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Another TIT question for the group


M20TN_Driver

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Odd that the last post was also TIT related...

I flew yesterday for the first time in a couple week and the TIT indication in the G1000 was all over the place...it would go up to Normal range 1600 (when leaned) then bounce down 300 degrees or more then back up.  Just this pattern of wild reading for the entire flight.  

So I have never messed with this before on the Acclaim.  My first thought is that it was a bad or loose probe.  Can someone tell me where this probe is located and if there is more than one?

From the prior post, if required, the correct part number for replacement is:  ALCOR PN: 86309. Is this also the correct part number for replacement?

 

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I would look for a wiring issue before replacing the probe.

The fact that it is changing by 300 degrees indicates that there is a short forming a thermocouple at a point 300 degrees colder. Also, a short by either conductor to anything could affect the reading depending on the signal processing circuit used.

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I replaced my TIT probe on my Acclaim at 960 hours. It started to be erratic and then it suddenly got a red X. Cleaned it and it looked great. Worked for a few more hours and then the dreaded red X again. Replaced it with same part number and it's been perfect since. BTW, it was reading 200 degrees low before which is an indication of it dying. Those probes live a rough life.

There's only one probe on the co-pilot side of the engine . Super easy to access and change. Good luck.

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 My engine eats EGT probes like they’re free.  TIT probe is the same, just 1/6 as often.  What you describe is typical of the failure mode I’ve experienced.  They start out reading low, then they wig out, then they “X” out.  Probably a good idea to have a spare.

In the PA46 world, I believe they are 500 hour replacement items.  Dunno if that is in the MX manual or received wisdom within the tribe.

-dan

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9 hours ago, flyfast said:

I replaced my TIT probe on my Acclaim at 960 hours. It started to be erratic and then it suddenly got a red X. Cleaned it and it looked great. Worked for a few more hours and then the dreaded red X again. Replaced it with same part number and it's been perfect since. BTW, it was reading 200 degrees low before which is an indication of it dying. Those probes live a rough life.

There's only one probe on the co-pilot side of the engine . Super easy to access and change. Good luck.

Thank you so much for that. Sounds like this is the beginning before the fall!  I’ll take a look but thanks again for the info. 

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11 hours ago, N201MKTurbo said:

I would look for a wiring issue before replacing the probe.

The fact that it is changing by 300 degrees indicates that there is a short forming a thermocouple at a point 300 degrees colder. Also, a short by either conductor to anything could affect the reading depending on the signal processing circuit used.

I am definitely going to inspect prior to replacing. Hopefully an easy swap of bad. 

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TIT probes are in the worst environment… ever!

EGT probes are closer to the fire… but they only see one flame front per two revolutions…

TIT sees six flame fronts pass by in the same amount of revolutions… so the peak isn’t as high being downstream from the fire…

But it sure stays hotter longer with each cycle….

Feel free to buy a spare probe to have on hand… inspect the probe’s tip…. Erosion of the metal jacket is the most probable source of a TIT gauge’s challenges… Also, check the ship’s MEL… the TIT gauge is probably on the list.

Higher TITs can be extra hellish… excess O2 by running LOP has not been known to increase the erosion…

If going full dragon mode… expect to use up cylinders and swap out some TCs… as part of the glory cruising 200+ kts…

NA engines don’t need to swap out as many EGT probes either… the non-confined flows drops the temps quickly over a very short distance…  great for exhaust system longevity…

Life inside a TC’d engine’s exhaust… between the exhaust valves and the turbo is as unfriendly as it gets… very high Ts and Ps have a tendency to erode everything including the pipe walls… over time…

:)

PP thoughts only, not a mechanic…

Best regards,

-a-

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On 1/23/2023 at 1:48 AM, M20TN_Driver said:

Thank you!  I’m assuming it’s shot. Just hoping not becuase they are super pricey. 

A physical inspection will probably determine if the casing is roughed up…

They are usually born with a smooth surface to keep things from sticking to it…

And of course… 2X… one for each turbo…

PP thoughts only…

-a-

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I don't know what type of probe you are using. I have JPI probes in my 231 for TIT and EGT and have never had to replace one. They have been in the engine for around 1700 hours at this point. I can't imagine the environment for the Acclaim would be different than in my engine, the probes are in the same places and see the same temps.

