The Dark Side of Maintenance

The Dark SideHave you ever put your airplane in the shop—perhaps for an annual inspection, a squawk, or a routine oil change—only to find when you fly it for the first time after maintenance that something that was working fine no longer does?  Every aircraft owner has had this happen. I sure have.

Maintenance has a dark side that isn’t usually discussed in polite company: It sometimes breaks aircraft instead of fixing them.

When something in an aircraft fails because of something a mechanic did—or failed to do—we refer to it as a “maintenance-induced failure”…or “MIF” for short. Such MIFs occur a lot more often than anyone cares to admit.

Why do high-time engines fail?

I started thinking seriously about MIFs in 2007 while corresponding with Nathan Ulrich Ph.D. about his ground-breaking research into the causes of catastrophic piston aircraft engine failures (based on five years’ worth of NTSB accident data) that I discussed in an earlier post. Dr. Ulrich’s analysis showed conclusively that by far the highest risk of catastrophic engine failure occurs when the engine is young—during the first two years and 200 hours after it is built, rebuilt or overhauled—due to “infant-mortality failures.”

But the NTSB data was of little statistical value in analyzing the failure risk of high-time engines beyond TBO, simply because so few engines are operated past TBO; most are arbitrarily euthanized at TBO. We don’t have good data on how many engines are flying past TBO, but it’s a relatively small number. So it’s s no surprise that the NTSB database contains very few accidents attributed to failures of over-TBO engines. Because there are so few, Ulrich and I decided to study all such NTSB reports for 2001 through 2005 to see if we could detect some pattern of what made these high-time engines fail. Sure enough, we did detect a pattern.

About half the reported failures of past-TBO engines stated that the reason for the engine failure could not be determined by investigators. Of the half where the cause could be determined, we found that about 80% were MIFs. In other words, those engines failed not because they were past TBO, but because mechanics worked on the engines and screwed something up!

Sheared Camshaft Bevel GearCase in point: I received a call from an aircraft owner whose Bonanza was undergoing annual inspection. The shop convinced the owner to have his propeller and prop governor sent out for 6-year overhauls. (Had the owner asked my advice, I’d have urged him not to do this, but that’s another story for another blog post.)

The overhauled prop and governor came back from the prop shop and were reinstalled. The mechanic had trouble getting the prop to cycle properly, and he wound up removing and reinstalling the governor three times. During the third engine runup, the the prop still wouldn’t cycle properly. The mechanic decided to take the airplane up on a test flight anyway (!) which resulted in an engine overspeed. The mechanic then removed the prop governor yet again and discovered that the governor drive wasn’t turning when the crankshaft was rotated.

I told the owner that I’d seen this before, and the cause was always the same: improper installation of the prop governor. If the splined drive and gears aren’t meshed properly before the governor is torqued, the camshaft gear is damaged, and the only fix is a teardown. (A couple of engine shops and a Continental tech rep all told the owner the same thing.)

This could turn out to be a $20,000 MIF. Ouch!

How often do MIFs happen?

They happen a lot. Hardly a day goes by that I don’t receive an email or a phone call from an exasperated owner complaining about some aircraft problem that is obviously a MIF.

A Cessna 182 owner emailed me that several months earlier, he’d put the plane in the shop for an oil change and installation of an STC’d exhaust fairing. A couple of months later, he decided to have a digital engine monitor installed. The new engine monitor revealed that the right bank of cylinders (#1, #3 and #5) all had very high CHTs well above 400°F. This had not shown up on the factory CHT gauge because its probe was installed on cylinder #2. (Every piston aircraft should have an engine monitor IMHO.) At the next annual inspection at a different shop, the IA discovered found some induction airbox seals missing, apparently left off when the exhaust fairing was installed. The seals were installed and CHTs returned to normal.

Sadly, the problem wasn’t caught early enough to prevent serious heat-related damage to the right-bank cylinders. All three jugs had compressions down in the 30s with leakage past the rings, and visible damage to the cylinder bores was visible under the borescope. The owner was faced with replacing three cylinders, around $6,000.

Sandel SN3308The next day, I heard from the owner of an older Cirrus SR22 complaining about intermittent heading errors on his Sandel SN3308 electronic HSI. These problems started occurring intermittently about three years earlier when the shop pull the instrument for a scheduled 200-hour lamp replacement.


