As you will see, even though the operator thought they were doing everything right, something unexpected can still bite you.
Further Key Information
Hot refuelling – where the engine is kept running while fuelling is taking place – is not allowed when the fuel is avgas.
Avgas has a lower flashpoint – the vapour will ignite at a lower temperature, than Jet A-1. As you can see in the video, the heat of the day and the location of the fuel tank meant the fuel was vaporised before the fuel container was opened and a static spark ignited that vapour.
They were lucky it was only the vapour that ignited, and that the resulting fire could be extinguished with the equipment available.
Colin Alexander, owner of Solo Wings and experienced engineer, gives some advice on fuelling.
The Advisory Circular, AC91-22, has a lot of good information and advice on fuelling.
There is also some good advice from the two major aviation fuel suppliers:
Containers and Drums
Colin Alexander, owner of Solo Wings and experienced engineer, gives some advice on using containers.
The transport of fuels is subject to several different sets of legislation, depending on the mode of transport. Fuels are Dangerous Goods, or Hazardous Substances, but if you need to transport quantities of fuel in containers, other than a dedicated and licensed tanker, you need to be aware of the relevant legal requirements.
The NZ Agricultural Aviation Association (NZAAA) have provided a Code of Practice for fuel storage and handling. It has some good advice and can be found here.
Before using any of these containers, get a full briefing from the operator or fuel supplier about their usage and the precautions you need to follow.
Metal is better than plastic, and plastic ones must have the approval for use with fuel embossed on them. Non-approved plastic containers have a tendency to accumulate static charge and the fuel degrades the container and cap gasket. To reduce the risk of static, just before filling the aircraft tank, place the fuel can on the ground, to earth it.
In any portable container, water can mix with fuel and other contaminants. Use an appropriate filter, as recommended by a fuel supplier, which will separate out water and other contaminants. In general, it is not recommended to use a chamois cloth as many are now synthetic, the filter does the job more effectively.
- Firstly, you should positively identify the type and age of the fuel before using it.
- Make sure the pump is fitted with a clean and serviceable.
- Check drums have been stored correctly.
- When opening a drum tilt it slightly by placing a chock under it.
- Ensure the standpipe cannot reach the lowest point in the drum. You should not need the last few litres badly enough to risk using it.
- Proper bonding is critical. Connect the bonding lead from the drum to the aircraft before opening any fuel caps, and leave it in place until all fuel caps have been replaced.
Water finding paste is used for detecting the presence of water in tanks and drums. It is smeared onto a dipstick and put into the tank where it will change colour if it comes in contact with water.
Colin Alexander, owner of Solo Wings and experienced engineer, gives some advice on the dangers of static electricity.
Static can be generated from many sources, typically by the flow of fuel from the fuelling equipment to the aircraft, and by synthetic clothing (high-visibility vests can be a hazard in this case). A resultant electrical charge can build up on an aircraft, the fuelling equipment, or a person, and when two unequally-charged objects are brought close enough together, the charge will equalise by means of a spark. Static sparks can be of the order of thousands of volts and combined with the presence of fuel vapour of sufficient concentration will result in a potentially catastrophic explosion. This can be avoided using the proper bonding leads or cables, coupled with procedures to equalise any electrical potential, before any hazardous vapour is introduced into the surrounding areas.
A high fuel flow rate results in higher fuel transmission speeds, which means greater risk of static electricity build-up and also more fuel splashing.
If splashing or spraying occurs during the fuelling process (most likely during top-loading of a tank) a charged mist or foam can be produced.
Hot and dry conditions pose the greatest atmospheric risk of fuel flammability.
The most important thing to do before fuelling is to correctly bond the pump or fuelling equipment to the aircraft. When fuelling from drums, always ensure there is a bonding lead connected to both the aircraft and the drum or container in use and make the necessary connections before removing any fuel caps. Additionally, it is good practice to keep the fuelling nozzle in physical contact with the filler aperture at any time fuel is being pumped, without ‘hanging’ the nozzle in the filling aperture. This also applies to the filling of portable containers – place the container on the ground, and maintain contact between the fuel nozzle and the container.
Containers complying with Australian/New Zealand standard 2906:2001 have this instruction on the label. Check the bonding to the aircraft of any stands or ladders used to access over-wing fuelling points.
Should the bonding cable be accidently disconnected during the fuelling process, stop fuelling immediately and wait for any static to dissipate before reattaching the bonding cable.
Despite the traditionally accepted practice of filtering fuel through chamois leather, this is now not recommended. Studies have found that the use of a chamois can be a static hazard, synthetic chamois even more so. Any drum pump should preferably be fitted with an appropriate in-line filter, and the delivery hose must be fuel-specific. The fuel supplier should be able to advise on the correct equipment, and it is very important that the correct equipment is used.
For helicopters, the grounding of helicopter skids does not necessarily equalise the electrical potential between fuelling equipment and the helicopter. The use of a bonding lead or cable is still recommended.
Civil Aviation rule 91.15 Fuelling of Aircraft states aircraft are not to be refuelled or defuelled with avgas or mogas (Class 3.1A flammable liquid) when a person is:
- on board, or
- disembarking the aircraft, or
- when one or more of the propulsion engines are running; or
In addition, the aircraft is not to be refuelled or defuelled with a Jet A-1 or diesel (Class 3.1C or a Class 3.1D flammable liquid) when a person is:
- on board, or
- disembarking the aircraft.
Over-wing fuelling with one engine running is not permitted under any circumstances.
Under no circumstances may fuelling take place on the same side of the aircraft as a running engine.
Passengers should not be allowed to remain on-board helicopters during fuelling/defuelling operations.
The argument for hot refuelling is to reduce engine cycles on turbine engines and save maintenance costs. So it is about saving money, and sometimes time, but there are inherently more risks.
The main dangers of hot refuelling are:
- the potential of any fire to become uncontrollable,
- moving rotors or propellers,
- noise and rotor/prop blast can create confusion – people can do silly things in a perceived ‘rush’, and
- increased chance of static electricity build-up.
Recommendations to mitigate these risks are:
- Only consider hot refuelling when allowed by the rules (ie, never with avgas), and also when permitted in the Flight Manual (not all manufacturers allow hot refuelling).
- You should be familiar with the minimum requirements for fuelling in rule 91.15.
- Part 135 operators must have documented procedures in their expositions (rule 135.73).
- An appropriate fire extinguisher should be immediately available. Locate it several metres from the fuelling point.
- Only those essential to the fuelling operations should be near the aircraft.
- The fuel nozzle should always be attended while fuelling.
- No cigarettes or cellphones near the fuelling operation.
- Within the vicinity of the fuelling operation, no radio transmissions should be made, or electrical switches operated.
- Only refuel to about 95 percent to avoid overflows.
- Always be aware of the potential for static electricity build-up and check that bonding to earth is in place.
Mogas Vs. Avgas
Colin Alexander, owner of Solo Wings and experienced engineer, gives some advice on choosing between mogas and avgas.