JT8D-9A N1 readings
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JT8D-9A N1 readings
We are having problems with our N1 readings on our C-9B aircraft. There is a flucuation in indication sometimes. Others times it works perfect. We have replaced the N1 Tach-Generator and the cocpit display. After doing this it stillcontinues to flucuate. We did a eng. run up and on eng. start N1 read 0 not dashes, so i know its getting a signal. As i ran the eng. up to 1.2 epr it began to flucuate and then at 1.2 returned to normal and continued to read normal for the rest of the turn. Any other ideas what to check for this problem...Thanks
Join Date: Jan 2004
Location: Hopewell, Nova Scotia Canada
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Check the pins and condition of the cannon plug on the N1 tach, then check the wiring where it comes out below the engine. That is where the wire is spliced due to fan changes etc. Cannon pugs may look OK but when you dismantle them you may see another story.
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Good point
It normally does.
The trap has a calibrated bleed orifice. Maybe it is the wrong type or dosen't match the FCU. Changing it has fixed fluctuations.
Have you serviced the Bellows with Silicon oil, that should be the first thing to do.
Would like feedback..........
The trap has a calibrated bleed orifice. Maybe it is the wrong type or dosen't match the FCU. Changing it has fixed fluctuations.
Have you serviced the Bellows with Silicon oil, that should be the first thing to do.
Would like feedback..........
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Normally the engine would have all parameter fluctuations if the FCU were faulting. The crew would definatly let you know. Slow to spool is an indication to add silicon to the bellows.
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FF,EGT,EPR, N2 are right on the money. There is not flucuation with any other displays. Could it be the houseing that the N1 Tach rides in? When i removed the Tach Gen (N1), the houseing looked fine and the spline shaft on the old one looked good. No indication of slipping or anything. Thanks for all the inputs everyone.
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Sorry it took me so long to get back to this subject. We did find the problem after several days of troubleshooting and replacement of parts. There are two terminal boards on top of the JT8D-9A. The boards are 913/914. Come to find out the board was several corroded and several of the leads were loose. After cleaning the termianl and tightening the captive nuts on them, we solved two gripes we had. One as stated was the fluctuation of N1 and the other was high fuel temp. on the same eng.. We knew it was a reading problem on temp, because no increase in oil temp. You got to enjoy putting all knowledge to the test on a very complex, but simple gripe...Once again thank you all for the inputs..
