Preliminary results of the ERAU PA-28 accident

Wow. In a weird way it makes you miss reading the reports of pilot error.
 
The fractured left wing main spar portions, along with the box assembly and attached inboard end of the right wing main spar, were forwarded to the NTSB Materials Laboratory for detailed examination. Preliminary examination of the left wing main spar revealed that more than 80% of the lower spar cap and portions of the forward and aft spar web doublers exhibited fracture features consistent with metal fatigue (see figure 1).
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uN9W8vb.jpg


:(:(:(
 
Manufactured in 2007 and has ~7700 hours on the airframe. Not very old by comparison to the rest of the fleet. Scary.

"Fractures consistent with over stress" Wow.
 
Think ER is in deep dodo!

I do not miss this one not being blamed on pilot error. As I write this KORL is shut down due to a collapsed (or ??) landing gear! And we still need the report on the KA90 that crashed into Lake Harney near KSFB from December. Think that one will come under PE.
 
So 7700 hours of bounced landings attributed to the failure?
 
jsstevens said:
Manufactured in 2007 and has ~7700 hours on the airframe. Not very old by comparison to the rest of the fleet. Scary.

"Fractures consistent with over stress" Wow.
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No, not scary, derelict. The pictures tell the tale. Both pre-existing fatigue cracks AND overstress fractures on the lower spar cap and attachment doubler on the outer spar. These aircraft are beyond abused and everybody is looking the other way at ERAU.

ERAU has an internal policy of pulling wings at 10K. They're dismantling another Arrow at 9K (early to them) to go hunting for a trend. They're basically trying to see if dye penetrant inspection can be instituted as a AMOC since the alternative (active pulling of the wings) would about kill the private and training PA-28 market (I certainly wouldn't undergo the expense, I'd just salvage the thing). The way that part 23 certifies airplanes, OEMs have the choice of an inspection program or a set life limit. This is why the seminole has a life limit of 12,633, then it turns into a pumpkin magically; Piper didn't want to go the inspection route with it. $ talks.

There is a provision as part of the service manual for the PA-28s that call for usage categories to be determined and depending on that category, an inspection of the spar structure. At any rate, what's interesting is that under that provision, the PA-28 wing doesn't call for inspection until circa 62,000 hours. You read that right. And to be frank, as an Arrow owner who flies with family on board, I'm comfortable with that. What's interesting here is that the provision allows for "normal flight training" to be considered under that "normal" usage category. I think that is a problem. ERAU is nowhere near a normal usage category operation. In addition to that, the provision dictates much lower inspection intervals for prior damaged aircraft, which this one factually was. The pictures are clear as day that thing was over-G, and had cracks in the lower bolts that were allowed to propagate to a degree even visual inspection would have uncovered it, which is why I think ERAU is in deep doo doo.

Here's the text I grabbed from the piper forum
"(9) WING SPAR INSPECTION.
WARNING: FAILURE TO FULLY COMPLY WITH THIS INSPECTION COULD
SERIOUSLY AFFECT THE STRUCTURAL INTEGRITY; SAFETY AND
AIRWORTHINESS OF THE AIRCRAFT.
(a) Background
On March 30, 1987, a PA-28 engaged in pipeline patrol operations suffered an inflight
wing separation resulting in a fatal accident. Investigation revealed the wing failure was
due to propagation of a fatigue crack, which originated in the wing lower main spar cap.
Based on more than five hundred (500) inspections of PA-28 and PA-32 airplanes with
more than 5000 hours total time-in-service, and extensive wing fatigue and fracture
analysis by Piper, the following inspection requirements have been developed.
NOTE: In the course of the inspections cited above, only two (2) negative findings were
reported on a pair of PA-32’s operating in a severe environment and with
considerable damage histories. Piper understands that the majority of aircraft are,
have been, and will continue to be operated well within the aircraft’s design
parameters during all of their operational life. HOWEVER, Piper also realizes
that some small number of aircraft engage in operations which are defined herein
as “severe” or “extreme” and those airplanes will require more frequent wing
removal and inspection.
(b) Procedure
First, determine the airplane’s “usage class”; second, determine the recurring inspection
intervals; and, third, when required, accomplishing the wing spar inspection.
1 Determining Usage Class
NOTE: Airplane operating history and usage class are established during initial
compliance with Piper Service Bulletin No. 886, check the logbook entry.
Complete documentation and/or knowledge of the airplane’s entire operating history
is required in order to make a valid determination of “Usage Class” and inspection
intervals.
a Usage Class “A” - Normal
All aircraft which do not and have nor engaged in operations considered as
“Severe,” “Extreme,” or “Unknown” in the Usage Classes described below.
Most aircraft will fall into this “Usage Class.” Normal flight training operations
fall into this class as well.
NOTE: If there is any doubt as to the airplane’s operating history, it is
recommended that the initial inspection be conducted in accordance
with the “Next 50 Hours” inspection requirement, below.

