It’s been long felt in the general aviation community that flights right after maintenance and inspections carry higher risks. And while there has been plenty of anecdotal evidence, there wasn’t really data to back that up.
Well, now there is.
In a new study, aviation consultants Daniele Paolo Scarpazza and Joseph A. Hutter analyzed 16 years of NTSB accident reports, from 2008 to 2024, and found that aircraft are significantly more likely to experience an accident or serious incident immediately after maintenance.
Their research, which examined more than 20,000 GA accidents, shows a 33.8% higher risk in the first hour of flight following an inspection. Even after that critical first hour, the risk remains elevated for at least 31 hours, according to the researchers.
Why Does This Happen?
The study points to two major culprits:
- Early Mortality of Components: Newly installed parts can fail soon after installation, often due to manufacturing defects or improper integration with existing systems.
- Maintenance-Induced Failures: Even the most experienced mechanics can make errors, from incorrectly torqued bolts to fuel line misconnections.
Because annual and 100-hour inspections require disassembling and reassembling various aircraft systems — even those in perfect working order — there is always a risk that something was reinstalled incorrectly or inadvertently damaged in the process, the researchers noted.
Recommendations for GA Pilots and Mechanics
Given the clear statistical increase in risk, the study suggests a more cautious approach to post-maintenance operations:
- Conduct a meticulous preflight inspection: Go beyond the standard walk-around. Check control surfaces, fuel lines, fasteners, and any system touched during maintenance.
- Plan a conservative test flight: Instead of heading straight into normal operations, conduct a controlled post-maintenance check flight in good weather, daylight, and over an area with safe landing options.
- Make a gradual return to normal operations: The study suggests that most failures happen in the first 31 hours after maintenance. Keep this in mind when planning critical flights.
- Get a second opinion: If possible, have another mechanic or experienced pilot review the maintenance work and confirm everything is in order.
- Mechanics: Double-check your work. This research isn’t just for pilots. A structured post-maintenance quality check — especially for critical systems — can reduce the likelihood of maintenance-related failures.
The Takeaway
This study provides hard evidence supporting what many pilots and mechanics have long suspected: The first few hours after maintenance are among the most accident-prone in GA operations. But armed with this knowledge, the GA community can take proactive steps to minimize risk and improve safety.
The next time you roll out of the maintenance hangar, remember just because an aircraft is airworthy on paper doesn’t mean it’s free of risk. Approach your post-maintenance flights with increased caution and you’ll dramatically improve your odds of a safe return to base.
You can read the full study, “Quantifying the Risk of Accidents and Serious Incidents Due to Maintenance in General Aviation,” at Preprints.org.
For all the pilots who would like to do their own maintenance. Get your A&P. There is a benefit to having someone else do your annual maintenance. As an A&P who is not the owner. They can look at the benefit of repairing or replacing a part or component thru the lens of is it airworthy or not or is this going to make it to the next inspection base on utilization or wear patterns. As an owner, I have often seen the first question be “what does that cost?”.
Most of us can’t allocate the 2 years of college study. Then, study for and take the 3 written tests. Finally, there is the practical test with an examiner.
I’d like to be able to take a sub-set of the tests , maybe as they apply to my aircraft with a non-turbo, fixed gear, piston engine.
Also, with documentation of 10-15 years of doing work on the owned aircraft, under the monitoring of an A&P.
I find it a bit absurd that I can remove and clean the spark plugs, then install and torque them, but I’m not allowed to do a compression check.
A borescope of the cylinders appears to be ok…but there’s no mention of it in the regs. ?
MSG-3 for all airplanes
https://www.federalregister.gov/documents/2024/01/31/2024-00763/inspection-programs-for-single-engine-turbine-powered-airplanes-and-unmanned-aircraft-and
Now if the FAA would revise 91.409 [a][1], for the rest of us flying piston engine aircraft,
to allow owners to do maintenance and inspections on just our aircraft, after some classes and testing.
I had 2 engine out failures both caused by maintenance induced failures. I was able to land at an airport in both cases.
Could you explain what failed on the engines.?
Was it the part/ area that was ‘touched’ ?
The study appears to have looked at early failures after maintenance where a replacement or removal and reinstall of some critical component fails, vs an inspection or oil change which occurs at 25 to 50 hours.
Annual inspections should not cause any induced failures, unless incorrect adjustments are made for items like mag timing, fuel mixture, cable tensions, wheel bearing lube and preload.
I have had a repaired magneto fail after about 50 hrs. I had both ‘rebuilt’, which replaces all the internal parts and get a ‘0’ time on the mag.
Intrusive annual inspections for most pilot owned aircraft that only fly around 50 -100 hours per year seem a little excessive. Considering the risk of maintenance induced failures and the growing mechanic shortage, it might be time for the FAA to look at extending the annual inspection to biannual.
Annuals are based on the assumption the previous annual or maintenance wasn’t correctly. Unfortunately it’s correct.
There should be a rudimentary mechanical test for mechanically inclined owners to maintain their own aircraft. All in all planes are pretty simple.
Maybe it’s time to make annuals less invasive – or less frequent.
I don’t know how to make them less intrusive.?
The Cessna 100 hour check list that I use has 83 items on it, and I add a few more, like draining the carb bowl, looking for any grit and water ….[ I usually find some !]
The cowl is removed, the wheel pants, the seats, carpet, and all 15-20 inspection covers.!
Then there is all the lube, grease, adjustments, mag timing . plug cleaning…
I believe the finding is that when you, for example, remove the carb bowl, there can be benefit from removing grit and water but there is also risk of replacing the carb bowl incorrectly. Same with the wheel pants and seats and spark plugs and mags. I’ve seen a liquid cooled engine loose coolant after an annual because when the carb was reinstalled a coolant line got pinned against the hot engine. Some planes have annual checks that include removing flight surfaces to inspect for corrosion – corrosion is bad, but so is incorrectly reinstalling a flight surface. Anything you remove, creates a risk.
Of course, eventually you want to do these checks. But you could probably make a bunch of the checks “every 200 hours or 2/3/4 years, whichever comes first”.
Here’s another way to think about it: why only check annually? If you opened the carb every 6 months do you think you’d find grit and water? Every 3 months? You could theoretically benefit from opening it on every preflight – but you’d also create a much greater risk of causing a problem (as well as consuming huge amounts of time).
I wasn’t clear on draining the carb bowl, by removing the drain plug. Then, of course, adding the safety wire.
I do this in late Spring/ early Summer, since our cool, rainy season is the most likely time for water to get into the carb. [ No. Calif. valleys don’t get very cold]
The main jet on an MS carb sits in the low spot where the drain plug is. So, that’s where the grit and water can be sucked up into the jet.
Wow, 33 % higher rate sounds really scary.!
But, 133% of a small number, is still a small number
Their data for SE aircraft is 6.9 /100k hours vs the baseline of 5.3 / 100k hours. So, their data indicates an added 1.7 incidents per 100k hours….not very scary.
Also their figure 7 graph showing a minimum rate a 188 hrs after maintenance doesn’t figure well with either 100 hr inspection or an annual , where most aircraft barely fly 100 hrs between them.
Their ‘peak’ failure rate at 487 hours, looks very close to the mandatory inspection of some accessories , like magnetos.
Also , why does their data show a much lower failure rate for twin engine aircraft vs single engine.? They don’t explain this….maybe twins fly longer flights, where there is a low failure rate in cruise ?
So, more questions on the validity of their results.