Going TBO and Beyond
Ever notice how some pilots consistently make TBO without so much as a penny spent on engine repair, while others can’t even get half way before they’re replacing cylinders, camshafts, or worse. There’s nothing mysterious or magic about those pilots who make TBO overhaul after overhaul; they just know a few simple truths about engine care and management, and they practice them religiously.
Over the years, many different sources have published information on how to make aircraft engines reach TBO. A few of the more notables are the Lycoming Flyer Key Reprint articles, “101 Ways to Extend the Life of Your Engine” by Kas Thomas and the Cessna Pilots Association’s Tech Note # 7, “TBO and Beyond”.
While there’ve been countless books and articles written on the subject, in essence they all say the same thing. What follows is a compilation of techniques, procedures and “magic” we’ve seen over the years, from the some of the very best pilots and engineers in the business. Follow this list and you’ll radically improve your chances of making TBO and possibly going well beyond.
1.) Fly and Fly Often
At a minimum, fly your airplane once a week, every week of the year that you possibly can. This simple act, combined with item number 2, are the two most important things you can do to extend the life of your engine.
When engines sit idle for more than a week, much of the oil film that coats internal parts drains back into the sump. The thin film that remains cannot provide enough of a barrier to stop rust formation on the ferrous parts of your engine. On highly polished surfaces like cam lobes, followers and lifter bodies, the oil film thins out even faster. Once rust starts, pitting soon follows and polished parts are the least able to withstand pitting. In short order, the microscopic pitting causes spalling and that always results in expensive repairs.
By flying at least once a week, you keep critical parts coated with a thick, heavy oil film that can to repel moisture and the rust that comes with it.
2.) Change Your Oil Often
Change oil at a minimum 50 hours if your engine has a filter, 25 hours if it doesn’t. But, hours are not the only guide to follow. Every engine manufacturer publishes Service Bulletins which require oil changes be based not only on hours, but on calendar time as well. Oil should never sit in your engine for more than 4 months (120 days), even if it’s clean looking and has very few hours on it.
Oil that sits without regular engine runs never gets a chance to boil off the moisture it absorbs during our humid winters and springs. This moisture combines with combustion by-products form very corrosive acids. High time engines or engines with low compression are especially prone to the accumulation of these acids because of blow-by.
Over time, these acids eat away at critical surfaces, especially cam lobes and lifter bodies causing pitting and spalling. Once those surfaces are pitted they lose their ability to withstand the intense compressive loads placed on them when the engine is running and they fail long before you make TBO.
We like to recommend 35 hour oil changes for filtered engines and 25 for non-filtered engines. And if you fly less than 100 hours a year, make sure that you do at least 3 oil changes in that year.
3.) Use ASL Camguard With Every Oil Change
While we generally advise against the use of oil additives, we believe there is enough evidence to prove Camguard actually works in protecting against internal rust. We've also seen statistical evidence that it can actually improve compression where sticky rings are the culprit.
ASL Camguard’s website provides a lot of useful technical information. It’s well worth checking out.
4.) Use an Oil Filter
If you don’t have an oil filter installed on your engine, and there's either an STC or manufacturer's unit available, have one installed. There are several STC'd aftermarket adapters available that are very reasonably priced. They take the same spin on filters as the OEM brands and provide far better engine protection than an oil screen alone.
5.) Inpsect Your Filter at Every Oil Change
Cut open and inspect your oil filter if you have one, or inspect your oil screen, at every oil change. This simple act just might save your life one day. We’ve encountered more than one engine that we’ve grounded after finding chunks of metal in the filter or screen.
And, if the inspection reveals a clean filter you’ll fly with the added peace of mind of knowing your engine is healthy.
top6.) Replace Your Air Filter Often
Dirty filters allow sand, grit and other abrasives to pass directly into your cylinders where they scrape and grind pistons and cylinder walls, shortening the life of your engine. Also check that your alternate air door is sealing fully. If it doesn’t seal completely, or gradually creeps open, as many do, you’re sucking dirty air.
