Most airplanes flight manuals require fuel pumps off after engine shutdown and on only before departure. Usually they don`t explain why they should be off for refuelling. I remember reading somewhere that having the fuel system pressurized will increase refuelling time, but I don`t remember where I read that!
We still have a requirement via NTC since Oct 07 to switch the Ctr Tank Pumps to OFF for refuelling (A320 Family). Could it be this which is causing confusion? Software fix due by end of 2008 still not seen!
According to an Airbus technical representative, unless there is a ban in the FCOM for your specific aircraft (probably through an OEB), there is no restriction to switching on the fuel pumps during refueling. It does not affect the rate at which fuel is uplifted. It must also be remembered that the A320 centre tank fuel pumps will only run when required when in Auto mode, and sitting on the ground with the engines off, these pumps will be de-energized.
"It must also be remembered that the Airbus fuel pumps will only run when required, and sitting on the ground with the engines off, the pumps will be de-energized."
Really? I thought it was the case only for the center tank pumps in auto mode (run when required). The pumps in the wings run continiously if selected on. And engines running or not has no effect for any fuel pump operation.
There was a notice out some years back from Airbus to the effect they had identified a potential problem with a number of fuel pumps made by Eaton Aerospace Limited. The recommendation was to ensure all pumps were off after parking and prior to refuelling and once refuelling was complete the pumps could be selected on.
This is still SOP in my company and have recieved nothing from the tech guys or fleet management to change this
I am not familiar with the A320 but on A300-600 when the inbd tank boost pumps are running, fuel pressure opens a valve allowing the refuel manifold to drain into the inbd tanks - if the pumps are on when refueling fuel will continue to go into the tank whether the refuel valve is open or closed and can lead to fuel spillage. I suspect the A320 uses a similar system.
Further to the above, the OEB referenced, related to runnng the pumps when uncovered. If I recall correctly there needed to be approx 2? tonnes in center tanks and appox 750 in the inners when selecting the pumps on. Thus the recommendation to select the center tank pumps off on the ground, during refuelling (lest there is a bug the system that caused the center tank pumps to run when they were uncovered). The EU AD related to this issue had a compliance date earlier this year.
The above guards against the case where center tank pumps can run with low quantities of fuel in the tank, often leading to Auto Feed fault or other wise, but if the Ctr Tk pumps do run in an empty tank the pressure switch would identify this causing LO PRESS indication (ECAM alert, master caution etc).
There is also a page in the FCOM that recommends that if the pumps do run with little or no fuel in the tanks then select them off during cockpit preparation.
Operation of the center tank pumps in Auto Mode depends on factors such as the state of wing tank and center tank level sensors and slat position, as well as engine speed - the pumps can run in auto, without the engines running.
From my understanding the refuel manifold on the A320 Family drains by a simple drain valve, and that the practice of the A300-600 where running the pumps opened the refuel manifold drain valve was not carried across. I think also there was a mod to address this issue on the A300-600.
There are OEBs that keeps coming back like a bad penny regarding the fuel pumps. They usually require all the fuel pumps to be switched off until refueling is completed. The OEBs might also require the mode selector to be on MAN and specify a refueling procedure. The OEBs only apply to specific serial numbers of specific types of pumps. Once the pump(s) have been modified or replaced, the OEB no longer applies, even if it's still in the QRH or wherever your company hides those things.
If there is no OEB, you might refer to the Normal Procedures section of the QRH. Under COCKPIT PREPARATION/OVERHEAD PANEL, the first item is:
OEBS aside, we've had a history fuel spills which we simply can't explain. We've considered the entire gamut of reasons. Airbus have loked at everything and were no help. We looked at density/temp issues - sensor faults, ramp gradient in both axes - , all we're left with at this point is that the fuelers are fueling in manual mode instead of in automatic. Proving that after the fact though is near impossible. In the end, we switch pumps off for refueling. Spill incidents have practically disappeared so we're content with the status quo.
Don't confuse an OEB regarding the use of Centre Tank pumps that had a problem (screws loosening and causing a potential electrical short) and now withdrawn for all pumps that have been modified (locktite!) with a load of BS about fuelling being slower with the pumps running. I have it staight from Airbus Flight Ops that this is not true. The FCOM on cockpit preparation clearly states "all while lights out" which includes switching the pumps ON - no mention of not doing it while refuelling. Some folks bring old habits to new airplanes and it aint any help! There is no evidence that fuelling with the pumps on slows the refuelling process so just do as the manufacturer suggests - unless of course you know better!! Those guys are usually the ones who don't want to comply with the SOPs too.
There is a train of thought that all electrical switching should be minimised during fuelling incase fuel vapour has built up and the relevant switching generates a spark due to a switching malfunction etc and the vapour is ignited... Maybe its oldschool but you dont need pumps on the refuel so why bother...?