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06-02-2019, 03:19 PM
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Join Date: Sep 2018
Location: Eatonton, GA
Posts: 180
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Tachometer or Engine Issue
Help me troubleshoot, please. My RV6A recently started reading about 500 rpm too low pretty consistently. I have mechanical cable from the engine with a transducer and Vans IE VTACH GEN 3500 with transducer. I?ve cleaned and lubed the cable and still reading low. The engine sounds like normal performance, has normal performance numbers, all other engine instruments reading normal. If I knock on the face of the tachometer, it has sometimes jumped up a couple of hundred rpms on the reading. How can I be sure if the issue is a tachometer issue (which seems the likely culprit) or an engine issue? Is there some sort of diagnostic testing I can perform?
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Jim Bedsole
N62MG - RV-6A "Promises" - bought flying
Dues Paid
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06-02-2019, 03:24 PM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,277
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Quote:
Originally Posted by FlyingBanker
. How can I be sure if the issue is a tachometer issue (which seems the likely culprit) or an engine issue? Is there some sort of diagnostic testing I can perform?
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Assuming an FP prop, at the same altitude and temperature, a given RPM should net a consistent TAS. Therefore, if your RPM reads 500 low for a known to you airspeed/altitude/RPM combo, you know it is an indication error.
Larry
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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06-03-2019, 12:51 PM
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Join Date: Sep 2018
Location: Eatonton, GA
Posts: 180
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I haven't had the plane that long and don't have an outside air probe, so hadn't yet calculated any TAS standards to measure against. Other thoughts on how I can troubleshoot this?
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Jim Bedsole
N62MG - RV-6A "Promises" - bought flying
Dues Paid
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06-03-2019, 12:57 PM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,277
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Quote:
Originally Posted by FlyingBanker
I haven't had the plane that long and don't have an outside air probe, so hadn't yet calculated any TAS standards to measure against. Other thoughts on how I can troubleshoot this?
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This applies to IAS as well. You can get an rpm reader at harvor freight. It uses a sticker on ther prop.
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
Last edited by lr172 : 06-03-2019 at 12:59 PM.
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06-03-2019, 07:32 PM
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Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 827
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There is no way to diagnose this without a digital tachometer, but my guess is that it is a reading issue. The transducer is prone to failure, as is the gauge. I had similar symptoms. I replaced the gauge with no improvement, so I replaced the transduce and that fixed it.
But "fixed" is a relative term. I never found the readings to be very stable, so I replaced it with a MGL RPM-1. It costs about the same as replacing the gauge and transducer.
https://www.aircraftspruce.com/catal...e-11-16591.php
With the mag sensor you will get rock solid readings
https://www.aircraftspruce.com/catal...ickkey=1900508 |
06-03-2019, 11:14 PM
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Join Date: May 2013
Location: Mount Vernon, Wa
Posts: 642
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I bought a TruTac some time ago, just out of curiosity. It works pretty good.
https://www.aircraftspruce.com/catal...es/trutach.php
__________________
Ken W.
Mount Vernon, WA
2020 VAF Supporter
Last edited by N804RV : 06-03-2019 at 11:20 PM.
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