TIT Probe

[blacknchrome]

Like a lot of your Bravos, I have the factory TIT guage and an EDM-700.  Do you guys know if they are both fed by the same probe or is it possible each has its own?  My EDM TIT has been reading low, so I'm thinking that it's time for replacement probe.  Tracking down the right probe is what I'm working on....and unfortunately there is no clear answer yet since there are several potential replacement parts, from JPI or Alcor.

I see the expected life is anywhere from 400 to 1200 hours, so this isn't uncommon.

Thanks

[FoxMike]

I would suggest that you find the probe you think needs replaced, remove it and use the part number on it to order a replacement.  I think you wil find two TIT probes at the end of the exhaust system.  The factory uses a screw type probe located in the exhaust transition next to the turbo inlet.  I would guess the EDM is located upstream of the factory probe.  

[johnggreen]

On my last cross country flight, eight days ago, I noticed what I thought were lower TIT's for the settings.  I was flying higher than normal power settings because I was low, 10m, and trying to make time around an area of thunderstorms.  Higher meaning only 2400/30" as I ususally fly at less so maybe it's just me.  

That being said, it never occurred to me that a TIT probe could have a mtbf of only around a thousand hours.  I'm going to order a new one today as my Bravo has just now passed the 1000 hour mark.

What mtbf have other's experienced and what were the failure indications.

Thanks for the heads up.

Jgreen

[Awful_Charlie]

I have a single probe for both the JPI and the factory gauge.  In the MM it is listed as a 200hr replacement item, and last annual as it looked like it had a bunch more than that on it, I replaced it with a genuine Mooney supplied part.  After less than 100 hours, looking at the JPI data shows that it is on a downward trend, although the EGTs are remaining constant.

Fortunately I kept the old probe when I replaced it, so I can see a swap back to the old one coming on for a test soon.  I've also got a few spare EGT probes lying around (mixture of old and new), so if the diagnosis with the old probe is inconclusive there are a few more options.

For those of you with two probes, where are you adding the second?  I was under the impression that adding a probe upstream of the turbo was frowned upon, which is why the factory probe is betrween the turbo and the wastegate

Ben

[carqwik]

My TIT probes last about 400 hours...failure mode is lowering of indicated temps.  Now on my third probe.  I have a single probe which serves both the JPI and ship's gauge.  I purchased a replacement probe from Alcor...it is an EGT/TIT probe with long lead wires which are needed (I think 30" or so)...at least for my engine set up.

[johnggreen]

Ben and Ken,

I called my shop and they are ordering me a new probe.  I flew yesterday to check everything out for an upcoming long cross country and if I saw lower temps, it was not by much.

From your posts about the frequency of replacement of probes and Ben's note on another post that the first owner of his airplane replaced turbos three times, again, I wonder if the longevity of both isn't tied to cool down procedures.

Pure speculation, but I am diligent in following the cool down procedure on my airplane.

Jgreen

[fantom]

Quote: JimR

I'm not a turbo driver, but I thought that APS had demonstrated on their test stand that turbo cool procedures were just an OWT.

[Parker_Woodruff]

Quote: fantom

That has been the word for 231's and 252's for some time. I don't know why it wouldn't apply to Bravo's also.

[johnggreen]

My shop called and has my new TIT probe in hand; about $130 material cost.  I'm taking the Bravo over tomorrow to have it installed.  I just went through my logs and saw that the original was replaced at about 400 hours so this one now has about 600 on it.

As to the advisability of cooling down the turbo.  My TIT temps fall almost 200 degrees, high 900's to low 800's during the time after I stop the airplane, come to full idle and provide rich mixture; it usually takes about 45 to 60 seconds to stabilize.

