RV-10 vs SR 22 accident history

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,980
Location
Rocky Mountains
About 27% of all homebuilt accidents are triggered by mechanical issues. Looking at Cessna 172s and the most common fixed-gear versions of the PA-28 from 2001-2010, 7.5% of the 172 accidents and 10.3% of the Piper accidents had mechanical issues at heart.

Ron Wanttaja
By "mechanical issues" I presume that this includes both parts that break due to age/damage/defect and improper assembly/maintenance? If so could you make a distinction between the 2 groups by separating those 2 versions of mechanical issues?

In other words did the certified group maybe have a higher percentage of parts that failed because they had been in service or rebuilt more times while the Experimental group had a higher percentage of mechanical issues caused by improper installation?

@Tspear "This is a catch 22 situation. ATSM, ISO and many other standard bodies are funded by membership fee<< >>"

Yes, there is a flip side argument, but IMHO it is outweighed by the public's right/need to know. Besides there are plenty of standards in use by industry that are not referenced by regulation and of that subset that are some are only referenced as an example of "best practices". There is very little public need to know with regard to these standards. In the case of standards like F37 LSA the standards ARE the regulation. There is no other source.

I've donated several hundred hours to ASTM over the years as have many on the standards committees. Yet the price ASTM charges for a standard is far too high for the average person to justify. Maybe not all standard organizations are as parsimonious but ASTM would not even give me, as a new member of one committee, a copy of the standard I was expected to consider to be fully informed before voting.

I don't expect these corporations to work for free, or even restrict their profit. There needs to be some mechanism in place so that individuals that have a legitimate need, or even desire, to see the standards that effect their lives through regulation - without individual cost.
 

Wanttaja

Well-Known Member
Joined
Sep 15, 2013
Messages
1,825
Location
Seattle, WA
By "mechanical issues" I presume that this includes both parts that break due to age/damage/defect and improper assembly/maintenance? If so could you make a distinction between the 2 groups by separating those 2 versions of mechanical issues?

In other words did the certified group maybe have a higher percentage of parts that failed because they had been in service or rebuilt more times while the Experimental group had a higher percentage of mechanical issues caused by improper installation?
The "Mechanical Failure" percentages I posted was a combination seven different categories in my database. Two of these are Builder and Maintainer error; I don't have any way to separate cases relative to age of the components or how many times they've been rebuilt. However, these often get listed as Maintenance Error when the NTSB investigator feels the problem should have been detectable at the last condition inspection.

5.3% of homebuilt accidents were due to Builder error, vs. 4.3% for maintenance error. That's about one-third of the "Mechanical Failure" cases.

For the 172s, 0.3% were Builder error, 2.3% were maintenance error. All three of the Builder Error cases were engine-related, one might assume they were engine-rebuilder errors rather than Cessna goofing up.

The Cherokee Set (PA-140, -161, 180, -181) had 0.4% Builder error, and 4.5% maintenance error. Actually a slightly higher percentage than the homebuilts.

I looked a while back at the specific systems impacted by Builder Error, and what kinds of mistakes were made. Probably time to repeat that study. Until then, here's a page from an EAA presentation five years ago where I covered ten years of homebuilt accident data.
Builder Error 2009.jpg

Ron Wanttaja
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,980
Location
Rocky Mountains
Thanks for taking the time to compile all of this. If we ever get around to replacing part 21 with ASTM standards this will be quite useful and you can expect more questions.

The "Mechanical Failure" percentages I posted was a combination seven different categories in my database. Two of these are Builder and Maintainer error; I don't have any way to separate cases relative to age of the components or how many times they've been rebuilt. However, these often get listed as Maintenance Error when the NTSB investigator feels the problem should have been detectable at the last condition inspection.

5.3% of homebuilt accidents were due to Builder error, vs. 4.3% for maintenance error. That's about one-third of the "Mechanical Failure" cases.

For the 172s, 0.3% were Builder error, 2.3% were maintenance error. All three of the Builder Error cases were engine-related, one might assume they were engine-rebuilder errors rather than Cessna goofing up.

The Cherokee Set (PA-140, -161, 180, -181) had 0.4% Builder error, and 4.5% maintenance error. Actually a slightly higher percentage than the homebuilts.

I looked a while back at the specific systems impacted by Builder Error, and what kinds of mistakes were made. Probably time to repeat that study. Until then, here's a page from an EAA presentation five years ago where I covered ten years of homebuilt accident data.
View attachment 30519

Ron Wanttaja
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,980
Location
Rocky Mountains
ASTM membership for average people should be $10 per year and $75 for manufacturers.
If we can't afford $75 per year how are we going to be able to afford the $2K it will cost to attend the meeting in Brussels next September?

I might be able to squeeze in Toronto - if I can convince the wife it can double as a vacation.

