. A number of pressure and temperature sensors are fitted through the gas path of the engine to enable the performance of each of the main modules (including the fan, the intermediate and high pressure compressors, and the high, intermediate and low pressure turbines) to be calculated. These sensors are fitted between each module, except where the temperature is too high for reliable measurements to be made.

Vibration sensors provide valuable information on the condition of all the rotating components. An electric magnetic chip detector is fitted to trap any debris in the oil system that may be caused by unusual wear to bearings or gears. Other sensors are used to assess the health of the fuel system (pump, metering valve, filter); the oil system (pump and filter); the cooling air system and the nacelle ventilation (nacelle is the cover housing – separate from the fuselage that holds engines, fuel, or equipment on aircraft). As engine operation can vary significantly between flights (due to day temperature or pilot selection of reduced thrust), data from the aircraft to provide thrust setting, ambient conditions and bleed extraction status is also used.