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EGT sensors, CTLSi maintenance, failure rate?


Blueyonder

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Hi everyone.

Is there an average MTBF time known or time recommended for replacement, other than when they error in the panel?

About how many hours before they may fail?

Is an intermittent EMS  light point to something specific, or more often than not, or it can be anything?

What is the recommend procedure to troubleshoot it if you have no BUDS tester?

Thank you.

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I just lost my third EGT sensor today. All have failed in last 130 hours, have 590 total time. So yes, they seem to have a service life of less than 600 hours. Keep a spare. Lockwood has been out of stock for weeks. leading Edge Airfoils still has some. 
Or you can do what I did today. Disable the audio alert and fly the plane with lane A flashing and caution and warnings.

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Hi.

Thank you, for the feedback.

Yes it doe look like around 4-500 hrs is a brake point. It's interesting that physically they do not look too bad, it must be something in the impedance that changes.

Is it recommended to just replace them all, or just wait for them to go out one, by one? Are there any that last longer than 600 Hrs?

Next on to EMS intermittent flashing. Is the BUDS tester able to pinpoint errors exactly, or is it just hit and miss?

I am just wondering if there is a procedure that can be established to troubleshoot / fix some of these problems, given what information is presently available, to try and fix some of these problems before they show up, i.e. EGT MTBF 500 hrs. just replace all at about that time?

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They're literally two pieces of metal in contact made of different materials encased in a shell, in the jet blast of your exhaust valve bathing them in 1800+ degree air. These are one of those items where if you tried to make them more resilient, they're probably then less able to do their job :)

You need the buds dongle to troubleshoot. There's no other way that I know of to pull the logs.

Where are you located?

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  • 1 year later...

My # 4 EGT probe is the only one I haven’t replaced. It’s reading slightly higher than the others so thought I would preemptively swap it out. (712 engine hours)
That joker is tight though. Im afraid of busting the welded fitting. Is that possible? I’ve tried hot, I’ve tried cold with penetrating oil but it won’t budge. 
Any suggestions!

18232A96-ECDB-4F16-869C-C5D215297207.jpeg

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Is that a female nut on a threaded male boss?  I would heat the nut until very hot (not quite a dull red, but close...) and I would spray the boss/bung female threads with an aerosol can of "dust off" or other product that sprays a freezing liquid when upside down (some medical skin freezing products available OTC will also work).  Applying a thin moly-based lubricant made for exhaust joints prior to heating may help.  

Alternatively, if you have not succeeded with heat and cold, you may also be able to cut the nut vertically with a Dremel cut-off wheel.  It will be hard to avoid touching the male threads with the cut-off wheel, however (if you are careful, you can avoid a deep cut to the threads).  Depending on what actually makes the seal on the sensor, a small vertical defect in the threads may not be a problem.  I don't know how the seal is made with that style sensor.

Your photo shows the appearance of a horizontal crack on the exhaust spigot/boss, so it may already be compromised.

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For maintenance yes that helps for some things like fine tuning like carb balance, but CHTs cast a wider net even with rotax.

A lot of "EGT Wisdom" is old fashioned and actually detrimental (though mostly applies to manual leaning technique). Anything weird going on will manifest in other issues than just EGTs.

On the other hand, silent issues will show up on CHTs. Heat is directly correlated to pressure in the cylinders. You can have detonation going on which WILL show on CHT, but it's possible that it will not show conclusively on EGT. Same with cooling issues, that also will show on CHT but may or may not show or be clear on EGT.

The value of a 4 place EGT is better, but I still wouldn't freak out if an EGT read abnormally unless there was a corresponding CHT reading or other issue like a rough running engine.

There really isn't any in flight emergency that I can think of that wouldn't reflect on CHT aside from an exhaust pipe breaking off.

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10 hours ago, Bill3558 said:

My # 4 EGT probe is the only one I haven’t replaced. It’s reading slightly higher than the others so thought I would preemptively swap it out. (712 engine hours)
That joker is tight though. Im afraid of busting the welded fitting. Is that possible? I’ve tried hot, I’ve tried cold with penetrating oil but it won’t budge. 
Any suggestions!

