TBO Question ... borrowed time?

velovp

Tach time is ticking on my Lyc IO-360C1C. 1920SMOH/5225TT. Engine is running strong; compressions are in the 70's; oil consumption is 1 quart every 6-hours. Asking the group for their experience and wisdom ref: operating beyond recommended TBO. Is it foolish to think the engine will go 2200 hrs or am I on 'borrowed time'?
Scott B
Arrow II
Sebastian, FL

Mountain Pilot

Take a few minutes and read this article from a very respected I/A and pilot. He has researched this area very completely.

http://www.avweb.com/news/savvyaviator/savvy_aviator_49_reliability-centered_maintenance_q_and_a_196179-1.html

I have a Pa-28-140 with 1960 hours and am going to extend its use for another year ( about 200 hrs ) and watch the oil tests and compressions very carefully. I use about the same amount of oil as you do. It has averaged about 100 hours a year since last overhaul.

GM

I also have four hundred hours on my Tulsa engine and probably will (if I still Have the aircraft) take it back to Tulsa for O/H at 2000 hours and buy a new cam and factory new cylinders as this engine had when I bought the aircraft.

I don't want to buy someone else's core as an exchange engine with a refurb cam and crankcase that was possibly repaired.

Even new parts can break though.

Jim H

Perhaps an equally interesting Lycoming number associated with TBO is time in service to overhaul, which is often overlooked. The IO 360 is not recommended beyond 12 years since last overhaul, per recommendation by Lycoming.

Recommendations are just opinions, and as such have to be sufficiently restrictive to cover all possible operating situations.

GM

Leigh Wrote:

---

> GM, want a gig flying DC3's again?

Now those 60 year old engines are another story. They will crank and run perfectly after sitting 15+ years after a little pre oiling, cleaning the plugs and soaking the carburetor seals for a couple of days. I've also seen one display only a little roughness with a cylinder lifted right off the crankcase held on by the plug wires.

Thomas

My mechanic told me a story of a guy leaving his Archer in front of the maintenance hanger one night with a note on it saying "engine's running a bit rough". When they took a look they found one cylinder nearly separated from the IO 360... simply amazing engines.

Mountain Pilot

It has been brought up on how a new engine ( new or rebuilt ) may be prone to failure...

Just got this in from the AOPA..


http://flash.aopa.org/asf/pilotstories/powerloss/?priority=F509RPS03&WT.mc_id=F509RPS03

Every time I have put a rebuilt engine into one of my airplanes I put about 35 hours on it before going far places or over remote areas.

SkipSinclair

I would continue to run it with the following caveats. I would do oil/filter changes at 25 to 35 hour intervals, with an oil analysis on each one. Also perform compression checks at same interval. Track the oil consumption closely. Any changes in the parameters must be given a close look at.

Normally these engines don't fail instantly due to high time without giving you some warning. You just need to be looking for the warning signs.

I would have no problem putting my family in an airplane that was past TBO that I was watching closely.

Just a note I had an O-320-E2D that I took to 3,200 hours.

Russell P

velovp

In line with Russell P's suggestion, I follow a 25-hour oil/filter change interval; and use Blackstone Labs to perform an oil analysis at every oil change. Oil analysis reports indicate a healthy engine with no apparent concerns or adverse trends. From what I hear from those with experience in such matters, running beyond the manufacturers suggested TBO is not necessarily a "wrong decision" - providing I properly maintain the engine and closely monitor its health. The motivating factor for me to consider operating beyond TBO is the additional time that I need to save $$$ for a major overhaul. Safety is a 'trump card' in making many maintenance decisions; and I do not want to let a lack of money blind me into thinking that "It is safe to operate beyond recommended TBO, just because I want to believe it so". Realizing that every engine is different, there appears to be a strong sampling of aircraft owners that have operated their engines beyond TBO with no mechanical issues. Thanks to everyone who posted comments in response to my question.
Scott B
Arrow II
Sebastian, FL

Mountain Pilot

A quick review of the 2007 accident reports on general aviation shows

973 Pilot related accidents

223 Mechanical related accidents of these 99 were engine failure accidents

You as a pilot has 10 times the chance of an accident because of your piloting techniques or decisions than a engine failure.

How much time do you spend at reviewing your aeronautical knowledge?

How much money do you spend at upgrading your flight skills?

You as a pilot can prevent 90% of the accidents. Spend as much time worrying about your performance as your engines performance.

Jump in and take at least one FAA or AOPA free online course a week, keep up-to-date maps and publications. Work in your instrument skills.

Your family will be far more safe with you being well prepared...

My 2 cents....

BMK

In addition to the Arrow, I also own 1/4 of a 140. It has about 2170 hrs on the engine and at last annual mechanic says he sees no reason to replace the engine yet. Engine's running strong and smooth with no metal and strong compressions.

It just recently flew from Pittsburgh to Augusta, GA (for the Masters), over to Boca Raton, then back to Pittsburgh. Not one hiccup.

flyguydon

If you fly normally and do not do a bunch of touch and goes... it is almost silly to OH at 2000 hours (especially a Lycoming). I have been through a few of them at TBO and in the clean ones that have been well maintained (oil changes especially) there is not even any detectable wear in the cylinder bores... These type of pull downs have the cyls honed, new guides... and go out OH to spec for another 2000 hours.

If an engine is making good power, good compressions, and not using oil in excess... it is not uncommon for them to be nearly perfect to well over 3000 hours.

NOW... that does not mean that you should not OH or change things (typically included in a real OH) that do wear out... MAGS, harness, alternator, vacuum pump, governor (if constant speed), fuel pump, etc.

