Table of Contents TP 10643
- How to Use This Manual
- Record of Revisions
- Foreword
- Chapter 1 - Air Law, The Clean Aircraft Concept
- Chapter 2 - Theory and Aircraft Performance
- Chapter 3 - Deicing/Anti-icing Fluids
- Chapter 4 - Preventative Measures and Deicing Procedures
- Chapter 5 - Ground Crew Supplement
- Chapter 6 - Aircraft Critical Surface Contamination Examination Questions
- List of Tables
- Acronyms
- Glossary
FPD Temperature Buffer
48. The freezing point of a fluid is normally a function of the glycol concentration. An assessment of the fluid concentration can be performed in the field by measuring the refractive index of the fluid. The magnitude of refraction (how much light bends) is related to the concentration of glycol in the solution and hence the freezing point. Fluid manufacturers provide fluid specification charts that correlate refraction index, also called BRIX, versus fluid freezing point. Since there could be some error in reading the BRIX, or the skin temperature could be lower than the outside air temperature, it was decided to add a safety buffer to all the calculations, and a value of 10°C was agreed for Type I fluids, by the SAE G-12 Fluids sub-committee, and 7°C for Types II, III and IV fluids.
This buffer allows for absorption of precipitation.