Anti-Icing Fluid Residues

Document Number: 2007-01-3302

Date Published: September 2007

Author(s):
Kirsten Patricia Dyer - BAE Systems

Abstract:
Aircraft ground anti-icing fluids, conforming to the Society of Automotive Engineers (SAE) AMS 1428, are used during cold conditions to remove frozen deposits, such as frost, snow and ice, from aircraft surfaces, and prevent further deposits from adhering for a period of time (holdover). To help the fluids remain on the aircraft and provide holdover, they contain a thickener.

These fluids are designed to flow off aircraft surfaces during take-off by shearing due to the flow of air. However, it has been found that they are collecting in aerodynamically quiet areas, such as on control hinges and gaps on the elevator and aileron primary flying control surfaces. During flight, or during warmer conditions on the ground, fluids in the quiet areas dry out and lose their freezing point depressants, leaving behind a residue.

These residues are known to rehydrate forming a gel, which, when exposed to moisture, either from wet conditions on the ground or during take-off, can increase in thickness up to 600 times. As they no longer have any anti-icing properties, they can freeze at temperatures close to zero degrees Celsius during flight, thus potentially restricting control movement and affecting the safety of the aircraft.

There have been a number of reported incidents in Europe since the mid 1990's. Over the last two winter seasons, however, the number has increased dramatically, with reports now on aircraft with powered flying controls, where traditionally this problem was seen as affecting only aircraft with non-powered flying controls.

The industry needs to urgently address this issue. So far, Regulators, airframe manufacturers and the SAE (Society of Automotive Engineers) have issued advisory material, with Airlines suffering the cost of frequent inspection and cleaning procedures to remove residues during the winter season, whenever they use these fluids. The solution requires the collective active input of the whole industry; including airframe manufacturers, to modify their current and future aircraft types if possible; service providers and airlines, to ensure the widespread availability and use of Type I fluids and the two-step process; fluid manufacturers, to develop fluids that have acceptable residue properties; SAE, to develop the SAE AMS 1428 specification such that only fluids demonstrating suitable residue properties can be approved in the future, as well as giving proper guidance on their application; and in particular, Regulatory Authorities, to put the correct measures in place to ensure that the above processes are implemented.

File Size: 324K
Product Status: In Stock

Included in: V116-2007

See other papers presented at 2007 SAE Aircraft and Engine Icing International Conference, September 2007, Seville, SPAIN, Session: Aircraft De / Anti-icing Fluids - Part I

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