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Author Topic: Is an engine reliabilty really good, or is it a myth?  (Read 7559 times)

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HalfFullGlass

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Is an engine reliabilty really good, or is it a myth?
« on: January 25, 2015, 01:04:39 PM »
Dealing with engine failure is one of those things we practice in training, check rides, and BFRs.  The NTSB aviation accident data base only has data on the bad outcomes of losing an engine.  That means it must understate the 'real' number of piston engine failures. Whether by a little or a lot is unknown. Could the relatively small number engine failure accidents in the NTSB data base perpetuate a myth of reliability?  Do most pilots who lose an engine avoid bending metal because of skill, luck, or both?

In February I will speak about engine failures and emergency procedures during a seminar at the Northwest Aviation Conference in Puyallup, WA.  I need your help!  Would you invest just 5 minutes and complete the linked survey? The survey has just four questions. The linked survey asks about your overall flight experience, then focuses on your experience in factory built, single engine, fixed wing, piston powered aircraft... Cessnas, Pipers, Maules, Mooneys, etc.

Please share a little about your flying experience AND whether you've ever lost an engine.     

Using data you provide I will estimate the ratio between the number of engine failures we experience, and the engine failures that result in accidents or incidents.  To accomplish this the survey data set really needs to include engine failure experiences from pilots who have NEVER lost their engine, as well as from pilots who have had multiple "opportunities" to demonstrate proficiency with emergency procedures.

Thanks for your help!  I'll share the results after the Northwest Aviation Conference.  Maybe I'll see some of our forum members there.

John
« Last Edit: January 25, 2015, 01:06:29 PM by jtownsley »

Florg

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #1 on: January 25, 2015, 06:57:07 PM »
Done!
Brett
KCOE Coeur d'Alene, ID
Air Coeur Flying Club

rwanttaja

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #2 on: January 25, 2015, 07:19:10 PM »
In the work I've done analyzing homebuilt accidents, I've made my own assessment of the causes of ~3400 homebuilt accidents over the past 16 years.  I actually assess the data differently from the NTSB; if the engine throws a rod but the pilot botches the forced landing, I list the cause as engine failure instead of pilot error.

I've combined Cessna 172 and Cessna 210 accidents to give me a "control group" to compare the homebuilts to, and my arm got twisted a couple of years back to perform the same sort of analysis for fixed-gear Cherokees.

(You can read the Cherokee presentation at http://www.wanttaja.com/pa28.pdf)

The upshot:  About 25% of the Cessna and Piper accidents *began* with an engine failure.  Mind you, the engine might have stopped due to fuel exhaustion, or the accident itself may have stemmed from a stall/spin in the deadstick turn to final.  But the event starting that Really Bad Day is the fan stopping to spin.

BTW, the value for homebuilts is about 33%...one third of all homebuilt accidents begin with loss of engine power.

Ron Wanttaja

will moffitt

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #3 on: January 25, 2015, 07:24:49 PM »
Done,

So, what do you think is the cause of the higher rate of engine failure in hope builts?

will
« Last Edit: January 25, 2015, 07:28:56 PM by will moffitt »

114SM

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #4 on: January 25, 2015, 07:44:30 PM »
Done

HalfFullGlass

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #5 on: January 25, 2015, 08:56:34 PM »
I actually assess the data differently from the NTSB; if the engine throws a rod but the pilot botches the forced landing, I list the cause as engine failure instead of pilot error....

Ron Wanttaja

This is exactly how I determined the 144 engine failure accidents in Washington State between 2001 and 2011.  Absent loss of power (partial or complete) the accident would not occur.  So far 34 respondents, and about a 5:1 ratio between engine failure (complete) and NTSB accidents.  The ratio is about 10:1  so far for partial power losses.  The textual information is interesting.  It runs a wide gamut, but mechanical deficiencies (some mechanic induced, some from other causes) seem to be predominant.

So far it looks like nearly all respondents have had one or more engine failures, partials look to be more frequent that complete failures.  I hope some pilots who have a "clean record"... they have never experienced partial or complete loss of power... will contribute their experience as well.

Thanks to all who have shared your experience.

The survey link is sinking slowly down the thread.  Here it is againhttps://www.surveymonkey.com/s/CCXT8XF
« Last Edit: January 25, 2015, 09:02:29 PM by jtownsley »

rwanttaja

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #6 on: January 25, 2015, 10:33:38 PM »
Done,

So, what do you think is the cause of the higher rate of engine failure in hope builts?
They are experimental aircraft.    The systems on Cessnas and Pipers are standardized and build and installed on production lines.  Any deficiencies were discovered long ago.  Every homebuilt that flies is a brand new aircraft that has to undergo a complete ground-up test period.  Sometimes, things aren't right.

