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Sampling Light Aircraft Crashes

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BrianW

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I took a look at an NTSC database of accidents. I sampled fourteen months of light aircraft 2007-2008
1 Champion
3 Cirrus SR22
1 Piet Aircamper
1 RV6
2 RV7A
2 RV8
1 Sonex
1 Sorrel SNJ7

I did not check the investigated source, instead supposing that most crashes are related to
pilot error - some after engine difficulty; I wanted a sense of the difficulty of reviewing airframe failure
due to pop rivet fatigue, composite fractures, glue line failures , plastic matrix failures.
Oh yes: getting good data on that topic is not easy!
 

12notes

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I took a look at an NTSC database of accidents. I sampled fourteen months of light aircraft 2007-2008
1 Champion
3 Cirrus SR22
1 Piet Aircamper
1 RV6
2 RV7A
2 RV8
1 Sonex
1 Sorrel SNJ7

I did not check the investigated source, instead supposing that most crashes are related to
pilot error - some after engine difficulty; I wanted a sense of the difficulty of reviewing airframe failure
due to pop rivet fatigue, composite fractures, glue line failures , plastic matrix failures.
Oh yes: getting good data on that topic is not easy!
Since that's only 12 aircraft, I'd just look at the individual NTSB reports on each accident for that type of information. They're linked on the actual database results page, it's the second column. The "good data" on this particular topic is trivially easy to get.

Not sure which 14 months you looked at, here's 1/1/07-3/1/08, there were 2106 accidents in that time period:

 

Wanttaja

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I would just ask Ron W.
Y'know, my ears WERE burning when I got up this morning.

The leading cause of both homebuilt and production-aircraft accidents is what I call "Pilot Miscontrol." These are cases where faulty pilot technique...not judgement or mechanical failure...were the main cause of the accident. Here's a comparison of what percentage of accidents is due to Pilot Miscontrol.
pilot miscontrol.JPG
One thing to be very, VERY aware of is the relative pilot experience. You can see the median pilot total time for each category. Although the fixed-wing homebuilts saw only 38% of their accidents due to pilot miscontrol, vs. 60% of the Cessna 172s, you can not assume that homebuilts are easier to fly! Rather, note that the homebuilt pilots involved have FOUR TIMES the flight experience of the Cessna 172 group.

With Pilot Miscontrol being a factor in 40 to 60 percent of accidents, this tends to overpower other accident causes in comparison. This diagram shows the relative occurrence of given accident causes as a percentage of the non-Pilot Miscontrol accidents:
non-miscontrol.JPG
The "Control Group" is a mix of Cessna 172 and Cessna 210 accidents, excluding those involving pilot training. This gives us a sample set of aircraft a homebuilt owner might otherwise be flying. Cessna 210s were added to put some complex aircraft in the mix.

About 8% of the homebuilt non-Pilot Miscontrol accidents are directly related to errors made during construction. Compared to ALL accidents, it's about five percent. Here's a breakdown of what systems were affected:
builder error.JPG
Note that errors involving the airframe are relative rare. Half the builder error cases affected engine operation (either for errors on the engine itself or in the fuel system).

About 6% of the homebuilt non-Pilot Miscontrol accidents were due to fuel exhaustion, but it is only about 3.8% of all homebuilt accidents, quite a bit lower than the Control Group. Again, I think, more experienced pilots are a factor...plus the fact that many homebuilts are just fun machines, and may not be used for traveling as much.

Ron Wanttaja
 

Dana

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So: Crashes related to structural failure are extremely rare. The OP was interested in the relative fatigue safety record of different types of construction, which is hard to do if there are few such crashes.

I suspect that most structural failures not related to overstressing the aircraft are found on the ground before they have a chance to cause a crash. Not that they don't happen-- as witness the string of Zenith 601 wing failures a few years back-- but they aren't common enough to serve as a comparison of construction techniques. In many cases, like Zenith, they're a design deficiency rather than the fault of the particular materials chosen.
 

TFF

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True structural failure, these come to mind. One was a Giles that lost its tail and a MXS also. Rans that lost its wing. There is videos of those on YouTube. All doing hard aerobatics. A couple of biplanes breaking rod ends in the elevator pushrod. That’s more mechanical. One I think attributed to rotted wood in the fuselage. Not a lot of structural problems.
 

rv7charlie

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Yep, there are even a few RV-x structural failures, all of which have very strong indicators of either radical overspeed events, or radical G-loading events. The only designs that get me a little uncomfortable from a structural standpoint are the moldless composites, where there's no way to evaluate whether all the layups were done correctly, and 'inspection' is...shall we say...difficult. To be clear, I'm not questioning the structural integrity of the designs; just the inability to *know* that the builder followed the build requirements of the design.

