1. Basic Parameters & Standards

• Composition & Standards:
  SKYDROL™ LD-4 is a phosphate ester-based, fire-resistant aviation hydraulic fluid classified as Type IV. Complies with international aviation standards including AS 1241, BMS 3-11M, DMS2014F, NSA307110, and certified by Boeing, Airbus, Lockheed Martin, and other aircraft manufacturers.
• Temperature Range:
  • Operating Range: -40°C to 180°C (short-term tolerance up to 200°C).
  • Low-Temperature Performance: Pour point ≤**-62°C**; kinematic viscosity ≤2500 mm²/s at -54°C, ensuring reliable cold starts.
• Physical Properties:
  • Density: 1.003–1.013 g/cm³ (25°C);
  • Flash Point: 160°C (closed cup); fire point ≥177°C; autoignition temperature ≥400°C.

2. Core Performance Features

• Fire Resistance:
  As a phosphate ester fluid, SKYDROL LD-4 is non-flammable, with a flash point significantly higher than mineral oils (e.g., MIL-H-5606E: ~104°C), reducing aviation fire risks.
• High-Temperature Stability:
  • Oxidation stability >30 hours at 100°C; evaporation loss ≤4% (71°C test), maintaining viscosity under heat.
  • Contains anti-corrosion additives and acid scavengers to protect valves and system components.
• Lubrication & Wear Resistance:
  • Four-ball wear test diameter: 0.45 mm; PB value ≥600N, ideal for high-load friction applications.
• Material Compatibility:
  • Compatible with metals (copper strip corrosion rating: 1a), rubber (swelling rate ≤5%), and seals.
• Environmental Adaptability:
  • Air release time ≤3 minutes; water resistance (total water content ≤0.05%), preventing cavitation and foaming.

3. Applications

• Commercial Aviation:
  • Hydraulic systems (landing gear, flaps, brakes) in Boeing 737/747/787, Airbus A320/A380, and MD-11 aircraft.
• Military & General Aviation:
  • Helicopters (e.g., Black Hawk) and transport planes (e.g., C-130).
• Industrial Use:
  • High-temperature gas turbines and high-altitude machinery hydraulic systems.

4. Key Technical Indicators

5. Market Positioning & Comparisons

• Competitor Comparison:

  Model	SKYDROL LD-4	SKYDROL 500B-4	SKYDROL PE-5
  Type	Type IV	Type IV	Type V
  Flash Point (°C)	160	171	170
  Autoignition (°C)	400	460	420
  Pour Point (°C)	-62	-62	-65
  Advantages	Mature & stable	Long service history	Superior low-temp

  • LD-4 Advantages: Highest market share (>60% in Type IV fluids); cost-effective (~80% of PE-5 price).
  • Limitations: Slightly lower high-temperature tolerance vs. PE-5 (long-term 220°C).

6. Usage & Maintenance Guidelines

• Storage:
  • Store sealed in dry, ventilated areas (10°C–25°C); shelf life: 5 years. Avoid direct sunlight.
• Application:
  • Do not mix with mineral oils, silicone fluids, or other hydraulic fluids.
  • Clean systems thoroughly before refilling; use SKYDROL-compatible filters.
• Safety:
  • Wear chemical-resistant gloves and goggles; use respirators in poorly ventilated areas. Wash skin with soap if contacted.

7. History & Market Status

• Development:
  Developed by Monsanto Company (now under Eastman) in the 1970s; commercialized in 1978 with over 40 years of service.
• Market:
  • Global Share: >50% of aviation phosphate ester fluids; annual sales exceed 12,000 tons.
  • Pricing: ~RMB 1,200–1,500/L (2025, tax-inclusive); sold in 3.78L containers for civil use.

8. Technological Trends

• Eco-Friendly Upgrades:
  Reducing sulfur/phosphorus additives; developing ashless formulas to comply with ICAO CORSIA.
• Synthetic Advancements:
  Exploring full-synthetic ester base oils to boost temperature tolerance (target: 220°C continuous operation), competing with Shell AeroShell Fluid 41.

9. Conclusion & Selection Guidance

Recommended For:

• Commercial aircraft (Boeing, Airbus) requiring mature, cost-effective hydraulic solutions.
• Budget-sensitive industrial equipment compliant with AS1241 standards.
  Not Recommended For:
• Ultra-high-temperature (>200°C) operations (use SKYDROL PE-5 or AeroShell Fluid 41).
• Strong acid/alkali environments (custom corrosion-resistant fluids required).

SKYDROL LD-4 remains a benchmark in aviation hydraulics due to its maturity, broad temperature adaptability, and cost efficiency, though newer variants (e.g., PE-5) are gaining traction for specialized needs.