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I am not sure, but I am reading a lot of notes from folks that have to replace theirs every few hundred hours.  The game I am trying to play is to determine if I can use a JPI TIT in place of the Alcor 86309.  They want $550+ dollars for that probe.  I called top gun here in Stockton and they told me that JPI PN 1210TIT-1 is a cross referenced to a mooney part number for this probe.  I called JPI and they have no spec sheet on this probe...at least the person I spoke with said that (clearly not an engineer).  

I'd prefer to save $400 if I can:  https://www.aircraftspruce.com/catalog/inpages/jpiscrewintypeprobe_10-05934.php

Anyone Acclaim drivers find a different/cheaper TIT that works with the G1000?

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1 hour ago, M20TN_Driver said:

I am not sure, but I am reading a lot of notes from folks that have to replace theirs every few hundred hours.  The game I am trying to play is to determine if I can use a JPI TIT in place of the Alcor 86309.  They want $550+ dollars for that probe.  I called top gun here in Stockton and they told me that JPI PN 1210TIT-1 is a cross referenced to a mooney part number for this probe.  I called JPI and they have no spec sheet on this probe...at least the person I spoke with said that (clearly not an engineer).  

I'd prefer to save $400 if I can:  https://www.aircraftspruce.com/catalog/inpages/jpiscrewintypeprobe_10-05934.php

Anyone Acclaim drivers find a different/cheaper TIT that works with the G1000?

Interesting . .  It’s the same thread. If you find that it’s ungrounded and has similar leads why wouldn’t it work? It might be worth ordering to compare and “test”.

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JPI uses grounded Type K probes (Red and Yellow) ever since '85. If the Alcor # is also a grounded Type K, then the JPI is compatible - but if not keep looking. JPI started using grounded probes since '85, before that they used ungrounded. Grounded probes are in theory faster acting probes which is why JPI made the switch. The thermocouple junction is grounded at the tip of the probe to improve heat transfer and make them more responsive. 

You can test a probe to tell if its grounded by disconnecting the probe from the instrument and measure the resistance between the probe body and the red wire. Also measure between probe body and yellow wire. ‘Ungrounded’ probes will show open circuit. ‘Grounded’ will show 5 – 10 ohms.

Getting off the subject, but the EI MVP-50/CGR-30 system can be interfaced with either grounded or un-grounded probes and can be type K or type J. But I believe that's a configuration change and requires the full set of probes to be of the same type. Their legacy units required un-grounded type K thermocouple.

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9 minutes ago, kortopates said:

JPI uses grounded Type K probes (Red and Yellow) ever since '85. If the Alcor # is also a grounded Type K, then the JPI is compatible - but if not keep looking. JPI started using grounded probes since '85, before that they used ungrounded. Grounded probes are in theory faster acting probes which is why JPI made the switch. The thermocouple junction is grounded at the tip of the probe to improve heat transfer and make them more responsive. 

You can test a probe to tell if its grounded by disconnecting the probe from the instrument and measure the resistance between the probe body and the red wire. Also measure between probe body and yellow wire. ‘Ungrounded’ probes will show open circuit. ‘Grounded’ will show 5 – 10 ohms.

Getting off the subject, but the EI MVP-50/CGR-30 system can be interfaced with either grounded or un-grounded probes and can be type K or type J. But I believe that's a configuration change and requires the full set of probes to be of the same type. Their legacy units required un-grounded type K thermocouple.

FWIW,

Type J thermocouples are only recommended up to 1400 F. They will not be reliable for EGT and TIT.

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Well the plot thickens.  I spoke directly with a Mooney tech yesterday.  He said they have been installing the Alcor 86240 probe on aircraft for more than 10+ years now.  So checking the specs out on that at aircraft spruce, the price is $122 and the ohm and grounding are completely different from the 86309????  I think I am going to source this plug and try it and just report findings back to the group. 

https://www.aircraftspruce.com/catalog/inpages/alcor_probes3.php

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  • 3 weeks later...

I did not. I pulled the cowl. Did a visual inspection. Nothing looked off. Fired it up and it’s hasn’t been a problem since. Go figure.  My guess is that is it likely going bad, but I won’t mess with it until it fails or fails more than once.  

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