Engine Trouble

[huntaero]

Glad you made that landing successful. Ive never seen the cyl base studs crack on a lycoming like these and I have years of maint experience on lycomings. Because it is a narrow deck eng make sure when you are reinstalling the cylinder hold-down plates to use use shims as per the manual attached.

[Nev]

Thanks for that - very much appreciate the advice.

[Bissetg]

Hmmm … red RTV rings a bell, as does a blocked oil gallery and a wreck bought off the insurance company of a plane I once flew. Be careful.

[svyolo]

Looking all over the engine, the only place it was visible was the accessory case. Vacuum pad and one other I can't identify off the top of my head. Oil sump, case, etc not visible.

[Nev]

Finally got my Bearhawk home today. My engineer Kevin and I got an early start at 5am, drove up and removed the sheared studs, and replaced the two cylinders. We changed the oil back to straight 100. Also found several very loose nuts and bolts on the engine - the vibration had taken a toll, and we spent a while checking everything once it was back together. I've started running the cylinders in on the way home. Once thats finished we will clean the remaining 4 cylinder flanges and complete an annual on the aircraft.

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[Steve W]

Congratulations Nev on a good all around job getting it down safely without any incident and getting it back to base after repairs.
Because of some recent cylinder trouble, I have been researching engine/cylinder break-in procedures at length, and cannot find anything concrete on gospel power settings quoting a reliable source. I am only asking this for the purpose of educating myself and for no malicious reasons. I see a power setting of 28” and 2300 rpm on the efis. I gather that is wot and a low prop setting at 1300’. I would like to know if there is any supporting documentation to use these numbers. I have walked away from the computer with the idea I had the right numbers of 25” at 2500rpm below 3000’ with variations on either side for proper initial ring seating. Friends of mine with recent OH engines have been told by the shop to set up their ground adjustable props for 2200 static rpm and run it at wot. Again I can’t find anything that supports this but looks similar to what your doing. I’d appreciate any help here. Thanks

[Nev]

Thanks Steve. Yes it was WOT at 2300 RPM. Those settings are not based on anything Gospel or scientific, just lots of reading and chatting with others, and my previous engine run-in went well. I think my engineers words were "don't baby it - best to give it some abuse on the way home".

First time around for run-in I used ROP and around 2400 RPM. Normally I cruise LOP at about 26" and 2200 RPM. Yesterday I wanted to keep the ICP relatively high, but without the cylinders getting too hot. It seemed easier yesterday because the other cylinders are already run-in and so I was able to keep cylinders 4 & 5 below 210c (410f).

The chart below from the Lycoming manual shows that the power setting is within the recommended envelope. The red dashed line is for my normal cruise operation, and 28.5" MAP is on the edge of the envelope at 2300 RPM.

There's others on the forum who might chime in here with a lot more specific experience than I have.

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[TJ_Slice]

Nev,

As someone who will be sourcing an overhauled IO-540 next year, thanks for posting all of this!

[Battson]

Because of some recent cylinder trouble, I have been researching engine/cylinder break-in procedures at length, and cannot find anything concrete on gospel power settings quoting a reliable source. I am only asking this for the purpose of educating myself and for no malicious reasons. I see a power setting of 28” and 2300 rpm on the efis. I gather that is wot and a low prop setting at 1300’. I would like to know if there is any supporting documentation to use these numbers. I have walked away from the computer with the idea I had the right numbers of 25” at 2500rpm below 3000’ with variations on either side for proper initial ring seating. Friends of mine with recent OH engines have been told by the shop to set up their ground adjustable props for 2200 static rpm and run it at wot. Again I can’t find anything that supports this but looks similar to what your doing. I’d appreciate any help here. Thanks

Based on research we did dozen years ago, for a Lycoming -540 engine, we arrived at 75% power (or more) for engine break-in.
Given the elapsed time, I can't recall where we sourced that from, but we have it documented in our test flying procedures. I thought it was authoritative, but I can't be sure sorry.

Which settings you choose, to achieve your desired power setting, are surely dictated by the Lycoming operating manual, the engine's performance (temperatures mostly), among a range of other factors. Some of the main considerations are the need to keep the engine below the redline CHT, and the maximum allowable difference in MAP and RPM.

I see you've heard people using 2200 RPM and WOT. That would be pretty close to the allowable limit, depending on the MAP the specific configuration is achieving. In my aircraft, that would be beyond the allowable limit at 1,000ft and just within the limit at 3,000ft. If engine temperatures allow, a lower MAP and higher RPM may be a lower risk option.

[Battson]

Lycoming's Operations Manual might be worth a look, in terms of reference material.

[Steve W]

Thanks Nev. That’s what I needed to see and hear. I am so old that when I hear high over square numbers I cringe! Have about 3000 hours sitting behind Conti 520’s and it was beaten in to my skull by the company engineers “square for climb and one inch off in cruise rpm. Helped take two engines to tbo without a cylinder change. Also no leaning below 5000’. These were factory OH engines but of course, Continental. Different beasts.

[jaredyates]

Reconfigure the manifold pressure to show hectopascals and the remainder of your oversquare concerns will be gone.

[Steve W]

Yup mind over matter. That will work!

[svyolo]

There are a few IO540 powered aircraft that are rated at 235 hp (Maule and Cherokee come to mine) that limit HP by limiting max rpm. Off the top of my head I can't remember the exact rpm, but 2350 or 2375 comes to mine. So seal level MP and those max rpm seem to be OK.

[kestrel]

Our RV-4 barely exceeds 2200 rpm on take-off and climb out. ...WOT, of course. Need to get above about 100 kts to get the rpm higher.

[Nev]

Here's another version of the chart posted earlier on this thread, showing that the lowest RPM for operating at 28" is 2200 (noting it's actually for a carburetored engine). Below that is an excerpt from the Lycoming website. Link to the full webpage HERE.

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