Turbo owners whose engines made TBO

[IO540]

.... without even replacing one cracked cylinder, or having a turbo failure.

What %, I wonder.

I don't think I know any personally.

[S-Works]

How many non turbo owners have made TBO without similar?

I have had to replace a cracked cylinder on my non turbo 360.

[Heliplane]

Of those engines that have/had not made their TBOs, also interesting to know:

1) whether those engines are consistently allowed to properly warm up pre-flight and properly/gradually cool down during descent and after landing;

2) whether those engines are operated at good power setting and properly leaned during cruise;

3) how often those engines fly; and

4) whether they have regular oil/filter changes.

[IO540]

I have never heard of such thorough research, but it seems to me that the majority of frequently run NA engines (the vast majority of which will be ones used by schools; private owners tend to fly a lot less) do make TBO.

It is the turbocharged ones that seem to be a total Russian roulette - looking at people I know.

And I don't see any obvious correlation between a lack of understanding of engine management on the part of the pilot, and getting cylinder cracks or turbo failures.

Also I see a much higher failure rate on 250HP turbo normalised engines than on identical NA 250HP engines (IO540-C4) so it isn't the HP alone... especially on an engine which exists in 350-380HP versions with almost no modifications. It has to be the much higher duty cycle spent at high stresses. A turbo engine tends to be flown at max cruise (say 75%) the whole time, and at high altitudes the air is a lot thinner.

[Pace]

10540

I know of few engines that run to TBO without problems. The question rarely is whether an engine goes to TBO but at what point is it not worth spending money when TBO is not far away.

A Seneca I flew had both engines rebuilt at 1650 hrs. The one needed major cylinder work and it was decided to rebuild it to Zero rather than spend a lot of money with the end result that the unit would still need rebuilding anyway.
Having made that decision it was decided to rebuild both as the aircraft was hard worked. We wanted to minimise the down time.

Add Turbos and yes they do go wrong but so do many other things enroute to TBO.
NB check your mail

Pace

[Marchettiman]

Perhaps not exactly relevant as my Lycoming is normally aspirated. I had new cylinders fitted 11 years and 600 hours ago. Unfortunately they were from a bad batch produced by Eci and subject to an AD limiting their life to 800 hours. On the recent annual 3 had cracks in the heads and as Eci were offering some form of compensation I phoned their warranty department in the States, expecting to be told to push off. I couldn't believe their response which was send us photographs of the cylinders and we will supply brand new ones (they now call them Titan cylinders) at a fraction of the list price. They even paid the freight to the UK! Eci couldn't have been more helpful, the cylinders arrived in 2 weeks, came with pistons, rings, valves and gaskets. They have transformed the look of the engine and restored all 260 HP maybe more as my SF260 is now faster than I can ever remember. If my Mercedes developed an engine problem after 11 years I know what the answer would have been to a warranty request! Thanks Eci!

[IO540]

I agree totally with your economic approach but your 1650hr engine did not make TBO ;)

No email received BTW.

[SNS3Guppy]

I've operated a number of Cessna 206's, 207's, 210's, 310's, 414's, 421's; Piper Navajos, Senecas, etc, without issue to TBO, or that have been flow to TBO without losing a turbocharger or having to replace a cylinder. Where cylinders have been replaced, it's a matter of course...aircraft piston engines are designed to have cylinders that are easily field replaceable.

The single biggest contributor to turbo failure or lack of longevity in the turbocharger is improper operation, followed by improper maintenance. The single biggest culprit in the improper operation category is failing to properly cool the turbo on the ground. Ham-handed use in flight, overboosting, and other poor practices also lead to lower component lives. Failure to properly lubricate, inspect, and maintain induction and turbo systems also reduces their lives. Turbo bearings lead a tough life style, and pilots can make it a lot tougher. Want to destroy a turbo overnight? Get on the ground and shut the engine down. Coke those bearings. Get that oil boiling.

