Epsilon Optics Aerospace Ltd

Epsilon Optics Aerospace Ltd is focused on providing bespoke solutions for the long term monitoring of Aerospace and other Critical Defence Related Structures.

Airbus A320

Epsilon Optics Aerospace have provided sensor systems for both fixed and rotary winged aircraft and for naval applications. These have included monitoring structures such as aircraft wing spars and landing gears for both manned and unmanned fixed wing aircraft. For helicopters, work has focused on measuring loads in critical rotor head components and rotor blades. On naval platforms hull structures are being monitored. The data from these systems is being used to support the introduction of “on condition maintenance”. It includes determining actual life usage and the detection of hazardous events such as impacts and, in the case of landing gears, heavy landings.

The system comprises three main elements:

Sensors: These contain the fibre optic strain measuring device including temperature compensation. Each is designed to meet the specific application, with the FBG tuned to measure the required range of strains. They may take a number of forms including embedded and surface bonded sensors. For certain applications, particularly complex metallic structures such as landing gears, sensor carriers may be used which are mechanically attached to the structure in such a manner that they sense the loads being applied. Aerospace qualified materials are used wherever possible and a number of sensors have been successfully tested to DO-160E.

Sensor interrogator: The EOAL interrogator uses Time Division Multiplexing (TDM) to provide a lightweight, compact unit that requires low electrical power. Further Information.. The rate at which it interrogates the FBG sensors is adjustable up to a maximum speed of 9.5kHz; it has been successfully used to detect impacts to composite structures. As it is fully solid state system, it is robust, and has undergone a full test programme to demonstrate that it meets the requirements of DO-160E. This robustness was demonstrated during tests where it was mounted on a helicopter rotor head. The data output is digital (currently RS422 but alternative Ethernet outputs are possible) and can be fed directly into the aircraft’s data bus for transmission to the maintenance management system. Alternatively self contained data storage is possible for post flight download. The unit can also be battery powered to provide a completely self contained system.

ConnectorInterconnecting Optical Fibres and Connectors: The interrogator is normally mounted remotely from the sensors, either within an avionics bay or other suitable location. The two are linked via a single mode optical fibre. Optical connectors are required to facilitate removal of the component being monitored for maintenance etc or to ease installation for instance where the fibre is routed through a major fuselage break point. EOAL is working closely with a number of specialist optical fibre and connector manufacturers to provide robust solutions to meet these requirements.

In-Axle Sensor:



EOAL has been involved in a number of programmes in the USA aimed at developing systems to support Structural Health Monitoring (SHM). In the main, these have been focussed on measuring loads in landing gears to detect both overloads from heavy landings and to collect data to support the move to on-condition maintenance. Under FAA, US Army and US Navy programmes, a number of successful flight tests have been carried out. Work was also carried out for Airbus UK and a sensor was developed for the A320’s main landing gear. Pictured below is an in axle sensor for a helicopter.
UK Patent #2522472, European Patent #3100008.

In-axle Strain Sensor
Published Papers

US Department of Transportation FAA June 2016.
Application of Rotorcraft Structural Usage and Loads Monitoring Methods for Determining Usage Credits, Final Report, DOT/FAA/TC-16/2

American Helicopter Society 72nd Annual Forum
May 2016.

Integrated Hybrid Structural Management System.
T. Cook, M. Davis, J. Cycon, Sikorsky Aircraft Corp

SAE International 2013-01-2222
Sept 2013

Fibre Optic Sensors for High Strain Composite Components.
B. Tucker, A Love, Bell Helicopter Textron Inc,
R. Caesley Epsilon Optics

Royal Aeronautical Society: The Future Rotorcraft: Enabling Capability through the Application of Technology,
June 2011

Use of Fibre Optic Sensors to Measure In-Service Loads in Critical Rotor Components.
R. Caesley, Epsilon Optics Ltd

American Helicopter Society 66th Annual Forum
May 2010

Advanced CBM Technologies for Helicopter Rotor Systems – Full Scale Rotor Demonstration and Test Results
J. R. Andrews, M. J. Augustin
Bell Helicopters Textron Inc

Development of Optical Fibre Strain Measurement for Monitoring Composite Structures.
D. Roberts and R. Caesley Moog Insensys Ltd

Structural loads monitoring of an Unmanned Air Vehicle
M. Frovel, G. Carrion, J.M. Pintado INTA. Area de Materiales Compuestos, Torrejon de Ardoz, Espana.

The Embedding of Optical Fibre Sensors for SHM
M. Volanthen, L. Rumsey, R. Caesley, Insensys Ltd, A. Ghoshal, G. Welsh and N. Bordick  United Technologies Research Centre and Aviation Applied Technology Directorate, US Army.

EOAL has and is working with a number of major Tier 1 aerospace companies in both Europe and the USA. EOAL and is familiar with the requirements of ITAR. Its success is built on a willingness to tailor the solution to meet the customer’s specific requirement.

Design and implementation of complete fibre optic sensing solutions