The International Cessna 170 Association

My airplane is finally coming out of its first post-purchase annual. The #2 cylinder finally failed, needed a carb overhaul, had an exhaust leak, needed a new tire, etc. etc. Anyway, after a month and a lot of money, I will be flying this weekend. My mechanic replaced my normal synthetic multi-grade oil with mineral oil for the break-in period of my new cylinder. He says to fly low and cool at 75% power for the first 10 hours. Do you guys have any other advice for me for the break-in period?

Yes, follow the recommendation from the manufacturer.

Besides following the manufactures break in procedure I'd run it much harder than 75 percent power. You don't want to be doing pattern work either. Pick a place. Fly it hard there and by hard I mean 2000 ft 2600 rpm. Land normally. Return running it hard. Land normally. The place doesn't have to be hours away it could be 15 minutes. Just don't loaf about the sky. Pattern work and the continual low rpm associated will glaze the cylinder.

As much time as possible at low altitude and high power. The horsepower output of the O-300 tapers off with altitude, and you don't have to go very high before you can't even achieve 75% power (hence the low altitude recommendation). Start it, get it in the air as quick as possible (to get cooling air over it), keep it there as long as possible, land and shut it down. Above all, follow the mfr recommendation as previously stated.

Sandy170 wrote:My airplane is finally coming out of its first post-purchase annual. The #2 cylinder finally failed, needed a carb overhaul, had an exhaust leak, needed a new tire, etc. etc. Anyway, after a month and a lot of money, I will be flying this weekend. My mechanic replaced my normal synthetic multi-grade oil with mineral oil for the break-in period of my new cylinder. He says to fly low and cool at 75% power for the first 10 hours. Do you guys have any other advice for me for the break-in period?

New Cylinder?? or overhauled cylinder?

Lots of advice here that is contrary to ECI's instructions.
http://www.eci.aero/pdf/BreakInInstructions.pdf

Bruce Fenstermacher wrote:Besides following the manufactures break in procedure I'd run it much harder than 75 percent power. You don't want to be doing pattern work either. Pick a place. Fly it hard there and by hard I mean 2000 ft 2600 rpm. Land normally. Return running it hard. Land normally. The place doesn't have to be hours away it could be 15 minutes. Just don't loaf about the sky. Pattern work and the continual low rpm associated will glaze the cylinder.

Doing that will give you a much better chance of over heating the cylinders and removing the temper from the rings which causes high oil consumption.

T. C. Downey wrote:

Bruce Fenstermacher wrote:Besides following the manufactures break in procedure I'd run it much harder than 75 percent power. You don't want to be doing pattern work either. Pick a place. Fly it hard there and by hard I mean 2000 ft 2600 rpm. Land normally. Return running it hard. Land normally. The place doesn't have to be hours away it could be 15 minutes. Just don't loaf about the sky. Pattern work and the continual low rpm associated will glaze the cylinder.

Doing that will give you a much better chance of over heating the cylinders and removing the temper from the rings which causes high oil consumption.

Doing that? Doing what Tom? Be more specific?

Bruce Fenstermacher wrote:

T. C. Downey wrote:

Bruce Fenstermacher wrote:Besides following the manufactures break in procedure I'd run it much harder than 75 percent power. You don't want to be doing pattern work either. Pick a place. Fly it hard there and by hard I mean 2000 ft 2600 rpm. Land normally. Return running it hard. Land normally. The place doesn't have to be hours away it could be 15 minutes. Just don't loaf about the sky. Pattern work and the continual low rpm associated will glaze the cylinder.

Doing that will give you a much better chance of over heating the cylinders and removing the temper from the rings which causes high oil consumption.

Doing that? Doing what Tom? Be more specific?

running at 75% or above. is where most overheating is done. most cylinders that do not break in correctly were over heated and the temper was taken out of the rings, which then fail to have the proper pressure to the cylinder wall. I replaced 3 sets of rings in one engine because the owner though high power setting were the way to get the breakin done quickly.

One of the most important things to insure is that the engine baffling is in as good a condition as possible. You can do everything else correctly and still have problems if baffles and baffle seals are not right.

Look inside the cowl with everything closed up. There should be no holes or gaps of any size, say larger than a dime. Make sure the inter-cylinder baffles are installed correctly.

T. C. Downey wrote: running at 75% or above. is where most overheating is done. most cylinders that do not break in correctly were over heated and the temper was taken out of the rings, which then fail to have the proper pressure to the cylinder wall. I replaced 3 sets of rings in one engine because the owner though high power setting were the way to get the breakin done quickly.

