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Why One Engine Fails Before The Others?  
User currently offlineJAM747 From United States of America, joined Feb 2005, 550 posts, RR: 1
Posted (9 years 5 months 2 hours ago) and read 3358 times:

If all the engines on an airliner have the same hours and flew in the same conditions why does one fail before the others? Sometimes the remaining engines can fly for many more hours. I hope this is not a silly question

17 replies: All unread, jump to last
 
User currently offlineOly720man From United Kingdom, joined May 2004, 6688 posts, RR: 11
Reply 1, posted (9 years 5 months 2 hours ago) and read 3337 times:

Depends what fails. There are many components in an engine and they are not absolutely identical. One engine might run slightly hotter than another, or vibrate slightly more than another and after a period of time it will cause a component failure.


wheat and dairy can screw up your brain
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 2, posted (9 years 5 months 1 hour ago) and read 3313 times:

A good position to start thinking about it: Why won't two matches thrown in a rapid river together end up in anywhere near the same spot?


I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineLeanOfPeak From United States of America, joined Oct 2004, 509 posts, RR: 1
Reply 3, posted (9 years 5 months 1 hour ago) and read 3309 times:

Frankly, identical is a myth.

In design, you have a bell curve that defines probabilities of failures, with a point at which the part is most likely to fail and the odds tapering off from that point of the part failing before then or lasting past that point. This variability is due to manufacturing tolerances, material imperfections, etc. The acceptable risk of failure varies with how critical the part is, but when that threshold is reached, the part is replaced or refurbished.

The parts are replaced or refurbished when the odds of failure are so infinitesimal that the odds of having two simultaneous failures are practically immeasurable.


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 4, posted (9 years 4 months 4 weeks 1 day 23 hours ago) and read 3241 times:

For the best answer read "The One Horse Shay" by Oliver Wendell Holmes.

Here http://www.readbookonline.net/readOnLine/1157/



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineRedFlyer From United States of America, joined Feb 2005, 4315 posts, RR: 28
Reply 5, posted (9 years 4 months 4 weeks 1 day 20 hours ago) and read 3188 times:

Another good analysis would be the UA DC-10 flight back in July '89 that had a catostrophic failure in Engine #2 (tail) and lost all hydraulic pressure, which disabled the control surfaces causing the plane to make a crash landing in Sioux City, Iowa.

I read in the NTSB report at the time that the engine had a failure because the fan-disk core (which was recovered in a corn field months afterward) had a tiny, hairline crack in it that had resulted during the manufacturing process. That engine and core had been in service since their original date of manufacture back in 1971. It's been a while, but I don't recall hearing about any other fans from the same manufacturing batch having the same problem.

So, since the production methods were identical, why did one engine end up with the crack while the others in the production batch didn't?

Now, I'm sure someone will elaborate on this incident further so, just to cover my bases ahead of time, if other engines from the same production batch did end up having the same manufacturing defect, the next logical question would be why did this particular engine fail first? Was it perhaps because it had the most hours in service?



I'm not a racist...I hate Biden, too.
User currently offlineCitationJet From United States of America, joined Mar 2003, 2425 posts, RR: 3
Reply 6, posted (9 years 4 months 4 weeks 1 day 20 hours ago) and read 3148 times:

In a light fixture in your house that has two identical light bulbs, both installed new. Many months later one burns out, yet the other one continues to burn much longer. Both have seen the same service, but have different lives. Would you be surprised that one burns out earlier than the other?


Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
User currently offlineBackfire From Germany, joined Oct 2006, 0 posts, RR: 0
Reply 7, posted (9 years 4 months 4 weeks 1 day 20 hours ago) and read 3140 times:

Scientists call it chaos theory.

Two situations which are apparently the same to the eye will inevitably differ at the microscopic level. As you look closer and closer you will find more and more differences between the two, and these minute differences will gradually cause differences at the observable level.

This ability for almost-undetectable differences in starting conditions to affect outcomes in the everyday world is also known as the 'butterfly effect'.

The theory is that tiny air currents produced when a butterfly flaps its wings are enough to completely change the way in which a weather system develops - so the weather in the USA really can depend on whether a butterfly is airborne in Hong Kong...


