Chapter 3 - Deicing/Anti-icing Fluids

Summary - Chapter 3

  • Frozen contaminants are most often removed in commercial operations by using Freezing Point Depressant (FPD) fluids.
  • It is the heat contained by the Type l (deice) fluid and hydraulic forces (high pressure spray equipment) that removes the frozen contaminants.
  • It is imperative that take-off not be attempted on any aircraft unless the PIC has determined that all critical surfaces of the aircraft are free of frost, ice or snow contamination.
  • Aircraft deicing/anti-icing fluids consist of four types. They are Type I, II, III, and IV.
  • Deicing fluids are typically ethylene glycol, diethylene glycol or propylene glycol based fluids containing water, corrosion inhibitors, wetting agents and dye.
  • Anti-icing fluids are similar in composition except that they also contain polymeric thickeners. They are formulated to prevent formation of unabsorbed frozen contamination for a longer period of time than deicing fluids; however, the protection is still for a limited period of time.
  • The operator is ultimately responsible for ensuring that only qualified fluids are used.
  • If the colour of the fluid being applied to the aircraft is NOT the colour anticipated, the procedure should be stopped and the situation investigated.
  • Type I fluids are used for deicing or anti-icing, but provide very limited anti-icing protection.
  • Type II fluids are designed to remain on the wings of an aircraft during ground operations, thereby providing anti-icing protection. This fluid should be used on aircraft with rotation speeds (Vr) above 100 knots, unless otherwise specified by the aircraft manufacturer.
  • Type III fluids are designed for aircraft that have a shorter time to rotation and this should make it acceptable for some aircraft that have a Vr of less than 100 knots unless otherwise specified by the aircraft manufacturer.
  • Type IV anti-icing fluids meet the same fluid specifications as the Type II fluids and have a significantly longer HOT.
  • The LOUT for a given fluid is the higher of:
    1. The lowest temperature at which the fluid meets the aerodynamic acceptance test for a given aircraft type, or
    2. The actual freezing point of the fluid plus its freezing point buffer of 10°C, for a Type I fluid, and 7°C for a Type II or IV fluid.
  • Some Type II or IV fluid residue may remain throughout the flight and this residue should be cleaned periodically. It is suggested that the use of heated Type I fluid/water high pressure washing may alleviate the occurrence of fluid dryout.