I flew for a company many years ago that had a fleet of turbo Cessna 207's. We didn't have turbo problems as a rule, even though we used a lot of fairly inexperienced pilots, because of the way we operated the airplanes. Even with a different pilot flying the airplane on every flight, and between two and three hundred hours a month on the average per airplane, turbo problems tended to be our smallest concern. On occasion we'd see someone lift a cylinder head by pushing the engines too hard, and we did see cylinder cracks from improper operation...but these were generally pilot error. At one point we had a series of bad cylinders from Continental, but this problem went away. Generally we had a lot of reliability, with very few turbo related issues. We also treated the engines like our lives depended on them...because they did.

One practice we used was to finish each trip with a five minute timed cool-down and spool-down. Passengers wouldn't be let out during that time; the airplane would arrive, and several other pilots would gather around the airplane as safety guards to prevent people from approaching the airplane (or getting out) while the engine turned...or to guide people away if we did need to hot load or unload with the engine running). Typical cool down was done monitoring CHT's as well as at a power setting that was conducive to best cooling (not necessarily idle), and where possible, into the wind.

Operating engines with a preventative schedule, spectrometric oil analysis, and regular, standardized operating practices did a lot to keep the airplanes running...and we changed engines routinely at TBO without any difficulty.

I operated Cessna Skymasters on a fairly rigorous schedule in a large fleet, with turbo issues being a rarity. Engine-changes at TBO were a regular fact of life, and that continues today. Our training airplanes were normally aspirated, but all the airplanes used in the field were turbocharged, without any problems.

I think there's a common misconception out there that a turbocharger implies a lack of reliability or an unlikelihood to make TBO, and this isn't true.

I should add a disclaimer that I didn't own the airplanes above; I operated them and in some cases maintained or helped maintain them. The thread asks specifically about owning airplanes, and I didn't own those...but operated a lot more than I could possibly have owned. In my experience, much of the time when there are turbo and cylinder issues (manufacturing defects not withstanding), it's a pilot issue.

[Big Pistons Forever]

I think there is an element of luck involved as some engins just never seem to be happy no matter how nice you are with them. Aside from the few unlucky ones every engine should make TBO with no major work. However for that to happen then 2 things are needed.

1) The aircraft must be operated properly. That is warmed up, smooth power changes, proper mixture setting for each part of the flight, stage cooled before landing and a proper Turbo cool down before shut down. ( as an aside; Continental says applying full power on a GTSIO 520 engine with the temps not in the green will subtract approximetly 50 hrs off the life of the engine)

2) The aircraft must be maintained properly. A privately owned Cessna 340 that I occasionally flew had both engines go to TBO with the original cylinders,turbos, and all exhaust components except a replaced tailpipe. However this owner was fanatical about maintainance. The aircraft got an oil change every 25 hrs with a good poke and prod with all systems lubed at the same time. The fuel system was carefully balanced and the plugs were serviced every 100 hrs with any suspect ones replaced and the Mags overhauled every 500 hrs. The baffles were kept in imacualate condition and he had an engine analyser with a trend monitoring problem, and all anomalies were immediately investigated. He also had the props balanced for smooth operation.

My personal experience is few owners are willing to put this kind of money and care and attention into maintaining and operating their aircraft. The result is little problems (the slightly clogged injector which makes a cylinder run hot, the old spark plugs that makes the engine run slightly rough, the deteriorating baffle that makes a hot spot on the cylinder, the gummed up waste gate linkage that allows a momentary overboost etc etc ) eventually turn into big problems like the requirement to replace a cylinder.

[A and C]

I have only seen one Turbo engine reach TBO, the owner I think never used full power in all the time he owned the aircraft and cruise was usualy at no more than 60%.

Guppy can you remember any numbers and best practices for the C421, your knowlage would be usefull to me in a project I have just undertaken.

[SNS3Guppy]

I don't believe we used any special procedures in the 421, beyond factory recommendations.