I’ve seen this in my own Sandel-equipped Cessna 310, and it’s invariably due to inadequate engagement between the connectors on the back of the instrument and the mating connectors in the mounting tray. You must slide the instrument into the tray just as far as possible before tightening the clamp; otherwise, you’ve set the stage for flaky electrical problems. This poor Cirrus owner had been suffering the consequences for three years. It took five minutes to re-rack the instrument and cure the problem.

Pitot-Static PlumbingNot long after that, I got a panicked phone call from one of my managed-maintenance clients who’d departed into actual IMC in his Cessna 340 with his family on board on the first flight after some minor avionics work. (Not smart IMHO.) As he entered the clag and climbed through 3,000 feet, all three of his static instruments—airspeed, altimeter, VSI—quit cold. Switching to alternate static didn’t cure the problem. The pilot kept his cool, confessed his predicament to ATC, successfully shot an ILS back to his home airport, then called me.

The moment I heard the symptoms, I knew exactly what happened because I’d seen it before. “Take the airplane back to the avionics shop,” I told the owner,  “and ask the tech to reconnect the static line that he disconnected.” A disconnected static line in a pressurized aircraft causes the static instruments to be referenced to cabin pressure. The moment the cabin pressurizes, those instruments stop working. MIF!

I know of at least three other similar incidents in pressurized singles and twins, all caused by failure of a mechanic to reconnect a disconnected static line. One resulted in a fatal accident, the others in underwear changes. The FARs require a static system leak test any time the static system is opened up, but clearly some technicians are not taking this seriously.

Causes of Accidents

Why do MIFs happen?

Numerous studies indicate that three-quarters of accidents are the fault of the pilot. The remaining one-quarter are machine-caused, and those are just about evenly divided between ones caused by aircraft design flaws  and ones caused by MIFs. That suggests one-eighth of accidents are maintenance-induced, a significant number.

The lion’s share of MIFs are errors of omission. These include fasteners left uninstalled or untightened, inspection panels left loose, fuel and oil caps left off, things left disconnected (e.g., static lines), and other reassembly tasks left undone.

Distractions play a big part in many of these omissions. A mechanic installs some fasteners finger-tight, then gets a phone call or goes on lunch break and forgets to finish the job by torqueing the fasteners. I have seen some of the best, most experienced mechanics I know fall victim to such seemingly rookie mistakes, and I know of several fatal accidents caused by such omissions.

Maintenance is invasive!

Whenever a mechanic takes something apart and puts it back together, there’s a risk that something won’t go back together quite right. Some procedures are more invasive than others, and invasive maintenance is especially risky.

Invasiveness is something we think about a lot in medicine. The standard treatment for gallstones used to be cholecystectomy (gall bladder removal), major abdominal surgery requiring a 5- to 8-inch incision. Recovery involved a week of hospitalization and several weeks of recovery at home. The risks were significant: My dad very nearly died as the result of complications following this procedure.

Nowadays there’s a far less invasive procedure—laproscopic cholecystectomy—that involves three tiny incisions and performed using a videoscope inserted through one incision and various microsurgery instruments inserted through the others. It is far less invasive than the open procedure. Recovery usually involves only one night in the hospital and a few days at home. The risk of complications is greatly reduced.

Similarly, some aircraft maintenance procedures are far more invasive than others. The more invasive the maintenance, the greater the risk of a MIF. When considering any maintenance task, we should always think carefully about how invasive it is, whether the benefit of performing the procedure is really worth the risk, and whether less invasive alternatives are available.

Ryan Stark of Blackstone LabsFor example, I was contacted by an aircraft owner who said that he’d recently received an oil analysis report showing an alarming increase in iron. The oil filter on his Continental IO-520 showed no visible metal. The lab report suggested flying another 25 hours and then submitting another oil sample for analysis.

The owner showed the oil analysis report to his A&P, who expressed grave concern that the elevated iron might indicate that one or more cam lobes were coming apart. The mechanic suggested pulling one or two cylinders and inspecting the camshaft.

Yikes! What was this mechanic thinking? No airplane has ever fallen out of the sky because of a cam or lifter problem. Many have done so following cylinder removal, the second most invasive thing you can do to an engine. (Only teardown is more invasive.)

