This AS describes a standard method for viscosity measurements of thickened (AMS1428) anti-icing fluids. Fluid manufacturers may publish alternate methods for their fluids. In case of conflicting results between the two methods, the manufacturer method takes precedence. To compare viscosities, exactly the same measurement elements (including spindle and container size) must have been used to obtain those viscosities.
Renamed the document from AIR to AS since it is meant to be used as a standard and has been used as such over the past 10 years, so AS seems more appropriate to reflect this.
Added “Laboratory” and “the Brookfiled viscometer” to the title to distinguish the document better from the AIR5704 (field viscosity test for thickened aircraft anti-icing fluids).
Text cleaned-up in whole document to make it more clear and better readable.
Deleted the reference to AS5485 as this document is not referenced in the text and has no relation to this AS9968 document.
Deleted the reference to ASTM D2196 as this AS9968 deviates from the D2196 document with specific requirements. Further, the reference was only to a small part of the D2196 document anyhow, which is replaced by referring to the instrument manufacturer’s instructions taking away the need for keeping track of changes to the D2196 document.
The role of alternate viscosity measurement methods established by fluid manufacturers is provided in the scope. This role is specified in the Transport Canada and FAA Holdover Time Guidelines.
Some items in 3.3 (Requirements) have been moved to get a more logic order of items.
A method for removing air bubbles from fluid samples has been added.
The UL Adaptor (including corresponding spindle) is added for measurements of very low viscosities for accuracy reasons.
A specific measurement container (600 mL low form beaker) is added for use with spindles LV1 and LV2 disc. This has been done as Brookfield states that beaker size/form can have an impact on viscosity measurement (narrower/smaller container = higher viscosity reading).
Words have been added to emphasize that in order to compare results of two viscosity measurements, the measurements MUST be conducted using the exact same method, including spindle and measurement container. This is made clearer by separating spindle selection into that for original/baseline (for fluid manufacturers) and comparative (for fluid users) measurements.
More detailed information is provided for spindle selection in the range of 10 000 to 20 000 mPa.s.