Trim tank pumps
 

Afternoon , do the trim tank pumps A340/330 have any overheat protection if the pumps or pump do not switch off after the trim tank is empty? ( I.e failed amber indication inline on the status page, Right hand Trim tank pump fault on ecam) Assuming it is not an indication problem are the dangers considerable ref long term running with an empty tank and fuel vapours etc, many thanks Pudd.
P.S I know there are 2 CB's in the avionics bay which will disconnect the pumps if required.

Trim tank pumps on the 330/340 are run on the same logic as the main and transfer pumps. In that they have pressure switches which monitor the pressure created by the pump. If that pressure disagrees with the status of the pump then trim tank pump fault is declared on ECAM.

The pumps should then be selected off on OHP. This will stop the pumps running.

You might want to check the indication logic before making such a definite statement.

Hi, on one occasion the Right trim pump was selected off on the OHP but indicated amber inline I.e stuck running, I suppose there is still a small quantity of fuel around the pump but I was wondering if there is any protection other than the OHP switch and CB's(last resort) in the avionics bay to prevent dry running and overheating with fuel vapours around if the tank was completely empty. Is the manual disconnection with CB's not required if OHP switch fails to turn off the pump,can the pump run for a number of hours with a dry tank without any danger of overheat? thanks, Pudd

As far as I know, going down in the avionics bay to pop CBs is not an approved Airbus procedure for flight crews, and none of the procedures by Airbus require the flight crew to have access to the CB panels. Some airline even prohibit the flight crew from going down into the avionics bay while inflight.

Hi, yep I'm aware of that, just giving the worse scenario,long range e.g. 2 hrs from nearest airfield, pump running (will not shut off via OHP) in empty vapour filled tank... does anyone know if there is an overheat protection where the pump will close due heat expansion etc to prevent a possible explosion or in those extreme circumstances would engineering allow a dispensation for you to pull a CB to ensure pump cut off, thanks, pudd

Don't operate the types mentioned but certainly a good question to think about I'd say. IMO it would fall under the authority of the commander acting in the interests of the safety of those on board, if you felt the pump may be running dry and there is no way of proving that it's not then, under the circumstances described at least, pulling the CB would seem a better bet to me than sitting and hoping it goes off of it's own accord or that it just won't overheat. I recall reading somewhere (perhaps QRH?) that a flight crew reset of CBs should only be undertaken where a checklist directs you unless it is felt it poses a significant risk to flight safety. My 2c at least.

I would have to agree, I was just curious about the pump protection if any, thanks for the constructive answers, safe flying, Pudd

Pudd,

Just to clarify can you confirm if you are looking at A330 or A3456??

As logic, and design, is slightly different on the two systems, if I understand correctly.....

Hi, mainly ref to 346. I have heard the pumps are bonded and have quite a bit of
fuel remaining in them when the trim tank indicates empty..