• The aircraft should be bonded (grounded) to the fuelling equipment using — Page 327, Lesson 415

Let's pick this up right where the safety rules get practical — the bonding and grounding of the aircraft during fuelling. The first point is about how the aircraft connects to the fuelling equipment. The aircraft should be bonded, or grounded, to the fuelling equipment using dedicated wires and clips. Now, "bonding" and "grounding" here mean the same thing in this context — creating a continuous electrical connection between the aircraft's metal structure and the fuelling equipment, so that any static electricity that builds up can flow away safely instead of sparking. The key word is "dedicated" — these are purpose-made wires and clips, not just whatever happens to be lying around. And here's the critical warning: reliance must not be placed upon conductive hoses for effective bonding. Even if a hose looks like it's made of conductive material, you cannot trust it to carry the bonding current. The hose might have a break, a dry joint, or a non-conductive section, and then you've lost your electrical path without knowing it. So the dedicated wire and clip is the only acceptable path. Now let's look at the two different fuelling methods, because the bonding requirement changes between them. First, overwing refuelling — that's the traditional method where you open a filler cap on top of the wing and pour or pump fuel in through a hose nozzle. The rule here is that the hose nozzle should be bonded to the aircraft structure before removing the tank filler cap. Think about the sequence — you make the electrical connection first, then you open the tank. That way, any static charge is already being drained before you expose the fuel vapour to the air. And it doesn't stop at the nozzle. Even funnels, filters, and cans should be bonded to the aircraft. If you're using a funnel to pour from a can, that funnel and that can are part of the fuel path, so they need the same electrical connection. And then the absolute prohibition: plastic funnels or pipes should never be used. Plastic is an insulator — it cannot carry static electricity away, so it lets charge build up on the fuel surface, and that's exactly the spark risk we're trying to eliminate. Now, underwing pressure refuelling — this is the modern method where fuel is pumped in under pressure through a coupling under the wing. Here the rule is different, and it's a nice contrast. The mechanical metal-to-metal contact between the aircraft fitting and the nozzle end eliminates the need for a separate hose-end bonding cable. So when the nozzle locks onto the aircraft's refuelling adapter, you have solid metal touching solid metal, and that physical contact itself provides the electrical path. No separate cable needed at the hose end. But notice — this only works because of that metal-to-metal contact. If there's any doubt about that contact, you'd be back to needing the dedicated bonding. There's also a note in here about the sequence of refuelling, and this is a separate concern from bonding — it's about the centre of gravity, the CG. The sequence in which you fill the aircraft's tanks can adversely affect the CG position, particularly if some tanks are only to be partially filled, and/or the aircraft has a vertical or horizontal stabilizer tank. A stabilizer tank is a fuel tank located in the tailplane — the horizontal stabilizer — or in the vertical fin, and filling those changes the balance of the aircraft dramatically because they're so far from the centre. So if you fill the tail tank first, you might push the CG aft beyond its limit. The rule here is simple and humble: if in doubt, consult the aircraft manual. The manual will give you the approved fuelling sequence for that specific aircraft. So to tie it all together — the core principle is that every piece of the fuel path must be electrically continuous with the aircraft structure, using dedicated bonding where there's no guaranteed metal-to-metal contact, and never trusting hoses or plastic to do that job. And separately, the order in which you fill the tanks matters for the CG, so you follow the manual.