The number of registered homebuilts is about equal to the combined fleet of 172s and 210s.   Over the same ten year period (1998-2007), homebuilts had

- More than twice as many cases of undetermined engine failure (e.g., NTSB unable to determine the reason)
- Three times as many engine mechanical failures
- Nearly twice as many cases of carburetor ice
- Over six times as many problems with fuel systems

...and, in addition, 110 more instances of outright builder error (114 homebuilt vs. 4 Cessna or approved vendor).

Keep in mind that many homebuilts have non-traditional engines as well; about half the homebuilts in my accident database has something other than a Continental or Lycoming.

Homebuilts came out second-place in all mechanical categories, and better in most pilot-related categories (fewer fuel exhaustion cases, etc.).   Of course, the homebuilt pilots have more flying hours... a median of 950, vs. 509 for the Cessnas.

An analysis I did a few years ago showed homebuilts having a fleet accident rate about 45% higher than production-type aircraft.  Once the homebuilt is past its test period, that drops to about 18% higher.  Of course, this is based on registered examples and does not take activity rates into account.

Homebuilt aircraft are built, maintained, and often designed by amateurs.  Of *course* they have a higher accident rate.

Ron Wanttaja


HalfFullGlass

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #7 on: January 26, 2015, 09:25:46 AM »
Thanks to all who have shared your experience.

The survey link is sinking slowly down the thread.  Here it is again: https://www.surveymonkey.com/s/CCXT8XF

The survey is now up to 48 respondents.  A few more pilots who have not experienced an in-flight engine failure have responded.  The average flight time of survey respondents in factory built, fixed wing, single engine, piston aircraft is now about 1400 hours.  The reported ratio among the respondent population between a complete engine failure (i.e. total power loss) and NTSB accidents has widened to about 6:1, the ratio of partial power losses to NTSB accidents has also widened a bit to a little over 8:1.  A lot of the partial (and complete) engine failures are from carb ice, though the number of mechanical problems (swollowed valves, cracked cylinders, mag issues) continues to dominate the narratives.  Several pilots reported experiencing engine failures very early in their flying... within the first 100 hours or less.

If you haven't contributed to the survey, please invest 5 minutes and share your experience.  FWIW, there's a clock that tracks actual time in the survey --It really is only 5 minutes... :D.

DRW

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #8 on: January 26, 2015, 12:15:07 PM »
...If you haven't contributed to the survey, please invest 5 minutes and share your experience.  FWIW, there's a clock that tracks actual time in the survey --It really is only 5 minutes... :D.

I did it in four   :D
Piloting 182 out of 3W7 (Electric City)
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Klaus

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #9 on: January 26, 2015, 01:20:43 PM »
  The survey doesn't work from my side of the accident equation. The A&P has a different perspective, many times the engine issues are preventable. Many times the operator was told to expect an engine problem if they don't do something to prevent it. "Preventive Maintenance" is not part of many Owner/Operator's vocabulary, they insist on fix it after it breaks maintenance.
  "I" as a mechanic and pilot, look at the details of the engine problem one at a time. A number of piston powered aircraft operated by commercial operators have over 15,000 hours with very few engine issues. The commercial operator is required to have a "Director of Maintenance", a mechanic that is responsible for preventing mechanical problems. The Piper Cherokee 6 and Cessna 207 are very highly used aircraft in Alaska, Africa and many other areas that lack roads. The combined number of hours flown between power failures on aircraft that practice the factories recommendations is huge (hundreds of thousands of hours between power irregularities). The engine manufacture probably possesses the statistics that you're looking for and they won't match the NTSB because the recommended preventative maintenance procedures are commonly ignored by the owner/operator of the equipment.

  Maybe this NBAA article will give you a better perspective of what's really happening in the aircraft accident world:
http://www.nbaa.org/ops/safety/stats/
Klaus Marx
Juneau, AK (PAJN) & East Wenatchee, WA (KEAT)

luvflyin

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #10 on: January 26, 2015, 01:49:58 PM »
Done.  Took less than 2 minutes.  All Zeros except for time.  Guess I've been lucky.  If I lose an engine now, I'll never take another survey about anything.  LOL
Mike G

baronet68

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #11 on: January 26, 2015, 07:45:29 PM »
Done.
- Michael
1946 Ercoupe N99089

HalfFullGlass

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #12 on: January 26, 2015, 10:52:09 PM »

Thanks to all who have shared your experience.

The survey link is sinking slowly down the thread.  Here it is again: https://www.surveymonkey.com/s/CCXT8XF

Papa Chuck

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #13 on: January 27, 2015, 01:43:18 PM »
Done! Happy to contribute.
Mark Ceccarelli
1978 Cessna 172N
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Stinson Pilot

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Re: Is an engine reliabilty really good, or is it a myth?
« Reply #14 on: January 27, 2015, 01:45:25 PM »
Done...
Flying is the Answer....What was the question?

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