These things are what will cause you reliability issues in most cases.

Especially 320s and 360s... folks will top them and run em another 1000 hours or so too. Usually only if they are having cylinder issues.

Change the oil... don't shock cool... lean properly... and you would be amazed at how well an engine holds up. They DO NOT wear out at TBO and become a time bomb... Mags... yes... cranks and cyls... no.

RayPhillips

I don't think shops color code engines.

There is a color code standard for reworked cylinders and cylinders with special surface treatments. Chrome, 10 over, etc.

alex

Lycoming recommends a valve wobble test after 600 hrs,does anyone have more information about this and has anyone here actualy done this to their O360's?

flyguydon

Leigh,

That is because they suggest to "stake" the valves and most folks don't. You really don't even need to if you lean properly or especially if you use mogas. Mostly the low compression Lycomings using 100LL... and especially the ones with students that run them rich all the time... build up carbon and lead deposits on the valve stems. If not staked off... they will run the risk of seizing in the guide resulting in a potential for a cylinder to fail. This is much less likely in the higher compression engines and those that have been leaned properly. It is very unlikely in an engine that runs mogas. (Oddly enough, this condition is even more common to Continental 0-200s)

Also what you mention about swallowing valves is a left over fear from many moons ago before the bulletin (might have even been an AD) requiring an increased valve stem size on the Lycomings. I believe they went from 5/16" to 3/8". The old original ones would sheer off just a little too often...

boothkc

There are lots of opinions here. Personally I like Mike Bush's position. We are seeing lots of SR22s approaching 2000h now and running strong. I'd have liitle anxiety running a strong engine (good compression, normal oil analysis, normal bore scope) past TBO. Depends on what kinda flying you do etc. and personal risk benefit analysis. It's pretty clear the riskiest time for an engine is the first 100h. And MIFs (maintenance induced failures) outnumber fatigue failures by a large margin.

If the top end becomes weak consider just a topend overhaul and replace the jugs. That is what I'd do if all else was equal and compression drops or oil use goes up.

Kevin

PaulR

boothkc

"Mike Bush's position. We are seeing lots of SR22s approaching 2000h now and running strong"

Kevin- Wondering if you saw an article about reaching 2000 tt by Mike Bush, as i would be interested in it? Last info I saw was the Continental in Cirrus were only making it to 1200 tt LOP, and that was some air taxi company flying the plane.

boothkc

I'm not sure it's worth opening the LOP vs. ROP debate, but the consensus from the COPA members (represents about 75% of the 4200 Cirrus fleet) is the LOP extends engine life. Many planes are making it to 2000h w/o big issues etc. I'm sure there are some failures and jug jobs but the clear feeling from the site is LOP leads to longer life cycles in this particular plane (matched injectors and sophisticated engine monitoring in every plane). Failure to follow propper LOP procedure will be problematic and has killed a couple of engines...this is complex but doable. Not sure what the airtaxi issue is, but every Cirrus I know runs primarily LOP.

There is an interesting follow up discussion in the current AOPA magazine that confirms this.

My point is that if this is true then we will see a lot of "young healthy" engines at 2000h asking what to do and there is good logic to refresh the topend or run until data (oil analysis, compression, bore scope etc) suggest and impending problem.

Finally, for those still on the fence keep in mind that ALL cars have run primarily LOP since the introduction of fuel injection and emission control issues in the late 70's w/o harm. If anything car engines last longer (for a variety of reasons) than they ever have.

Food for thought.

Kevin

velovp

As the originator of this thread, wanted to update the group on the IO-360C1C in my Arrow II. I typically perform oil changes every 25-50 hours and have an oil analysis done by Blackstone Labs. Lab reports have always been very good, given the age of the engine. About 10-flight hours ago I discovered iron filings in the oil filter. Analysis of the metal pointed to cam shaft wear. I flew an additional 10-hours and examined the oil filter - to find a noticable amount of filings. Tear down of the engine confirmed that two cam followers and one of the cam lobes were worn/pitted. The engine is now going through a major overhaul. Not happy about the $$$, but cannot be too disappointed given the engine gave 2,200 hours of faithful service before the cam wear issue came up. Important note to those who get involved with their own preventative maintenance ... be sure to inspect the oil filter following every oil change.
Scott B
Arrow II
Sebastian, FL

flyguydon

Scott,
Did you get your mags back? Also, no matter what you do (did) I hope you used a NEW cam. OH cams rarely make TBO because when they grind them they take off any of the original hardened layer and then they wear faster. Two of the forward lobes on a Lycoming do double duty too. They run two valves and thus get twice the use/wear of the others. Also, might I suggest using the Exxon Elite or the Aeroshell 15/50 semi-synthetics on the OH. Better corrosion control and I feel they lubricate better on any engine that sits more than a week at a time...

fmmike

I have been reading the posts on the TBO subject. I would add that a borascope of the cylinders be done. Good compression doesn't always mean anything. A borascope could reveal impending failure of a valve or valves. A valve could fail without warning. I also read in one of the post that the writer was told the paint on the cylinder was put on by the engine rebulder to identify that shop. That isn't what the paint means. Below are the color codes and what they mean.
Grey or Unpainted = Standard cylinder barrels
Orange Stripe = Chrome plated cylinder barrels
Blue Stripe = Nitrite hardened cylinder barrels
Green Stripe = Steel cylinder over sized .010
Yellow Stripe = Steel cylinder over sized .020

http://www.lycoming.textron.com/support/tips-advice/key-reprints/pdfs/Key Maintenance.pdf
See Page 9

fmmike
A&P