I can't imagine that following Bruce's (and other's) suggestion would mean instant death to a good set of rings... no one is proposing to run the engine beyond its designed capabilities. Of course, you should be mindful of any temperatures you have the capability to monitor so as to avoid overheating.

I wouldn't argue against T.C. Downey's personal experience, but my own has been such that I've not experienced any ill effects from performing break-in on mulitple cylinders, both individually and as entire sets, by a high-power / low altitude method for a few hours.

My $0.02

-Kennet

So what DOES the manufacturer suggest?

Greg Bockelman wrote:So what DOES the manufacturer suggest?

ECI's recommendations, other manufacturers will be different.

http://www.eci.aero/pdf/BreakInInstructions.pdf

is it an ECI cylinder? other manufacturers have other ideas.... just sayin'


for what it's worth from TCM... pretty much the same:

http://www.tcmlink.com/visitors/carenfeed/brkin.pdf


or from Penn Yan:

11. All takeoffs should be performed at full power. There should be no rush to reduce power to climb settings. Most engines are designed and built to operate at maximum power indefinitely. A few models are time restricted at maximum RPM; those restrictions will be called out in the Aircraft Operating Handbook as well as being marked on the tachometer.

12. The first flight should be at least one hour in duration, climb speeds should be kept high when practical and leaning in climb avoided except as necessary to maintain smooth operation at high altitudes and lean to best power. Cruise settings should be maintained at 75% power or more whenever possible. Any sort of abusive operation such as touch and goes, power off stalls, and 0 thrust should be avoided for the first 30 hours.


or.... http://www.ramaircraft.com/Maintenance- ... Flight.htm
15 minutes at 30", then reduce power

The apparent differences of opinion (i.e., Tom vs Bruce) is likely due to perceived differences in definitions.

The reference each makes to "75%" power may not be using the exact same definition, but results in similar recommendations. (Yet another I.D. problem. ID = Internet Disagreement)

In Tom's reference, he is probably using the same criteria as indicated in the ECI document he linked, i.e., the theoretically-calculated 75% using mfr's data referencing MP/RPM,.... while Bruce is recommending "Reality".....that power-setting which is actually available in real life (with our C-145/O-300 installations using fixed pitch propellers.) They are actually the same.

If one resources the data from the Owner's Manual or the TCM Operators Manual it will be evident Bruce's recommended high-power-settings, even at take-off a maximum of only 120 H.P. is available on a standard day using full throttle at sea level (presuming one has a standard propeller which only makes about 2230-2330 static RPM.) Therefore, using Bruce's suggested method, one will only produce about 70% power at full throttle at sea level, and if running the airplane a lower altitudes, i.e., say 2500 MSL for the first few flights, even full throttle with a standard propeller will only produce about 2500-2600 RPM which still equates to about 75% power or less, exactly what both ECI and Tom also suggest. (And if one flies higher than 2500 MSL one will realize even less percentage of power settings.....so stay low for both reasons of per-cent-power and better cooling from denser air.)

Therefore, what at first appears to be different positions, is in fact similar ones, and also in agreement with the ECI recommendations and most other authorities: During break-in, for the first few hours (until CHTs and oil consumption stabilizes) run the engine at lower altitudes for better cooling and at varying power settings in the 65-75% power-range (likely near full throttle), keeping cylinder and oil temps in as reasonablly cool range as possible with good baffling and higher forward speeds.

I did exactly just that with a new, replacement cylinder in my No. 2 postion just prior to convention and it settled-in just as expected and gave us a good run for the summer vacation/convention run. I expect good service from it for the rest of the TBO period. (TSOH now 900 hrs.) P.S.: I also used single-weight SAE-50 AD oil, AeroShell 100W, just like ECI and RAM engines concede is appropriate for engines in less-frequent service like most of ours....not the XC20W50 many folks seem to think is mandated by ECI.)

Thanks for all the advice! Last weekend for the first flight, I minimized taxi time and runup then tookoff as normal. After climbout to about 1500-2000 AGL, I throttled back to 2200 RPM and did wide circles around the airport for 30 minutes - just in case. Then I flew low and medium-slow (i.e. kept the cylinder head temp as cool as practical) to an airport normally about 30 minutes away. We checked the oil to confirm low usage. By the way, it's much easier to check the oil gage when it's a bit dirty. Kind of hard to read that clear stuff. All in all, my baby is purring like a kitten and so am I for finally getting back up in the air. Next 20-30 hours will also be slow and easy, no pattern work even though I could probably use the landing practice.