b Usage Class “B” - Severe
Aircraft which have engaged in severe usage, involving contour or terrain
following operations, (such as power/pipeline patrol, fish/game spotting, aerial
application, aerial-advertising, police patrol, livestock management or other
activities) where a significant part of the total flight time has been spent below
one-thousand (1000) feet AGL altitude.
NOTE: Aircraft with part of total time-in-service in Usage Class “B”
operations and part in Usage Class “A”, may adjust inspection intervals
by a “Factored Service Hours” calculation. See “Factored Service
Hours,” below.
c Usage Class “C” - Extreme
Aircraft which have been damaged due to operations from extremely rough
runways, flight in extreme damaging turbulence or other accident/incident
which required major repair or replacement of wing(s), landing gear or engine
mount.
d Usage Class “D” - Unknown
Aircraft and/or wings of unknown or undetermined operational or maintenance
history.
e Factored Service Time
NOTE: This formula applies only to airplanes in Usage Class “B” - Severe. It
may be used to calculate the initial and repetitive inspection times in
factored hours, provided a portion of the airplane’s operating time-inservice has been in Usage Class “A” - Normal.
2 Inspection Requirements.
a Next 50 Hours:
For airplanes in “Usage Class D” (i.e. - unknown usage), conduct Wing
Spar Inspection and establish usage class for next inspection based on
current aircraft operations.
b Each 800 Hours:
In PA-28-235’s only, for airplanes in “Usage Class B” (i.e. - severe usage),
beginning at 1,800 hours total time-in-service, and each 800 hours
thereafter, conduct Wing Spar Inspection.
In PA-28-235’s only, for airplanes in “Usage Class C” (i.e. - extreme
usage), conduct Wing Spar Inspection, each 800 hours time-in-service.
c Each 1600 Hours:
In PA-28-140/150/160/180’s and PA-28R-180/200’s, for airplanes in
“Usage Class B” (i.e. - severe usage), beginning at 3700 hours total timein-service, and each 1600 hours thereafter, conduct Wing Spar Inspection.
In PA-28-140/150/160/180’s and PA-28R-180/200’s, for airplanes in
“Usage Class C” (i.e. - extreme usage), conduct Wing Spar Inspection,
each 1600 hours time-in-service.
d Each 3000 Hours:
In PA-28-235’s only, for airplanes in “Usage Class A” (i.e. - normal usage),
beginning at 30,600 hours total time-in-service, and each 3000 hours
thereafter, conduct Wing Spar Inspection.
e Each 6000 Hours:
In PA-28-140/150/160/180’s and PA-28R-180/200’s, for airplanes in
“Usage Class A” (i.e. - normal usage), beginning at 62,900 hours total
time-in-service, and each 6000 hours thereafter, conduct Wing Spar
Inspection."
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According to the discussion on the Piper Board, ERAU is scrambling to strike a deal with the FAA. This can get ugly money wise for them if they don't act proactively in establishing an inspection schedule that is to the satisfaction of the FAA. I own an Arrow with prior damage history and 0ver 5000 hours, and I fly without fear. And I'm also telling you no effing way I get on an ERAU airplane as a student at this point until they publicize an inspection methodology that addresses and admits to the fact that flight training environment is not anywhere near in the vicinity that of private use. That's what I need to hear from ERAU. Anything less and no way I get on a tail of theirs if I was a student. PLenty of other outfits whose airplanes see much less abuse, even in a training environment and even with less mx support. That's how strongly I feel about ERAUs dereliction on this one.
 
