What are the two types of hydraulic fluids?

What are the two types of hydraulic fluids?

• A. Houghto-safe 273 and Ethylene Glycol
• B. Ethylene Glycol and Silicone Oil
• C. Water and Mineral Oil
• D. Houghto-safe 273 and Silicone Oil

Answer: (B)

Hydraulic fluids used in aircraft are often categorized by their chemical base into two broad families: glycol-based fluids and silicone-based fluids. Ethylene glycol represents the glycol-based family, typically used in water-glycol blends to provide fire resistance and acceptable performance over a wide temperature range. Silicone oil represents the silicone-based family, known for excellent thermal stability, dielectric properties, and stable performance across extreme temperatures. The pairing of Ethylene Glycol and Silicone Oil clearly shows these two distinct fluid families. The other options mix fluids from different families or include a fluid (like Houghto-Safe 273) that belongs to a different category altogether, so they don’t illustrate the two main classes as cleanly.

Hydraulic fluids used in aircraft are often categorized by their chemical base into two broad families: glycol-based fluids and silicone-based fluids. Ethylene glycol represents the glycol-based family, typically used in water-glycol blends to provide fire resistance and acceptable performance over a wide temperature range. Silicone oil represents the silicone-based family, known for excellent thermal stability, dielectric properties, and stable performance across extreme temperatures. The pairing of Ethylene Glycol and Silicone Oil clearly shows these two distinct fluid families.

The other options mix fluids from different families or include a fluid (like Houghto-Safe 273) that belongs to a different category altogether, so they don’t illustrate the two main classes as cleanly.