As the Northern Hemisphere’s winter season sets in, Europe’s regulator is cautioning industry about the harmful effects of organic, salt-based, aircraft-deicing fluids.
In a recent Safety Information Bulletin (SIB), the European Aviation Safety Agency (EASA) notes that although the fluid is not prevalent—it knows of no European airports that use it for aircraft—operators should be vigilant nonetheless. Most so-called Type 1 deicing and anti-icing fluids use glycol to keep aircraft surfaces clear of ice. In recent years, sugar-based fluids have come onto the market, and a few providers use fluids with organic salt, or alkali metal.
Salt-based fluids present several hazards to aircraft, EASA warns. Among them: residue from the fluids can cause glycol-based fluids applied later to break down prematurely, which can reduce the holdover time, or the maximum safe-time a deiced aircraft can sit in winter weather before departing.
The problem is exacerbated when the fluid types are mixed in a two-step process that first involves salt-based fluid for deicing of contaminated aircraft, followed by application of a different anti-icing fluid. “This effect has been proven by research, being its quantitative impact dependent on the particular anti-icing fluid used and on the salt and its concentration in the deicing fluid, but only low concentrations are required to decrease the anti-icing fluid thickening properties,” EASA explains. “This is an immediate effect with consequences potentially affecting safety.”
A more commonly known ramification is salt-based fluid’s contribution to corrosion of metallic parts. EASA and other regulators have cautioned operators about this condition in relation to organic, salt-based, runway-deicing fluids for years. The problem came to light in the 1990s as airports adopted the fluids—considered more environmentally friendly than glycol-based products—for runway deicing. Soon, operators noticed that their carbon brakes were experiencing excessive corrosion. The problem was soon linked to the salt-based fluids splashing onto the brakes while aircraft were on runways.
Among the changes: aircraft manufacturers developed new inspections to identify the oxidation problem early, and issued recommended landing procedures aimed at lowering brake temperatures, which helps reduce oxidation.
EASA urges deicing service providers “to consider this SIB when deciding which fluids to purchase.” During two-step operations involving organic salt-based fluid, “consider mitigating measures to counteract the potential effect on holdover time reduction.” Among the suggested steps: ensure the salt-based fluid is completely washed off before applying anti-icing fluid, and perform special pre-takeoff checks for contamination.