I have always observed cool downs so I don't have personal experience with not doing it.  I do have personal experience with a couple of pilots who don't; one flew a Seneca and the other a Chancellor.  They both went through turbos like corn through a goose.  Every piece of equipment I have at the ranch, tractors, dozer, excavators and trucks, recommends a cool down.  Some of the times they suggest are excessive and unreasonable.  At the least, I always bring the engine to idle for ten seconds to let the turbo spool down.  You can easily hear the turbo on a diesel engine whining after quick shut down, when there is no oil flowing to the unit.

The drop in TIT on the Bravo indicates to me that it is a reasonable practice and it's not much trouble as I'm securing everything in the cockpit so I certainly intend to continue.  I'm going to check TIT at a specific power setting and fuel flow going over and then coming back with the new TIT.  it will be interesting to see if and how much difference.

Jgreen

[blacknchrome]

So we pulled the cowl, and I've got a single probe.  Here's what looks to be the right part according to previous replacement part number in the logbook. 

http://www.alcorinc.com/index.php/products/egttit-type-k-thermocouple-716-20-screw-in-ungrounded-2/

http://www.skygeek.com/alcor-86309-egt-tit-thermocouple.html

I find it for about $400.  I wonder if it's different than the one mentioned for $130...I see that's about JPI's specific part price. 

 

[carqwik]

You need the $400 probe you've identified...the cheaper one ($130) does not have leads that are long enough for the Bravo installation.  BTDT.

[KSMooniac]

APS showed the data that the turbo itself does nothing but get warmer after touchdown, since it was in a low power state (ie descent/approach/landing) with cooling airflow around it to wick away the heat.  Taxiing and especially idling while stopped just gives it a chance to heat up again since there is much lower (or no) airflow to cool it down.  TIT =/= turbo component temp, only the incoming air.

[johnggreen]

Yep, it was time!

Had the new probe put in today and my old one was pretty corroded.  I checked TIT's at a given power setting and fuel flow going to the shop and again coming back with the new probe; about 50 degrees difference.

This probe had 600 since being changed over and that was too long.  From now on, it's going to be a 300 hour replacement item. 

If a guy was regularly flying his Bravo at high power settings, the 50 degree error could be a real issue.  Fortunately, I almost never fly at more than 65%; which may be why I didn't catch the lower temps earlier.

As for the cool down fellows, it's not a do or die issue to me.  It only takes 45 seconds or so for my TIT's to stabilize once I come to full idle  and rich mixture so it just makes me happy.

Jgreen

[johnggreen]

Ken,

The parts number supplied by Mooney was for the shorter leads and that's what we got.  The longer lead probe was installed, but we had plenty of wire.  Just to be sure, we insulated the wire from lead to connection and it worked fine.  My mechaninc couldn't understand the longer lead as just about every other airplane he works on has the shorter leads and the probe is in a lot hotter and tighter area than the Bravo.  In fact, sitting right next to the Bravo was a Cessna Ram 340.  it had the shorter leads and talk about a hot box of a nacelle !  If you think the Bravo looks tight, relax.

Actually, Mooney quoted $500 for the longer lead, not $400, but did not have any in stock nor the the aftermarket supplier so we didn't have much choice.

Jgreen

[carqwik]

That's interesting...I originally got the shorter lead version ($130) and it clearly wasn't going to work...way too short to meet the connection.  So the longer lead version ($400) worked just fine.  Perhaps there is a difference in Bravos?  My guess is later models could use the short lead?  My bird in 1998 vintage...

Btw, I got the shorter lead version originally from Aircraft Spruce....they did not have the longer lead version...which I then obtained from Alcor.  This was last year...

[jetdriven]

I am out of my knowledge tree here, but here is a Mooney TIT probe for 175$

 

http://www.ksavionics.com/products/catalog_ksa_probes.php

 

[carqwik]

Good find...someone needs to get one from this shop and report back! 

[AndyFromCB]

John,

I could be wrong but as far as I am concerned, the probe plugs in into the exhaust transition (a little piece of pipe that costs $5000 or $8000 MSRP, don't you love certified aircraft). I have two probes. On is a screw in type, an Alcor probe that runs about $430

http://www.aircraftspruce.com/catalog/inpages/alcor86309.php

I'm not sure any other type of probe works there but maybe it's different for the Moritz gauge panel.

