Ask Paul: Fly more, get longer TBO?

Q: I bought my first plane, a 1981 Cessna T182RG, in May 2012. I have been flying this plane frequently and have put over 300 hours on it in the last calendar year. I can tell you that in 2005 it received a factory remanufactured engine from Lycoming and at the 1,000 hour mark got a complete top end overhaul. Now Lycoming shows the TBO at 2,000 hours, but I have found documentation from Lycoming that put the TBO at 2,200 hours providing you are running at 40 hours a month. For me that translates to the more you run the engine the more hours you can squeeze out of it.

How do they quantify that number? Is that based on history of engines running those hours having less mechanical issues at higher hours? Does that simply translate to 2,200 hours TBO for my engine?

How does the top end overhaul effect my TBO?

I can tell you that the compression is 4-6 pounds higher per cylinder now than when I did a pre-buy on the plane a year ago. It hadn’t run much in the few years previous to purchase so I am thinking blow-by was the culprit. I ran it wide open everywhere I went for the first six months and there were some pretty good oil stains on the belly from the exhaust, along with higher than expected oil consumption. The compression is now in the mid to high 70s and barely any exhaust streaks and low oil consumption. Not sure if that was a good idea but the results seem to indicate it helped.

I love the plane and the engine has been rock solid.

DONNIE SNIDER

A: Donnie, I’m certain many others have had this question in the back of their minds at some point.

Your particular engine, the O-540-L3C5D in the Cessna T182RG, does in fact have a TBO (Time Between Overhaul Periods) of 2,000 hours. Even with the 1,000 hour complete top end overhaul, the TBO time remains at 2,000 hours…sorry.

The Lycoming documentation you discovered where it mentioned a 2,200 hour TBO is found in Lycoming Service Instruction 1009AV dated July 8, 2013. This Service Instruction lists TBO times for all models of engines, but does contain Notes that are very important. These Notes vary from model to model, and should be read carefully to determine if they apply to your specific engine model and how it may affect that model’s TBO time.

The O-540-L3C5D engine model has two Notes that apply, the first of which simply tells you that this engine was designed to incorporate exhaust turbocharging. The second speaks specifically about TBO times. The requirement for obtaining the 2,200 hour TBO time for this engine clearly states “if an engine is being used in ‘frequent’ type service and accumulates 40 hours or more per month, and has been so operated consistently since being placed in service, add 200 hours to the TBO time.”

From the information you provided, I don’t think you have met that criteria, but I’m certain you can understand the reasoning behind Note 11 in the Service Instruction. The secret to adding the 200 hours to the TBO time comes from the “frequent” operation and must be accomplished as mentioned in the publication from the beginning of the engine’s service life.

The worst thing you can do to any aircraft engine is to expose it to long periods of inactivity. This becomes a breeding ground for serious internal corrosion, which will contribute to a shorter service life. Some of the results of internal corrosion come in the form of camshaft and tappet spalling, and increased oil consumption from corrosion on the cylinder walls, which accelerates ring wear.

There is no substitute to flying the aircraft as frequently as possible, but not everyone can do 40 hours or more per month. However, those who can receive the reward of adding 200 hours to their TBO time.

Regarding your operation of the aircraft following its purchase, it sounds to me like you did a good job of saving the engine from a shorter life because of its past inactivity. This is not always the end result, so Donnie, I compliment you on your success here.

Comments

  1. If your not using the airplane commercially (where you would have been doing 100 hour inspections) then you can run well past TBO, in some cases with FAA approval. I was at a large flight school 40 years ago that had approval to run O-320′s to 3000 hours and they were working on getting that upped to 4000 hours when I left. The engines were running about 6-8 hours a day unless the weather was bad, 30-40 hours a week for 9 months of the year, less in the summer. The deal they did with the FAA was tore down the engines at 2000 hours to show that were was no measurable wear, then at 3000 hours showing the wear was still within the high serviceable range on all parts. They had there own A&P school so had lots of help to spec the engines and prove to the FAA that they had been running them right. I know of several people who fly there airplanes 15-30 hours a month and they have gone well beyond TBO, as much as 1000 hours on O-320 and O-360/O-540 series engines (normally aspirated). They all do Oil sampling(AVlab kits) and watch it religiously to find out what metals are showing up in the oil, they also have oil filters on there engines and monitor them for any weird sounds. Resently my neighbor tore his engine down at about 500 hours over TBO and after 30 years of use, oil test were OK but there was a tapping on one of the cylinders. Come to find out the hydraulic lifter on that cylinder was stuck so it was a good time to do the engine before any damage was done. He just got his crank and cam back with a .003 grind on the crank and all the AD’s complied with. I personally don’t want to be taking any long trips with an engine that is much beyond TBO but it can be done and is legal.

  2. Corrosion is indeed the biggest danger to an engine. The more frequent the operation the better off it is with any engine, start cycles may cause some wear but not as much potential damage as long inactivity. The TBO is manufacturer recommended not an FAA requirement for most part 91 operations (LSAs must follow manufacturer schedules). the opening of an “properly running” engine for any reason should be avoided as much as possible. Early failure rates after overhaul “infant mortality” are not unusual, that is the big danger of the proposed ECI cylinder A.D. that would require replacement of cylinders that do not have an “in-service” physical problem.

  3. Charlie Kile says:

    There is way too much attention paid to the manufactures TBO.
    Past history is much more important.
    I bought a 1959 Cessna from the original owner. He used the plane to
    fly between his home near Springfield Mo, His business in St Louis Mo, and
    his clients scattered all over the mid west.
    He claimed, and the logs indicated, that the engine had never been opened.
    It had right at 3300 hours on it when I bought it. I flew it about two years then sold it. It still hadn’t been opened up. The compression was still in the 70lb range. It was however using about a quart of oil about every 6-7 hours.
    charlie

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