What does this mean for the many many many 10,000+ hr Cherokees at many other schools and clubs? When I first started flying aging old derelict Cherokees I got worried about their wings, but I've read that these things are routinely flown into the 20,000 and 30,000 segments.. https://www.pprune.org/archive/index.php/t-534863.html

Sure, Cessna wings seem safer because they're braced with the struts, but you also have two more potential failure points.. then again, I don't think I've ever heard of a 172 losing its wings

So.. what does it all mean?

Also makes me appreciate the Cessna, Cirrus, Grumman Cheetah, etc., landing gears than don't directly punch right into the wing strut

I love low wings, but damn. this sucks.
 
hindsight2020 said:
PA-28 wing doesn't call for inspection until circa 62,000 hours
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I remember reading that too, and it made me feel better originally "hey this plane only has 12,000 hrs, cool! It is only 19% through its life" - but I mean, this does make me question two things:

A.) how seriously are the ERAU planes abused? And if they're getting that seriously abused to cause a wing to break barely 10% through its life, then why is that? Maybe because I trained with CFIs who owned their planes, but in my training I don't recall ever "abusing" an airplane. Va and non-bouncy landings were well respected

B.) 7,700 vs 62,000 is a major difference. Even if "training" is not a normal category usage, that's like 12% of its actual alleged lifespan.. something doesn't add up. Either this plane/ERAU has some real issues beating their planes to death.. or, the calculations that Piper engineers did back in the 1960s (presumably that's still the foundation) need to be revisited

I always thought it would be interesting to have a lab, maybe someone like UL, etc., disassemble an aging plane (but still technically within its lifespan) and check out its overall condition, and even stress one to failure and see how it stacks up against textbook numbers
 
Tantalum said:
I remember reading that too, and it made me feel better originally "hey this plane only has 12,000 hrs, cool! It is only 19% through its life" - but I mean, this does make me question two things:

A.) how seriously are the ERAU planes abused? And if they're getting that seriously abused to cause a wing to break barely 10% through its life, then why is that? Maybe because I trained with CFIs who owned their planes, but in my training I don't recall ever "abusing" an airplane. Va and non-bouncy landings were well respected

B.) 7,700 vs 62,000 is a major difference. Even if "training" is not a normal category usage, that's like 12% of its actual alleged lifespan.. something doesn't add up. Either this plane/ERAU has some real issues beating their planes to death.. or, the calculations that Piper engineers did back in the 1960s (presumably that's still the foundation) need to be revisited

I always thought it would be interesting to have a lab, maybe someone like UL, etc., disassemble an aging plane (but still technically within its lifespan) and check out its overall condition, and even stress one to failure and see how it stacks up against textbook numbers
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Disbelieve all you want, ERAU airplanes are flown round the clock and abused with impunity. For the benefit of the untrained eye in aircraft structures fatigue, that spar had both classic crack propagation to the degree it was 80 pct through when it ultimate failed, and it also had striations congruent with prior overload (over g). so its not conjecture, the spar reads like a journal of what that airplane went through and it is NOT normal piston aircraft use.

As to your assertions regarding the engineers getting the fatigue life number wrong, you need to understand how these numbers come about. this isnt the forum to post a lecture on fatigue crack propagation, but as someone whose MSAE concentration and capstone defence is structural fatigue and aging aircraft structures, i can tell you the calculations make several assumptions, and over g is not one of them. once you overstress the structure, you effectively reset the delta k, and that fatigue cycle number becomes garbage. The point is that it's on ERAU to inspect the things in accordance with how they re being used, and they didnt. they hide behind the rules to behave as though the use these cans see is nominal, and it cost two people their lives in the interest of saving money.

whats worse, look in here and this is already spreading panic that all pa 28 owners are gonna get told to wear diapers because of ERAUs dereliction. Considering the manner in which other overzealous ADs have been fieleded (the non suffix prop hub 100 hour inspection, the beech lower spar carry through inspection extnended to the lighter models, et al) i suppose it wouldn't be unheard of to see an ad for the pa 28 regarding this. i fly an arrow with 7k and prior wing damage repair, and im not losing any sleep over it. if they kill the airframe by some onerous wing pulling ad or a seriously repetitive and expensive recurring, ill just sell off the thing and do something else with my time and money. But one thing i do know, this has nothing to do with the design of that spar. And i put my money where my mouth is, as someone who flies my most precious life possessions in an arrow with remarkable frequency. i dont have much need for the panic and fear mongering.
 
