(Piston) Engine Failure Rate: 1/3200 hrs, yikes!

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infrequentFlyer

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infrequentFlyer
Hello,

Was just looking up engine failure rates for piston engines and came across this Twin & Turbine article which states that piston engines fail at a rate of about 1 per every 3200 hours (can't find official source). Furthermore, they go on to say this is likely a low-ball number based on the fact that many engine failures which go on to a safe landing may not be reported.

Based on this number it seems like the question is not "if" you will experience an engine failure, but "when". I knew GA flying wasn't anywhere near as safe as 121 flight for various reasons, but going up into the sky knowing I'm just waiting for my turn puts a bit of a damper on the whole thing!

A good maintenance dept, thorough preflight, and careful route planning with many outs seem to be our best defense to not experiencing or surviving an engine failure. I don't really have a "question" for this thread. I guess I just wanted to vent my discomfort and hear what other pilots think on the subject of engine failures.
 
Based on my interest in aviation accident I feel my odds of having an in flight engine failure can be dramatically reduced if I manage the fuel and pay attention to what my engine is trying to tell me.

It is my observation that many in flight engine failures are the direct result of stupid pilot tricks.
 
infrequentFlyer said:
oing up into the sky knowing I'm just waiting for my turn puts a bit of a damper on the whole thing!
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The problem with statistics without context they are meaningless. I've seen those same recip engine failure rates expressed as .4/ 100,000 hours to 1 in 7500 hrs. For example, to use your 1 every 3200hrs ratio there are a number of private GA pilots that never attain 3200 flight hours in their entire life, so does that mean they'll never have an engine failure?

While piston engines do not have the same failure as turbines for many different reasons its a red herring when comparing those rates in your scenario. If you really want to bring this into context compare the private GA piston engine failure rates to the failure rates of private GA pilots and you may never want to be a pilot. Regardless, in the big picture, risk factors are subjective to the person and if you believe the smaller percentage of engine failures eclipses the higher percentage of pilots running out of fuel or flying into IMC while VFR then perhaps flying isn't your cup of tea. But if you want to fly, fly and be smart about it.
 
Chrisgoesflying said:
That puts the number to 1 in about 5,500 hours.
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Thanks for the article and revised statistic :) I believe that still means roughly a third of careful GA pilots will draw that card once in their life. (if they fly 50 hours per year, flying for approx. 35 years).
 
infrequentFlyer said:
Thanks for the article and revised statistic :) I believe that still means roughly a third of careful GA pilots will draw that card once in their life. (if they fly 50 hours per year, flying for approx. 35 years).
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No, it means some of us will have a ****load of engine failures, and most of the pilots we know won’t ever have one.
 
Bell206 said:
But if you want to fly, fly and be smart about it.
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100% agree, I just like to know my odds before I go into the casino. Especially when I will be bringing passengers on board. I still plan to fly I was just a bit surprised at the number being as low as it is. Like you are all saying, some context may be missing.

MauleSkinner said:
No, it means some of us will have a ****load of engine failures, and most of the pilots we know won’t ever have one.
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Ha! If that's true then I'd like to read more articles like the one Chris posted so I can stay in the "most" group as long as possible.
 
I began my flying life in ultralights with two stroke engines. There were a few times that the engine decided to quit working before the flight was over.

I'm now a dedicated four stroke flyer but I still use an experimental engine (Corvair) that has been extremely reliable. Still, I expect it to quit at anytime.

But even in the certified world I don't believe that anyone has yet built the unbreakable powerplant for light aircraft ...
 
My flying experience just hit 2,000 hours. I'm glad I've got 1,200 more before the engine fails.:cool:
 
How would anyone know how much I fly my aircraft?
 
mandm said:
How would anyone know how much I fly my aircraft?
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Every single engine piston comes with a little timer hidden inside during assembly with an "hours to engine failure" countdown. No way out, sorry.
 
mandm said:
How would anyone know how much I fly my aircraft?
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The FAA would know if you responded to the annual GA survey. Other than that, the FAA uses the survey results to predict the average number of hours flow each year by certain classes of airplane.