This is a game for rich dudes :gig:
:confused:
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,281
Location
Port Townsend WA
Yes, thanks Ron. To summarize: homebuilders have somewhat more builder errors than factory built. No surprise.
Anything assembled in a factory is likely to have fewer assembly errors.
But certification doesn't improve assembly errors. Certification is nothing more than a mandatory compliance demonstration of meeting approved design standards.
Is there any evidence that the Kitplane industry is at all lacking in voluntary self- compliance with critical established design standards?
 

Wanttaja

Well-Known Member
Joined
Sep 15, 2013
Messages
1,825
Location
Seattle, WA
Is there any evidence that the Kitplane industry is at all lacking in voluntary self- compliance with critical established design standards?
What would you consider acceptable evidence that proves it is lacking?

Ron Wanttaja
 

Wanttaja

Well-Known Member
Joined
Sep 15, 2013
Messages
1,825
Location
Seattle, WA
Crashes caused by obvious design flaws where the Kitplane designer ignored the standards in Part 23.
Are you limiting "design flaws" to structural? Many homebuilts don't meet 23.49. Would a stall-spin accident qualify?

Ron Wanttaja
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,281
Location
Port Townsend WA
Are you limiting "design flaws" to structural? Many homebuilts don't meet 23.49. Would a stall-spin accident qualify?

Ron Wanttaja
Well if you are talking about the 61 kt. stall peed limit, does that apply to many Kitplanes? If so, then I suppose the study should have a few categories to compare, such as Cub types and RV or Lancair types. Could be drastic differences with different types.
I would not include stall spin cases because Part 23 hardly protects from stall/spin in any manner other than proof that the aircraft must be able to recover from a spin. I suppose some homebuilts may not recover, but I doubt that any popular Kitplanes would fail to comply with part 23 for spins in any meaningful manner. Off hand, I can't think of any performance safety hazards, so I think it is mostly hardware or structure related causation to look at.

Or the study could be limited to a few of the more popular Kitplanes. For example, the Glasair Sportsman with about 1000 units flying or being assembled*. The company brochure says the design went through a rigorous certification process as the Symphony 160. We can ponder, would a fully factory built but uncertified Sportsman airplane be significantly more or less accident prone than the fully certified Symphony 160.? Or the Two Weeks to taxi Kitplane version?

*source, company brochure
 

Wanttaja

Well-Known Member
Joined
Sep 15, 2013
Messages
1,825
Location
Seattle, WA
Well if you are talking about the 61 kt. stall peed limit, does that apply to many Kitplanes? If so, then I suppose the study should have a few categories to compare, such as Cub types and RV or Lancair types. Could be drastic differences with different types.
Sorry, I was posting from a tablet and when I do so, am more terse than normal.

My objection was more to the wording of your challenge: "Is there any evidence that the Kitplane industry is at all lacking in voluntary self- compliance with critical established design standards?" The fact is, such evidence is impossible to obtain.

When (for instance) an overstress accident occurs, the NTSB doesn't often do an independent determination of the design margin vs. the predicted number of Gs the accident airplane pulled vs. a design requirement that doesn't apply to the airplane anyway. The report states that the wing failed in overstress, and that's it. So "proving" whether any company is lacking in compliance with critical established design standard is impossible. Years ago, an "Air Progress" article about a new kitplane quoted the designer as saying something along the lines of "We've never spun it...I don't think it'll recover from a spin. If someone wants to go and kill themselves, that's their business." (got the exact quote somewhere).

That company didn't last long...but the designer formed a company for a new design, and it has been selling kits for almost 20 years.

And of course, there's the traditional aviation practice of blaming the pilot. Lancair IVs have a somewhat higher rate of stall-related accidents, and their stall speed is above the 14CFR23 limits. Yet few blame the higher rate on the lack of voluntary compliance to Part 23; it's the blankety-blank pilots' fault!

Kit manufacturer's failings *have* been cited in NTSB accident reports...see DEN99LA062, SEA01LA104, and CHI05CA003, for example. Some designers strive for compliance to the spirit or even the letter of Part 23, and I honor them for it. But we have to take their word that they're doing it; it's impossible to prove or disprove based on accident reports. A claim that "We are designed in accordance with Part 23" may only mean, "We comply with the portions of Part 23 that we think are important." Not necessarily the same thing....