Hey Ron, have you ever tried to filter the pilot loss of control accident figures to remove EDIT: show only the ones that *don't* have the words, "A contributing factor" following the assignment of 'cause' to the pilot's loss of control? (Barely) facetious example: "Accident caused by the pilot's failure to avoid hitting trees. A contributing factor was a thrown propeller blade, which caused the engine to depart the aircraft."
 
Last edited:

Wanttaja

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So: Crashes related to structural failure are extremely rare. The OP was interested in the relative fatigue safety record of different types of construction, which is hard to do if there are few such crashes.

I suspect that most structural failures not related to overstressing the aircraft are found on the ground before they have a chance to cause a crash. Not that they don't happen-- as witness the string of Zenith 601 wing failures a few years back-- but they aren't common enough to serve as a comparison of construction techniques. In many cases, like Zenith, they're a design deficiency rather than the fault of the particular materials chosen.
From what I've seen, design deficiencies are pretty rare. I think, too, that most designs have considerable margin built in. A single bad rivet won't matter, but, of course, it could be indicative of the builder having workmanship issues.

I searched my database for accidents involving airframe failure in the 1998-2018 period, and there were just 78 cases. This is sorted by aircraft type. The last column is the airframe hours; not all accident reports include it.
NTSB
Date​
Type​
AF Hrs​
SEA01LA008
10/23/2000​
ADVENTURER​
N/A​
WPR14LA104
1/25/2014​
Amphibeous Trike​
N/A​
DEN00LA155
8/20/2000​
Avid Flyer​
35​
WPR09FA234
5/9/2009​
Bakeng Deuce​
N/A​
LAX98LA271
8/18/1998​
Barnett J4B-2​
7​
ANC16LA068
9/16/2016​
BDK Carbon Concepts​
N/A​
LAX03LA092
2/21/2003​
BEDE BD-10​
N/A​
CHI02FA140
5/23/2002​
Berkut​
N/A​
ATL99LA092
5/22/1999​
Bowers Fly Baby​
216​
NYC00LA134
5/13/2000​
Bowers Fly Baby​
N/A​
CHI98LA146
5/11/1998​
Challenger II​
2​
MIA99LA119
4/7/1999​
Challenger II​
9​
WPR09LA453
9/16/2009​
Challenger II​
N/A​
CEN11LA050
11/1/2010​
Challenger II​
N/A​
ERA17FA038
11/9/2016​
Challenger II​
142​
SEA07LA155
6/12/2007​
Challenger II Quad City Ultralight Aircraft​
1291​
FTW98LA368
8/20/1998​
Christen Eagle II​
607​
ATL06CA125
9/3/2006​
Christen Eagle II​
60​
GAA18CA329
6/6/2018​
COOT​
538​
WPR13LA050
11/23/2012​
Coot A-Amphib​
N/A​
MIA98LA084
2/24/1998​
CUMULUS​
100​
LAX02FA188
6/8/2002​
Fisher Celebrity​
N/A​
CEN13LA186
3/4/2013​
Fisher Celebrity​
N/A​
CEN18FA282
7/19/2018​
FISHER CELEBRITY​
N/A​
ERA16FA089
1/14/2016​
FLIGHTSTAR II​
N/A​
ERA17FA265
8/6/2017​
Freedom​
26​
ERA15FA331
8/28/2015​
Giles G-202​
400​
FTW03LA061
12/20/2002​
Harmon Rocket​
N/A​
LAX04LA253
7/7/2004​
Harmon Rocket II​
250​
ERA18FA240
9/1/2018​
Jet EZ​
100​
CHI01FA232
7/21/2001​
Kelly-D​
60​
LAX06CA027
11/4/2005​
KOLB MARK 3​
545​
ATL03LA094
5/16/2003​
Lancair 4​
N/A​
NYC05LA096
6/12/2005​
Maxair Drifter​
N/A​
LAX00LA325
9/5/2000​
MITE M18L​
1116​
CHI01FA186
6/22/2001​
Murphy Renegade​
108​
CEN16LA230
6/17/2016​
NIEUPORT 11​
579​
DFW07CA025
11/11/2006​
Quickie Q-200​
425​
CEN10CA200
4/8/2010​
QUICKSILVER SPORT 2S​
N/A​
CHI01LA002
10/4/2000​
RAF 2000 GTX SE​
N/A​
CEN14FA140
2/16/2014​
Rans S-10 Sakota​
390​
ERA09LA492
8/30/2009​
RANS S-9​
52​
ATL01LA003
10/3/2000​
Revolution MINI 500​
16​
LAX04LA274
7/21/2004​
Rotorway Exec 162F​
200​
CHI07LA273
8/18/2007​
Rotorway Exec 162F​
99.9​
ERA19FA068
12/18/2018​
Saberwing​
101​
CEN15LA104
1/16/2015​
SAFARI​
N/A​
CEN17LA224
6/7/2017​
SD-1A​
N/A​
ATL98LA123
9/7/1998​
SeaRey​
95​
ATL04LA171
8/26/2004​
SeaRey​
143​
ERA13LA199
4/11/2013​
SeaRey​
880​
ERA10LA328
6/23/2010​
Seawind 3000​
43​
CEN14FA072
11/27/2013​
Smyth Sidewinder​
1909​
NYC99FA097
4/25/1999​
Sonerai IIL​
181​
ERA12FA018
10/22/2011​
Sonex Waiex​
300​
FTW99FA265
9/25/1999​
Spacewalker II​
115​
LAX04LA163
3/17/2004​
Steen Skybolt​
815​
FTW04LA148
5/23/2004​
Steen Skybolt​
116​
WPR11LA459
9/19/2011​
Steen Skybolt​
320​
FTW00LA254
9/5/2000​
STREAKER​
1123​
ERA13FA071
12/1/2012​
Thorp T-18​
N/A​
LAX04LA041
11/11/2003​
Thorp T-18C​
N/A​
ERA16CA102
1/16/2016​
TUCKER MITCHEL C H 13​
N/A​
FTW98FA145
3/8/1998​
Vans RV-3​
755​
WPR17FA128
6/17/2017​
Vans RV-3​
N/A​
DEN06LA116
8/23/2006​
Vans RV-3AB​
500​
WPR13FA056
11/26/2012​
Vans RV-6-CH​
577​
ERA13FA424
9/20/2013​
Vans RV-7A​
455​
LAX98FA171
5/24/1998​
Vans RV-8​
400​
ATL00LA055
5/9/2000​
Velocity RG​
668​
ATL01LA029
2/3/2001​
Velocity XL RG​
1​
CHI99LA020
11/3/1998​
Wag-Aero SUPER SPORT​
1800​
CHI00LA043
12/12/1999​
Wittman Tailwind W-8​
119​
FTW02LA187
6/23/2002​
Wittman Tailwind W-8​
N/A​
LAX06LA105
2/8/2006​
Zenair CH-601 XL​
60​
WPR09FA141
3/3/2009​
Zenair CH-601 XL​
14​
LAX03FA102
2/28/2003​
Zenair CH-801​
N/A​
LAX02LA043
12/9/2001​
Zic Zac Bird​
5​

