500B4-5GL - Skydrol 500B-4 Aviation Hydraulic Fluid, 5 Gallons

Skydrol 500B-4 is a Type IV phosphate ester aviation hydraulic fluid with the longest service history among phosphate ester products. Originally introduced as part of the Skydrol 500 series in 1952, the B-4 formulation was refined in 1977 and remains widely used today. Its proven track record makes it a trusted choice for many commercial and military aircraft hydraulic systems.

Yes, all approved phosphate ester hydraulic fluids are miscible and compatible with each other in any proportion. This means Skydrol 500B-4 can be used for top-off when converting from other approved Type IV or Type V fluids, provided the aircraft manufacturer allows it. Always consult the applicable CMM or QPL for fleet-specific guidance.

Skydrol 500B-4 holds approvals from numerous airframe manufacturers, including Airbus, Boeing, Embraer, and others. However, there are limitations for certain aircraft models, such as the Airbus A320neo family and the Boeing 787. Maintenance teams should verify fluid approval against aircraft documentation before use.

Skydrol 500B-4 maintains controlled viscosity across a wide temperature range, with 11.40 to 12.40 cSt at 100°F and a maximum of 2900 cSt at -65°F. This ensures reliable hydraulic system response during both cold starts and high-temperature operations. Stable viscosity is critical for maintaining consistent actuator and control performance.

Skydrol 500B-4 offers strong fire-resistance properties, with a minimum flash point of 350°F and fire point of 375°F. Its autoignition temperature is at least 860°F. These characteristics help reduce ignition risk in high-temperature aircraft hydraulic systems.

Aircraft hydraulic systems are designed with materials compatible with phosphate ester fluids, but not all materials are resistant to them. Certain metals, such as copper, magnesium, lead, and zinc, are not recommended for long-term exposure. It is important to avoid unauthorized substitutions of materials and to follow manufacturer recommendations.

Small spills should be wiped up immediately with a dry cloth, while larger pools should be absorbed with a sweeping compound. Residue can be removed using an approved solvent, followed by washing with water and detergent. Prompt cleanup helps prevent damage to paints and certain plastics.

The SDS and safety bulletin recommend wearing gloves, safety glasses, and appropriate protective clothing when handling Skydrol fluids. In situations where mists or vapors may form, respiratory protection may be required. Proper PPE reduces the risk of skin and eye exposure.

According to the Safety Data Sheet, Skydrol 500B-4 is not regulated as a dangerous good under IATA, IMDG, or U.S. DOT regulations. This simplifies shipping logistics for aviation maintenance facilities. Always confirm current transport regulations before shipping.

The fluid meets strict particle contamination limits, including maximum counts for multiple micron ranges as specified in the sales specification. Clean hydraulic fluid is essential to protect pumps, valves, and servo components from wear. These limits support overall system reliability and reduce maintenance events.

The SDS recommends storing Skydrol 500B-4 in a cool, dry, well-ventilated area, away from oxidizing agents. Containers should remain tightly closed to prevent moisture contamination. Proper storage helps maintain fluid quality over time.

Moisture content is limited to a maximum of 0.20%. Excess moisture can reduce hydraulic system efficiency and contribute to corrosion or fluid degradation. Monitoring moisture levels is an important part of fluid management programs.

Skydrol 500B-4 has a specific gravity range of 1.050 to 1.062 at 25°C. This higher density compared to some newer fluids is characteristic of Type IV phosphate ester formulations. Understanding density helps maintenance teams accurately calculate system fill volumes.

Used Skydrol 500B-4 may qualify under U.S. EPA used oil standards (40 CFR 279) and should be recycled or disposed of in accordance with applicable regulations. Facilities should consult local environmental authorities to ensure compliance. Responsible disposal minimizes environmental impact.

Skydrol 500B-4 is described as the most worker-friendly of the aviation phosphate esters and is less prone to forming irritating mists. This makes it especially suitable for maintenance hangars and test bench environments. Its long service history and balanced performance continue to make it a dependable choice for aviation hydraulic fluids.