For instance, in 2021, the survey estimated that single-engine piston-powered aircraft with four or more seats flew an average of 110 hours per year. You might fly less, but of course, the FAA number is an average, so that means someone else flew more.

The same survey estimated that about 15% of the single-piston-engined crowd killers are inactive.

Ron Wanttaja
 
Pilots like to look at statistics and accident reports so they can justify to themselves that it must have been the pilot or there was something they would have done different if it was them. Almost every pilot in an accident thought before takeoff “it wouldn’t happen to me. I’m a better /more careful /more experienced pilot than average”. Yet statistics show that just isn’t true. You will face an in flight emergency if you fly enough and there is a possibility you may die because of it. We can do things like recurrent training and keeping up on maintenance to try and tip the scales a little more in our favor but the truth is that flying is risky and every time you go up there is always a chance you may not come back. The best you can do is make sure you are proficient enough to not make an emergency any worse than it needs to be. An engine failure isn’t a death sentence but trying to stretch a glide to the airport and stalling it in after the engine failed sure is.
 
That data seems suspect without context. What was it based on NTSB information? Survey data? What?

Tim
 
infrequentFlyer said:
Hello,

Was just looking up engine failure rates for piston engines and came across this Twin & Turbine article which states that piston engines fail at a rate of about 1 per every 3200 hours (can't find official source). Furthermore, they go on to say this is likely a low-ball number based on the fact that many engine failures which go on to a safe landing may not be reported.

Based on this number it seems like the question is not "if" you will experience an engine failure, but "when". I knew GA flying wasn't anywhere near as safe as 121 flight for various reasons, but going up into the sky knowing I'm just waiting for my turn puts a bit of a damper on the whole thing!

A good maintenance dept, thorough preflight, and careful route planning with many outs seem to be our best defense to not experiencing or surviving an engine failure. I don't really have a "question" for this thread. I guess I just wanted to vent my discomfort and hear what other pilots think on the subject of engine failures.
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So, Aviation is more dangerous than sitting at home.? I already knew that. So is riding my motorcycle. I manage the risk. I take good care of my airplane. But it is a disposable item. I do engine oil analysis regularly. I don’t fly at night. I am involved with my aircraft maintenance. But I accept the risk. my finances are in good shape, and everything is set up in the event of my demise. And for what it’s worth, I have had an engine failure on takeoff. (It was my fault and a learning experience that I pass onto others), And lived to tell the tale. The next flight could have a different ending. Oh well. Most pilots die at home or in a nursing home of old age.
 
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infrequentFlyer said:
Hello,

Was just looking up engine failure rates for piston engines and came across this Twin & Turbine article which states that piston engines fail at a rate of about 1 per every 3200 hours (can't find official source). Furthermore, they go on to say this is likely a low-ball number based on the fact that many engine failures which go on to a safe landing may not be reported.

Based on this number it seems like the question is not "if" you will experience an engine failure, but "when". I knew GA flying wasn't anywhere near as safe as 121 flight for various reasons, but going up into the sky knowing I'm just waiting for my turn puts a bit of a damper on the whole thing!

A good maintenance dept, thorough preflight, and careful route planning with many outs seem to be our best defense to not experiencing or surviving an engine failure. I don't really have a "question" for this thread. I guess I just wanted to vent my discomfort and hear what other pilots think on the subject of engine failures.
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Did they define an engine Failure? Is it just loss of power or is it Total Loss of power?
I have 8000 hours, Well 2000 hours are in sailplanes so I was pretty safe from the possibility of an engine failure for that 2000hrs. In the other 6000 hours I have had a number of "engine failures" just never a complete power loss...
I have had...
A Stuck intake valve take one cylinder of line on an O-235 Tomahawk
A Magneto go bad causing the engine to run very badly, intermittently every few seconds going from almost no power to full power and back to no power.
Have had a Carburetor Heat cable break on me causing it to turn on loose some power.
Have had Carb ice on a couple times, Once on TO at 400ft to the point I couldn't climb any more, turned back to the runway, had it made so continued downwind was about mid-field downwind before the Carb Heat finally melted the ice away and I got full power back.