The issue with the 421 isn't the turbos; it's the geared engine. Not a problem if it's flown properly, but a very big problem if it's not. Rapid power changes, failure to plan ahead, etc, account for the lions share of problems on that airplane with engine operation. Planning ahead includes early climbs, early descents, planning power reductions and increases, planning for cooldown and spooldown times, and so forth.

[A and C]

Thanks for that...........I shall place the flight manual in the outhouse three weeks before I fly the aircraft.

[IO540]

I suspect there is a strong correlation between turbo engines which make TBO, and "very traditional" by the book ROP operation which yields CHTs some 20-30F lower at a ~ 20% fuel cost.

From what I hear, the big piston twins are sufficiently awesome gas guzzlers to make a TBM850 look economical.

NA engines are routinely operated (with proper instrumentation) peak/LOP without problems. But even in my installation I have to work hard to keep the CHT down; if doing the constant-EGT climb technique I have to trim forward ASAP for 120kt otherwise the hottest pot (#3 in my case) goes through 400F. After a few mins the problem goes away because the MP drops off. OTOH a turbo engine, in the same aircraft, will be facing that issue all the way up to FL150 or whatever, and it gets worse as the air gets thinner.

Even my tablet computer nearly overheats at FL180, due to the air density being 50% down :)

[Doodlebug]

Guppy, remind me of the reason why the GTSIO-520-engined Titans were the only light twins in the fleet the boss insisted we idle at 1000 immediately after startup? Something about the flyweights?

[Big Pistons Forever]

I don't believe we used any special procedures in the 421, beyond factory recommendations.

The issue with the 421 isn't the turbos; it's the geared engine. Not a problem if it's flown properly, but a very big problem if it's not. Rapid power changes, failure to plan ahead, etc, account for the lions share of problems on that airplane with engine operation. Planning ahead includes early climbs, early descents, planning power reductions and increases, planning for cooldown and spooldown times, and so forth.

I have to respectfully disagree with Guppy. I flew a corporate 421 for a couple of years and I am quite familiar with the type (The aircraft was sold with 1450 SMOH and all original cylinders, turbo's and exhaust components).

The fact that it is geared is not the principal issue with the 375 hp GTSIO 520, although it is a consideration. The main problem is that the engine is aside from the one big reduction spur gear, identical to a 285 hp TSIO 520. To get all that extra horsepower it has to run at high RPM and be heavily boosted. Therefore there is a lot of extra heat and cylinder pressure generated which makes life difficult for the engine top end. The secret to long life for these engines is managing temperatures and the secret to managing temperatures is proper use of the mixture control. My recommendation is as fol

1) Lean aggressively on the ground to keep the plugs clean

2) Always use full power for takeoff and always climb at full rich.

3) Keep the TIT in cruise at or below 1450 deg. You simply must throw gas at these engines to keep the temperatures down (ie run well to the rich of peak). Flight plan for at least 3 GPH per engine more than book.

4) Leave the mixture leaned on descent all the way to the flare. The worst thing you can do is go full rich on descent as the cylinder head temps will instantly plummet shortly followed by cracked cylinders. In any case the engine will not run smoothly at low power settings and full rich

Other points of note

a) Having proper operating temperatures is vital before exceeding idle power

b) Proper maintainance is vital to engine health. The ignition system has to be top notch with strong mags, a good harness and clean properly gapped high quality spark plugs. Fuel Distribution is also important and the entire fuel system should be flow checked every 500 hrs. Finally the baffling must be perfect to ensure all the cooling air goes to the right place.

c) The fact that it is geared does have some operational significance. The chief issue is the prop should never be driving the engine so you want to avoid having high RPM and low MP. For this reason I leave the props at crusie RPM for the approach and landing only going to full fine if an overshoot is required. I also only cruised at 1800 RPM as this is (according to my engine shop) the most favorable setting for minimizing harnfull drive shaft harmonics.

[SNS3Guppy]

A&C, The 421 manual is typical of any other, especially with respect to the vintage of the airplane. It doesn't provide much, other than elementary systems descriptions, procedures, and performance.

