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Thread: IO-520A pre-buy advice?

  1. #11

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    I operate one IO-520 on a Cessna 185 and nine O-470 on Cessna 180 (4)/182 (5)s. All professionally flown for natural resource work in the upper midwest. We rarely get above two thousand feet MSL and spend a lot of time at reduced power settings (15-20 inches,2000-2200 rpm), but when we do cruise we cruise hard (24/2400) to get where we are going. The aircraft are keep in a heated hanger (46 f) and never spend the night outside, they average 600 hours a year.

    We are half way thru the third overhaul of the 520 and have yet to change a cylinder between overhauls, we could be just be very lucky, but I am very particular about how it is operated. I personally fly 99% of the hours on the 520 and am religous about cooling the engine for shutdown.

    When I was first checked out in the 185, my former boss told me they were famous for warping exhaust valves (then burning them) and the secret was to get them as cool as you could and then to minimize the windmilling at actual shutdown (lowest rpm possible). I actually pull on the throttle when I am closing the mixture. We set idles at 500 rpm and I usually see 450 by pulling on the vernier throttle. They warp because they draft in cold air while windmilling just those few blades at shutdown, particularlly in winter.

    Our overhauls are done at Popular Grove airmotive and we have had good luck with them. We did have several of our engines with the bad batch of cylinder, including the IO- 520. I put 395 hours on those cylinder without any problems and they were warrantied (had to come off at 400hrs.)

    We did have the cases cracked at the last overhaul of the 520, but at the bases of the middle cylinders. We have a rear mounted belt driven alternator on it.

    The O-470s seem to crack more cylinders than have bad valves problems.

    Again, we could be very lucky,

    Luke

  2. #12

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    Have you gone to the faa website and looked up AD's? Complying with ad's at overhaul can be expensive and most engine ads have to be cw at overhaul....just a thought

    Sent from my DROIDX using Tapatalk

  3. #13

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    LLuke, that's great info. I think one of your secrets is that you spend most of your time at low power steady cruise, and a low altitude so that would be very easy on an engine; and is unlike what most of us probably fly.
    For instance , I go back a forth from Aspen at 7800 feet to Denver at 5280 often, and I have to climb to 13,500 or 14,500 maybe higher enroute. The trip is less than an hour, but a climb and descent at ethier end. I have also flown to Texas, Phoenix, Santa Fe, and Oshkosh. I have done all of these in my T-34A (0-470)and Beech 36 TC. The 34 tends to run high oil temp in climb, and the 36 definitely tends to have high cly head temp in climb, right up to red line in the summer, even at 120 knots and full rich climb.

    As for the valve troubles, none in the 0-470, but a lot in the TSIO -520 UB. I don't think it is related to valve warping or cooling. I have never heard of that before, and also it is standard to cool down the engine at 1000 rpm idle for 4 min to cool the turbo oil and bearings.
    As far as everything that I have heard and seen and read the problem in not valves overcooling and warping; rather it is exhaust valves burning, seats burning, and leaking, from overheating. If cooling and warping was the issue it might also hit intake valves and we don't see any trouble with them.
    Also running your engines in the 180 , 185 may offer more air flown and better cooling over the engine that the tightly cowled Bonanza.
    Thanks a lot for your input.

  4. #14
    FlyingRon's Avatar
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    To my knowledge the big Continental engines doesn't have much in the way of AD's. There are a few to make sure you don't have certain after market parks (certain Superior Air Parts cylinders, etc...).
    The biggy is the crank controversy of the early-to-mid nineties but hopefully all that has been taken care of by now.

  5. #15
    Mike Busch's Avatar
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    Quote Originally Posted by Bill Greenwood View Post
    I am not personally familiar with I 0 -520, but I know a lot about the TSIO 520, mine and friends. I have not heard of any of them making it past 1000 hours without some problem with exhaust valve leaking, burning.
    Both TSIO-520-BB engines on my Cessna T310R made it to 1900 hours without a cylinder coming off. The engines are now at 2800 hours SMOH and 4700 hours SNEW, and I still have 9 out of the original 12 cylinders in service, only three had to be removed in 4700 hours. So I have to disagree with Bill's assessment. If you treat these engines right, they will treat you right.
    Michael D. Busch A&P/IA CFIA/I/ME
    President, Savvy Aviator, Inc.
    President, Savvy Aircraft Maintenance Management, Inc.
    2008 National Aviation Maintenance Technician of the Year

  6. #16

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    I am not an A&P, but I have been shopping for a Navion for a while.
    You might even be looking at the same aircraft that I have already looked at.
    My mechanic advised me that there are two things on the IO-520A that might make an overhaul a less viable option than a factory reman, depending on the individual engine. Check these two things:
    1. the light case was known to crack, so the particular case might be unusable.
    2. the crank, if not a VAR crank, will not be usable.

    In other words, if your aircraft has an unusable crank and case, then plan on a factory reman replacement, not an overhaul.

    Again, these are specific to the engine in a particular aircraft, I am not saying all io-520a's are bad.
    You might want to get the serial nbrs from the engine, and give them to somebody smart.


    Bill

  7. #17

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    The "heavy case" may have helped lessen cracks, but did not stop them altogether, it still happens.