Brian
 
tspear said:
What was it based on NTSB information? Survey data? What?
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brcase said:
Did they define an engine Failure? Is it just loss of power or is it Total Loss of power?
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I frustratingly cannot find the source, so I'm left with the same questions. The statistic is quoted here and there in many journals, none saying where it's from. It might come from this MDPI journal article. The article cites the FAA for the statistic but then - if you go to the bottom - the actual citation links to this ATSB (Australian Transport Safety Bureau) paper, clearly not the FAA. I didn't read the full 200+ ATSB report but searching it could not reveal any similar statistic.

I also found this article in The Economist which says piston engines have a failure rate of 300 per 1 mil hours (very close to 1 per 3200 hrs, I suspect from the same source. They may have just reformatted the statistic for comparison with jet engines.).
 
I'm curious as to the sources as well. I've known about several failures and partial failures that probably were never reported to any tracking entity.
 
infrequentFlyer said:
Thanks for the article and revised statistic :) I believe that still means roughly a third of careful GA pilots will draw that card once in their life. (if they fly 50 hours per year, flying for approx. 35 years).
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I don't quite get your math. 5,500 hours @ 50 hrs/yr comes to 110 years. Fortunately, my wife (the pilot in the family) had a catastrophic engine failure at 100 hours and we lived to tell about it.

Ok, I kinda see where you are coming from. A third of the pilots will draw that card and two thirds wont. But I am still foggy on that logic. I should have stayed awake that day in statistics class.
 
I would argue that we're less likely to get into trouble flying our bug smashers than many other activities we undertake on a daily, weekly or yearly basis and not think twice about them. The difference is that IF we do get in trouble with our bug smashers, the outcome usually isn't as favorable compared to other activities. For sh**s and giggles, here are some interesting stats. Not sure how "scientific" they are, but according to this, we should all just stick to board games and computer games - but make sure to not become obese while doing so, or else. https://www.besthealthdegrees.com/health-risks/
 
I like the chart you posted but the problem is I have a hard time comparing "1 in a XYZ" chance.

There is another way to quantify risk--micromorts--here is a wiki: https://en.wikipedia.org/wiki/Micromort#Further_reading

Basically it is a 1 in a million chance of dying, depending on where you live when you wake up you have a certain amount of micromorts on your "counter" statistically. Anything you do that can result in dying--which is basically everything--adds to your count

So it is a good way to compare the relative risk of stuff--how many micromorts you add to your counter:

Here are some examples--note that it is MUCH safer to drive than walk or bicycle! Also note if you are an old guy you may has well BASE jump, whatever, your micromorts for death by Covid are way up there

Activities that increase the death risk by roughly one micromort, and their associated cause of death:

  • Travelling 6 miles (9.7 km) by motorcycle (collision)[23][verification needed]
  • Travelling 17 miles (27 km) by walking (collision)[24]
  • Travelling 10 miles (16 km)[25] or 20 miles (32 km)[24] by bicycle (collision)[a]
  • Travelling 230 miles (370 km) by car (collision)[23][verification needed] (or 250 miles)[24]
  • Travelling 1,000 miles (1,600 km) by jet (collision)[25]
  • Travelling 6,000 miles (9,656 km) by train (collision)[23]

​

Increase in death risk for other activities on a per event basis:


I didn't see flying by small plane there but I am sure somebody has the micromorts for it
 
JOhnH said:
I don't quite get your math. 5,500 hours @ 50 hrs/yr comes to 110 years.
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I was hoping no one would check my math ;)

But here was my logic:

( 5500 hours per engine failure ) / ( 50 hrs per year ) = 110 years per engine failure (as you said above)

If you or me plan to fly for 35ish years, and the rate is one failure per 110 years, then I was claiming we have about a 1 in 3 chance of having an engine failure.

It has been a while since I did any statistics, so take my math with a few servings of salt. And this is all based on questionable data to begin with.