Basic piloting techniques are sufficient. A good warmup on the ground is important, though one should be careful of too much of a good thing. With respect to leaning, remember that the turbocharged/boosted/normalized/supercharged airplane thinks it's at sea level or lower. It operates at much higher pressures, and potentially temperatures, and the potential for detonation and other undesirable conditions is greater if mismanaged.

The higher you go, as IO540 noted, the more critical cooling and rates of cooling can become. While temperatures do decrease as one climbs, so does air density. One can be in cold enough temperatures to cause rapid changes at lower power settings, yet be in rare enough air that despite cooler temperatures one doesn't have a great deal of mass airflow to carry off the temperatures, and one can enter into issues with hotspotting cylinders, etc. Normal operation, not a problem. Just be careful.

When starting a descent, begin to make gradual power reductions. Don't simply pull the power back and push the nose over. When taking off, set barometric power at the end of the runway (30 inches at sea level, for example), and let it stabilize while holding the brakes. Do this before you ever begin pushing up the power to use the turbo.

On takeoff, feed in the first few inches of manifold pressure above barometric, before releasing brakes, and then feed the power in smoothly, noting any discrepancies in indication or feel. Watch everything...not just manifold pressure. Note your oil pressure, look for any fluctuations.

It's tempting in cruise when starting a climb, to push the power up and pitch up. Or visa versa. How you do it, of course, makes a difference. Push it up a couple of inches, smoothly, letting your speed build slightly, and then start a very small climb. Continue to smoothly and gradually increase power, as well as gradually increasing your climb. Level off, allowing speed to increase while you gradually decrease power back to your cruise setting again. Nice and easy, gently.

Adhere to the mixture schedule for your engine at your power setting. Running lean of peak works great when operating at 75% power or less...and it can be done at higher power settings, too. The difference is that you really can't hurt the engine by messing with the mixture at settings below 75%, where you certainly can at higher power settings. A normally aspirated engine is typically already below 75% power as a function of manifold pressure loss, by the time it reaches 3,000' density altitude or so. That's the reason that many manufacturers recommend leaning above these altitudes (three to four thousand feet...it's not because leaning should start there, but rather a liability issue and a method of pilot-proofing (idiot proofing) the leaning process. The higher the power setting, the greater the possibility of messing something up. Follow the manufacturer schedules; you'll find them, for example, in the cruise power charts. These will tell you the power settings to use, and the performance you can expect as a result.

Turbocharged airplanes can fly to higher altitudes while maintaining all or a percentage of their rated power, than normally aspirated airplanes. This is, in large part, why we use turbochargers. The formula for climb performance is excess thrust, and that's what turbochargers give us; increased climb and takeoff performance at higher density altitudes.

With this in mind, however, simply because the airplane is rated to higher altitudes and the engine can do it, doesn't mean we should. With oxygen equipment, the 421 can bounce up to 30,000...which in my opinion is really too high for a light twin like the 421. It's not really high enough to get above significant weather, but definitely high enough to conflict with much faster traffic and to put you into the middle of weather.

Even with slightly more advanced turboprop light twins like the King Air 90 or 200, much above 18,000 doesn't benefit the airplane, and the airplane struggles at altitude. You're not doing yourself or the airplane any favors. The 421 isn't exactly overpowered (it's a dog on one engine, like most light twins); there's really no need to go to the max ceiling of the airplane or engine. In fact, as an aside, the only light twin that I've found to be worth much of anything, is the turboprop powered Piaggio Avanti...which will cruise at 41,000. Everything else wallows and struggles much above 18,000'. The King Air's will struggle at 24,000', and any light piston twins end up at high enough angles of attack at higher altitudes that cooling is reduced and temperature management becomes a real issue.

Piston engines shouldn't be operated in a state where the propeller is driving the engine, as a rule. You'll read various treatises that try to say otherwise (avweb has produced a lot on the subject), but believe it at your own peril. This is true for most any piston propeller airplane engine, but especially so in geared engines like the GTSIO-520 and others. No pulling the power to idle in the pattern and doing gliding approaches; don't do that in training, either. It's a good way to start making metal, in the engine.