The owner wisely decided to seek a second opinion before authorizing this exploratory surgery. I told him the elevated iron was almost certainly NOT due to cam lobe spalling. A disintegrating cam lobe throws off fairly large steel particles or whiskers that are usually visible during oil filter inspection. The fact that the oil filter was clean suggested that the elevated iron was coming from microscopic metal particles less than 25 microns in diameter, too small to be detectable in a filter inspection, but easily detectable via oil analysis. Such tiny particles were probably coming either from light rust on the cylinder walls or from some very slow wear process.

I suggested the owner have a borescope inspection of his cylinders to see whether the bores showed evidence of rust. I also advised that no invasive procedure (like cylinder removal) should ever be undertaken solely on the basis of a single oil analysis report. The oil lab was spot-on in recommending that the aircraft be flown another 25 hours. The A&P wasn’t thinking clearly.

Even if a cam inspection was warranted, there’s a far less invasive method. Instead of a 10-hour cylinder removal, the mechanic could pull the intake and exhaust lifters, and then determine the condition of the cam by inspecting it with a borescope through the lifter boss and, if warranted, probing the cam lobe with a sharp pick. Not only would this procedure require just 15% as much labor, but the risk of a MIF would be nil.

Sometimes, less is more

Many owners believe—and many mechanics preach—that preventive maintenance is inherently a good thing, and the more of it you do the better. I consider this wrongheaded. Mechanics often do far more preventive maintenance than necessary and often do it using unnecessarily invasive procedures, thereby increasing the likelihood that their efforts will actually cause failures rather than preventing them.
Mac Smith RCM Seminar DVDAnother of my earlier posts discussed Reliability-Centered Maintenance (RCM) developed at United Airlines in the late 1960s, and universally adopted by the airlines and the military during the 1970s. One of the major findings of RCM researchers was that preventive maintenance often does more harm than good, and that safety and reliability can often be improved dramatically by reducing the amount of PM and using minimally invasive techniques.

Unfortunately, this thinking doesn’t seem to have trickled down to piston GA, and is considered heresy by many GA mechanics because it contradicts everything they were taught in A&P school. The long-term solution is for GA mechanics to be trained in RCM principles, but that’s not likely to happen any time soon. In the short term, aircraft owners must think carefully before authorizing an A&P to perform invasive maintenance on their aircraft. When in doubt, get a second opinion.

The last line of defense

The most likely time for a mechanical failure to occur is the first flight after maintenance. Since the risk of such MIFs is substantial, it’s imperative that owners conduct a post-maintenance test flight—in VMC , without passengers, preferably close to the airport—before launching into the clag or putting passengers at risk. I think even the most innocuous maintenance task—even a routine oil change—deserves such a post-maintenance test flight. I do this any time I swing a wrench on my airplane.

You should, too.

Mike Busch is arguably the best-known A&P/IA in general aviation, honored by the FAA in 2008 as National Aviation Maintenance Technician of the Year. Mike is a 8,000-hour pilot and CFI, an aircraft owner for 50 years, a prolific aviation author, co-founder of AVweb, and presently heads a team of world-class GA maintenance experts at Savvy Aviation. Mike writes a monthly Savvy Maintenance column in AOPA PILOT magazine, and his book Manifesto: A Revolutionary Approach to General Aviation Maintenance is available from in paperback and Kindle versions (112 pages). His second book titled Mike Busch on Engines was released on May 15, 2018, and is available from in paperback and Kindle versions. (508 pages).


  1. Dan H Kelly Jr

    June 10, 2014 at 6:34 pm

    Umm. No. As a retired military maintenance tech (1976-1997) we were definitely NOT taught RCM. Scheduled P.M. is scheduled P.M. Phased and Iso inspection and maintenance occur on schedule.

    • Dan, the military usually refers to it as CBM (condition-based maintenance). I know that the military helicopter folks have been very big on CBM beginning in the late ’80s and early ’90s. I’m less sure about fixed-wing, but I’m pretty sure it’s been widely adopted there, too. Perhaps after you retired. If you Google “condition-based maintenance” you’ll find a bunch of PowerPoint presentations on the subject that are clearly focused on military aviation.

