Jet A-1: understanding aviation fuel quality requirements

Jet A-1 is the kerosene-type fuel used by civil aviation worldwide. Because it powers engines working in extreme conditions (temperatures close to −50 °C at cruising altitude, varying pressures, an absolute reliability requirement), its quality is framed by recognised international specifications such as ASTM D1655 and DEF STAN 91-091.

Jet fuel cannot be judged by eye: it is proven by analyses, documents and an unbroken chain of control, from the refinery to the wing of the aircraft.

Two specifications, one common baseline

Two documents carry authority. The American standard ASTM D1655 defines kerosene-type aviation turbine fuels, including Jet A-1. The British specification DEF STAN 91-091 covers the same product with a few additional requirements, particularly on additives and qualification testing.

To avoid every operator applying its own reference document in shared airport depots, the industry uses a consolidated document, the AFQRJOS (Aviation Fuel Quality Requirements for Jointly Operated Systems), commonly called the "Check List". For each characteristic it retains the more stringent of the two limits. Product that meets the Check List therefore meets both specifications at once: this is the usual basis of international contracts.

The characteristics that matter

Behind the words "Jet A-1" sits a list of some thirty laboratory-tested parameters. A few of them capture most of the technical constraints:

• Freezing point: −47 °C maximum. This is what distinguishes Jet A-1 from North American Jet A (−40 °C) and what makes long-haul flights at high altitude possible, where the fuel must never begin to crystallise.
• Flash point: 38 °C minimum. It governs the safety of storage and ground handling.
• Density: between 775 and 840 kg/m³ at 15 °C. It feeds directly into the calculation of the mass uplifted, and therefore into the flight plan.
• Sulphur content: 0.30 % by mass maximum, with a specific limit on mercaptan sulphur, which is corrosive to certain alloys.
• Electrical conductivity: 50 to 600 pS/m where a static dissipator additive is used, so that charges generated by high-rate pumping can drain away.

Thermal stability, aromatic content, lubricity, fouling tendency and behaviour towards water complete the picture, each measured by a standardised test method.

Strictly controlled additives

Unlike road fuels, Jet A-1 admits only a closed list of additives, in capped quantities: antioxidant, corrosion inhibitor and lubricity improver, static dissipator and, depending on operator requirements, fuel system icing inhibitor. Anything outside that list disqualifies the product. This is an important cultural difference for anyone coming from other petroleum markets: in aviation you do not improve a batch, you either certify it as compliant or downgrade it.

Preserving quality along the chain

Compliance is not settled once and for all at the refinery gate: it has to be maintained at every transfer.

• Documentation. Each batch travels with a Refinery Certificate of Quality, supplemented at each stage by certificates of analysis. Where product is commingled or doubt arises, full recertification is required.
• Dedicated equipment. Vessels, trucks and pipelines assigned to aviation fuel must not have carried incompatible product; failing that, cleaning and requalification procedures apply.
• Filtration. Depot and into-plane facilities use filter water separators and monitors qualified to Energy Institute standards, replaced at defined intervals.
• Pre-transfer checks. Draining low points, a visual check in a clear jar, free-water detection, density measurement and a conductivity check precede every product movement.
• Microbiological monitoring. Residual water at the bottom of tanks encourages micro-organisms to grow; standardised rapid tests detect contamination before it reaches aircraft filters and probes.

From refinery to aircraft: who controls what

The aviation supply chain involves successive players, each responsible for one link. The refinery produces and certifies the batch. The trader or supplier arranges shipping and answers for compliance on delivery. The import terminal receives, stores and re-tests. The airport depot, often jointly operated by several companies, handles final storage and filtration. The into-plane operator carries out the transfer to the aircraft and the last checks before uplift.

Industry reference documents, those of the Joint Inspection Group and the Energy Institute, set out precisely the operations, testing frequencies and records expected at each of those stages. They are the basis of the audits that facilities undergo regularly. For a buyer, knowing which link a supplier occupies, and which responsibilities it takes on contractually, matters as much as the analysis sheet itself.

What this means for the buyer

For a buyer, the quality of a Jet A-1 supply is read as much in the paperwork as in the product. Three habits avoid most of the difficulties: check that the contract explicitly references the AFQRJOS Check List or the applicable standard; require full traceability of the batch, from the refinery certificate to the last certificate of analysis; make sure the logistics involved comply with the applicable dedication and filtration rules.

These requirements may look heavy. They are the price of a product that tolerates no surprises: once on board, the fuel can no longer be checked.

Talk to us

Looking for a reliable supply of Jet A-1, with complete documentation and compliant logistics? Contact our team or read our Jet A-1 product page.