18232A96-ECDB-4F16-869C-C5D215297207.jpeg

Same difficulty! So cut the wire lead off, heated nut - not a lot, slipped a 12 sided 17 mm box end wrench over it and it easily released.

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CHT's read too slow and there are only 2 (#2 & #3 cyl) of them and they only read head temp because that's the only place the water cooling is and unless you have the new heads the CHT only reads metal temp. EGT's read instantly and tell you there's an instant problem in the combustion chamber which will affect other readings.

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13 hours ago, Anticept said:

Honestly, EGTs aren't very useful outside of troubleshooting. CHTs on the other hand, I consider those critical instruments.

My 07 CTSW only has the little UMA gauges and no EGTs, and frankly I've always been happy about that.  EGTs seem to cause a lot of people stress, and with no mixture control as long as your carbs/FI are properly adjusted, there's not really anything you can do about it anyway.  If I had EGTs I know my OCD would kick in and I'd be stressing over more other thing.

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On 12/8/2023 at 8:54 AM, Roger Lee said:

CHT's read too slow and there are only 2 (#2 & #3 cyl) of them and they only read head temp because that's the only place the water cooling is and unless you have the new heads the CHT only reads metal temp. EGT's read instantly and tell you there's an instant problem in the combustion chamber which will affect other readings.

Unfortunately that's not always true.

CHTs always tell you about what is going on inside, and yes I agree EGTs can clue you in, but they don't catch everything.

To me personally, it's helpful to have EGTs to confirm another indication. They don't really indicate anything alone without another instrument warning too (or trending towards a warning).

Which is why I say that they're real misleading at times and nobody should freak out if you see a weird EGT reading without any other symptoms. More than likely the probe is dying.

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This is why you should not believe everything from Bush's post and advise. If you turn the prop backwards to try and burp the engine you will damage the sprag clutch and put air into the system. He thinks Rotax is like Continental's and Lycoming's and some of his thoughts are old school. The person that sent him the email was only worried that the engine might start when burping it.

Mike thanks for your answer 
 
Sent from my iPhone
 
On Oct 11, 2023, at 6:59 PM, Mike Busch <mike.busch@savvyaviation.com> wrote:
 

Steve, the safer way to "burp" the Rotax 912 is to turn the prop in the opposite direction of normal rotation. That will accomplish the goal (of returning any oil in the engine to the oil tank prior to checking the level) while minimizing the chance of an unwanted combustion event.
 
Also, many RV owners use toggle switches for the ignition and a starter pushbutton switch instead of the key-operated switch. It's much safer and longer lasting, with no ADs to worry about. --Mike
 
On Wed, Oct 11, 2023 at 7:54 AM <> wrote:

Mike:

Thank you for contributing to GA knowledge as you kindly do.

I just read your article in AOPA Pilot and started sweating bullets. As part of our preflight routine on our RV12 equipped with a Rotax 912 ULS 100 H.P. engine, we routinely “check the oil” by removing the oil cap, rotating the prop (counterclockwise when facing it toward the cockpit) until we hear the “gurgle” twice, then checking the dipstick. How necessary is this, and how stupid or not is this.

Thanks in advance for your reply.

Best,

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1 hour ago, Jim Meade said:

The comment about burping the engine has nothing to do with the cited article about CHT and EGT, and it is misleading and false to imply it does.

I never said it had anything to do with the other article. All I inferred was to make sure what is said applies to our engine and not something else that when someone tries to compare and make assumptions comparing other types of engines. He has been wrong numerous times comparing Rotax to other engines.

Education is key.

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No, Roger, you stated that he had made a mistake about a Rotax.  You provided no reference to support your assertion.  The form of your statement was to infer that his comments on EGT and CHT were not credible because of your unsupported assertion about a totally different matter.  It's a fallacious argument known as a non sequitur. 

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