Giving ice the boot

Atmospheric icing was for many years one of the major threats to aircraft safety-and it potentially still is. Researchers at Dunlop Aviation Ice Protection and Composites continue their development of deicing and anti-icing technologies.

It was not until the early 1930s as aircraft performance and navigation systems improved that icing conditions became a significant and increasingly common problem. Research work into countering the effect resulted in several experimental systems, including the use of hot exhaust gas piped along wing leading edges. Unfortunately, it tended to have a detrimental effect on engine performance-in just the conditions when it was particularly needed. An alternative approach was needed, and in 1935, Dunlop Aviation pioneered what was one of the first truly practical airfoil deicing systems. It fitted a leading-edge pneumatic deicing boot to a de Havilland Leopard Moth. Air was pumped into the device to break up ice as it formed. Later, in cooperation with the Royal Aircraft Establishment (RAE), the company experimented with deicing methods involving the forcing of ethylene glycol through porous membranes.

At the end of World War II, the gas turbine engine was clearly going to have both civil and military applications, while turboprops had considerable potential in the commercial markets. But the engine technology brought its own problems, and in 1948, the first electro-thermal Dunlop deicing system was developed to counter the susceptibility of turboprops to ice ingestion. Fitted to the air intake of the Rolls-Royce Dart, a heater was developed from a stamped sheet of resistance alloy profiled to provide controlled-area heating. A sandwich, with molded rubber on each side, protected the element and ensured reliable bonding to the metal intake leading edge. In 1970, the first solid-state electronic heater controller was introduced by Dunlop.