I just about crapped when I read this report, even though anyone following this story was pretty well expecting something along these lines. The fact that the OTHER spar was already fractured and starting to propagate is the real eye opener. There were reports (no source) that this particular plane had been in the shop recently due to a hard landing. I wonder if there were in fact more than one of those, enough to cause this issue some time ago.

I wonder if the FAA lab will be able to determine how long ago this may have started, and more importantly I wonder what else they will find on all the rest of ER's PA-28's.

This was my exact "worst nightmare" when doing my initial training. Absolutely nothing you can do as you auger into the ground from 1000'. Hell I was worried with the few losses of elevator control reported by fractured yoke/arm connection I read about. But at least that you can (probably) survive by flying with the trim.

Question for the A&P's on here: How big a job is it to do this sort of inspection (the right way)? Like actually pull the wings and do a dye penetration test on the spar caps. Might be something I'd consider for a new purchase.
 
And the Arrow is usually not considered a primary trainer. Trainer, yes, but usually used in the complex training portion. Makes one wonder. I was surprised no corrosion was found considering the area these planes fly. Maybe they were keeping up with that and not paying enough attention to stress. Sad. Two people lost their lives due to negligence.
 
Cherokees have been plying the skies since the 60s without this sort of incident. And many, if not most, started out as primary trainers or served that role for a time. I can't imagine what they put that poor airplane through.
 
So question for those much more familiar with the inards of PA-28s than me - can the spars be inspected without removing the wings? Or is this a "take the airplane down and do major surgery" kind of inspection?
 
Something unusual happened to this airplane. Someone made an awful landing, badly dished a roll and pulled lots of G's, or something else. That, ultimately is the causal factor.

And there's probably a guy sitting left seat in a RJ today who's thinking "I wonder..."
 
hindsight2020 said:
Disbelieve all you want, ERAU airplanes are flown round the clock and abused with impunity
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Why are they abused so heavily? I'm not disbelieving the figures, but 7,700 vs 62,000 is a massive difference. I'll keep flying the Archers in our club, sure and not turn into a nervous wreck, but either that plane lived a horrific life, or the 62,000 figure assumes the plane is flying in a straight line in smooth air at 90 knots. Chances are the engineers are correct, and the thousands of PA28 out there are proof of that.. so that just leaves ERAU then.. how did they establish a culture of treating their planes so poorly. Don't their CFIs teach respect for Va, load limits, go around if a landing looks like crap, etc. The whole thing just stinks. Perhaps it was the alleged hard landing the day before, but then how hard did that plane have to land to nearly break both wings off, and how crappy was their maintenance that it missed the cracks??

jbrinker said:
The fact that the OTHER spar was already fractured and starting to propagate is the real eye opener
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Yeah. I mean, to get even a remotely significant statistical sampling they'd need to take apart more than just one other ERAU plane, closer to at least 30. If they pulled the wings off 30 of their Arrows I wonder what it would show. AND, if it really is that common at ERAU to beat the snot out of their planes then it may be smart to check the rest of their fleet as well

jbrinker said:
This was my exact "worst nightmare" when doing my initial training. Absolutely nothing you can do as you auger into the ground
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Seriously. Scary stuff here. I know "real pilots" don't need no stinkin parachute, but the more I fly the Cirrus the more I love having it
 
jbrinker said:
I just about crapped when I read this report, even though anyone following this story was pretty well expecting something along these lines. The fact that the OTHER spar was already fractured and starting to propagate is the real eye opener. There were reports (no source) that this particular plane had been in the shop recently due to a hard landing. I wonder if there were in fact more than one of those, enough to cause this issue some time ago.
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The language in the FAA report indicated that the cracks were predominately fatigue and not overstress. Fatigue would be the result of hundreds of hard landings over the aircraft's 7,600hr life. Overstress would be more like a single event.
 
kyleb said:
Something unusual happened to this airplane. Someone made an awful landing, badly dished a roll and pulled lots of G's, or something else. That, ultimately is the causal factor.
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and therein lies the core of the issue, was it a freak incident where someone seriously botching a landing or someone pulling a stunt, or is this kind of thing "common" at ERAU. I mean, if you want to tool around in the air, find a freaking Aerobat, Citabria, Great Lakes, something other than an ARROW!
 
