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-   -   WX Radar and Exterior ligths test during re-fuelling? (https://www.pprune.org/tech-log/552002-wx-radar-exterior-ligths-test-during-re-fuelling.html)

Manicured garden 27th Nov 2014 21:02

WX Radar and Exterior ligths test during re-fuelling?
Hey guys, I'm a B737 pilot and my question is; as my company SOP has (some other companies have) a rule/recommendation about not testing WX Radar and exterior lights during re-fuelling. I do not see any statement regarding this on Boeing formal documents that's why I'm curious about the probable reason of this prohibition.

Can anyone inform me?

Thanks in advance

Dash8driver1312 27th Nov 2014 21:05

WX Radar and Exterior ligths test during re-fuelling?
Breaking/making high energy electrical circuits while fuel is flowing is the logic I've always heard...

dash6 27th Nov 2014 21:06

No,carry on doing anything you feel like. Thank you,in advance,for freeing up a job.

JeroenC 27th Nov 2014 21:43

WX Radar and Exterior ligths test during re-fuelling?
Dash6, you're rude. He's merely inquiring. Answer or refrain.
Ontopic; our SOPs allow all switching except keying HF during refueling.
Having said that, I would not test the wx radar either, but that's not more than, hmm, common sense but not based on any facts, so might be overly cautious.

grounded27 28th Nov 2014 06:01

Bullshit, test away. Especially with current EWIS electrical standards and low wattage WXR. There is no reason to believe that lights or WXR would be a threat during fueling (might piss the fueller off with the wingscan). No threat.

Capt Quentin McHale 28th Nov 2014 06:30


Could you please publish the EWIS electrical standards for all to see as you have my curiosity. Also, if all is ok in the electrical world, then why is it that it is MANDATORY for the refuel truck to be grounded to an earthing point AND the aircraft..... static discharge perhaps?

Manicured garden,

I think common sense would prevail here and not give Murphy's (law) any source of ignition whilst refuelling. You may recall that as fuel is getting pumped in, fuel fumes are escaping out of the fuel tank vents.

STBYRUD 28th Nov 2014 06:36

Even if that WXR is only radiating a couple hundred watts... Ever accidentally left something metallic in your microwave? :}

grounded27 29th Nov 2014 00:46

Also, if all is ok in the electrical world, then why is it that it is MANDATORY for the refuel truck to be grounded to an earthing point AND the aircraft..... static discharge perhaps?

Yes, age old practice to ground or "earth" both the truck and the aircraft. To to say we do not encounter fuel leaks today but they are less that they were years ago. Also to mention The high flash point of jet fuel as opposed to 100LL when the practice was initiated.

EWIS, here is an outline (the FAA take on it)..

It was a knee jerk reaction to TWA flight 800. Routing, terminating and protecting of wires especially in a fuel tank is taken much more seriously. Fuel pump C/B's do not get reset w/o isolating a fault first. Fuel tank inerting has become common in the civilian world.

The only rule that ever made sense to me was keying up an HF on a 74C as the couplers are out on the wing tips close to the vent boxes. WXR that is contained in the front of the aircraft and is much lower wattage with flat panel systems or nav/high intensity lights out on a wing tip that have been maintained and designed to higher standards would not make me think twice about turning on. Every aircraft I have ever been around in the last 20 years has had nav lights burning during refuel.

May it be that earthing is not as safe as grounding:O, I think not.

Capt Quentin McHale 29th Nov 2014 04:04


Many thanks, a very interesting read.

TURIN 29th Nov 2014 12:12

Standard practice has been no Wx Radar, HF transmitting, Strobe lights or engine/APU starting during refuelling.

It is apparently to avoid the chance of any fumes from the fuel tank vents igniting from high energy discharge or jet pipe heat source.

I think the engine/APU exhaust has to be more than 15m from the fuel vent which places the likes of the A330 stab tank vent a bit close to the APU jet pipe.

As I say, all this has been standard practice with my employer for as long as I can remember. Whether or not it is still relevant on a practical day to day operational basis is open for discussion. :ok:

Chu Chu 29th Nov 2014 13:09

If the glass envelope of an incandescent (or halogen) bulb had broken since the last time it was used, the exposed filament would make a pretty good ignitor. I guess it's pretty unlikely for this to happen without being caught, and even less likely that an explosive mixture of fuel fumes would be present if it did. But maybe still enough of a risk to think about?

390cruise 29th Nov 2014 14:12

SOP is don't do it...........

Don't do it !

RAT 5 29th Nov 2014 14:28

It used to be, in an older airline and older a/c, that use of the toilets was forbidden during re-fueling due to activating the flush motor. Now, in a more modern airline and more modern a/c with suction systems (still activated by an electric motor) Boeing OK'd their use during fuelling. No reason, just OK'd it. Could this be the same 'old wives tale' as the use of personal devices and mobiles etc? The rules are now much relaxed. I see the dispatcher walking near the bowser radio in hand and talking. I see ground staff using mobile phones all over the aprons. I know nothing of output power of isolation systems etc. it's just observation.
It clouds the truth.

deptrai 29th Nov 2014 15:12

It's a good idea to err on the side of caution. While I cant recall wx radar, exterior lights, or mobile phones ever caused an accident..there's always the odd freak accident coming your way if you test your luck. “lets see if we can retract the landing gear while on the ground. I bet we can't” comes to my mind

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