Q: I am purchasing a 1969 Piper PA-32-300 that has 1,814 hours. Should one always rebuild at 2,000 hours? Does this require new pistons and/or cylinders, or does re-honing and new rings fit that need? Any benefit of following with oil samples at changes to get more life from the engine? With your experience I would like your thoughts.
Chaillie Daniel
A: Your question “should one always rebuild at 2,000 hours” is a little difficult to answer. I could take the easy way out and tell you that, in accordance with Lycoming Service Instruction 1009AW, the recommended Time Between Overhaul Periods is 2,000 hours.
However, that’s only a recommendation and there are many factors that need to be considered before you can make a decision about your particular engine.
First of all, I’m concerned about the total time versus calendar time. If I did my math correctly, this engine has been operated approximately 38 hours, on average per year, during the 47 calendar years of its life.
That leads me to believe this engine has suffered several periods of extended inactivity, which is detrimental to the engine from the standpoint of internal corrosion taking place. Conducting a thorough borescope inspection of all cylinders would be highly recommended to look for signs of corrosion.
I would also recommend you do a very close review of the engine logbooks, paying particular attention to the oil and filter change frequency compared to the actual flying and calendar time.
Also do a close review of the logbooks for general maintenance that has been performed over the life of the engine, such as hot differential compression checks, etc. What is and has been the typical oil consumption between oil changes?
My biggest concern regarding this aircraft, as I mentioned earlier, is its age. I would take into consideration when making an offer on this aircraft that you will soon be required to take some type of action regarding the engine.
You have several choices, of course, including a field overhaul where the cylinders could possibly be reworked depending on their condition.
I suggest you obtain a copy of Lycoming Service Bulletin 240W, which covers “Mandatory Parts Replacement at Overhaul and During Repair or Maintenance.
You may also want to consider a factory “rebuilt” exchange engine, which would provide you with a “Zero Time” new logbook, but before you go that route, please check your options with a Lycoming distributor because there may be some restrictions due to the age of your engine.
There is no doubt money becomes a big issue in making any decision here.
Let me step back just a bit and respond to your question regarding oil analysis.
If oil analysis has been a routine at every oil change on this engine, then it can be a powerful tool when it comes to assessing the health of the engine. However, if you are asking if beginning oil analysis at this point in the engine’s life is a good idea, my answer would be maybe.
If the aircraft is put into service and oil analysis is going to be considered, it should be done over a period of several oil and filter changes. One oil analysis sample doesn’t tell us anything, really, because we have nothing to compare it with.
Just as a suggestion, I’d consider doing an oil and filter change now, then the next one in about 10 hours, followed by another in 10 hours. This should give us a pretty good baseline to make our comparisons.
If the first sample shows, for example, high iron content and possibly high aluminum content, I’d be thinking we have severe corrosion in the cylinders, which probably is a result of the extended periods of activity. It could also be an indication of camshaft and tappet wear caused by corrosion.
I don’t want to discourage you from purchasing this aircraft, but I want you to know what the risks are before you put any money on the line.
Honestly speaking, you should be prepared to spend some money on the engine in the very near future.
I wish you the best and urge you to proceed with caution.
While the above advice is sound, be sure to check your insurance requirements. Some require maintenance in accordance with the manufacturer’s recommendations = overhaul at TBO.
The idea of “don’t touch it if it is running fine no matter how many hours are on it” makes me nervous. You can’t tell if the valve springs are getting tired (and after 2000+ hours, they will be), you can’t tell if the head is about to fall off the valve (and I’m told high time engines will do this), and you have NO way to determine what parts are fatigued and really ought to be changed before they fail outright.
Helicopter rotor blades also have life limits, and there is a reason. Much as we would like, our engines will not last forever as long as we keep changing the oil. Personally, I have no problem at all spending some thousands of dollars on preventive maintenance. I’d rather utterly waste the money replacing seemingly good parts than have the engine stop at night, over water, in IFR, and when I’m temporarily unsure of my exact position.
We were never promised this was going to be cheap, so let me ask you, is your life worth the price of a top end job at 2,000 hours, even if the engine is running “just fine”? It is worth it to me simply in peace of mind. It is also worth it to my family, because they have NO idea what makes an airplane fly (money), and they have to trust me and trust the equipment literally with their lives.
Please excuse me while I go write some checks . . .