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 8, posted (9 years 4 months 4 weeks 1 day 10 hours ago) and read 3033 times:

Or, paraphrasing Terry Pratchett: If all the weather here is caused by a butterfly flapping its wings in the Amazonas, isn't it about bl**dy time someone finds that butterfly and makes sure it stops flapping? Big grin


I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineJfkaua From United States of America, joined Aug 2004, 1000 posts, RR: 3
Reply 9, posted (9 years 4 months 4 weeks 17 hours ago) and read 2925 times:

now why the hell would you sensor the word bloody? lol

User currently offlineNewark777 From United States of America, joined Dec 2004, 9348 posts, RR: 30
Reply 10, posted (9 years 4 months 4 weeks 15 hours ago) and read 2899 times:

This has turned into a very deep conversation, and it started with a simple engine failure. Big grin

Harry



Why grab a Heine when you can grab a Busch?
User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 11, posted (9 years 4 months 4 weeks 7 hours ago) and read 2840 times:

Jfkaua,
to avoid upsetting oversensitive Americans. It's your b****y fault!  Wink

Seriously tongue-in-cheek,
/Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 12, posted (9 years 4 months 4 weeks 6 hours ago) and read 2816 times:

Quoting Backfire (reply 7):
Two situations which are apparently the same to the eye will inevitably differ at the microscopic level. As you look closer and closer you will find more and more differences between the two, and these minute differences will gradually cause differences at the observable level.


Well & Simply put Big grinD
regds
MEL



Think of the brighter side!
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 13, posted (9 years 4 months 4 weeks 6 hours ago) and read 2817 times:

Quoting Backfire (reply 7):
Two situations which are apparently the same to the eye will inevitably differ at the microscopic level. As you look closer and closer you will find more and more differences between the two, and these minute differences will gradually cause differences at the observable level.


Well & Simply put  goldmedal 
regds
MEL



Think of the brighter side!
User currently offlineCaptjetblast From Argentina, joined Aug 2001, 281 posts, RR: 0
Reply 14, posted (9 years 4 months 3 weeks 1 day 22 hours ago) and read 2668 times:

"If all the engines on an airliner have the same hours and flew in the same conditions why does one fail before the others?"

This tends to be untrue as time passes, as some engines are replaced and maybe others not. So it is not uncommon to find an aircraft with its engines having different running hours.


User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 15, posted (9 years 4 months 3 weeks 1 day 20 hours ago) and read 2634 times:

Most of the engine failures I've seen on modern airliners are the result of poor maintenance. Maintenance is the variable.

The design of airplanes including the engine are pretty conservative and forgiving. However, you never have just one person doing the servicing on the airplane and/or engine.

All it takes is a single mistake during servicing to cause accelerated wear or a condition couducive to failure.

So the chances of an engine failing increases a great deal the first time the cowls are cracked....


User currently offlineA/c train From United Kingdom, joined Jun 2001, 501 posts, RR: 4
Reply 16, posted (9 years 4 months 3 weeks 1 day 20 hours ago) and read 2625 times:

I'd agree with Airplays experience entirely there, the odd few now and then are manufacturing defects which end up in warranty claims, but classic things such as wiring looms chafing on pipes/ducts are a result of poor mx, whn the a/c was delivered there was adequate clearance between duct and loom, when the pipe was changed, the p-clip was undone, someone drops a stand off and loses it, doesnt replace it and the clearance gone, 50 cycles later and a load of vibration, you get an IFSD.
I give an example, new a/c off the production line 2 engines "zero hours in service", first flight, left engine has 1.9 CTA (Switzerland)">BB vib, the right has 0.2, the bearings, pipes, labyrinth seals etc etc are all given a good shaking and wear begins too occur quicker, small seeps from seals = more engine oil uplifts, engine begins too run hotter and burns a little more oil. Fan trim balance carried out and Vib gone.
The left engine is coming off wing earlier than the right. But the same may happen too the left, it could all come down too a filler seal not seated correctly !!
its a 'how longs a piece of string' question, but I agree with maintenance being the variable.
regds a/c
p.s, cant get rid of the CTA swiss thing so ignore !


User currently offlineFlyabunch From United States of America, joined Nov 2004, 517 posts, RR: 4
Reply 17, posted (9 years 4 months 3 weeks 1 day 18 hours ago) and read 2614 times:

Why do two identical automobiles have different lives? In the real world, there is no such thing as identical.

If you look at the complexity of a modern jet engine, it is absolutely remarkable that they are as dependable as they are. I salute those who keep them flying. You are the true heroes of aviation to me.

Thanks,

Mike


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