Misfuelling

What is misfuelling?

Delivering the incorrect type of fuel into an aircraft is known as misfuelling. This risk exists because aviation aircraft are generally fuelled via the over-wing method using a hand held trigger nozzle.

What can happen if you misfuel

The consequences of a misfuelling can be devastating, especially when jet fuel is delivered into piston-powered aircraft, which require avgas. The blend in the aircraft's fuel tanks that results from misfuelling can severely affect engine performance and lead to total engine failure – probably just after the aircraft has taken off.

This is because jet fuel (kerosene) does not burn particularly well in an internal combustion engine. It is like putting diesel into your petrol-operated car.

Ordering your fuel

When ordering fuel, you should specify the type of fuel you need and seek confirmation from the refueller. If you forget to specify the fuel type, understand that when you are asked what type of fuel you want the refueller has your safety in mind. Stating your requirements and confirming them should be part of every order, regardless of how obvious the type of fuel required may seem or how frequently your aircraft is refuelled. 

Aviation industry personnel are trained to be alert to the detail of their work and to the discipline of cross-checking. This safety culture is part of the industry and matched in few other workplaces.

Preventing misfuelling

The refuelling industry has several mechanisms to help prevent misfuellings, including colour coding of equipment and forms. 

Wing decals

The use of wing decals provides an additional barrier against misfuelling by providing a powerful visual confirmation of fuel type immediately before fuelling. The wing decals are colour coded, as are the refuelling nozzles.

Pilots are strongly encouraged to fit and regularly replace wing decals, which are readily available from your local refuelling company. We have a policy of ‘no decal, no fuel.’ Wing decals must be fitted before refuelling.

Fuel-type (grade) decals

Fuel-type decals are large and clearly visible colour-coded decals that are positioned on all fuelling storage, bowser and vehicle equipment. This also assists in fuel-type recognition.

Always check for the correct grade of fuel when your aircraft is refuelled.

Fuel-grade verification forms

Fuel-grade verification forms are used to gain written confirmation of the type of fuel required. They are used where the fuelling operator is uncertain about the correct grade to supply or where a selective spout cannot be used. 

Selective nozzles

Selective nozzles utilise different-sized spouts for avgas and jet fuel. Jet fuel nozzles utilise a larger spout than avgas nozzles. The wide jet spout will not fit into the selective avgas fuelling port.

There are many avgas aircraft that aren’t, or can’t be, fitted with a selective fuelling port, so many will accommodate the wider nozzle. Additionally, some jet fuel aircraft – particularly helicopters – have fuelling ports too small to accept the wider spout, so a standard nozzle has to be fitted.

We strongly encourage pilots to fit the selective port modification kits which are available for most avgas-powered aircraft. 

Fuel-grade carnet cards

When you order a carnet card for your aircraft you will be asked whether you require an avgas or a jet fuel card.

Our card swipe bowsers are grade-specific: an avgas card will not operate a jet fuel bowser and vice versa. 

Drums

Before filling, drums are colour-coded and clearly marked with the grade of fuel. 

Causes of misfuelling

Misfuellings are fairly rare. The industry gets it right most of the time, but when it doesn’t, the outcomes may be tragic. A slight difference in routine, a last minute change in aircraft type, parking closer to the wrong fuel bowser can all cause misfuelling.

Most of the time it is because both refueller and pilot have made assumptions. At many locations, pilots and refuellers know each other well – the same aircraft is fuelled in the same location every day at the same time. It is important to correctly confirm the grade for every refuelling.

There are quite a few examples of similar looking aircraft that require different grades of fuel. The increasing numbers of aircraft undergoing engine conversions and the recent development of the diesel cycle aviation engine have added to the risk of misfuelling.

There are many documented cases of misfuelling and one common factor that is almost always present has been a failure to specify what type of fuel is required in the first instance. 

Case studies

  • After jet fuel was used to refuel a piston-engine aircraft, it lost power from both engines and crashed shortly after takeoff. One occupant was killed and several others badly injured. No mention was made of the type of fuel required in the order process.
  • A Cessna 402C was fuelled with jet fuel instead of avgas. The 402 was operated by a company that owns several Cessna Conquests and no other avgas-powered aircraft. The refuelling location had previously only ever seen the operators’ jet-powered aircraft. The order was assumed to be for a Conquest. Both engines on the 402 required a full rebuild.
  • A passenger flight had a last minute change in aircraft type from turbine engine-aircraft to piston-engine aircraft. The fuelling staff were not told of the change and the fuel order simply specified a volume. As a result, the aircraft was misfuelled with jet fuel instead of avgas. A bystander noticed this and averted a possible tragedy.
  • A Piper Chieftain aircraft arrived and the pilot requested fuel by stating, ‘Fill the mains’. He was not aware the location had only jet fuel. Fortunately, during the fuelling, he noticed the jet fuel sign on the fuelling truck.
  • A piston-engine aircraft parked closer to the jet fuel pump than the avgas pump. The pilot requested a volume and did not notice the refuelling staff pull out the jet fuel hose. Luckily, the mistake was realised when the fuelling operator went to fuel the other side.

Lessons to learn

Misfuellings are fairly rare. The industry gets it right most of the time, but when it doesn’t the outcomes may be tragic because of a slight difference in routine, a last minute change in aircraft type or parking closer to the wrong fuel bowser.

Most of the time it is because both the refueller and pilot have made assumptions. At many locations, pilots and refuellers know each other well – the same aircraft is fuelled in the same location every day at the same time. It is important to correctly confirm the grade for every refuelling.