No, one should NEVER overhaul an engine at TBO if the pilot is operating under part 91. One should collect operational data, then inspect and repair as necessary based on science and data, not superstition. There are a few things that are life-threatening that are hard to inspect without disassembly, , like magnetos and some Lycoming fuel systems: You need convincing evidence that they have been rebuilt by a reputable agency within a reasonable time frame or hours, especially the two-in-one Bendix -D mag. Otherwise: If it ain’t broke, don’t let’em fix it! Too often, maintenance leads to maintenance induced failures -MIFs.
Vacuum pumps are an odd case where infant mortality often exceeds old age failures. If you fly IFR than redundancy is the only logical option, but that isn'[t what the writer asked.
The article implies that the engine is a virgin, never touched since it left the factory since 1969, or has it had repairs, inspections and appliance replacements? Is it carbed or FI? Turbo? -D mags? Why the concern about honing the cylinders, is it burning or blowing oil? Too many questions, not enough info. So I’ll blather on and hope I hit on what you are really asking.
From a buyer’s point of view, if daylight has not shone inside the engine since 1969 the engine ran out Lycoming’s 12 year calendar and only has core value. The prop as well. Corrosion: Does it live in Seattle or Tucson? Corrosion for the whole aerospace vehicle is a concern here, not just the noisy end. Negotiate accordingly with an overhaul priced into the purchase. If you get more you win. Fly it like you stole it. You did.
On the other hand, Engine cylinders, starters, alternators, propellers are all appliances that can be budgeted for and replaced ‘on condition’. Even an engine is an appliance, so your real concern should be things you can’t repair or replace cheaply, like wing spar corrosion, spar cap cracks, landing gear trunnions – stuff that requires tens of thousands of dollars to fix that come as a surprise to new owners.
And AD compliance: The FAA had an AD on certain Hartzell props that require either a 50 hr eddy current inspection or new prop hub. Plan on dropping $5k if that hasn’t been done, and don’t be surprised when that explodes to $15,000 when they condemn the blades and prop governor. The FAA also had a 1999 AD on Lycoming oil pumps. The labor to replace it can be considerable – plan $2000. ADs against the airframe are equally onerous. If the seller can’t prove they have been complied with, you get to pay to do it again.
If the engine has been disassembled, inspected and and time continued, what’s the concern? Your real concern should be the magnetos, vacuum and fuel system. They can ruin your day. But if the plane has been flying, respect the killers and go fly.
In general, inspect those things you can, repair or replace only what you have to and motor on. Engines, props and avionics, interiors and paint are all replaceable or repairable and one can budget for it. Corrosion, spar cap cracks and other tidbits can cost more than a plane is worth to repair. Those are the buyer’s first order of business.
Knowing where to look for those things best comes from a type club. Join the one for the plane you are interested in, get their pre-buy checklist and maybe they have a person who is expert enough to travel and do the inspection for a fee. The Cardinal Flyers have such a checklist and person who knows where the bodies are hidden on Cardinals. He has saved potential buyers hundreds of thousands of dollars and provided points for the buyer and seller to negotiate over.
I know I’m repeating myself, but a few thing need to be made clear,so I’ll steal Mike Busch’s genius: http://www.avweb.com/news/savvyaviator/savvy_aviator_63_recommended_or_required-199001-1.html
TBO is an obsolete concept, and if the alleged new owner is operating under part 91,
“nothing in the manufacturer’s recommendations are mandatory unless specified:
1.In the Type Certificate Data Sheet (TCDS) for the aircraft, engine or propeller;
2. In an FAA-approved “Airworthiness Limitations” section of a manufacturer’s maintenance manual or Instructions for Continuing Airworthiness; or
3. In an Airworthiness Directive.”
‘Overhaul’ is a dangerous term. Nobody should use it, instead ask for an inspection and reseal or inspect and repair as necessary – IRAN. When you ask for an overhaul you force the mechanic to follow the manufacturer’s overhaul manual that generally forbids reusing serviceable parts. So good parts get scrapped. For what? So you can enjoy infant mortality?
And ‘zero time’ is a marketing gimmick. Only the OEM can issue a zero time logbook with a rebuilt engine – but it can be built from 100% used parts that meet new limits.
The writer didn’t specify the engine in question, so we don’t know if it has the two-in-one Bendix D-mag that has been orphaned. Converting to two separate mags is major surgery, tho I hear that the aftermarket is filling in with repair parts for the -D.
Lycoming camshafts are a weakness: There are many theories, but the one I like is that a valve sticks, the valve train unloads and the cam hammers against the cam follower, cracking the hardened surface on both. Then the valve unsticks and you fly along merrily. Corrosion sets into the cracks, prying off flakes of metal. Years later either the follower or cam spall: The big chunks stay in the oil pump suction screen, the small slivers make it to the spin-on oil filter if so equipped. Only cutting and inspecting the filter with a magnet discloses them, and since the engine is running fine, nobody makes a fuss. I’ve had that happen to 4 cyl lycs on oil analysis – no hint there were parts banging around in the oil sump, and the engines all ran smooth.
