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Airtech

Dunlop Aviation icing protection

07 September 2001

Dunlop Aviation Ice Protection & Composites (DAIPC) has entered into an agreement with Cranfield University for the joint development of a icing wind tunnel.

To be used for certification work and research into aircraft ice protection systems, the wind tunnel will be built at the University campus. Atmospheric icing is probably the greatest natural hazard faced by any aircraft in flight. To counter this a number of systems have been developed since the early 1930s when it first became a significant problem.

Dunlop Aviation introduced the first practical aerofoil de-icing systems in 1935. Today, the company specialises in the provision of integrated ice protection systems incorporating electronic control and composite structures with integral heaters. These can provide three basic types of protection; anti-icing provides continuous heating at controlled temperature which prevents ice formation, de-icing provides intermittent heating to areas in a predetermined sequence allowing the ice to be shed in a controlled manner and there are also combination systems.

Icing severity varies with airspeed and temperature and helicopters are often more susceptible as they spend a longer time in any particular situation and by definition, especially in SAR or combat roles, operate in adverse conditions. Often, helicopters are hovering for extended periods so ice builds up on rotors which adversely affect performance by creating drag. Ice build up on the engine inlet screens can cause air starvation reducing power output, with immediate and fatal consequences.

Engine intakes for helicopters are three-dimensional composite structural mouldings incorporating undercuts and compound curved surfaces to meet aerodynamic requirements. A high temperature epoxy resin/hybrid reinforcement system with a non-metallic honeycomb is used. Moulding is by conventional hand lay-up techniques in clean room conditions followed by autoclave curing and a number of features unique to DAIPC are incorporated. One such feature is the resin's filler/hardener system which has been developed from commercially available materials to produce high temperature operational properties. Another is that the company manufactures the resin-impregnated fabric (pre-preg), in-house using a special solventless process. This provides complete control of resin formulation, pre-preg manufacture and storage management. Ceramic fibres in the lay-up can provide the ability to meet fire barrier requirements.






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