Jump to content

Digital fuel indication went off during normal flight


bruno_Tuga
 Share

Recommended Posts

I´m working in a c130 H, s/n 5115, equipped with digital fuel indication.

During normal flight, the pilots loose all fuel indication minus in the EXT LH and #3, whem they set the aircraft to a high velocity. In the begening they said that it was with a certain atitude. But after a new flight test, they saw that in all atitudes that they give to the aircraft the problem is the velocity.

The indication goes off, like losing power, and goes on with a smaller velocity.

Can someone help?

Thank You

Link to comment
Share on other sites

So the indicators remain Blank (off) NO indications except #3 and Rt Ext at airspeed above_____KIAS? (Same TAS or same IAS)

Or do they go to 0.00?

What does the Totalizer do? Blank or still reads same fuel quantity or less?

Any other indications like TIT Flags in view?

Link to comment
Share on other sites

So the indicators remain Blank (off) NO indications except #3 and Rt Ext at airspeed above_____KIAS? (Same TAS or same IAS)

Or do they go to 0.00?

What does the Totalizer do? Blank or still reads same fuel quantity or less?

Any other indications like TIT Flags in view?

More information about the problem:

- The indication went off with aircraft in level flight 17000 ft 240 kts and 3000 ft 220 kts. This is TAS and not IAS has i said in the last post

- The totalizer went off, no power . Start indicating when all the other indication came on

- The pilot didn t saw na failure in other inditations (TIT), everything was good except some fuel indications.

We already check the bondings off the indicators. The values of wiring and tanks are OK.

Link to comment
Share on other sites

Check the Fuel Quantity CB bus bar. The screws may be loose or the bar cracked...

Also check the wire bundle where and as the CB panel closes...

This is very strange...

We think that we found the problem. It seems that a voltage surge supressor in the pilot CB, near the fuel indication CB, had the wiring loose. Because of that whem there was a high voltage peak, the indicators where not protected. We read this in a USAF manual.

But you may ask, why there were two that didn´t went off?

We think that is because of the type (p/n) of the indicator installed. The indicators in #3 and Ext LH have the same p/n, diferent from the other six.

Tomorrow the aircraft will fly and i will them tell you if we are right.

Thank you NATOPS1 for you help.

[ATTACH=CONFIG]3350[/ATTACH]

Link to comment
Share on other sites

Bad news, today... the problem ins´t solved.

We did 3 flight´s today and still have the problem. During the day we found some more clues:

- During flight at high altitute, 16000 fts the problem doesn´t happen

- Fly level 500- 900 Fts, TAS more than 240 kts, the problem happen

- If during the low altitude flight we change from Ess AC to inverter, the problem doesn´t happen, the indication is OK

- We have diferent P/N in the indicators, those who are equal go inop. The one that is alone work good. In other aircraft we have diferent P/N in the indicators and never had this kind of problem

- We cheked all the wiring in the pilots CB, and relays behind the CB´s, all good

- We change two relays (see schematic)

We think that should be something in the power bus...

Someone want´s to give a attempt???

Thank You[ATTACH=CONFIG]3353[/ATTACH]

Link to comment
Share on other sites

This is why I asked about the TIT gage flags (off indicatiors) I think(thought) it was a power issue at the beginning.

Check the voltage on #2 Gen (A Phase) at the higher airspeed when the power goes out to the gages it must be dropping.

Turn off the #2 Gen, #1 Gen should power your Ess AC and see if your problem is resolved.

If it is resolved I think you have a wing flex issue with the #2 Gen A phase feed line.

If not turn on the inverter which provides power to the AC Inst EFC bus and is inside the aircraft so no "Speed" relationship.

Link to comment
Share on other sites

This is why I asked about the TIT gage flags (off indicatiors) I think(thought) it was a power issue at the beginning.

Check the voltage on #2 Gen (A Phase) at the higher airspeed when the power goes out to the gages it must be dropping.

Turn off the #2 Gen, #1 Gen should power your Ess AC and see if your problem is resolved.

If it is resolved I think you have a wing flex issue with the #2 Gen A phase feed line.

If not turn on the inverter which provides power to the AC Inst EFC bus and is inside the aircraft so no "Speed" relationship.

The TIT gauge were ok. I forgot to tell that we made that test od the GEN. During flight we turn off the gen #2, and the problem happened with the other 3 Gen in the BUS.

I dind´t understand clear what is your ideia and you say:

If it is resolved I think you have a wing flex issue with the #2 Gen A phase feed line.

If not turn on the inverter which provides power to the AC Inst EFC bus and is inside the aircraft so no "Speed" relationship.

Thank you, again.

Link to comment
Share on other sites

Ok... #2 Gen Off same problem.

So Not a gen Issue its a ESS AC suppy to AC Inst EFC Bus issue.

Inverter ON no problem.

Your wiring to your instruments is good, check all your connections from the Normal power fail Cb to Power relays.

Changed Power relays #1 and #2?

(They are denergized to allow ESS AC to power the AC Inst EFC Bus so I hope it works but not sure it will)

Link to comment
Share on other sites

  • 3 weeks later...

Reading your message traffic,

Was an electrical component or elec. maintenance done prior to the prob.?

Look for compatability of parts. We had an elec prob on a H2, the gen was changed also the compatable GCU. They must match.

I think your on the right track with the suppressor, that is what directly protects the digital gages.

Just a thought.

Steve

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...