Richard Connell

Richard Connell

Well Known Member
Question for you all:
This is a 2hr flight a few weeks back. Uneventful, smooth LOP cruise at 9500' for around 90 mins.
Any ideas on what could cause the oscillation in the #3 CHT? Im leaning towards erroneous data or electrical gremlin, but curious to hear other theories.

Im not overly concerned about it at the moment. Im currently doing my annual and have had a good look over #3 and associated probes. no obvious issues.

Cheers
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Hi Richard,
I remember Mike Busch commenting on this phenomina but not sure if it was related to the EGT or CHT. Basically he says this is characteristic of a hotspot on the valve and the fluctuations are as a result of the valve turning (as it should) modulating the temperature. Period would be about 60-90 seconds iirc.

I'd be taking a look at the valve to see if it has signs of a hotspot - if it is the case consult the experts.

BTW I did get through to Narromine but needed to track to Young to clear the low cloud.

Regards,
 
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What Doug said. Have a look at Busch's most recent seminar (available on the EAA website) where he shows some similar fluctuating temp data that indicate potential exhaust valve failure in the near future. His data are more extreme than yours in the temperature fluctuation, but I would see how they compare and consider having the cylinder borescoped.

My two cents.

Greg
 
Thanks Guys.
Ive seen Mikes webinar. My understanding is that its oscillations in EGT that may indicate exhaust valve issues, not CHT, hence my curiosity. I think something else is at play here.
Glad you got to Narromine uneventfully Doug. I went south coastal and got on top of SCT around Nowra. Beautiful 3.0 coastal to Melbourne.

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Cheers
 
Agreed, did GB talk to you about my theory?

Richard, look at the climb and descent. Did he mention anything else?

Call me when you get a minute.
 
Just one more suggestion based on my recent experience: I had an erratic, fluctuating reading on my #3 CHT, which seemed to be gradually worsening. It was very rapid, with the reading on my EI monitor jumping around through about a 20 degree spread on a second by second basis. I had an experienced tech helping me with my annual; she checked the probe and it appeared to be fine, but found the spade connector between the probe and the monitor's wiring harness, which was quite close to my oil filler neck, had some oil in it. Bit of contact cleaner, put things back together, and the reading was rock solid after that. Interesting thing; the reading with the slightly degraded connection was not only erratic, but consistently lower than the other cylinders, but is right where it should be now.
 
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