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ON-Wing Ice DetectioN and MonitorinG System

Tags: Air

State of the Art - Background

When an aircraft flies in cold, moist air, especially at low altitudes, ice can form rapidly, both on and behind the leading edge of aerofoils and other structures. The growth of the ice disturbs the local airflow and can radically alter the lift of the aerofoil and hence the handling characteristics of the aircraft. This phenomenon has caused a number of fatal accidents and loss-of-control events, and is a problem that will intensify as increased pressures on airports mean that aircraft will spend much longer in low-altitude holding patterns. Large aircraft use hot gases diverted from the engines to remove ice from flight-critical surfaces, while smaller aircraft sometimes use pneumatic 'boots' which expand under pressure to shed the ice layers. These technologies are incompatible with future generations of air transport, in which composite materials will be used extensively. Furthermore, current ice detectors are insensitive, cannot distinguish between ice types and are not co-located with the safety critical zones. Building on electro-thermal de-icing technology now widely used in helicopters, the ON-WINGS project will develop a smart, autonomous, composite electro-thermal de-icing system for fixed-wing, helicopter rotor blade and engine inlet applications.


The initial objective is to produce a robust fixed-point optical ice-detector sensor whilst the ultimate objective of the programme is to develop and demonstrate sensor technology that is fully integrated into an ice-protection system mounted into a composite structure and offering real-time control. The sensor will be capable of detecting:

- the onset of icing,

- ice presence, and at a later stage

- ice thickness.

The sensing system will be made 'smart' by using dedicated algorithms, and will be integrated in a representative wing-slat, along with composite electro-thermal zone heaters.

A second work package of advanced sensing concepts will develop a multi-zone-based system, each with its dedicated sensor and control electronics.

As part of the advanced concepts:

- use the point ice sensor to investigate parameters for detecting ice thickness and roughness;

- specify, design and develop a quasi-distributed fibre-optic ice sensor which will be integrated in the wing-slat coupon with electro-thermal heating capable of detecting the presence of ice at a multitude of points.

Another focus is on health monitoring, and in particular distributed temperature sensing of the heating zones using fibre optics.

A 'threshold' impact detection method will also be investigated with the aim of detecting impacts that may lead to de-lamination of an electro-thermal ice-protection system.

Description of Work

A generic air-conformal direct ice-detection technology, based on optical methods capable of being adapted and multiplexed in the wing-slat of an aircraft, will be developed and calibrated to measure the ice thickness and accretion rate of ice in real time, as well as ice roughness to determine the criticality of ice type. This will be further developed and calibrated to measure the onset of icing and used as an engine inlet ice sensor. A distributed ice sensor will also be developed and calibrated to detect the presence of runback ice and used in fixed-wing aircraft. A generic data acquisition system will be developed with suitable algorithms that will be able to interrogate the ice sensors described above.

'Smart' composite electro-thermal heaters will be achieved by developing and integrating a generic composite-zoned electro-thermal heater with the ice sensors and controllers. Generic distributed temperature sensing and interrogation electronics will also be developed and integrated in the composite heaters.

The prototypes will be manufactured, tested and evaluated with the integrated de-icing system in an icing tunnel.

A prototype parasitic 'coupon' will be manufactured to flight standards and proof of concept validated, thus paving the way to case-specific certifications.

The technology will be disseminated to aviation and more generally to the transport industry.

Expected Results

The resulting system will incorporate, for the first time, the following:

- a primary 'on-wing' ice detector used to activate the ice-protection system;

- a 'smart' electro-thermal de-icing system to demonstrate the interaction and control of electro-thermal heater elements and an integral aero-conformal ice detection and distributive temperature/health monitoring system;

- air conformal optical ice detectors used for primary activation of the ice-protection system;

- novel concepts based on sophisticated fibre-optic methods capable of measuring ice distributed over large areas.

A complete smart air conformal ice-detection system will be demonstrated, capable of detecting the ice thickness and roughness for critical aerospace applications.