PilotBrent
Well Known Member
I am scratching my head regarding some anomalies with my Skyview/Rotax engine monitoring observations and I’d appreciate some advice on where to focus my troubleshooting.
Background:
First, it may not be relevant but before first flight I did occasionally see RPM readings above 4000 during ground testing that were best described as erratic (as has been discussed on this forum before) and per Skyview installation manual, I added a 30kOhm resistor to the F776 wire that feeds into the Skyview EM-220 engine monitoring module. Have not had any issues with the RPM readings sense.
A few weeks ago I began to notice occasional fluctuations in the EGTL reading where the values would rapidly jump to redline numbers, then to zero etc… then a few minutes later they would settle down. Nothing else went out of range, especially the cylinder head temps, so I speculated it was either a loose connection or a failing sensor. I did not find any loose connections upon initial inspection, so I was next going to switch the left and right sensors to see if it was in fact just the sensor, but I had not done that yet.
However, more recently on a flight (Engine TACH at about 22 hours at this point), the EGTL and both the CHTL and CHTR displayed similar erratic values. (see chart below generated from the data logs). Since some of the values would go to zero and stay there for a period of time I was sure the values could not be real. Its probably very unlikely that the three sensors would all fail at the same time so I was again looking at a loose wire(s), loose wiring harness to the EM module or the module itself.
Red line is EGTL and green line is CHTL
After going over all the connections I could not find any obvious issues once again, so Dynon agreed to swap out the EM-220, which I replaced on the aircraft a few days ago. (BTW, Dynon tech support has been easy to get on the phone and while they won’t try to troubleshoot Rotax related issues, they are more than willing to check/replace their products in my experience). With the replaced EM-220 installed, the CHT and EGT values were initially all generating what appeared to be normal readings on the ground without engine running. So far so good.
But!, I flew today and on the ground initially everything looked normal. Shortly into the flight the CHTL reading seemed unusually low vs. the right (they are rarely more than 10 degrees C different in the data logs, but you can see below they trended to about 30 degrees apart early in the flight), then the values dropped off to nothing, only to return sporadically from time to time.
In this chart, blue line is CHTL
We stopped for lunch and upon return, the CHTL values looked fine initially, did drop off for a short time, but recovered for the the rest of the flight. In any case, not very reliable. So far both EGTs seems to function normally and also the CHTR.
So, I’m looking for troubleshooting suggestions. Wiring or connection issue that I just haven’t found yet? Failing CHT temp sensor on the Rotax? I’m just over 24 hours on the engine so I will do the 25 hour engine inspection this weekend and will once again inspect all the wiring. Anyone seen something like this before? Looking for suggestions. thanks,
Background:
First, it may not be relevant but before first flight I did occasionally see RPM readings above 4000 during ground testing that were best described as erratic (as has been discussed on this forum before) and per Skyview installation manual, I added a 30kOhm resistor to the F776 wire that feeds into the Skyview EM-220 engine monitoring module. Have not had any issues with the RPM readings sense.
A few weeks ago I began to notice occasional fluctuations in the EGTL reading where the values would rapidly jump to redline numbers, then to zero etc… then a few minutes later they would settle down. Nothing else went out of range, especially the cylinder head temps, so I speculated it was either a loose connection or a failing sensor. I did not find any loose connections upon initial inspection, so I was next going to switch the left and right sensors to see if it was in fact just the sensor, but I had not done that yet.
However, more recently on a flight (Engine TACH at about 22 hours at this point), the EGTL and both the CHTL and CHTR displayed similar erratic values. (see chart below generated from the data logs). Since some of the values would go to zero and stay there for a period of time I was sure the values could not be real. Its probably very unlikely that the three sensors would all fail at the same time so I was again looking at a loose wire(s), loose wiring harness to the EM module or the module itself.
Red line is EGTL and green line is CHTL
After going over all the connections I could not find any obvious issues once again, so Dynon agreed to swap out the EM-220, which I replaced on the aircraft a few days ago. (BTW, Dynon tech support has been easy to get on the phone and while they won’t try to troubleshoot Rotax related issues, they are more than willing to check/replace their products in my experience). With the replaced EM-220 installed, the CHT and EGT values were initially all generating what appeared to be normal readings on the ground without engine running. So far so good.
But!, I flew today and on the ground initially everything looked normal. Shortly into the flight the CHTL reading seemed unusually low vs. the right (they are rarely more than 10 degrees C different in the data logs, but you can see below they trended to about 30 degrees apart early in the flight), then the values dropped off to nothing, only to return sporadically from time to time.
In this chart, blue line is CHTL
We stopped for lunch and upon return, the CHTL values looked fine initially, did drop off for a short time, but recovered for the the rest of the flight. In any case, not very reliable. So far both EGTs seems to function normally and also the CHTR.
So, I’m looking for troubleshooting suggestions. Wiring or connection issue that I just haven’t found yet? Failing CHT temp sensor on the Rotax? I’m just over 24 hours on the engine so I will do the 25 hour engine inspection this weekend and will once again inspect all the wiring. Anyone seen something like this before? Looking for suggestions. thanks,