Chrisgoesflying said:
I would argue that we're less likely to get into trouble flying our bug smashers than many other activities we undertake on a daily
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I'm sure it's possible that gardening is as dangerous as (more than?) flying a piston single! But 1 unexpected trip to the ground every 3200 hours is creeping towards my "do I really want to do this?" zone. Everyone has there own risk comfort level. Where is your line? If the actual engine failure rate was 1 per 2500 hours, would you still fly? 1 per 1000? 500?

That's all I'm trying to uncover here, how risky is this, really. Then I will decide if the joyrides are worth it. It's becoming apparent that the numbers aren't so clear, just have to work with what you know.

This is not an attempt to dissuade anyone from flying - I'm just a newbie trying to get informed and hear others' thoughts on the topic. Talking it out with others helps me process my own thoughts.
 
infrequentFlyer said:
But 1 unexpected trip to the ground every 3200 hours is creeping towards my "do I really want to do this?" zone.
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1 in 5,500 hours ;-) I don't think you will dissuade anyone from flying with this thread. I went through the same thought processes a few years ago when I got into this hobby. I read all sorts of stats. Some more reliable than others. At the end of the day, I think flying small planes isn't the safest, nor is it the most dangerous hobby one can have. I also think I have done more risky things (like living in St. Louis for a while lol) than flying. Control what you can, and whatever you can't control, well, decide if it's worth it for you. Perception wise, I feel much safer at 9,500 ft. with my plane than in my car going 55 mph on the freeway, with idiots passing me at 75+ mph in wet or even snowy conditions. I fly mostly to travel. Business and personal. Thinking of doing all these trips by car I'm doing (I don't do airlines - first I dislike people, second I take my dog everywhere I go and there is no way I put him in cargo) by plane right now, I think the individual risk is probably close to flying. Driving would take me 3 or more times longer. I would be much more tempted to push through bad weather or drive while being fatigued than I would when flying.

Going back to stats: Only 1 in 4 engine outs end fatal so that puts the above number to 1 in 22,000 hours.
 
infrequentFlyer said:
I also found this article in The Economist which says piston engines have a failure rate of 300 per 1 mil hours (very close to 1 per 3200 hrs, I suspect from the same source. They may have just reformatted the statistic for comparison with jet engines.).
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I'm a bear of very little brain that can't even spell MTBF, but let me take a look at it based on my data.

I've got a tally of Cessna 172 accidents from 2006 through 2021. 1,817 accidents with the aircraft involved overwhelmingly having Continental or Lycoming engines. There three "Aero Engines" cases, which probably can be treated the same, and three more in weird corners of the certification envelope. Plus one PFM, one PZL Franklin (not THAT far from normal), and one Theilert. (One Porsche, one Pole, and one beer.....)

For each accident, I flag whether it was engine-power-related, and whether it was pilot or mechanical issues. 269 of the total featured a loss of engine power, for ANY reason. I treat a partial loss of power the same as the full one.

I do a bunch of alternate flags. Let's use the one that is set when the reason for the failure is confirmed as being mechanically-related to the engine (and NOT related to the fuel system). There are 78 of those...over a 16-year period. Averages a bit less than five per year. With over 20,000 aircraft in the US fleet, that's not bad odds right there. However, understand that in addition to those 78, there are 117 more cases where the NTSB was unable to determine the cause of the loss of power. Often, the engine even restarts during the investigation process.

For now, let's just use those 78 known cases. So...how many hours?

Just by chance, I have the FAA registration database running back to the year 2000. The 172 Fleet Size in 2006 was 26,719, tapering down to 20,619 at the end of 2021.

How many hours per year per aircraft? We don't actually know for specific aircraft types. The annual FAA GA survey typically says that 4+seat single-reciprocating engine airplanes fly around 100 to 110 hours a year. I picked 100 hours...and with that and the number of aircraft registered in a given year, I can estimate the number of hours flown each year by Cessna 172s. This comes out, roughly as about 2.7 million hours in 2006, tapering off to about 2 million even in 2021 (due to the smaller fleet size).

