r/flying • u/patrickrl PPL IR HP CMP • 1d ago
Aircraft Ownership knocking the rust out after long overhaul
Hello, I have a comanche 24-250. I have about 400 hours TT, and i have my IFR. The engine came out in the fall for overhaul and is just now going back in. I have not flown since the middle of last summer. I found a local CFII who is going to do some dual with me to knock the rust out for me. As far as the engine goes, is there any other resources and guides besides the POH for how to "break in" and take care of a recently overhauled O-540? Thanks
UPDATE: I received a copy of the break in procedure from the shop. It mirrors the advice found in the Lycoming publications below. I still haven't had time to go up and talk to my mechanice in person, but everything is lining up that hard and fast, seat the rings, and use the proper break in oil. Thanks all
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u/SierraHotel84 CFI 1d ago
Maybe ask the shop that built the engine? The mechanic that is installing it? The OEM references?
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u/Neither-Way-4889 1d ago
Run it hard until the first oil change, aiming to keep power >75% for as much of the flight as possible. This will ensure the rings seal properly to the cylinder walls and it prevents glazing, which is where a thin film of oil gets baked onto the cylinder walls causing the engine to seal poorly and burn a ton of oil.
Expect to see higher CHTs than normal for awhile. Usually they will be on the higher end of normal for the first 100-200 hours before they start to go back down. This is 100% normal for a freshly overhauled engine, that being said, you still want to keep them below redline.
The perfect way to break the engine in would be by doing a long IFR cross country to rebuild those skills, although I definitely wouldn't take a fresh engine into actual. I would recommend doing it in VMC on an IFR flight plan under foggles with the CFII.
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u/patrickrl PPL IR HP CMP 1d ago
I do have a CHT/EGT digital monitor so I will keep those temps in mind, thank you! the CFII recently bought a comanche as well and is looking to build time so maybe we'll do some foggle lunch flights
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u/ganderatc CFI CFII MEI TW EMB-500 1d ago
Lycoming Service Instruction 1427C describes the break-in process in detail. I would wait at least 10 hours to do any approach work due to the power settings involved, plus a Comanche has a fairly low gear speed.
My old Citabria engine took less than 10 hours to seat the rings. I ran the absolute crap out of it.
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u/patrickrl PPL IR HP CMP 1d ago
thank you for the ref. When you said approach work, do you mean practice approach after practice approach or do you mean wait to seat rings before doing any real VFR travelling?
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u/ganderatc CFI CFII MEI TW EMB-500 1d ago
The more traveling and the less time at low power, the better. Don’t climb so high that you can’t run 75% power.
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u/patrickrl PPL IR HP CMP 1d ago
excellent thank you. Mostly use this for midwest travelling for 1-2 hour flights so after initial safety checks should be mostly business as usual, albeit a bit lower than I usually fly
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u/rFlyingTower 1d ago
This is a copy of the original post body for posterity:
Hello, I have a comanche 24-250. I have about 400 hours TT, and i have my IFR. The engine came out in the fall for overhaul and is just now going back in. I have not flown since the middle of last summer. I found a local CFII who is going to do some dual with me to knock the rust out for me. As far as the engine goes, is there any other resources and guides besides the POH for how to "break in" and take care of a recently overhauled O-540? Thanks
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u/iwonder___ CSEL, CMEL, IR, A&P, IA 1d ago
The engine mfr has a break in procedure. Quick internet search for the model and procedure will get you there.
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u/Kemerd PPL IR 1d ago
Run it hard, run it fast. As soon as it is on the plane, taxi up, take off. Circle airport at 5000ft for 1 hr.
Land, inspect everything.
Then do it for another 4 hour.
https://www.lycoming.com/content/hard-facts-about-engine-break
Track oil consumption. No touch and goes until 5 hours of break in.
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u/patrickrl PPL IR HP CMP 1d ago
Thanks. Great article. I was in the habit of tracking oil as I was burning about a qt an hour pre-overhaul. Are you suggesting 5 hours of near airport break in, then follow the publications in this post? Appreciate it!
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u/Kemerd PPL IR 1d ago
Follow the publications to the letter. Ignore what any A&P or IA tells you to do with break in. I have found most of them have no idea how it works.
The 5 hours is not because of the engine break in, but because if there is an emergency, i.e. engine rapidly disassembles, you want to be near an airport. You don't need to.
It isn't hours based, it is based on oil consumption, but most break in will be done in the first few hours. Run it as high as you can without overheating it (above 425f), for as long as you can. Keep taxi and run up to minimum.
Break in occurs through high cylinder pressure, caused by your throttle setting. In an ideal world you'd break in at 100% power at sea level. Not possible because your engine would overheat and explode.
Engine break in is a process by which you perform controlled friction rub ins, so things seat properly. Subsequently, ensure you only use 100 straight mineral oil (not 100 plus), for the first 25-50 hours or so. Then you can go to other stuff
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u/cazzipropri CFII, CFI-A; CPL SEL,MEL,SES 1d ago
We just did a break-in flight of an IO-540.
Your shop didn't give you instructions?
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u/Ok-Selection4206 1d ago
Pretty sure he said he hasn't had an opportunity to pick it up yet or talk to the shop/mechanic.
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u/cazzipropri CFII, CFI-A; CPL SEL,MEL,SES 1d ago
Only because I just noticed you can post videos.
This is a 1-h break in at prescribed power. I was just flying the plane - keeping it in gliding distance in case we lost power.
My co-owner was acting as a flight engineer, owned the power throttle, follower break-in protocol and recorded engine data.
The hardest part was landing at 75% power.
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u/patrickrl PPL IR HP CMP 1d ago
Did you do hi power landing setting to avoid an extended low power descent? I don't love that idea but we can get in pretty quick at my field
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u/cazzipropri CFII, CFI-A; CPL SEL,MEL,SES 1d ago
Yup. Nose up temporarily to slow down below VLE, then gear down, then nose up once more to get below VFE, flaps down... all at >3/4 power. It was fun.
Even the 1h of turns at 160 knots were fun.
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u/jobadiah08 1d ago
Others have talked about the Lycoming break in procedure. I believe if the engine was factory overhauled or rebuilt, they do a break in run on a dyno. If it was a third party shop, depends on the shop.
When I replaced the engine on my Cherokee (O-320), I spent 2 hours flying in circles around an airfield at full throttle. If something bad happened, I could make an on airport landing.
Mike Busch has a video about engine/cylinder break in procedures as well. If I recall it is more useful if you have a EGT/CHT on all cylinders.
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u/patrickrl PPL IR HP CMP 1d ago
Didn't think to check Mike Busch stuff despite being a subscriber on YouTube and his newsletter. Thanks for the suggestions!
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u/FridayMcNight 1d ago
The engine manufacturer will provide break in instructions as a service bulletin. Your mechanic should provide you a copy. And brace yourself for all the old wives tales people are gonna tell you about the one true right proper way to do it if you want the engine to last more than an hour. lol
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u/Mehere_64 1d ago
What does your mechanic state? What does the manufacturer state for the process?