B737 fuel pump circuit breakers
 

Hi folks, does anyone know why boeing does not allow resetting of tripped fuel pump circuit breakers?
I would guess thats to prevent faulty wiring within the tanks from causing a spark but I am just guessing...does anyone know better?

Thanks,
SW.

That's my interpretation, certainly. Since they are ALL not really 'needed', unless you know why the CB tripped................................

thank you guys !!!
Any other comments will be greatly appreciated !!!

THANKS !!
SW

In my company resetting of circuit-breakers is a maintenance item, unless absolutely necessary for the remainder of the flight.

Policy used to be that there was two resets allowed.. then more thought and only one reset allowed and finally, most operators have shifted to a policy that says it tripped for a reason and unless absolutely required, NO resets for an CB trip.

What happens on the line, as we know, can vary.

The wire insulation is not electricaly conductive.In case of any malfunction ,the wire will become very hot,and the insulation will most often carbonize.The CB will pop up. Any reset will put the wire under tension,but now the insulation will be very conductive,so a spark it's very probable.
IMHO this is why you should not reset a tripped cb.

Fuel Pump CBs
 

You will find that your are not allowed to reset a Fuel Pump CB on any Boeing aircraft any more, until you have found out why it tripped.
This has come from the FUEL SYSTEMS AIRWORTHINESS LIMITATIONS section, which is in Chapter 9 of the Boeing MPD and has come about from SFAR 88.
It is not mandatory as yet on most types, apart from l believe that new delivered aircraft have to be included.
Even though it is not mandatory yet, all Boeing aircraft have had Chapter 28 of the AMM amended to list all the requirements from the CDCCL's into the AMM & FIM.
Here is an example of a CB CDCCL.
Resetting Tripped Fuel Pump Circuit Breakers
Concern: Potential for arcing or sparking inside the tank between fuel pumps and fuel pump housings and outside the tank between pump wiring and structure in flammable leakage zones.
Verify it is safe to reset the circuit breaker(s) by following the applicable OEM troubleshooting procedures. Fault(s) that resulted in circuit breaker trip must be isolated and corrected prior to reset.
I hope this helps.:ok:

fuelpump cb's
 

hello every one,

the fuelpump cb' s are in the e&e compartement(b737 ng), so no access in flight.
on the ground it is definitely a maintenance issue.

kind regards,
bm,

Sure I've seen on other types/operators NO reset of any system CB after one unsuccesful reset. One CB trip could be viewed as a 'spike' , but any more i would say indicates a genuine defect, so no resets after one try presumably.