Thread: Best Point for Grounding Strap Attachment During Fueling

Hey Gang,

What is the best point to use to attach a grounding strap during fueling? Wheel bolt? Exhaust pipe? Somewhere else?

Thanks.

Andy
N547AW

Exhaust Pipe

Hi Andy,

The exhaust pipe.

Thanks. That's where I've been doing it. Brought up the question because a fueler mentioned some other aircraft owners had requested he not attach it there.

This is a good metal to metal contact point that joins the entire engine and system that connects to all the other grounds.

Just out of curiosity, has anyone ever checked to see that there's actually a ground path from the filler ports to the exhaust pipe? I bet there isn't, and that's the whole point of the ground connection.

I took a Flukemeter out to the hanger and measured the resistance from the filler fittings to the exhaust pipe. Left side was 82k ohms, right side was 800k ohms. Not exactly a good bonded connection.

I don't know quite what to make of this. I think grounding the fuel truck to the exhaust is still the best bet, but I'm a bit concerned by these numbers.

I wonder is there an FAA spec? My guess is that 800k is probably just about acceptable, given that high static buildup is a requirement for a spark, and that some current leakage is better than none. But I dont know how quickly static builds up; thats the other side of the equation. Anyone got references?

Originally Posted by hhobbit

I wonder is there an FAA spec? My guess is that 800k is probably just about acceptable, given that high static buildup is a requirement for a spark, and that some current leakage is better than none. But I dont know how quickly static builds up; thats the other side of the equation. Anyone got references?

While I'm not an expert on this, a quick look through "NFPA 77: Recommended Practice on Static Electricity" (free registration required) states that 1 megaohm maximum is accepted and a dissipation time of less than 1 minute is needed (1 minute would be for up to 20m^3 (5283 gallons)).