The other is just a hole drilled in the transition pipe that runs to my GEM/G1 engine monitor.

Let me know if the cheaper probe works out. If it does, can you name the source?

Andy

[jetdriven]

Whoever needs the proper TIT probe, contact KS and they will make you one.

via email:

We can provide a screw-in TIT probe but need to know the configuration of the threaded well on the exhaust transition, ie thread size and whether or not the well has a bottom surface with only a small hole for the probe tip to go through into the exhaust flow.  The most common well has a 7/16 NF machine thread and a bottom surface which the probe face seals against.  The threaded mount is nothing more than a stainless steel bolt drilled through 1/4 " which slides over the probe body and takes the place of the clamp which normally retains the probe. Wells with pipe threads require the probe to be contained in a pipe threaded body as they have no bottom for the sealing face of our probe to be pressed against.
 So let us know what you need and we can help you.
                                                                              Bill Simpkinson, K S Avionics, Inc.

[AndyFromCB]

Thanks Byron,

Well, having just spent the $430 on a new probe, I'll keep this in mind for the future. Might just mail them my old one and have a spare one sitting around (I'm kind of obsesed about spares, that's why I don't want to upgrade my panel too much, I have almost a full spare set of avionics sitting around I bought for less than 3K on ebay over last year)

Now if someone could just come up with exhaust clamps that don't cost $800 a pop, it would be great. The whole set of clamps set me back close to $2K. I'm glad my exhaust transition was in great shape. How a piece of pipe that weights a few lb can cost $8000 retail is beyond me.

Andy

[bbillb]

Just wondered if anyone had the part number of the $130 probe??

My instrument leads are long enough so that the short length probe leads should be fine

Thanks

Bob

[bbillb]

Mooney just quoted me the 880055-505 for $372.14

I asked for the cheaper one but no response yet.

[blacknchrome]

FYI, We had our MSC replace the probe, they used part number 86309 - the $400ish one. 

[Awful_Charlie]

Just re-visiting this topic, as I'm going through the TIT probe replacement time again.

 

The Bravo should have an *ungrounded* 7/16-20 screw in probe, ideally on a longer than normal lead with reverse stagger. The nearest Alcor part is 86309, which is correct in every way apart from the reverse stagger. Alcor make the Mooney part 880055-505 and sell it as an 86291, but that one is only available to Mooney - the 86309 you can order as Joe Public.

 

Ungrounded probes can replace grounded probes, but not the other way around. This is a shame, as grounded probes are much cheaper, and can be got for USD80-90 or so and should last longer. Ungrounded probes start at 300USD or so.

 

If you have a second probe for eg a JPI or GEM, then these are happy with grounded probes

 

My thanks to my A&P Fritz for getting to the bottom of this.

 

Now the question - do those running grounded probes on the ship gauge notice any sort of problem? According to http://www.alcorinc.com/index.php/learning-center/ , ' grounded probes can lead to electrical “noise” or interference in a digital instrument.' and 'Ungrounded thermocouples are easier to design and are used on amplified meters with circuits requiring that style to avoid this issue'. On the basis the pre-Moritz Bravos are certainly not digital, the former doesn't look like it should be an issue, but the latter might be.

 

I guess as a result of the longer longevity of the grounded probe, they come with a 5 year warranty as opposed to 1 year on the ungrounded one. That, and being a quarter of the price, would seem to suggest that if the grounded probe is a satisfactory replacement, then it is the way to go

[LANCECASPER]

On 7/24/2012 at 4:33 PM, jetdriven said:

I am out of my knowledge tree here, but here is a Mooney TIT probe for 175$

 

 

 

 

http://www.ksavionics.com/products/catalog_ksa_probes.php

 

 

 

 

Did anyone ever try this less expensive probe?