      The transition wasn’t sudden. It was mostly a matter of gradually reducing fixed-interval maintenance and increasing condition-based maintenance, and a transition from scheduled replacement/overhaul to scheduled inspection with replacement/overhaul done on-condition (based on the inspection findings) rather than at fixed intervals.

      • Dan H Kelly Jr

        June 11, 2014 at 2:00 pm

        After I retired? Possibly. That was in 1997. At that time I had risen to Maintenance Supervisor, and was working on helicopters (H-60 Pavehawk) and HH-130. Prior to that I’d been on F-111, F-4D, UH-1N, F-16 (A & B) back to RF-4C, and KC-135. Never once heard the term CBM. Maybe the Army or the Navy? Definitely not the Air Force.

  2. I enjoyed reading that article very informative for a pretty new pilot. I’ve had quite a few MIF’s already in my Vtail but nothing major thank god.

    • Thanks, Shane. Every aircraft owner has had that experience. Most of the time, the MIFs are ones that don’t cause us to fall out of the sky. From time to time, we’re not quite that lucky.

  3. Spooky to say the least. Long ago I was the lucky rentor who flew a 152 right after some invasive MX. Fortunately I never left the pattern before the engine gave up.
    Just had a friend lose all oil (and the engine) 10 minutes into a flight. He landed safely on a road. The plane had some cylinders replaced. He took it up around the pattern after, but then this trip.

    • I doubt there exists any aircraft owner that has not suffered from MIF syndrome one time or another. Fortunately, most MIFs don’t result in accidents. But unfortunately, some do.

  4. Robert Matteson

    June 11, 2014 at 6:55 pm

    Working for a major airline with one of the best safety records in the industry for over 30 years, I can agree with most everything Mike says. We had a saying “Everything works until it doesn’t, so don’t mess with it unless you have to”. Unfortunately, the periodic inspection/checks (not necessarily a bad thing, many important problems were found this way) of the airplanes wouldn’t let you do this. At times during preflight run ups and inspections you would have a problem, go back in the paperwork to see what was done to the system, and find there was a mistake of some sort. Even with all the checks and safe guards required by airline maintenance procedures, s*** happens.

    • And the MIF problem tends to be significantly worse at small piston maintenance shops, where the quality-assurance protocols tend to be much less robust, particularly with respect to having multiple sets of eyes to inspect work before it goes out the hangar door.

      • Robert Matteson

        June 12, 2014 at 8:39 pm

        Absolutely true. When I worked in GA, I was almost always the only eyes that looked at my work, and I was almost straight out of school. Hardly an experienced mechanic.

  5. Douglas Cooke

    June 11, 2014 at 7:01 pm

    When I was a student pilot, I was doing an engine runup prior to departing on a solo flight. The engine idled fine, but ran horribly at 1700RPM. Taxied to the hangar where my instructor and I took the cowl off to find all four top plug wires loose! My guess is someone was changing the plugs and got interrupted before torquing them down.

    • Indeed, distractions are responsible for more MIFs than any other single cause. And unfortunately, most piston GA maintenance shops tend to be distraction-rich environments. Certainly more so than at big turbine Repair Stations. Of course, the big shops can have their own problems, such as poor handoffs at shift changes. But in general, the MIF rate at large turbine Repair Stations tends to be significantly lower then at small piston shops.

  6. I was interested in joining the Coast Guard Auxiliary Aviation program, and they were very interested in me and my Mooney. However, when I found out that my ~1000 hour, trouble-free engine would need to be overhauled first because it had been ~10 years since last rebuild, I decided that they didn’t need me after all.

    • I’ve been working with some key executives in the Coast Guard auxiliary in an attempt to get that brain-damaged policy changed. It’s too early to tell whether we will be successful.

      • as a member of the USCG Aux, I am rooting for you. We lose a depressing number of really good SAR airplanes because of the TBO (calendar and time) issue.

  7. Brent Roberts

    June 11, 2014 at 9:17 pm

    What a load of horse ****! I’m appalled that a fellow A&P would write such article. I have been in the turbine maintenance sector for 35 yrs with Zero MIF”S, why because of PM. I think you have the M in MIF confused with a P, the lions share of failures are induced. I wonder during your inspections as an IA how you tell you customer, I won’t be inspecting that part of the aircraft or engine today because it’s to invasive. 14 CFR Part 91.409 (f)(3) doesn’t give the latitude to pick and choose. I for one follow the inspections to the letter of the law as required by the FAA, if your are getting anything less your better find a new shop. Less is more only applies to the aircraft owner that can’t afford to maintain their aircraft correctly.

