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fuel qty indicator shows off scale high


sdt636
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Failure or malfunction of any fuel quantity indicator is indicative of a possible failure that would, with the proper sequence of events, allow the introduction of high voltage electrical power into that associated fuel tank.

In the event that a fuel quantity indicator goes to OFF SCALE HIGH or OFF SCALE LOW pull the associated fuel quantity indicator circuit breaker.

That's what you need?

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I have had to much beer induced memory damage, but back in the early 70's we had a Navy crew from Pax River at the Langley sim.

Not long after they put a herk in the mud on the Eastern Shore.

I know they reset a CB in flight and blew part of the wing off. I think it was a fuel pump CB but it might have been a quantity indicator.

Anyone remember?

Trying to recover the aircraft back to Pax River, the navy dropped it in Chesapeake Bay.

Moral of the story don't reset fuel CB's in flight!!

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Our crews were always told to pull the breaker. Once pulled, the breaker could not be reset until maintenance ran the GTF-6 or "silver suitcase" to check the tank readings for the wiring and probes. FE's were to dip the tank in question in order to fly. Most older Hercs had numerous splices in the wiring especially in the flap well area. Some of these splices were non-environmental. Over time and subjected to water, the wire and metal portion of the splice would corrode and readings would become erratic. During ISO's, I replaced the entire wire between connectors when time permitted. If not, I replaced the splices with environmental splices. It took a few years to get all the planes right, but when that was completed the only problems we had with erratic readings were due to the indicators themselves. As to power, the wiring going from the tank to the indicator is not to be routed in the same bundle as other systems wiring that would have power running on it.

Rich

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We have often problem with Fuel Qty Indicators. The problem is often two symmetrical indicator goes Off Scale High/Low. One of the practice i saw that our maintenance personnel does is that; "They reset the CB on the ground. If the Quantity indicator comes back normal they release the aircraft for flying. Even it happened with me that I taxi back the aircraft they reset the CB while engines were running and when the indicator was alright we went for flying." I request your valuable opinion regarding the practice. Another query i have that is"How many hours can we continue flying with two symmetrical fuel quantity indicator unserviceable? What is the procedure we should follow while such flying?"

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I doubt if I would fly with symmetrical indicators out. Once the symmetrical tanks were dipped the symmetrical fuel gage was used as the "fuel quantity reading" for the inop symmetrical tank. It would take a critical situation or a command directive to get me in the seat.

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  • 3 weeks later...

which tank are speak of?

We currently had a problem with an aux tank indicator, we replaced teh wiring, compensator, measured the wiring toward the cockpit, it was ok for the first flight but than when the tank was empty simular problem...:(

Any how further investigation we came to the conclusion that the vent system didn't worked properly, due to this errnously working vent system the bladdercel implodes, not completly but step by step, so we looked a litlle futher and we have seen that the knots of the cords which holds the bladdercel open came lose, and damaged the compensator (full scale)

greetz:cool:

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hercmylove,

I would fly without gages (don’t need no stinking gages...or is it gauges???) long before I would just reset the CB.

Explosions are explosions no matter what the location of the aircraft!

I would say to your people that "resetting a CB" is NOT maintenance and they run the risk of BLOWING the WING OFF!!! If they insist or continue this practice maybe it’s time to walk away before they rest it!

You only get so many "that was stupid" passes in this life and to let fools use yours up is not cool!

As far as flying with bad gages as long as you have a fuel flow meter for each engine you should be able to fly normal profiles (might increase you min fuel limit) we are only required to have 2 gages. (1 and 3) or (2 and 4) or (1 and 2) or (3 and 4) but even with less a fuel chart and operation proceedures should allow for near normal operations.

Continuously scan your aileron trim and disconnect your autopilot on the top of each hour to check wing balance and you should have no problems.

If you only have main tank fuel I would say you can safely fly 4-5 hours. and have approx 10,000 total fuel remaining. Aux would extend that time by 2-2.5 hours.

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The problem with resetting the CB on an indicator that has gone off scale high or low is that the fuel probes in the wing can fail in such a way as they actually become a capacitor and can shoot a high voltage discharge right into the tank.

In the USAF fuels TO there must be at least a hundred warnings not to reset these CB's until the proper troubleshooting is complied with.

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