Ironically, neither OEMs or FAA care a wit about flying with worn cams and followers. Lyc has a 400 hr valve wobble test to head off stuck valves. That is a good time to measure cam lift, and it’s easy. But usually neither are done. I’ve spoken to engine shops who report bad cams on 200 hr ‘zero time’ engines that come in for prop-strike inspection, so it happens to new engines. Worn cams aren’t life threatening, just low power. The pilot never knows if a constant speed prop is fitted – it compensates for lower power output. Is it worth pulling the engine and splitting the case to replace a worn cam? Apparently not. (This is one area where Continental did it right: They rarely have stuck valves and worn cams. Some say that they have 4000 hour bottom ends – nothing goes bad, corrosion is not common, and very little wears).
Compression tests. You can learn a lot simply by turning a warm engine by hand and comparing cylinder resistance. But, FAR par 43 says it has to be done. If a shop will follow the Continental Service bulletin SB03-3 on Lycs then you have a better way of learning useful things about the ‘hot section’ of the engine. Lycoming’s guidance is not as enlightened.
Most pilots think it is about cylinder rings and corrosion. It is, but it has little impact on power and more on oil burning and plug fouling,which is pretty obvious to everyone. But it is also about those pesky $400 sodium filled hollow stem exhaust valves. If the valve guide is too tight it sticks and causes excitement. If the guide is too loose the valve wobbles, burns and begins to form a hot spot, readily visible with a borescope. If the valve head breaks off in flight it gets even more exciting. If the shop doesn’t have a bore scope, take what they say with a grain of salt. http://www.avweb.com/news/savvyaviator/188758-1.html I bought my own inspection camera on Amazon for a fraction of the price of a Blackhawk borescope, and it records on a smartphone/tablet or pc for sharing and comparing.
There is a lot to learn about engines and engine management out there from GAMI.com, Savvyowner, EAA and the advanced pilot seminars – APS – on the web for free and for a fee. They work hard to dispell urban legends and old wives tales in GA using an engine test cell. They also re-discovered how airlines operated those huge radial engines for millions of hours. GAMI,APS, John Deakin and Mike Busch et al distilled it down to our fleet, going thousands of hours past TBO safely and confidently – using modern instrumentation and meaningful inspections.
Legacy aircraft had crap for instrumentation. Maybe one cylinder head temp probe as a proxy for six, no EGT gauge, oil temp and pressure gauges with color coding, not digits, and gas gauges that were simply appalling. That and factory redline CHTs in the 500F range ruined a lot of good cylinders – and they were operated per the manual – such as it was. The use of the red knob was met with a lot of obfuscation and hand wringing with the thought that pilots were just too stupid to understand. With crude instruments from Piper, Beech and Cessna, they were right.
Today, JPI and others have digital engine management systems that alert the pilot when the engine exceeds a parameter and gives time to react – pre-ignition is a great example where a damaged spark plug sets a cylinder on fire within seconds of takeoff. If missed it can melt a hole in a piston in under a minute. If the pilot reacts correctly, he can land where he came from, tell the mechanic which spark plug he dropped and the system records the even to share with others.
So rather than euthanizing an engine because it is old, why not spend that money on an engine analyzer and see for yourself how well it is running – send the data to Savvy for analysis, and take action based on data and science, not ignorance and superstition. But negotiate a price that includes the cost of an overhaul. Then fly it like you stole it. If it goes another 500 hours, you did!
Old engines with intermittent use tend to be the ones with corrosion issues, so often times have spauled cams and other issues. Usually this is reflected in the logs by a top overhaul or individual cylinder replacements. Yes, Flight schools typically run their engines well past TBO. But those engines fly daily. Sitting is the enemy of longevity. I don’t advise overhaul at TBO. But I would be very leery of an engine with the time spread out across so many years.