    • Brent, I guess we will just have to agree to disagree. Apparently you do not respect the research performed in 1943 by Professor Waddington that resulted in a 60% improvement in force readiness of the RAF the B-24 fleet by drastically reducing the amount of preventive maintenance performed on those aircraft. Nor apparently do you respect the pioneering work done by Nowlan and Heap at United Airlines in the late 60s and early 70s that resulted in decreases and preventive maintenance of nearly two orders of magnitude and radically improved the dispatch reliability of air transport jets. If you missed my AOPA Opinion Leaders Blog posts on those subjects, you might find them enlightning. Or maybe not…

  8. Very interesting. The FAA just ordered 6000 engines with Titan cylinders be replaced because there had been something like seven cases of shock cooling engine failures. Keep in mind five of those were from Alaska pizza delivery planes… Not kidding.

    So assuming that these replacements happen over the next three years how many planes and people are going to die from MIF? Note – the nations top shops have tried to tell the FAA their experience with warranty repairs is much Lower with the Titan product but noe one is listening… Do they even read the proposed AD comments, some of which are from the most experienced shop owners in the US who would benefit from all the extra work?

    • David, actually your conflating two different cylinder 80s. The one against ECI Titan-brand cylinders is still an NPRM, has been very strongly opposed my industry (including yours truly), and is presently under review by an internal FAA advisory committee. We hope that the FAA will reconsider its seriously flawed proposal before issuing any final rule.

      The AD that arose out of the Alaskan operator’s head-to-barrel separations was actually against Superior Millennium-brand cylinders. That AD went to final rule, but we very recently got the FAA to agree to an alternative means of compliance (AMOC) that will allow those cylinders to remain in service for 17 years rather than the original 12 years.

      • Mike, awesome my conflation makes my point… Two problems that the FAA fixes?

        How many planes will be toast because of the improvement to safety?

        Thanks for setting me straight and thanks for what you do!

  9. Mike;I am of the class that say”if they are not going to fly or ride with you,check @ lest twice on thier work”it is less stressful that way.If it is aircraft main.The wrench always was with me.Almost never a problem,good work long life [employment].I have been flying & Comm.driving [4500000miles]retired driver,still active pilot.[if it ain’t broke don’t fix it]

  10. Ben Rosenberg

    June 13, 2014 at 1:19 pm

    Ever since I started flying my own plane I have one guideline. After any maintenance I always fly the next flight solo. I’ve used the same maintenance company and I respect them but even they acknowledge that my “guideline” makes sense (and, to their credit, they don’t take it personally). As the article points out there is always a risk when you take something apart and have to put it back together again that something breaks or isn’t put back together 100%. Over 22+ years I am fortunate that the “after-maintenance” glitches have been small.

    • Ben, that’s a good rule. The only better one I could think of would be to require the mechanic who signs off the approval for return to service to actually participate in the return to service by going up with you on the post-maintenance test flight. I’ve often said that if I ever had the chance to be FAA Administrator for a day (don’t worry, it ain’t gonna happen), I would revise the regs to require mechanics to fly in the aircraft that they sign off. I figure that would give them some excellent motivation. It certainly motivates me.

  11. Re: your statement–“(Every piston aircraft should have an engine monitor IMHO.)” You and I visited at the CPA tent a couple of years ago at Oshkosh. As I remember, you said the engine monitor does not help that much for a carbureted engine–like on my older C182. If I mis-understood that please correct me.

    • As an aside from a fellow Carb guy, we have engine analyzers in our fleet of six Cessna’s. They have been invaluable to detect potential root causes to issues that pop up, and they help us keep fuel burn on the safe side of thrift.

    • I never said anything of the kind, Dick. You must be confusing me with someone else who gave you that advice. I suspect that whoever said that was thinking about the value of an engine monitor as a leaning reference. I don’t believe in using an engine monitor for a leaning reference. From my perspective, it makes absolutely no difference whether an aircraft is carbureted or injected; an engine monitor is a must-have.