One indication that you may have intake side air leaks is high silicone levels in your oil analysis.
We think manufacturer’s recommendations are too conservative when it comes to air filter change intervals. Change that filter often and your engine will reward you with less internal wear and much longer life.
top7.) Start Your Engine Gently
Be nice to your engine. When you first startup, limit RPMS to around 700 until you see the oil pressure needle start to climb. Then, slowly raise the RPM to between 1000 and 1200. For Lycoming engines, idle at 1100 to 1200 RPM to ensure adequate cam lubrication. Continentals can idle for warm up between 1000 and 1100 RPM.
Make sure your engine is sufficiently warmed before you do your run-up. Ideally, the oil temp. gauge should be at least at the bottom of the green zone before you start your run-up.
If your oil pressure does not show full normal idle pressure within 30 seconds, shut down. Do not rev the engine to get oil pressure to rise. Wait 30 seconds and then restart your engine. Chances are on the restart, your oil pressure will show normal indications within a few seconds. If the problem persists on every first start of the day, have us check it out. Your oil pump may be on its last legs and that could lead to engine failure.
top8.) Do Not Cold Start Without Pre-Heat
We consider any start where the ambient temperature is 0° C or below to be a cold start. Starting a cold soaked aircraft engine causes serious internal stresses as the aluminum pistons heat and expand at almost twice the rate of the steel cylinders liners. This causes a lot of piston wear and can eventually lead to compression problems.
Here’s what Lycoming has to say about cold starts in Service Instruction 1505
There are many different pre-heaters on the market, most of them quite expensive. We’ve found that in our relatively mild, west coast climate, a couple of 60 watt or a single 100 watt incandescent shop light (trouble lights) placed in the lower part of your cowl, with a thick quilt or blanket over top of the cowl are adequate.
For a small aircraft like a Cessna 150, two 60 watt light bulbs in the cowling can easily maintain engine temperature 10 - 15° C above ambient temparature.
Note: do not place lights near fuel sources or use them at all if you have fuel leaks.
If you’re unsure of how to place the lights, let us show you.
top9.) Let Your Engine Cool Before Shutdown
Never, ever pull the mixture on a hot engine. Killing a hot engine causes intense metal stress and warping as internal hot spots in the cylinders remain expanded while exposed cooler areas rapidly cool and contract. The metal stresses at this time can be extreme, especially inside turbo chargers.
Your engine should idle between 1000 to 1100 RPMs for at least 3 minutes to cool down evenly. The easiest way to do that is to taxi in slowly. A slower taxi will keep your RPMs low enough to allow engine cooling on your way back to your hanger or tie down. It may take you a minute or two longer but when you get there, you can pull the mixture knowing your engine has dissipated enough heat so parts can contract at an even rate as they cool.
Besides, you’ll be taxiing like a pro; ever notice the really good pilots never taxi very fast.
top10.) Don't Over Prime When Starting
Don’t over prime when starting. Lycoming engines are especially prone to problems when over primed. We think most pilots prime too much, especially in the summer. On warm days, one or two squirts is often all you need…try it. Over priming can wash the lubricating film from cylinder walls causing metal to scrape on metal at startup. The resulting wear on cylinders and piston rings eventually leads to low compression, which can only be cured by an expensive cylinder replacement or overhaul.
11.) Face Directly Into the Wind During Run-up
On hot summer days, your engine is really feeling the heat during run-up and airflow over the cylinders is almost never adequate. Even a small increase in airflow, like 5 knots of wind, makes a big difference to the cooling of your cylinders during run-up. When ever possible, face directly into the wind.
top12.) Keep Your Engine Run-up Time to a Minimum
We’re not very far from the run-up bay of Runway 01 and we constantly hear pilots running up engines far longer than necessary. On hot days, cylinder temperatures are going through the roof during extended run-ups, causing wear equivalent to many, many hours of air time. A big cause of stuck valves is overheated cylinders, often caused by extended run-ups.