Somebody knows what happened but the chance of ever finding that person is virtually nil. More than likely this was something that had been progressing for awhile before fatigue finally won. May or may not have been any single person who caused it from the get-go, but rather a cumulative effect.
 
The other idea that needs to be addressed is that of landing cycles, and the frequency of stressful maneuvers. Most private pilots do not regularly put their planes through slow flight, chandels, high bank turns, repeated landings, etc. A plane being used for training is by necessity, undergoes multiple times more landings etc., then a private owner who tanks off, goes more or less straight and level, is in the air for several hours, and then lands.

This basic air frame has been used for around 50 years at this point, and this type of failure has proven to be rare. People here are talking about this event, and a very small handful of other events (2 or 3 I think I have seen). There is going to be a AD on this, anyone that thinks otherwise is likely kidding themselves. It will likely be similar to the most recent one requiring inspection of the spar and possibly the installation of a new access point if the area is not readily visible.

ERAU is going to be the group that is most likely to take a hit on this. That plane was just inspected 28 hrs before the accident, and had a history of at least one if not more noted hard landings. At a school how hard is a hard landing before it gets noted as a hard landing? If that potion of the spar is relatively easy to inspect, and as noted was 80% damaged prior to failure, I would guess that some type of damage should have been visable. Granted that type of damage would likely have raised some red flags and possibly led to an AD regardless. but at least 2 lives may have been saved.
 
Ryanb said:
More than likely this was something that had been progressing for awhile before fatigue finally won. May or may not have been any single person who caused it from the get-go, but rather a cumulative effect.
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This is what I gathered from reading the prelim report. The full analysis will give a more detailed picture.
 
Video of an ERAU Cessna landing:

 
I'm glad it happened right after takeoff and not at 6500 feet or something where they would have at least a minute to contemplate what's happening...
 
kyleb said:
Something unusual happened to this airplane. Someone made an awful landing, badly dished a roll and pulled lots of G's, or something else. That, ultimately is the causal factor.

And there's probably a guy sitting left seat in a RJ today who's thinking "I wonder..."
Click to expand...

I'm wondering if it is more of a sign of a repeated behavior by students and/or their instructors. Repeatedly maneuvering above Va perhaps?

I have no knowledge of ERAU practices or their students but I know people who have graduated from two other collegiate flight schools. Some of the stories I've heard of what the students did to airplanes and some of the procedures would make you shudder.
 
The other thing I noted in the article is the student was at 201 hrs, and going for his commercial rating (obviously the student is not at fault), but how fast do these types of flight schools push pilots through. I know the national average to get a PPL is abound 65 hours, but I would imagine at schools like this they attempt to get people though faster. Does this rate of training, not only push the student harder but also the planes?
 
drotto said:
The other thing I noted in the article is the student was at 201 hrs, and going for his commercial rating (obviously the student is not at fault)...
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I wouldn't go that far, I watched a Indian student prang the heck out of a 172, coming in for landing on short final I could tell this was going to be good, walked out and he must have been pumping the heck out of that yoke, after a few major hits it went off the edge of the runway nearly flipped but settled back on its gear.

I ran over and the guy was OK, asked if he wanted to use my phone to call his instructor, he said he just got his CPL! and was using the last bit of the hours he had in his "program".

I'd imagine he's flying a B737 or A320 back home now.