      • No it was you, but you are right!! It was a specific discussion on leaning now that I remember it. I stand corrected.

  12. I am not a A&P but I do work on industrial production equipment and have seen the whole gambit of maintenance programs. Lots of PM’s and lots of maintenance induced problems to run it till it breaks and then fix. The old adage of “If it ain’t broke don’t fix it” still applies.

  13. As an A+P and DOM in a high end corporate flight department, I’m required by Chapter 5 to perform certain tasks, at specified times, on our fleet. Often, the same tasks year after year. Often (always? ) , with the same results, no faults found. You’d think that after 10 or 12 years of this on a particular aircraft, someone, somewhere would get the message. It’s simply unnecessary maintenance. And, I will admit to inducing unnecessary damage, however minor in nature. One can only remove interior components so many times without obvious damage to “high end” materials. Thank God I’ve not created any significant, or expensive damage,,,yet…

    With all that in mind, the sole exception to all of this is our low utilization Eurocopter EC-135 helicopter. It seems to fail, even under mild conditions and moderate use. Simple disassembly of major components and careful inspection regularly reveals catastrophic faults caused by poor design, corrosion between components of dissimilar metals, poor construction techniques, and, of course “ramp rash”. Our last blade set lasted 390 hours before failing, and the rotor mast 900 hours before the bearing race cracked due to dissimilar metal corrosion. If anything, our EC-135 would point to an opposite conclusion. It’s in need of constant maintenance and flight critical parts replacement.

    • Robert Matteson

      June 13, 2014 at 9:51 pm

      I like your first paragraph. We had a test on the Lockheed L-1011 on a pneumatic valve in the wing that would fail every time. We would pull it, put in a shop overhauled valve and sign off the operation, which fulfilled the requirement. But then, we would test the new valve and it would fail the test every time. The crazy part was the failure of this valve would have been picked up by the flight crew in flight if it failed, and would have been written up by the flight crew (it was not a flight safey item). I never, ever heard of a write up on this valve, but we kept doing the test.

    • You are only required to comply with Chapter 5 items because you’re working on multiengine turbine aircraft and/or large airplanes above 12,500 lbs. MGTOW. Blissfully, us little guys who fly pistons (or even single-engine turbines like TBMs and PC-12s) aren’t required to comply with Chapter 5 items unless we feel like it.Chapter 4 items (Airworthiness Limitations) are mandatory, but there usually aren’t many of them, and for older CAR 3 aircraft there usually aren’t any. So unlike heavy iron, we who fly flibs are free to adopt minimalistic reliability-centered condition-based maintenance if we like. And I do like!

      • Mike, I like the fact that you are diligently informing aircraft owners/operators/mechanics about this subject. I agree with every one of your points. How can we do a better job of informing others? In particular, I’d love to see objective data in chart or graph form, as it’s easily and quickly understood. The engine reliability chart was quite interesting to me, and I suspect others feel the same. If I can help you in any way, let me know.

        Gulfstream uses an MSG-3 (maintenance steering group) based maintenance program on the newer jets. It was my understanding that part of this program was designed to modify maintenance requirements based on real world, accurate data. Mechanics fill out the CMP cards after performing a task, including the required “results” box (no fault found, squawks requiring immediate action, or deferred) which leads to even more things to fill out if squawks are found. Often it’s done via computer. I can’t remember the last time I checked the block that indicates I found a squawk during an invasive inspection. I’d love to see their data, because I don’t believe they’ve made any effort at extending inspection intervals on even a single subject. We do the same tasks, year after year. So, while the idea was good, the inspection requirements only become more invasive over time. Ugh.

        • Indeed, I’ve heard from a number of Repair Stations that work largely on high-end bizjets complaining that the MSG-3 feedback mechanism never seems to result in any beneficial changes to the manufacturers’ recommended programs. Personally, I think manufacturer decisions have more to do with their legal department than with their engineering department.

          My company limits its managed maintenance practice to piston and single-engine turbine airplanes so that we have the flexibility to say “no” to any manufacturer-prescribed inspection, overhaul and retirement intervals that we don’t agree with, and establish our own condition-based protocols. I suspect that many business aircraft owners don’t realize that when you move from a C-421 or PC-12 to a King Air, you’ve crossed a very significant regulatory boundary and you’re required by regulation to do whatever the aircraft manufacturer says to do.

