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Prelim NTSB Report for Embry Riddle Arrow w/Structural Failure


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This is some scary stuff. Prelim accident report for the wing separation incident on April 4th.

https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20180404X13226&AKey=1&RType=HTML&IType=FA

An airplane manufactured in 2007 with metal fatigue on the spar, undetected at annual just 28 hours prior. Although, I don't know how extensive the 100 hour annuals are. Gives me a little bit if an unsettled feeling flying a 50-year old airframe...especially one that likes the yellow arc so much.

Edited by AlexLev
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The plane was an Arrow, so I’m guessing was used in a lot of instrument and commercial rating training. The pilot was already private and instrument rated. The other pilot was the DPE with 27,000 hours of experience. I doubt it was subjected to a lot of primary training and all that comes with it.

The plane had 7,900 on it since its manufacturing in 2007. That works out to a little over 700 hours per year, 60 hours per month, 15 a week, a little over 2 hours a day. Hopefully they will be able to determine what caused it to fail.


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10 minutes ago, Marauder said:

The plane was an Arrow, so I’m guessing was used in a lot of instrument and commercial rating training. The pilot was already private and instrument rated. The other pilot was the DPE with 27,000 hours of experience. I doubt it was subjected to a lot of primary training and all that comes with it.

The plane had 7,900 on it since its manufacturing in 2007. That works out to a little over 700 hours per year, 60 hours per month, 15 a week, a little over 2 hours a day. Hopefully they will be able to determine what caused it to fail.


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That's a lot of hours per year but many working planes do like that.  A local airline, Cape Air flies a fleet of C402's.  I was talking to the mechanics and if I remember correctly they are overhauling the engines on those things every 2 or 3 years with 2600hrs on them by then.  (Remember the TV show Wings?  That was them...) And they have been in service for years - I would guess they have somewhere like 25,000 to 50,000 hrs on them.  I have heard of DC3's with upwards of 250,000 hrs on them.  

A wing should not be falling off a piper at 7000 hrs unless something went terribly awry.

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That's a lot of hours per year but many working planes do like that.  A local airline, Cape Air flies a fleet of C402's.  I was talking to the mechanics and if I remember correctly they are overhauling the engines on those things every 2 or 3 years with 2600hrs on them by then.  (Remember the TV show Wings?  That was them...) And they have been in service for years - I would guess they have somewhere like 25,000 to 50,000 hrs on them.  I have heard of DC3's with upwards of 250,000 hrs on them.  
A wing should not be falling off a piper at 7000 hrs unless something went terribly awry.


I do remember Wings! Yeah, 7900 sounds like a lot from a typical GA perspective, especially in 11 years. But I have to believe there a number of other flight school planes that have many more hours on them.


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18 minutes ago, bluehighwayflyer said:

Do a search on trade a plane using total airframe time as a search criteria. There will be a boat load of hits on 7000 hour plus general aviation airframes.  I think that this was either caused by unreported or detected damage history or a manufacturing or materials (not design) defect.  Or possibly a faulty structural repair, but I doubt that at ERAU. 

Yeah, 7000 hours doesn't seem excessive IMO.  I think some underlying factor exacerbated the problem.  

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5 hours ago, Marauder said:

 


I do remember Wings! Yeah, 7900 sounds like a lot from a typical GA perspective, especially in 11 years. But I have to believe there a number of other flight school planes that have many more hours on them.


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One of the planes in the Cape Air fleet actually was THE airplane used in the tv show - and they have a special sticker on the side that says so. I have been in that very plane several times.

I remember when I was Mooney shopping maybe 10 years ago, I think there was an ex Embry Riddle M20J and It had something 10 or 11 thousand hours on it.

Before this Mooney, I owned N805ER, a 2003 Diamond DA40 that was a former Embry Riddle plane, and it had about 4000 hrs on it despite being so young.  But it was in fine shape.  Other than the seats looked like they had 4000 hours with of pilot butts sitting in them fidgeting for 4000 hrs.

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9 hours ago, rbridges said:

Yeah, 7000 hours doesn't seem excessive IMO.  I think some underlying factor exacerbated the problem.  

I am going to speculate, because this is the internet, that wing was removed in the past and/or damaged by a hard landing necessitating some other type of repair that was done improperly.

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Or it could have been a machining defect or the defect in assembly or maintenance induced failure. Highly loaded beams such as this, any stress riser such as a nick or a scratch, can cause failure of the part.  sometimes decades later.

