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Difference between a Repaired and Overhauled engine

I’ve just come across this very good article, written by the man who started Barrett Precision which is the top grade US engine shop that rebuilt my engine for SB569 (the Lyco crank swap).

Administrator
Shoreham EGKA, United Kingdom

A bit dated I’d say. One doesn’t use overhauled/remanufactured cylinders anymore as there is a large choice of affordable new cylinders and people have become aware that it is wrong to reuse cylinders. It was different 15 years ago.

Airplanes with the big Contis such as Cessna P210 or Malibu typically get new cylinders every 700-900 hours.

That’s only typical if the engine was ruined – by the operator. This happens a lot, but it’s not typial for the engine, but for pilots :-) There’s MANY big bore Contis in SR22s and Bonanzas that are running at the first set of cylinders beyond TBO, some at +3000 hours

What’s also very “typcial” is that these engines have a compression in the low 60s at maintenance and the service center recommends pulling and exchanging the cylinders. Also, many Service Centers REFUSE to sign off an engine just because it had 55/80 on one or more cylinders. Happens all the time – and is against the recommendation of the manufacturer.

Last Edited by Flyer59 at 04 Feb 11:15

You won’t find a P210 with 2000+h on the cylinders. 800h is a typical life limit for its cylinders. The engine has a TBO of 1600h. The P210 is rather underpowered and constantly operated at high power settings.

I would be surprised if a lot of the SR22T cylinders made it to engine TBO. It not necessarily a bad thing. Cylinders are engine “accessories” and neither overly expensive nor difficult to replace.

I don’t share the “accessories” p.o.v. Cylinders are the heart of the engine, the place where power is generated.

Accessories: vacuum pumps, generators, starters, carburetors, injection systems.

Yes, 22 T engines are tortured even more. But very few pilots really treat engines right. Will check COPA for stats …

Cylinders are engine “accessories” and neither overly expensive nor difficult to replace.

That view (not my view) is held by many in the USA, and crops up in the “did my turbo engine make TBO” debates.

I have been asked by a TB21 owner to remove the comments in my writeup about TB21 (TIO540) engines not making TBO. I asked him for proof of somebody who has got to 2000hrs with a TIO540 and I don’t recall yet seeing such proof. Admittedly it will be hard to get unless you owned that engine since new, because cylinders can get changed “off the books”. I am sure some have made it but no TIO540 owner I know personally has told me so, yet.

I agree one would always use brand new cylinders nowadays. The Q remains: whose. I see adverts in the US mags for various 3rd party cylinders but some have had some major QA issues (was it Superior or was it somebody else?) and Barrett tell me they use only original Lyco cylinders.

I would not regard a cylinder as an accessory because if a vac pump or an alternator falls off, you can fly on. But if a cylinder falls off, you aren’t going to flying very far afterwards (I have seen the result, close up). OTOH if the D3000 magneto falls off, you are finished too, and that is an “accessory”, isn’t it?

And a cracked cylinder (by far the most common cylinder end-life scenario) is only going to get worse over time. I have been shown how and where to look for the cracks (they often start at the spark plug hole) at every 50hr check and if you see any crack at all, it’s a new cylinder and then you have to fly c. 150F ROP and > 75% power for as many hours as it takes to bed the rings in on that cylinder, which translates to some 4 figure extra fuel cost, and – in theory at least – not being able to do high altitude flights unless turbocharged.

Last Edited by Peter at 04 Feb 12:02
Administrator
Shoreham EGKA, United Kingdom

Here’s a link to a Mike Busch webinar that looks at the subject of cylinders in detail:

http://www.eaavideo.org/video.aspx?v=1204537102001

EGSC

I hold the view that cylinders are bolt on accessories and a first run overhaul of a cylinder will normally last longer than factory new as overhaul shops do a better job with the valve guides and seats. If the aircraft is an N number, then as long as the cylinder doesn’t have an exhaust leak thru the valves or a crack, but just past the rings, then for TCM cylinders, the TCM specification is based on a go-no go value that is specific to a compression tester and determined by a compression test performed on a master orifice tool which is not 60/80. On my compression tester, this is 48/80. I would also do a bore scope. If a shop or an IA would not sign off an annual as airworthy for this reason, below 60/80, besides being incompetent, I would have him sign off the engine annual as unairworthy and provide me with a written discrepancy list. He is required to do this by regulation to do this and can’t refuse without me reporting him to the FAA for a violation. Once I get the list, my A&P can return the aircraft to service. The annual requirement is satisfied regardless if it is listed as airworthy or unairworthy.

KUZA, United States

People may say that Cylinders are a disposable item but they cost a bloody fortune to replace and a fair amount of downtime, loss of income, inconvenience, call out fee etc

One of the o200 has about 90 hours to go and thats had two new cylinder heads in its lifetime and a sticking exhaust valve that needed work.

My local maintenance companies off the back of a fag packet reckons that only about 10% of TCM cylinder heads make it to TBO. Does anyone have any input on the EFI Titan or Millennium equivalents longevity?

I tend to be with Achim here. Continental cylinders usually won’t last until TBO (definitely the case in turbo engines, but tends to be true also for normally-aspirated engines) and that’s often not the fault of the operator/pilot. These cylinders just don’t hold up any better. It also appears to a bit of good luck/bad luck on what type of batch your cylinders are from.

Some people go absolutely anal about their operating techniques and maintenance practices for their engines; and still many won’t reach TBO at all. I am all for taking good care of the engines (for example I never go above 370F, always move the throttle slowly, etc.), but pilots can’t make up for the bad quality of the cylinders.

But sometimes it may make sense to repair a cylinder instead of getting a new one. The weak spot of Conti cylinders are the exhaust valves and their seats. My shop has developed a tool that allows them to hone the valves with the cylinder installed on the engine. Isn’t that neat? Takes minutes. Oh, and my service centre won’t even touch a Continental cylinder until it goes below 50/80.

Last Edited by boscomantico at 04 Feb 19:08
Mainz (EDFZ) & Egelsbach (EDFE), Germany
47 Posts
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