Puppy mills gonna puppy mill





I'd also be interested in the manufacturing differences between Piper and the New Piper company, seem the older pipers took a good amount of abuse without falling apart.
 
drotto said:
The other thing I noted in the article is the student was at 201 hrs, and going for his commercial rating (obviously the student is not at fault), but how fast do these types of flight schools push pilots through. I know the national average to get a PPL is abound 65 hours, but I would imagine at schools like this they attempt to get people though faster. Does this rate of training, not only push the student harder but also the planes?
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I went to an accelerated training flight school. That school wanted to get everyone through the separate courses with the minimum hours required, but if a person took longer, then they would take the time necessary to get that person up to standards. No one was "pencil whipped" through training to get them out the door quicker. Especially me. How ever there were several students that had hundreds of hours at the controls of their dads plane. Some of those guys went through private pretty quickly as the met standards. I had never been in a small plane before my first lesson.

ERAU charges by the hour, or at least did when I talked to them 26 years ago. If they were only interested in money than it seems they would take longer to train someone to up the income instead of pushing some one through.
 
Tantalum said:
Seriously. Scary stuff here. I know "real pilots" don't need no stinkin parachute, but the more I fly the Cirrus the more I love having it
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Chute is awesome but please train for its use and be decisive. N28GX had a chute, spun in from about 500-700 ft. Had time to deploy but didn't.
 
F01LA said:
Video of an ERAU Cessna landing:

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That’s fairly tame for the primary training environment but it is the beginning of how pilots bend firewalls in 182s. Definitely not spar cracking in a Skyhawk but done enough over a long period of time, not great.

That pilot was already fast and then dove to hit a landing spot in a spot landing practice or competition judging by the cones there on the runway. There’s collegiate level competitions between schools and the spot landing is one of the events. Then the pilot kept trying to force the airplane that was still flying back down onto the runway.

But yes. This is the sort of “normal abuse” these flight school aircraft see fairly regularly. To bust a spar on a PA28 the overstress and abuse had to have been higher than something like this at least once, and then progressed, perhaps from stuff like this, and also wasn’t caught on any inspections to have “old cracks” for lack of a better term, in the spar box area.

CFIs know some abuse is going to happen and try to mitigate it as students learn but a couple of bounces in a Skyhawk is pretty common. Driving the nosewheel into the ground while still flying is a serious technique problem that MUST be addressed and stopped if a pilot is doing that, though. That’ll break things up front sooner than it’ll break the wings off.
 
F01LA said:
Video of an ERAU Cessna landing:

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That could have been saved by just a little back pressure on the yoke, level off, and land. As James mentioned, porpoising is caused by the pilot yanking the yoke back and forth, usually after landing nose wheel first.
 
Zeldman said:
That could have been saved by just a little back pressure on the yoke, level off, and land. As James mentioned, porpoising is caused by the pilot yanking the yoke back and forth, usually after landing nose wheel first.
Click to expand...

Yup. Just pull and wait. Let the mains take the load. Sigh. I’m sure that collegiate student’s instructor saw that video and slapped their head and realized that they need to go work with the pilot some more. Go around or pull and wait. All depends on airspeed.

Move em up to a 182 or any number of be heavier Cessna singles and you bark real loud about forcing it on because they’ll easily do $10K in firewall damage where the nosewheel assembly is attached to the flat aluminum there.

Wrinkles, rip the assembly off the plate, all sorts of badness happens when landing Cessnas on nosewheels while driving downward with the entire weight of the aircraft plus aerodynamic downward force.
 
Zeldman said:
That could have been saved by just a little back pressure on the yoke, level off, and land. As James mentioned, porpoising is caused by the pilot yanking the yoke back and forth, usually after landing nose wheel first.
Click to expand...

"Good god man, it's a yoke not a shake weight" lol

HApAqWd.gif



But yeah, just crap fundamentals.
 
C-1 PILOT said:
On another note, my Hats Off to the NTSB on this. Never have I seen a preliminary report, so extensive and with in a week of the accident. Good work...
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Yep. But I'm also sure that there was pressure to get something preliminary as quickly as possible. Count me among those that would not be surprised to see an AD.
 
If I was ERAU I would have G-Meters in the airplanes that could not be reset except by the A&P at inspection. I realize that doesn't tell the whole story. I could certainly envision a bunch of college kids who are into flying treating a rental like a rental and trying a roll, loop or who knows what. Easy enough to mess up pull a crap ton of Gs and walk away that time but leaving the next guy to pay the bill. :(
 
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