  14. Ok, so here’s the biggest question in my mind: Who is responsible for the MIF’s? Who pays the freight if it is clearly a MIF, and not just a new issue that pops up shortly after deep service?

    • That is my question as well, if the mechanic forgets something or messes something up that the requires thousands of dollars to fix, why should the aircraft owner be on the hook for it. If I take my car in to replace a cracked head and my mechanic forgets to put in a head gasket and the motor burns up, it his dime to fix it not mine; why should an incorrectly installed cylinder on an airplane be any different?

    • That depends. It depends on (1) whether you can prove that the failure was caused by a maintenance error (often you can’t), and (2) whether the mechanic or shop that worked on your airplane carries E&O insurance (small shops and individual mechanics often don’t). Even if you can prove the failure was a MIF, if the mechanic or shop isn’t insured, you basically have no practical recourse.

      Even in the best of cases, getting a shop’s insurance to pay isn’t easy. One of my clients had his Cessna 206 get seriously damaged during the final runup after an annual inspection when the mechanic let the airplane get tail-to-the-wind and it tipped over, damaging one wing and having a full-power prop strike that destroyed the prop and required a full teardown of the engine. It took six months of haggling before the shop’s insurance agreed to pay to get the airplane repaired. Another client had his engine damaged when a shop replaced the gear-driven alternator on his Continental IO-550 and didn’t properly secure and safety the alternator drive hub; the hub came loose and damaged the crankshaft gear, requiring a teardown. It took six months and a battle of expert witnesses to get that insurance to pay, although ultimately they did. Another client had a starter adapter improperly replaced on one engine of his Cessna 340; the replacement starter adapter came apart and destroyed the engine. The one-man shop that did the starter adapter replacement was uninsured, and went bankrupt, leaving my client holding the $40K bag.

      Be careful out there. Do not be shy about asking any shop or mechanic who works on your airplane about what insurance coverage he carries.

  15. Hard to believe but a few years back when I was running a flying operation at a New Mexico airport, I helped retrieve no less than seven airplanes from where they landed on an interstate highway during one year. Every one of them had lost its oil through the little line supplying oil to the rocker arm assembly on the Lycoming engines. The nut securing the line to the cylinder heads had been left loose after recent maintenance. In one case, all the nuts had been left loose. All had been worked on at different shops! All were returning home after maintenance. All had successfully landed within a 25 mile stretch of highway. One had the bolt holding the throttle linkage at the carburetor fall out.

    Some MIFs I personally have experienced: All the nuts securing the two halves of the elevator hinges being left off after surgery on the tail.(potentially fatal). Both mags failed shortly after takeoff after a mechanic improperly assembled the mags he had rebuilt. Mechanic had reversed the up-and-down limits of the elevator. (exciting). etc..

    As much as possible, I watch everything the mechanic does to my plane and when finished, recheck everything he did. And of course test fly with no passengers.

    • If you’d told me that story ten years ago, I would have found it amazing. But now, nothing amazes me. There are some truly excellent GA shops around the United States, but the number of less-than-competent ones is breathtaking.

      My company maintains a large database of maintenance facilities and a proprietary Google Maps application that allows us quickly to locate the shops in a particular geographic area. The shops are color-coded as green, yellow or red depending on our past experiences using the shops. There are some parts of the country that are just a sea of red icons.

      It’s depressing.

  16. The even darker side of maintenance is how smart “savvy” mechanics charge people for service, then screw it up and don’t take responsibility. I’m talking about Mike’s own company, Savvy, which he gets free advertising for here on this blog. That seems to be a tacit endorsement from the organization I pay to be a member of for good advice. When Savvy screws up and it costs you thousands of dollars, they won’t stand up and take any responsibility. Mike may know a lot about fixing planes, but he and his team know nothing about customer service, and they alienate more than a few maintenance shops along the way, too. That and at a non-alcoholic event – an AOPA fly-in no less he called me half in the bag and had to admit he was a little fuzzy on a few things as a result (at least in Plymouth there wasn’t a drop of alcohol unless someone brought it with them, I doubt Spokane was any different). AOPA members beware.

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