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10 hours ago, David Herman said:

 

That’s just wild! How do both wings just fall off like that?!

That’s what happens with hand me down aircraft. 

“...The total cost of a CWB kit in 2011 was $6.7 million, including installation which takes about 10 months...”

 

 

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22 hours ago, Mark89114 said:

I am going to speculate, because this is the internet, that wing was removed in the past and/or damaged by a hard landing necessitating some other type of repair that was done improperly.

The fracture line is through the outer 2 bolt holes on the lower spar cap.  Where do you see evidence of a repair in the picture posted in the NTSB report?  The opposite spar cap shares the start of the same fracture according to the NTSB report.  I doubt the same exact damage or repair was made to both wings at the exact same location.

There is clearly more to the story.

Clarence

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On 4/18/2018 at 8:37 AM, aviatoreb said:

That's a lot of hours per year but many working planes do like that.  A local airline, Cape Air flies a fleet of C402's.  I was talking to the mechanics and if I remember correctly they are overhauling the engines on those things every 2 or 3 years with 2600hrs on them by then.  (Remember the TV show Wings?  That was them...) And they have been in service for years - I would guess they have somewhere like 25,000 to 50,000 hrs on them.  I have heard of DC3's with upwards of 250,000 hrs on them.  

A wing should not be falling off a piper at 7000 hrs unless something went terribly awry.

Lowell Mather (the mechanic) was played by Thomas Haden Church, or Tom Quesada as he went by in High School. He makes down to Harlingen every once in a while

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On 2018-04-18 at 6:37 AM, aviatoreb said:

That's a lot of hours per year but many working planes do like that.  A local airline, Cape Air flies a fleet of C402's.  I was talking to the mechanics and if I remember correctly they are overhauling the engines on those things every 2 or 3 years with 2600hrs on them by then.  (Remember the TV show Wings?  That was them...) And they have been in service for years - I would guess they have somewhere like 25,000 to 50,000 hrs on them.  I have heard of DC3's with upwards of 250,000 hrs on them.  

A wing should not be falling off a piper at 7000 hrs unless something went terribly awry.

A little overstated.  Highest time DC3 - 91,000 hours.  747 - around 135,000 hours.  I remember reading about Braniff's 747 spent 10 years of its first 12 in the air.

20,000 hour 172's and Cherokees are not unheard of.

7000 hours should not be an issue, but a lot can happen in that time.  Rather than making mundane statements about design flaws, I have no doubt this accident will be thoroughly unwrapped, and we will all learn from it.  IMO, Cessna has done a good thing with the SIDS inspections, and I can see similar inspections being applied to other manufacturers.

Aerodon

 

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5 hours ago, Aerodon said:

A little overstated.  Highest time DC3 - 91,000 hours.  747 - around 135,000 hours.  I remember reading about Braniff's 747 spent 10 years of its first 12 in the air.

20,000 hour 172's and Cherokees are not unheard of.

7000 hours should not be an issue, but a lot can happen in that time.  Rather than making mundane statements about design flaws, I have no doubt this accident will be thoroughly unwrapped, and we will all learn from it.  IMO, Cessna has done a good thing with the SIDS inspections, and I can see similar inspections being applied to other manufacturers.

Aerodon

 

I can imagine the FAA dusting off AD 87-08-08 on Piper wing spars and re applying it to some airframes.

Clarence

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23 minutes ago, M20Doc said:

I can imagine the FAA dusting off AD 87-08-08 on Piper wing spars and re applying it to some airframes.

Clarence

Didn't Piper issue a SB to install extra inspection holes on the Cherrokee wings?

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6 hours ago, Aerodon said:

A little overstated.  Highest time DC3 - 91,000 hours.  747 - around 135,000 hours.  I remember reading about Braniff's 747 spent 10 years of its first 12 in the air.

20,000 hour 172's and Cherokees are not unheard of.

7000 hours should not be an issue, but a lot can happen in that time.  Rather than making mundane statements about design flaws, I have no doubt this accident will be thoroughly unwrapped, and we will all learn from it.  IMO, Cessna has done a good thing with the SIDS inspections, and I can see similar inspections being applied to other manufacturers.