Whenever possible, keep run-ups to a minumum. If you know exactly what you’re looking for, the whole process should easily be over in less than 30 seconds.
If you want some advice on run-ups and what to look for when doing them, come see us and we'd be happy to sit through a run-up with you.
top13.) Avoid Rapid Throttle Movements
This is epsecially important at takeoff. Suddenly fire-walling the throttle can cause your engine to falter, or even quite entirely. But, far worse is what’s it's doing inside your engine.
That sudden burst of combustion heat causes engine parts to expand at radically different rates. The resulting metal stresses over time cause leaking gaskets, premature cylinder wear, cracked piston domes, broken pistons and cylinder head cracks...we see them all the time.
The best engine control technique we know of for takeoff is as follows:
- Line up with the runway centerline then hold the brakes
- Slowly bring the throttle up to between 1600 and 1800 RPM
- Quickly scan the key engine gauges for normal indications; 2 to 3 seconds is about right
- If all looks good, release the breaks and s-l-o-w-l-y advance the throttle the rest of the way
Your engine will love you for it. Those few short seconds you give it for temperatures to stabilize will be rewarded with longer engine life and much lower maintenance costs.
And there’s an added bonus. Those of us on the ground will nod our heads in approval at the sound a highly experienced pilot managing his or her engine with skill and finesse, rather than wince at the sound of an engine being abused abuse by some ham fisted ignoramus.
Strong words, but we feel strongly about the subject.
top14.) Avoid Unnecessary Thermal Cycles
It’s not hours that wear out your engine, it’s thermal cycles. If you ran your engine 24x7 on a test stand, it could quite easily go 6000 or 7000 hours. Metal stress induced by thermal cycles is what cause engines to wear prematurely.
The act of starting, especially when cold, takes more life out of your engine than many hours of running, so avoid starts whenever you can. If you need to move your airplane only a few feet, use the towbar rather than taxi it. And, since starting a warm engine causes significantly less wear than starting a cold one, consider re-fueling after your flight, rather than before.
Full fuel tanks are also less likely to take on water from condensation between flights.
top15.) Keep Your Engine Baffles in Tip-Top Shape
To check your baffles, shine a strong light in the back side (behind the baffles) of the engine and look through the front for light leaks. Wherever you see light, you’re seeing an air leak. Air leaks mean your cylinders aren’t getting all the cooling they should, nor are they getting even cooling. We know from long experience that cylinders that run hot almost never make TBO. Ask us to check your baffles for you; it only takes a few minutes.
top16.) Keep Your CHTs Below 400° F
Cool running cylinders are less prone to valve wear, valve sticking, detonation and all kinds of other life sucking engine problems. Consider installing a modern, all cylinder, engine monitor to really keep track of what your engine is doing. Once you do, you'll wonder how you ever flew without one.
top17.) Lean Aggressively But Prudently In Flight
During cruise, even at lower altitudes, don't be afraid to lean. Many flying schools teach students to avoid the red know like the plague, especially below 5000 feet. They do this because student pilots are apt to mis-manage the mixture control and cause redline CHTs or worse detonation. For an experienced pilot, and we stress the word experienced, we think leaning in cruise is prudent anytime you're above 3000 feet ASL.
Lycoming offers sound advice on leaning in Service Instruction 1094D
top18.) Use Conservative Power Settings
Go easy on your engine and it will go easy on your bank account.
You’ll also be surprised at how much lower your fuel burn is. Not only will you save on your hourly fuel cost, you'll also save on your hourly overhead cost by getting more hours between overhauls
top19.) Avoid Sudden Throttle Reductions in Descents
Too rapid cooling can be a significant factor in valve sticking. Like all aspects of flying, your throttle management should be smooth. Gradually reduce power and plan your descents so you never have to descend with a closed or almost closed throttle.
In the end, you can boil all these points, and about a hundred others that we didn't include, down to one simple rule of engine management.
Be nice to your engine and your engine will be nice to you.
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