Getting into bigger and more complex airplanes involves more complex fuel management, too. Remember that fuel management continues to be one of the primary causes of aircraft mishaps. Understanding where your bypass return fuel is going, when using a particular tank, for example, may make a big difference in what fuel you can use or can't. The fuel that the engine doesn't use gets bypassed and returned to a tank...but not necessarily the tank from which you're drawing fuel at the time...this is important to know, especially if you're crossfeeding with an engine-out!


I suspect there is a strong correlation between turbo engines which make TBO, and "very traditional" by the book ROP operation which yields CHTs some 20-30F lower at a ~ 20% fuel cost.

Rich-of-peak and lean-of-peak both run at temperatures less than peak with respect to CHT and EGT, if done properly...but can differ substantially in their application and results when considering operating at higher power settings.

I operated the TSIO-360 at lean of peak nearly constantly, though I did it generally at lower power settings. Without exception, I always burned about 25% less fuel than anyone else in our operation. I was even called on the carpet once about it, with a demand to know why I was burning so much less fuel. The daily reports would show a consistent 80 to 95 gallon burn for everyone else on a given night, and I'd have burned 60 or a little more, for example. I flew a little slower (speed wasn't the object there), and ran lean of peak. I wasn't nearly so concerned about the cost of the operation as I was conserving fuel (we operated remotely and had to bring in fuel in 55 gallon cans from outside the country), and increasing my reserve. By saving fuel, I increased my loiter time (potential time aloft) to 12 hours...where others were lucky to get 8 to nine hours before dry. This had the potential to become really important.

At higher power settings on the same engine, I burned more fuel, and had a lower total endurance time.

The TSIO-360's we operated nearly always went to TBO without issue, whether I operated them at lean-of-peak, or others operated them at rich-of-peak.

OTOH a turbo engine, in the same aircraft, will be facing that issue all the way up to FL150 or whatever, and it gets worse as the air gets thinner.

This isn't an issue if the engine is operated properly, and one isn't hanging on the prop to get to altitude.

Guppy, remind me of the reason why the GTSIO-520-engined Titans were the only light twins in the fleet the boss insisted we idle at 1000 immediately after startup? Something about the flyweights?

You'd probably need to ask your boss about that. The engine can take a while to warm up if cold, and perhaps a thousand RPM offered a smoother warm-up; they do tend to chug and shake at idle settings.

Being thoroughly warmed before departure is proper, but that's the case with any piston twin or single.

Flyweights are part of the propeller governor, but the propeller isn't governing at idle; the propeller sits on the low pitch stops (unless feathered obviously). Perhaps your boss was referring to the crank counterbalances and the issue of de-tuning (which can happen with a lot of abuse and excess RPM operation, but not at idle).

The GTSIO engines on the 421 (and the engine/propeller combinations on the 400 series airplanes, generally), in concert with the propeller combination, do have harmonic issues and RPM limits, with a caution range that should be respected.

[Doodlebug]

'Perhaps your boss was referring to the crank counterbalances'

Yes, I do believe that's what it was. That operating practice, together with a host of others, definately worked as far as getting the maximum of hours out of the powerplants was concerned. In spite of about 10 different pilots operating the two aircraft we had few engine-issues. Lovely airplane, the 404. Pity it is around less and less, I understand the ones I knew are long replaced by 406's.

[IO540]

It's a good way to start making metal, in the engine.What is the physics behind that?

I can see that on a geared engine you could knacker the gearbox by letting the prop drive the whole thing, but on a non-geared engine if the prop is driving the crankshaft then none of the items ordinarily driven by the crankshaft can possibly detect whether the crank is driven by the prop or driven by the other cylinder(s).

[SNS3Guppy]

Geared engines are designed to be driving the propeller...they are not designed to have the propeller drive the engine. Start applying the load in the wrong direction and reverse-loading the gears, and plan on finding metal before long.