    If you are looking at a Navion with a 520, be sure to check the paperwork. My friend bought a really nice looking Navion with a 520 engine, but turns out there is a question of the legality when the O-470 was replaced with the 520. The seller was working with the FAA to get full approval, but he passed away and not it is in limbo. He may get it resolved or may be able to fly in experimental category, don't know yet.
    I guess most of the crank problems were resolved some years ago unless it is an older engine.

  8. #18

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    Mike, it's not "Bill.s assessment" that there are both exhaust valve problems and case cracking problems on Cont 520s, and to some extent 550s.
    Check with any good oh shop, Aviation Consumer, and /or the Bonanza assoc or owners.
    I don't know many people who fly 310s. It is possible that you have different cowlings and therefore better cooling in that engine installation. Also you may spend more time in level long distance cruise than others do, maybe even on IFR plans, and that may be easier on the engine. I would like to read your methods of operating that make your engines last so long.

    Cont likes to make out like it is the pilot who is "not treating the engine right". Funny thing, when I flew a Mooney 201 with a Lycoming for 10 years all the way to TBO, same pilot, mostly same airports, same weather; I never had a case crack or an exhaust valve problem. I only got dumb when I got the Bonanza? Maybe if I wrote Lycoming on the engine it would last longer.

    Kind of like some years back about 400 people were killed over the years in Bonanza v tail breakups. Of course, Beech did not want to admit that something might be wrong with their design. Therefore it must be the pilots fault. Nevermind that Mooneys were not coming apart in the air, even with less expericened pilots. Author Barry Schiff even wrote a puff piece on how good the Beech must be and therefore it must be the pilots fault.
    Finally after many Aviation Consumer articles the FAA could not ignore it any longer,and they issued an AD to inspect the tails and to rebalance and in some cases reinforce the tail structure.
    VIOLA! Virtually overnight the stupid pilots that had broken all those planes for years suddenly got so much smarter and nowadays tail failure and breakup is almost unheard of in a Bonanza.
    Last edited by Bill Greenwood; 01-05-2012 at 04:17 PM.

  9. #19
    Mike Busch's Avatar
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    Quote Originally Posted by Bill Greenwood View Post
    ...there are both exhaust valve problems and case cracking problems on Cont 520s, and to some extent 550s.
    Two different issues, Bill.

    Case cracking is (and always has been) a known problem with big-bore Continental engines. I have never heard anyone suggest that pilot technique has anything to do with case cracking. Some models crack more than others. (Permold-case engines crack more than sandcast-case engines. Continental IO-360s crack more than any other model. Permold TSIO-520s crack more if they are red-lined at 325 or 335 HP than if they are red-lined at 285 HP. Etc.)

    Exhaust valves are another issue. There have been periods of time (specifically the late 1990s and early 2000s) when TCM had problems with their cylinder manufacturing process, resulting in premature exhaust valve failure even in the face of perfect pilot technique. Those exact same factory cylinders when re-valved by a good cylinder shop (who post-reamed the guides and got the geometry right) would routinely make it to TBO with no valve issues. On the other hand, TCM cylinders manufactured in the 70s and 80s, and those manufactured after about 2005, do not have that problem so far as I've been able to tell.

    Another problem is that tens of thousands of TCM cylinders have been pulled because of alleged exhaust valve problems that actually don't exist. Since 2003, TCM's guidance (SB03-3) states that the cylinder is airworthy unless the compression gets down to the 40s. Even if it gets down to the 40s or below, SB03-3 requires that the cylinder be borescoped to determine the true condition of the exhaust valve. If the valve looks normal under the borescope, then SB03-3 requires that the aircraft be flown for at least 45 minutes and then the compression re-tested.

    Case in point: About two weeks ago, one of our Savvy-managed Cirrus SR22s went into annual inspection. The shop reported that one of the cylinders measured 38/80 with leakage past the exhaust valve. We had them borescope the cylinder and it looked normal. We dumped and analyzed the digital engine monitor data, and saw absolutely no evidence of exhaust valve leakage. We then directed the shop to complete the annual, sign it off as airworthy, then had the owner fly the airplane for an hour and bring it back to the shop, where they pulled the top cowl and re-tested the one cylinder. On the re-test, the cylinder measured 72/80.

    Compression tests are highly unreliable and non-repeatable. No cylinder should ever be pulled based solely on a single compression test. The borescope is the gold standard for assessing cylinder airworthiness. The compression test is highly unreliable, primarily because it tests the cylinder under conditions that have no relationship whatsoever to the conditions that are present when the engine is running and making power. This is precisely why TCM wrote SB03-3 the way it did. IMHO, SB03-3 is the best guidance that has ever been written on the subject of when to pull a jug and when not to. On our professionally-managed Continental-powered aircraft, we always require that shops follow the guidance of SB03-3 to the letter. I can't count the number of unnecessary cylinder removals and valve replacements we've prevented by doing that.
    Michael D. Busch A&P/IA CFIA/I/ME
    President, Savvy Aviator, Inc.
    President, Savvy Aircraft Maintenance Management, Inc.
    2008 National Aviation Maintenance Technician of the Year

  10. #20

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    Thanks for all the great advice. IF we buy it, will most likely take the Factory Reman option due to the Case/Crank issue.

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