Note that the FAA survey also predicts how many aircraft in a given category are active. I'm leaving that off, but the crowd-killer category that the 172 falls into is about 85% active.

So, what does it come to?

Over the 2006-2021 time frame, I'm estimating the Cessna 172 fleet flew 37,750,000 hours (Fleet size per year multiplied by 100). During that same time frame, there were 78 known cases of loss of power due to engine mechanical issues (doesn't include fuel-system-related issues). This is about 484,000 hours per loss of power case, or a bit over 2 per one million flight hours.

Note a couple of sources of error, here. First, of course, is the undetermined engine failures. SOME of those were probably mechanical, and the wreckage was too badly damaged to find the cause. There were 117 cases, which would add about three per 1 million flight hours.

Mentioned the active percentage; if this were incorporated, the figures would rise by about 15%.

But finally, one has to consider the fatalities involved. My figures look at ALL accidents, not just ones where people were killed. Engine failures have generally a lower fatality rate than other issues, and the Cessna 172 is a very survivable aircraft. In the time frame we're looking at, only four of the engine-failure cases resulted in a fatality. That is about one fatal accident per 10,000,000 flight hours.

Ron Wanttaja
 
robertb said:
My flying experience just hit 2,000 hours. I'm glad I've got 1,200 more before the engine fails.:cool:
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I had two engine failures in my first 500 hours. One was bad maintenance, the other was a really poor overhaul where NDT was not done. Therefore, the engines themselves were never at fault. It was the people working on them.
kmacht said:
The best you can do is make sure you are proficient enough to not make an emergency any worse than it needs to be.
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Proficiency makes a difference alright, but a poorly-maintained engine or ancillary system raises the chances of a failure much, much higher, and so you are more likely to have a failure in a really inconvenient spot, like over a city, or at 100 feet over the departure end of the runway, or in IMC or on a dark night.
wanttaja said:
However, understand that in addition to those 78, there are 117 more cases where the NTSB was unable to determine the cause of the loss of power. Often, the engine even restarts during the investigation process.
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Such cases are often blamed on carb ice if the conditions at the time were conducive to icing. After the forced landing, the ice melts and the engine works just fine.
 
wanttaja said:
I've got a tally of Cessna 172 accidents from 2006 through 2021
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Holy smokes - looks like I barked up the right tree. I trust your numbers way more than the ones magazines are seemingly pulling out of thin air. Thanks for settling this.

What database are you searching? (Your own?) And I had to google MTBF lol.
 
That engine need plenty of clean fuel, it needs spark, and it needs air.

Running out of fuel is inexcusable. Even an airliner will have a forced landing if that happens.
Dirty fuel is a result of lousy storage, lousy delivery filtration, or simple neglect of the fuel screens and drains in the airplane.
Inadequate fuel happens if the system is badly maintained. A dirty fuel screen in the strainer or carb/injector servo inlet screen will restrict fuel flow. A selector valve that has never been drained is another, and I have found plenty of those that have never had their drain plugs removed in thousands of hours. Lots of crud in them. An old fuel hose has a liner that may be crumbling with age, and those crumbs will pile up somewhere and block the fuel. And some people will use RTV or teflon tape on fuel fittings, stuff that can go where it shouldn't and block the flow.

Spark. Most owners are running their mags until they quit. That's insane. You at least lose some power if one quits, and if they're both the same age and hours, you might lose both of them on the same flight. At the very least, you're stuck somewhere. That tends to be far more costly than just doing the manufacturer's recommended maintenance on those mags.

Air? Carb ice has a way of blocking that airflow, and if the pilot is not well-educated on what causes the ice and in what conditions he/she should expect it, an accident is quite possible.
Induction filters can and sometimes do fail. There are ADs on paper filters to force their replacement, as paper ages and gets wet and falls apart. Filter or induction flange gaskets have been known to get sucked into the carb and block the secondary venturi, causing the fuel flow to fail. ADs on that, too.
 