Aerodon

 

I can't point to any website without doing a good bit of work, but I once saw a documentary about the flying business in the Amazon.  Where they would always have a mechanic on board to trouble shoot a breaking airplane during flight since something was always going wrong.  And they would fly around with barrels of fuel inside the airplane and the mechanic had a ferry-like system of levers and so forth to switch the fuel flow between the various barrels.  It looked pretty precarious.  Anyway in that documentary I am pretty sure they mentioned 250,000 hrs. Those things fly continuously some of them, for like 70 years now.  So I believe it.  Also they said that a lot of the equipment they had a different standard of servicing - instead of replace on hours, or replace on inspection - they would replace on failure.  Including critical items - like engines!  Fly them til they fail and then fix it!  Heck you got two engines so whats the problem?  And they showed several DC3 carcasses they would over fly on their route...old crashes. 

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 I imagine more investigative insight will be forthcoming from the NTSB given the huge number of old or high time PA-28s out there. Without this insight, it remains to be seen whether or not the structural differences between the Mooney and Piper spar designs are relevant considerations. The irrational freak out urge before more substantive info is available might be hard to suppress for a Piper owner.  However the lack of precedent for this kind of failure on even the oldest vintage metal wing Mooneys leaves me less concerned at the moment.  When hitting bumps in the yellow arc in my '68 C, I'm also comforted by the realization that this structure was deemed worthy of raising Vno/Vne to 175mph/200mph in 1969 without any structural change.  

 

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I snapped this picture of a Cherokee 140 wing spar today.  It’s not really that difficult to inspect.  There are a few sealing foam blocks removed to make the inspection easier.

Clarence

19374BB4-8E09-45A9-B7DD-88E1505040CC.jpeg

Edited by M20Doc
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21 hours ago, Aerodon said:

A little overstated.  Highest time DC3 - 91,000 hours.  747 - around 135,000 hours.  I remember reading about Braniff's 747 spent 10 years of its first 12 in the air.

20,000 hour 172's and Cherokees are not unheard of.

7000 hours should not be an issue, but a lot can happen in that time.  Rather than making mundane statements about design flaws, I have no doubt this accident will be thoroughly unwrapped, and we will all learn from it.  IMO, Cessna has done a good thing with the SIDS inspections, and I can see similar inspections being applied to other manufacturers.

Aerodon

 

I flew the highest time 747-200 that ever existed, or maybe ever will exist, about 2 weeks before it went to the scrap yard. N748SA, (ex PH-BUH) had about 135-137,000 hours and ~26k cycles..... All the way across Africa and a couple thunderstorms.   My buddy Mark was the FE on the last flight, to the boneyard at Mojave. Over AZ, the old girl wasn't done yet, they took her up to FL450 (wrong way) and set off the clacker at .92 Mach.Still had some thrust left over.   It still made book speed and fuel flow...Then the long, slow, decent down to Mojave, and floated the landing, she wasnt done yet, , for one final stop.

http://opennav.com/forum/airchive/5200853

http://www.airliners.net/forum/viewtopic.php?t=1348429

IMG_3030.JPG

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14 minutes ago, jetdriven said:

I flew the highest time 747-200 that ever existed, or maybe ever will exist, about 2 weeks before it went to the scrap yard. N748SA, (ex PH-BUH) had about 135-137,000 hours and ~26k cycles..... All the way across Africa and a couple thunderstorms.   My buddy Mark was the FE on the last flight, to the boneyard at Mojave. Over AZ, the old girl wasn't done yet, they took her up to FL450 (wrong way) and set off the clacker at .92 Mach.Still had some thrust left over.   It still made book speed and fuel flow...Then the long, slow, decent down to Mojave, and floated the landing, she wasnt done yet, , for one final stop.

http://opennav.com/forum/airchive/5200853

http://www.airliners.net/forum/viewtopic.php?t=1348429

IMG_3030.JPG

Sort of a shame to drive that thing around empty.  To bad I couldn’t go - I bet it would still make w&b if I were on board.

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2 hours ago, Hyett6420 said:

I agree Clarence and a lot of the spculation ignores the fact that at the fracture point it was heavily corroded but not visible to inspection, which is more worrying. 

I dislike the speculation that forums bring out, give a person a keyboard and they feel obligated to type on subjects they have little experience.  

I posted pictures of a Cherokee spar in my shop yesterday it tooks a few minutes to expose it for inspection.  The level of inspection required is the question.

In the picture on the NTSB report you can see the beach marks which show the progression of the crack.  

“Beach marks are macroscopic progression marks on a fatigue fracture or stress-corrosion cracking (SCC) surface that indicate successive positions of the advancing crack front. They take the form of crescent-shaped macroscopic marks on fatigue fractures representing positions of the crack propagation, radiating outward from one or more origins.

Beach marks are also known as clamshell marks, arrest marks or growth rings”

Clarence

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