Fire-Resistant Phosphate Ester Hydraulic Fluid for Commercial Aircraft

Product Overview

Skydrol® LD-4 is a low-density, fire-resistant hydraulic fluid manufactured by Eastman and specifically developed for modern commercial aircraft operating under high-pressure and high-temperature conditions.

Unlike mineral-based hydraulic fluids, Skydrol LD-4 is formulated using advanced phosphate ester technology, providing excellent fire resistance, superior thermal and oxidation stability, extended fluid service life, and improved system cleanliness.

It is widely approved for use in Airbus, Boeing, and other commercial aircraft hydraulic systems where phosphate ester fluids are specified.

Key Performance Advantages

• Excellent fire-resistant properties
• Superior thermal and oxidation stability
• Extended hydraulic fluid service life
• Improved deposit control
• Enhanced overall system cleanliness

Skydrol LD-4 is designed to protect critical hydraulic components including flight control systems, landing gear systems, thrust reversers, actuators, and servo valves.

It is globally recognized and used by airlines, MRO organizations, and OEM-approved maintenance facilities.

Product Specifications

• Product Name: Skydrol® LD-4
• Manufacturer: Eastman
• Fluid Type: Phosphate Ester
• Density: Low Density (LD)
• Application: Commercial Aircraft Hydraulic Systems
• Fire Resistance: Yes
• Color: Purple
• Base Chemistry: Synthetic Phosphate Ester
• OEM Approvals: Major Commercial Aircraft OEMs
• Performance Level: Very High

Technical Information

• Excellent fire-resistant characteristics
• High thermal stability
• Superior hydrolytic stability
• Improved elastomer compatibility
• Low foaming tendency
• Good low-temperature performance
• Designed for 3,000–5,000 psi hydraulic systems

Important: Skydrol LD-4 must not be mixed with mineral-based hydraulic fluids such as MIL-PRF-5606 types. Always follow aircraft maintenance manual (AMM) guidelines.

Possible Alternative Product Numbers

The following products may be considered alternatives, subject to OEM approval:

• Skydrol 500B-4
• Skydrol PE-5
• HyJet IV-A Plus (subject to aircraft approval)
• HyJet V (where approved)
• Other phosphate ester fluids meeting OEM specifications

Note: Mixing different phosphate ester brands may require complete system flushing procedures.

Packaging & Commercial Details

• Available Packaging:
  • 1 US Quart Cans
  • 1 US Gallon Cans
  • 5 Gallon Pails
  • 55 Gallon Drums
  • Bulk supply for airline and MRO contracts
• Commercial Support:
  • Certificate of Conformance (CoC)
  • Safety Data Sheet (SDS)
  • Batch traceability
  • Global export documentation
  • Airline and MRO volume pricing

Ideal For

• Commercial airlines
• Aircraft Maintenance, Repair & Overhaul (MRO) facilities
• Aviation distributors
• Fleet operators

Frequently Asked Questions (FAQ)

Q1. What type of fluid is Skydrol LD-4?
It is a phosphate ester–based, fire-resistant aviation hydraulic fluid.

Q2. Can Skydrol LD-4 be mixed with mineral hydraulic fluids?
No. It must not be mixed with mineral-based fluids such as MIL-PRF-5606.

Q3. What aircraft use Skydrol LD-4?
It is commonly used in Airbus, Boeing, and other commercial aircraft requiring phosphate ester hydraulic fluids.

Q4. Is it fire resistant?
Yes. Fire resistance is one of its primary performance advantages.

Q5. What color is Skydrol LD-4?
It is typically purple for easy identification.