Chewka

500 hr mag inspection occurred about 100 hrs ago and timing has recently been checked. Still digging though.

Hi folks, I graphed some CHT's and EGT's last weekend. When I compare to a test I did a few years ago it looks like all CHT's are UP about 30 degF and we are just noticing #1 because it is the highest and now gets over 400 degF. It is also interesting to note that the EGT's are all DOWN about 35 degF. Some of this difference can be attributed to a slight difference in test conditions: 2011 Test: 22", 2500 RPM, -4 degC OAT, a29.92, 8500 ASL 2014 Test 20", 2500 RPM, 10 degC OAT, a30.14, 9500 ASL The OAT was about 14 degC cooler in the old test so I am not sure if that accounts for 14 degC of the 30 degC (also understanding air density between conditions is slightly different). If I am interpreting the data correctly (attached) it looks like #4 is not the oddball out like I originally thought. #1 and #4 were always the hottest running. In response to the last post, we haven't noticed an increase in oil temps. Also, yes, I have tried LOP operations and it seems to work quite well. I was talking to a friend over the weekend about how he got his cowl flaps adjusted 1/8" on his M20K and it would affect temps significantly. In fact, they would change the settings on the cowl flaps seasonally for the cold winters up here. I wonder if a slight adjustment was done that just bumped all the temps up enough for us to start noticing? I am attaching charts of the old (2011) and recent (2014) test. Thanks again for everyone's input. Brenden March_2011_ROP-LOP_TEST.pdf Aug 2014 - CHT-EGT Test.pdf

The exhaust was checked for leaks by visual inspection around the exhaust port and also by pressuring up the system and using soapy water to check for leaks. The intake was also visually inspected and then they ran the airplane and sprayed brake cleaner around the intake port to check for leaks. An intake leak would be identified by a sudden rise in engine RPM as the flammable substance is pulled through the intake into the combustion chamber and ignited. Neither of these tests indicated any leaks on either the intake or exhaust systems. I will do some temperature graphing this weekend.

Also, no evidence of pre-ignition during a borescope inspection. Engine has about 1000 hrs on it since factory overhauled (1845 hours since new at time of overhaul).

I will graph out some CHT's and EGT's next time I fly and post.

A recap of what's been checked: 1) CHT probe #1 swapped with #3. No change in readings. 2) Air cooling baffles checked - ok 3) Fuel flow divider recently checked - clean 4) New injector installed - no change 5) Fuel lines tested last year for even flow from divider to injectors - ok 6) Intake system checked - no leaks 7) Exhaust system checked - no visible issues 8) Mag timing checks out ok 9) Spark plug is black showing we are running rich (matches with what we are doing to keep CHT below 400) In addition to the things listed, we have also recently replaced the spark plugs. Our AME says that there is no evidence of cam shaft lobe wear. Compressions are good on all cylinders and other cylinders are operating in a more "normal" range. Cylinder #2, the other one up front is operating about 40-50 degF cooler. The AME used a handheld thermometer during ground runs to verify that the EI engine gauge is displaying the accurate temperature. Our AME also had a conversation with a Lycoming technical rep resulting in the following response: Lycoming’s published red line for the CHT on that engine is 500 deg. They recommend not running the engine at CHT’s above 435 for extended periods of time but that is just a recommendation. Operating the CHT above 400 degrees is perfectly ok and normal according to Lycoming. Lycoming also says that a difference of up to 50 deg between cylinders is normal and not to be of concern. His suggestion is that based on all the inspections and troubleshooting that we have done that there is no problem with that cylinder. He recommended that you fly the airplane based on the fuel flow/power settings in the POH and as long as you don’t exceed the redline for any parameter there is nothing to be concerned with. He also asked “If you didn’t have the EI gauge to look at would you think there was anything wrong with the way the engine was running or performing”? I have two concerns with this response. One is that everything I have ever read suggests that you shouldn't run over 400 degF for long periods. Second, this is a definite change from what we usually see. Ignoring it for the long term doesn't sound like a good idea.

