Chapter 5 - Ground Crew Supplement

Proper Coverage

95.  Proper fluid coverage is absolutely essential for proper fluid performance. It is imperative that the personnel applying the fluid are properly trained and that a consistent fluid application technique is utilized. Adequate fluid quantities must be expended to accomplish the de/anti-icing tasks. Proper training will help ensure that the de/anti-icing task is accomplished in a manner that utilizes the fluids most effectively and that the aircraft is subsequently rendered safe for flight.

96.  The deicing with fluids process is not completed until the aircraft's critical surfaces are completely free from frozen contamination. This can only be accomplished with the use of a sufficient quantity of deicing fluid to complete the task.

97.  For the purpose of deicing, hot Type I fluid is generally applied directly onto the total aircraft surface to be de-iced. If applied only to the front part of the wing, allowing it to flow back to the aft part, the fluid will cool down significantly as it moves on the surface of the wing making it less effective, or even ineffective in melting frozen contamination on the aft part of the wing.

98.  It is considered imperative that the leading edges of the wings and control surfaces be thoroughly cleaned of any contaminant. No frozen precipitation or contamination can be allowed to remain underneath the deicing fluid. Hot deicing fluid must be applied in sufficient quantity that the remaining fluid on the surfaces to be protected has a freezing point at least 10°C below Outside Air Temperature (OAT). As the fluid is applied, it is being diluted by the melted ice, snow or whatever frozen accumulation it is removing. Its freezing point is thus increased.

99.  Sufficient hot deicing fluid must be applied to make sure that fluid diluted by melted slush, snow or ice is flushed away. This is best accomplished by applying the fluid from the high point on the wing to the low point on the wing. Typically from wing tip to wing root.

100.  The anti-icing with fluids process is not properly accomplished if an insufficient amount fluid has been used and which results in incomplete or inadequate coverage of the surfaces to be treated.

101.  For the second step of a two step procedure, a sufficient amount of aircraft anti-icing fluid must be applied that can completely cover the surfaces and form an adequate coating. The HOT table values are based upon the application of sufficient fluid. Insufficient coverage results in a thin layer and reduced protection of uncertain duration.

102.  The application process should be continuous and as short as possible. Anti-icing should be carried out as near to the departure time as possible in order to utilize available holdover time. While thickness will vary in time over the profile of the wing surface, the anti-icing fluid should be distributed uniformly. In order to control the uniformity, all horizontal aircraft surfaces should be visually checked during application of the fluid. The amount of fluid required, will be visually indicated by the fluid just beginning to run off the leading and trailing edges of the surfaces.

103.  For a typical ethylene based Type IV fluid, between 1 mm and 3 mm thickness layer is required. It takes 2 litres of fluid to cover 1 square metre to a depth of 2 mm. Since application is never perfect, it will take more than 2 litres/square metre to achieve this 2 mm fluid thickness (In non-metric units, it will take at least 2 U.S. gallon/40 sq. ft. to achieve 0.08 inches). Conversion factors:

  • litre = 0.5284 U.S. gallon;
  • mm = about 0.08 inch; and
  • 1 square metre = 10.76 square feet.

Note:  For more detailed information on specific fluids, contact the de/anti-icing Fluid manufacturer.