I used to work for a company that put about 20,000 hours a year on IO520s. They had three total engine failures I can think of in 5 years, one was caused by bad fuel (Pilot didn't sump) , one was unknown (the engine ran fine on a test stand) and one came from together. Thats 1 in 33,000 hours, not too bad I think.

edit: Side note: The guy who had the engine come from together on him had 40,000 hours behind IO520s, and it was his first engine failure.
 
kmacht said:
Pilots like to look at statistics and accident reports so they can justify to themselves that it must have been the pilot or there was something they would have done different if it was them. Almost every pilot in an accident thought before takeoff “it wouldn’t happen to me. I’m a better /more careful /more experienced pilot than average”. Yet statistics show that just isn’t true. You will face an in flight emergency if you fly enough and there is a possibility you may die because of it. We can do things like recurrent training and keeping up on maintenance to try and tip the scales a little more in our favor but the truth is that flying is risky and every time you go up there is always a chance you may not come back. The best you can do is make sure you are proficient enough to not make an emergency any worse than it needs to be. An engine failure isn’t a death sentence but trying to stretch a glide to the airport and stalling it in after the engine failed sure is.
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A great complement to that is adding a BRS to your plane.
 
You have an equal chance with every flight. Fly accordingly.
 
Not buying the OP stat. I would bet that the average hours per aircraft in the GA fleet is over 3500. That means more aircraft have had a failure than not. Doesn't pass the sniff test.
 
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I (like most of us) accept the risk of injury or death as a consequence of flying, and am happy to do so. I love to fly. But the issue is passengers. They don't get the thrill necessarily of flying (some might but most are along for the ride without any ability to control the outcome). They might enjoy the convenience if it means shortening a 4h drive into a 1hr flight (plus 20min on either side getting the plane ready and put away). And this applies to family members as well. None of my family "love" to fly. They tolerate it, as long as it gets them somewhere they want to go. When I compare dangers of driving they don't seem to get it.
 
infrequentFlyer said:
Holy smokes - looks like I barked up the right tree. I trust your numbers way more than the ones magazines are seemingly pulling out of thin air. Thanks for settling this.

What database are you searching? (Your own?) And I had to google MTBF lol.
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I download the NTSB accident database every year, extract aircraft of interest, and transfer them to my own database. There, I examine each accident, record what I think the cause was (could be different from the NTSB Probable Cause), and generate various statistics.

My primary interest is homebuilts, but I occasionally compare homebuilt accident statistics with production-type airplanes, so often have data available for common types (though it usually doesn't cover the complete time period).

I've got a simplified version of my database at:


This has some of the NTSB summary data, coupled with my own assessment of each accident's cause. There's a Data Dictionary providing explanations for the columns.

Ron Wanttaja
 
Dan Thomas said:
Therefore, the engines themselves were never at fault. It was the people working on them.
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Well, a distinction without difference from where I sit, as a [former] cErTiFiEd captive audience. But to your point, yes, MIF is rampant in this space. It's human politics and plausible-deniability bad faith arguing that makes it so hard to overcome.

--brk brk---


OP, for my part as someone who had an engine attempt to come from together (cylinder mating fastener fatigue failure, progressing into cascading secondary ultimate overstress failures of the rest) and leading to a forced landing under minimal partial power, I hear ya. And I do consider the nature of these engines sketchy and anachronistic. The more salient point to me is that, I am willing to accept that risk.

What does grind my gears is the ghastly costs for the already stipulated sketchy odds I'm enlisting for in the first place... but that's for another thread. *whistles past the graveyard*
 
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MountainDude said:
A great complement to that is adding a BRS to your plane.
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Except that the BRS is of no use on takeoff when the engine quits at 100 feet. That 'chute takes much more altitude to open than that. And takeoff failures are, according to Bertorelli, the biggest chunk of failures.

The chute installation for a 172 weighs about 78 pounds. It goes in the baggage compartment, and so you lose nearly half of that space and 78 pounds of useful load. The thing has to be taken out and sent to BRS for inspection, repacking and a new rocket every 10 years or so, IIRC, and costs $10K+. At least, that's what it was 12 years ago. Likely more, now.
 
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