Hi folks, I have been seeing high CHT temperature on cylinder #1 over the last year and am having trouble nailing down the culprit. CHT often exceeds 400 degF in cruise when running 100 degF ROP when it used to operate well below that. We are having to run super rich (150-200 degF ROP) and often fly with the cowl flaps open. We have recently changed this cylinder due to a small crack at the spark plug hole discovered during the annual inspection, however, this high temperature issue was apparent before this replacement. I also notice that the EGT on this cylinder is the lowest of all. Here is what has been checked so far: 1) CHT probe #1 swapped with #3. No change in readings. 2) Air cooling baffles checked - ok 3) Fuel flow divider recently checked - clean 4) New injector installed - no change 5) Fuel lines tested last year for even flow from divider to injectors - ok 6) Intake system checked - no leaks 7) Exhaust system checked - no visible issues 8) Mag timing checks out ok 9) Spark plug is black showing we are running rich (matches with what we are doing to keep CHT below 400) Anyone engine gurus out there have any advice? Brenden 81 M20J Calgary

Pics and exploded view Actuator - exploded view.pdf

Photos from previous year

Sounds like the chattering, play in the jackscrew and the wear of other internals is just wear and tear. I am hoping they can do a good job of the rebuild. I hear they are the go-to shop for this.

Turns out it is a Vickers NOT an Eaton. The first picture I attached is actually of the emergency gear mechanism. Our AME thinks that by unlatching the safety and then attempting to operate the gear this could have caused damage to the mating parts before the circuit breaker popped. I don't completely understand how the safety engages / disengages the gear from the actuator and motor assembly but am hoping some exploded view drawings from the maintenance manual will clear it up. We are sending it into LASAR for an overhaul.

Hello again folks, Another issue we are facing on our 81 M20J during a very painful annual inspection is an aging gear actuator. Our AME did a closer inspection after hearing a rachetting sound coming from the actuator during the gear swing. Upon closer inspection they found that the jackscrew has play in it, part of the emergency system is damaged and other integral parts are showing wear. There was an instance about 4 years ago that passengers of mine had accidentally dislodged the safety on the emergency gear handle. No one touched the handle itself but when I went to retract the gear on takeoff, the actuator circuit breaker popped ie) the motor wouldn't run because the emergency gear safety was dislodged. Not knowing what had caused this at the time, I returned to land and we had our then AME inspect it. He just reset the system, swung the gear and said we were good to go. Since the circuit breaker popped right away, I am hoping it did it's job to protect the actuator by keeping the motor from running (this appeared to be the case). Is dislodging the safety on the emergency gear handle then selecting gear up, causing the circuit breaker to pop enough to have caused damage to this system or is it likely that 30-some years of operation has just taken it's toll? I believe it's the original unit actuator which would be about 33 yrs old with about 2500 hrs on it. You can't see a whole lot except for some metal filings but I have attached a few photos from this inspection. Thanks again guys! Looking forward to your input. Brenden Calgary, AB

Thanks for the input guys. The cylinder was put on as part of the factory overhauled engine that was installed about 900 hrs ago in 2002. This factory overhauled engine had 1845 hrs since new when it was installed. We ended up getting a cylinder kit from Progressive in Kamloops, BC for 2700 CAD. I saw that Air Power had it for 2050 USD but with exchange, shipping, duty?, and tax and the fact that we could have it here the next day, we went with Progressive. I suppose the old one will make a nice, expensive paper weight for my desk. It would be nice to know what causes these types of things without just accepting them. I have only seen photos so far of the hairline crack and I can't tell yet if there is evidence of spark plug over tightening or a casting flaw.

Hi folks, I just got the bad news that my #1 cylinder is cracked from the spark plug hole to the intake port on my 81 J model. Engine is 900 SMOH. Could this be due to overheating or manufacturing flaw? What are you folks in states paying for new cylinders these days? $1800? Thanks, Brenden Calgary, AB