Five years ago I bought an engine that had logs that read almost exactly the same as the engine in this article. It came from a mid 70s model aircraft with 1800 hrs since new. On paper and in the logs the engine looked really good. It had a couple of hundred hours on a new top end with good compressions and came from a dry area that’s not prone to corrosion. Since it was going onto a plane I was building and I like to get intimate with my engines before I fly them, I chose to tear it down for inspection anyway. What I found was, 1 cylinder that had been badly overheated, 4 cracked cylinder heads, a cracked crankshaft, a case that was out of spec and cracked, and 2 spauled lobes on the cam. Realisticly, I could have not torn this engine down and put it on my plane and flown it for a while. The cylinder heads weren’t cracked so deep that they were whistling or leaking yet. The cam would have caused it to be down a bit on power, but not exceptionally so. The cracked case would have just caused some oil seepage, and the cracked crank probably would have held together. So I would have likely been fat, dumb and happy flying this engine for a while. But I’m glad I chose to tear it down for a look rather than blindly follow the logs and hope for the best.
No, don’t overhaul the engine for tach time. But the sitting time on that engine is death. Financially, I’d plan for an overhaul. Then sit on the money if the engine happens to continue on without showing problems. Chances are that it won’t.
If the engine is showing good compression readings and normal oil burn there is no reason to think of an overhaul. If those two items are in check the engine is doing what its suppose to do, and everything is working accordingly. Why do you think some and most of the flying schools run there engines well over TBO. I have visited flying schools that run there engines at 3000, and 4000 thousand hours before overhaul is considered, and if you talk of abuse on an engine It would certainly be done by novice’s don’t you think, that is student pilots, for some reason they just don’t treat an engine like it should be, that is most of the time. Nothing personal just saying that students don’t know and sometimes do the unjust to an engine. An engines worst enemy is a, ” bad pilot ” I have seen near new engines at the shop that are almost scrap because of pilots that do not care and some don’t know a damn thing about aircraft engines and some just don’t care period. The most abused engines are the turbo charged, I have seen 200 hour new engines come apart because the pilot was in a hurry to get to altitude and literally melted the tops of the pistons. So my friend if your somewhat concerned about TBO on an 1800 hour engine, rest assure it will not come unglued on its own, It takes a lot of trying on your part, just keep an eye on compression and oil burn you should be o.k.
If the engine is showing good compression readings and normal oil burn there is no reason to think of an overhaul. If those two items are in check the engine is doing what its suppose to do, and everything is working accordingly. Why do you think some and most of the flying schools run there engines well over TBO. I have visited flying schools that run there engines at 3000, and 4000 thousand hours before overhaul is considered, and if you talk of abuse on an engine It would certainly be done by novice’s don’t you think, that is student pilots, for some reason they just don’t treat an engine like it should be, that is most of the time. Nothing personal just saying that students don’t know and sometimes do the unjust to an engine. An engines worst enemy is a, ” bad pilot ” I have seen near new engines at the shop that are almost scrap because of pilots that do not care and some don’t know a damn thing about aircraft engines and some just don’t care period. The most abused engines ate the turbo charged, I have seen 200 hour new engines come apart because the pilot was in a hurry to get to altitude and literally melted the tops of the pistons. So my friend if your somewhat concerned about TBO on an 1800 hour engine, rest assure it will not come unglued on its own, It takes a lot of trying on your part, just keep an eye on compression and oil burn you should be o.k.
Inspect closely yes, but if it aint broke DON’T fix it.
The aviation industry suffers from a great deal of misguidance when it comes to maintenance and things like TBO and time limited components. I think there is enough clinical evidence out there to show that TBO is a meaningless value and for Part 91 is a recommendation only (and a poor recommendation at that).
Rather than go into a whole diatribe I would steer you towards Mike Busch’s work, specifically his advice about RCM – Reliability Centered Maintenance. (http://www.avweb.com/news/savvyaviator/savvy_aviator_47_reliability-centered_maintenance_part_1_195709-1.html)
In a nutshell, if an engine is running well and various inspections like Borescope inspection and measuring valve life to determine the condition of the camshaft, as well as oil samples and other various diagnostic tools is a far better means of determining when it’s time for an overhaul.
It is very true that an engine that has seen very little activity over a 47 year period may very well suffer from internal corrosion leading to poor power output. But the key takeaway from this statement is “may” suffer, not “will” suffer. A thorough inspection along with various diagnostics will help determine the true condition. It is not unheard of for an engine such as the one described above to be torn down and show little to no signs of wear.
So forget TBO. It is not regulatory and lately is only meaningful for resale value (due to the entire market being misguided by its significance) .
Excellent advice!
It is also not unheard of for an engine such as the one described above to be a complete pile of corroded nearly useless parts. As you describe, a very close inspection by a competent mechanic will tell most of the tale.
Personally, I would not like to find the definitive answer to your questions at 500 feet on a full-power climb-out. For your peace of mind, it’s possible you’re not finished shopping.