JP-4 (Jet Propellant 4) is a wide-cut aviation turbine fuel developed primarily for military jet and turboprop aircraft operating in extreme cold climates. It is produced by blending gasoline-range naphtha with kerosene fractions, resulting in high volatility, rapid ignition, and an exceptionally low freezing point.
JP-4 served as the standard U.S. Air Force jet fuel from the 1950s through the early 1990s. Although largely replaced by safer fuels such as JP-8, it remains relevant for legacy aircraft, historical operations, and specialized military environments.
Key Characteristics
Wide-Cut Hydrocarbon Composition
Carbon range: C4–C16, combining light naphtha and kerosene hydrocarbons. This produces a broad distillation range, high volatility, and rapid vaporization.
High Volatility & Fast Ignition
Ensures reliable cold starts and quick ignition in low-temperature environments, but increases fire and explosion risk during handling.
Exceptional Cold-Weather Performance
Freezing point around –60°C allows operation in arctic, high-altitude, and extreme winter conditions.
Low Flash Point (Safety Trade-Off)
Flash point typically below –18°C, making JP-4 significantly more flammable than JP-8 or JP-5 and requiring strict safety controls.
Refining & Production Properties
Wide-Cut Distillation: Fraction collected between ~30°C and 280°C.
Blending Strategy: Straight-run naphtha blended with light kerosene to meet volatility and freezing requirements.
Hydrotreating: Removes sulfur, nitrogen, and trace metals.
Additives: Antioxidants, corrosion inhibitors, and static dissipaters for military handling.
Typical Physical & Chemical Properties
| Property | Typical Value | Operational Significance |
|---|---|---|
| Fuel Type | Wide-cut turbine fuel | Military aviation |
| Hydrocarbon Range | C4–C16 | High volatility |
| Flash Point | ~ –18°C | High flammability |
| Freezing Point | ~ –60°C | Extreme cold operation |
| Density @ 15°C | 0.75–0.78 kg/L | Fuel planning |
| Energy Content | ~42–44 MJ/kg | High power output |
| Appearance | Clear to pale straw | Visual inspection |
Applications
Military Aviation: Legacy jet fighters, turboprops, training and support aircraft.
Cold-Region Operations: Arctic and high-altitude bases.
Historical & Research Use: Museums, fuel testing, and legacy aircraft programs.
Safety, Handling & Storage
Highly flammable fuel requiring strict grounding and bonding.
Explosion-proof storage tanks and vapor-control systems recommended.
Not suitable for confined environments such as aircraft carriers.
Standards & Specifications
MIL-DTL-5624 (U.S. Military Specification)
NATO legacy equivalents
Military quality assurance protocols
JP-4 vs Other Military Jet Fuels
| Parameter | JP-4 | JP-8 | JP-5 |
|---|---|---|---|
| Fuel Type | Wide-cut | Kerosene | High-flash kerosene |
| Flash Point | Very low | ≥ 38°C | ≥ 60°C |
| Freezing Point | ~ –60°C | ~ –47°C | ~ –46°C |
| Safety | Low | High | Very High |
| Current Usage | Legacy | Primary | Naval |
Advantages
Outstanding cold-weather operability
Rapid ignition and reliable starts
Suitable for early-generation military jet engines
Limitations
High fire and explosion risk
Higher evaporative losses
Strict storage and handling requirements
Largely phased out in favor of safer fuels