Over the past couple of flights I have noticed that the tach time has been increasing at an unbelievable rate. In particular, my last flight which lasted 1.35 hours (hobbs) showed an increase in tach time of ~4 hours. Tach speed for cruise is set at 2250rpm but most of flight was at less than 2000rpm. Also, after landing I noticed that the tach time was fluctuating between 14 hrs and 18hrs, but the next day it was reading a solid 18 hrs. Any thoughts? Yes I'm running version 3.0 and for the first 12 hours or so I didn't see this happening.
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Tach Time Reading Funny
- Thread starter N930RV
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Can you go into a bit more detail about the fluctuation you mentioned? Do you mean that while you're looking at the tach timer, it's actually dithering between those two values?
That's correct. The digits would change as I watched them after the flight, but the next day the numbers held steady. If this was an alpha/neumeric display I would have said I had a loose connection for the particular sigments but this is not the case with this type of display. I have not flown since resetting the tach time back to a more reasonable number so I don't know if resetting will take care of the issue or not. Perhaps some heat related problem? Any other ideas to try this weekend. I guess I could try re-installing the software?
Thanks
Bill
Thanks
Bill
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If you can hang on a few more days, we'll have firmware release 4.0 up on the web for download shortly. Our software guys are a bit baffled by your issue. If 4.0 doesn't fix it, we may need to take a look at your unit. Also, try adjusting the tach time, even moving it to a new value, exiting the menu, re-entering the menu, and setting it back to the correct value may be enough (we want the unit to actively set the tach time).
Just another data point. After flying last night the Tach time read 19.2 hrs with engine at idle. I normally keep the EMS and EFIS powered up even after engine shutdown. At engine shutdown tach time started jumping between 19.2 and 22.6 hrs. I then powered down the D120 and then repowered the unit. Tach time was a steady 22.6 hrs. I reset tach time to correct 19.2 hrs. Next test will be to turn off D120 prior to engine shutdown and then power up unit and see. Hope this info will help the software guys in figuring out where the bug is. Better yet perhaps version 4.0 already has the fix.
Bill
Bill
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What is the frequency and duration of the flickering?
I didn't time it, but something like one reading for a second or two then the other reading for about the same length of time. It really isn't a flicker but rather it was just updating the display number on a one or two second interval. I didn't let it run for any length of time to see if it would stop and settle on one of the numbers. That's something else I can test, but first I think I'll power down the unit before shutting the engine down and see what I get.
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If the 4.0 update doesn't fix it once it's available, we may need to have that unit back for a look.
One more line of questions - does it only seem to exhibit this behavior after an engine shutdown? Does power cycling the unit lock it in to one value? What is the behavior in-flight?
One more line of questions - does it only seem to exhibit this behavior after an engine shutdown? Does power cycling the unit lock it in to one value? What is the behavior in-flight?
I have a new data point for the software folks concerning the jumping Tach time. After flight if I first turn off the D120 then shut engine down and then restart D120, the Tach Time reads correctly. Perhaps the Tach Time is read from two different memory locations while still on and reads from only one of these during bootup. Somehow one of these locations is getting corrupted during the engine shutdown sequence (loss of oil pressure & RPM in some unpredictable sequence). Anyway. with version 3 I'll continue turning off unit prior to engine shutdown. As soon as version 4 is out I'll see if same problem exists.
Bill
Bill