Keep in mind that not all were builder or design-related.

Ron Wanttaja
 
Last edited:

Topaz

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One of the Challenger II crashes in that period (either 2009 or 2010, I'd have to check) was a wing fabric attach failure due to commercial (non-aviation) "pop" rivets being used in place of the specified part on a repair/restore operation. Not sure that it's on your list. Depends on the criteria for "airframe failure." Anyway, I knew the guy.
 

Marc Zeitlin

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The only designs that get me a little uncomfortable from a structural standpoint are the moldless composites, where there's no way to evaluate whether all the layups were done correctly, and 'inspection' is...shall we say...difficult. To be clear, I'm not questioning the structural integrity of the designs; just the inability to *know* that the builder followed the build requirements of the design.
It's funny - as someone who works with moldless composite construction airplanes every day, I feel the same way about AL planes - who knows where corrosion is hiding - there are a zillion places on an RV that you can't see with an inspection mirror :).

In any case, while there have been a few cases of structural failures in correctly built (per plans/kit) AL planes (although very rare, to be sure), there have been, to my knowledge, NO failures of Rutan derivative moldless composite aircraft that were built to plans. Yes, that was the crux of your point above - you can't tell, by non-destructive inspection, whether the plane was built to plans. But out of the ~4000 planes of this type that have flown, I only know of one that had a fatal composite structural failure in flight, and that one was due to the builder leaving out all of the structural attach layups from the winglet to the wing, that take the inward air loads. And the **** thing still made it through the 40 hour test period (indicating, pretty clearly, that the pilot did not explore the full extent of the operating envelope during Phase I) before the winglet departed the plane and there was a fatality in the crash.

Anyway, I think the level of comfort that one has with a particular technology is very dependent on how much experience one has with that technology. While I work on AL planes occasionally, I'm far more conversant and comfortable with the composite ones, and I imagine folks like Vic Syracuse, who specializes in RV's, feels the same in the opposite direction :).
 

rv7charlie

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Messages
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Location
Jackson
I get what you're saying, but I've had a bit of experience with both types. Multiple metal types, a 'true' composite (AL fuselage with AL spar/'glass ribs & skin wing), and one moldless composite, a Dragonfly. The builder had broken and repaired the canard twice in the 1st 3 hrs of test time (disclosed in the logs) before I bought the plane as a student pilot. On the 2nd flight after I bought the plane, my instructer/test pilot had a bit of PIO on landing and the canard broke again. when I looked at the core in the canard, there was a significant quantity of urethane spray insulation foam where the structural foam should have been, obviously in the area where it had broken in the past. I considered myself lucky that the failure happened on the ground, and no one got hurt.

Charlie
 
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