Ron Wanttaja
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
15,617
Location
Memphis, TN
I dont believe it is PT23 that is the full problem. What costs so much in certifying an airplane is the FAA testing. Once you design your airplane, you have to deliver one to the FAA and they need to fly it about 200 hours on your dime and possibly do landing drops and what ever you are claiming destroying your airplane. The Aircraft company has to flip that bill and essentially subsidize FAA pilots, engineers, ground crew, and office staff assigned to your airplane. There are legendary stories of the 2 seat Pitts being certified. The parachute on a Cirrus was to get out of spin testing because the company could not afford the tests; not that it could not recover. Europe made them spin test it before it was allowed there. They got out of the cost for about 3 years while their bank account got full enough to pay for it. That is no problems not needing redesigns.
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,980
Location
Rocky Mountains
I dont believe it is PT23 that is the full problem. What costs so much in certifying an airplane is the FAA testing. Once you design your airplane, you have to deliver one to the FAA and they need to fly it about 200 hours on your dime and possibly do landing drops and what ever you are claiming destroying your airplane. The Aircraft company has to flip that bill and essentially subsidize FAA pilots, engineers, ground crew, and office staff assigned to your airplane.
I can't speak for BBerson but this is what I'd like to see changed. Aircraft are the only consumer product here in the US that has to be totally vetted by a government agency. Even drugs and medical devices are produced after acceptance with quality control that is substantially based on industry standards and the honor system.

I'd like to be able to argue, with numbers to back me up, that this second layer of testing oversight does little to improve the safety of the public or the occupants of the plane. If you want to go down the paranoid conspiracy path - it could be argued that the reason the FAA recently came down so hard on the "hired gun" builders of experimental aircraft is that if this trend would have continued it would have proven that the FAA's insistence on personally verifying every claim and test is a waste of time and money.

We have the limited history of LSA's and their self certification process to draw on. It really doesn't cost much to do the testing for LSA certification. Phase one for an Experimental, if done well, is almost as as complete. Extend this self certification model to all non-commuter aircraft, restrict the FAA to an oversight role, and I doubt there would be any reduction in safety. We may even see in increase in safety because it would then be economical to change a design or feature for the better.

So far the "boldest" idea presented to reduce the cost of FAA oversight is to allow for the remote witnessing of tests via cameras and such by the DER's and FAA. The more "outsiders" we can get to join this ASTM process the better.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,281
Location
Port Townsend WA
TFF- I am not sure that you deliver the airplane to the FAA for them to test. I think the majority of the testing is done by the company. I was at the NW Aviation Trade Show last Saturday. The FAA Certification office had a booth with one lonely lady. I stopped to ask a few questions. First question: does the FAA charge for their time? Answer "No. But you might want to hire a DAR if you need approval fast, so that would cost you. We at the FAA can do it but it might take six months to two years for an STC. Then you need to go to a different FAA office for your PMA"
I didn't even bother to ask about a Type Certificate time estimate.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
15,617
Location
Memphis, TN
Pretty much now the FAA has no qualified pilots to do the work so they have a pool of acceptable people that they hire and you pay for. You can talk to them a ton, but until you show up with the money they will not give you the secret handshake. I know a company we deal with is starting a "new" aircraft, but they can only deviate so much from their type certificate before they have to start a new one. They once piggybacked a bigger design on their old design but if they tried today it will cost them $20M+. So they pretty much have to hide new stuff in the old stuff and this is a $400M company.
 

tspear

Well-Known Member
Joined
Feb 12, 2014
Messages
1,012
Location
Outside Boston
Hot Wings,

Just a minor correction, most medical products have to be approved by the FDA; especially drugs. Vitamins, Supplements, and a few other categories are exempted.
Most devices also most go through FDA testing before they can be used (e.g. a knee brace does not need testing, but a stent does).

Tim
 

Hot Wings

Grumpy Cynic
HBA Supporter
Log Member
Joined
Nov 14, 2009
Messages
7,980
Location
Rocky Mountains
Hot Wings,

Just a minor correction, most medical products have to be approved by the FDA; especially drugs. Vitamins, Supplements, and a few other categories are exempted.
Most devices also most go through FDA testing before they can be used (e.g. a knee brace does not need testing, but a stent does).

Tim
Yes, they are tested and approved. That's the "after acceptance" phrase, and in some cases the FDA makes the FAA look down right speedy.
 

Wanttaja

Well-Known Member
Joined
Sep 15, 2013
Messages
1,825
Location
Seattle, WA
Back when Frank Christensen certified the Husky, he gave a talk at Oshkosh. Someone asked him how tall the paperwork was for getting the Part 23 certification for the airplane.

He indicated a stack about two inches high. Just two inches.

Simple airplane, true, but most of what had to be shown to the FAA was proof that the engineering was done, and that the testing verified the design. He didn't think the process was that onerous.

A lot of folks think the standards are reasonable. If you look at the ASTM standards for Light Sport, you'll see numerous pages that were just ripped out of Part 23.

Most of the clauses in Part 23 were added for a reason, and those reasons usually involved blood and death. The Feds instituted the first certification standards in the '20s as a reaction to the mayhem across America. Aircraft are unusual; it's probably the most complex deadly machine operated by non-specialist users. Got a problem with a car? Turn the power off. Got a problem with a lathe? Turn the power off. Got a problem with an airplane? If you don't have the skills, you're likely dead.

The first certification requirements didn't apply to all airplanes, just those that were going to sold commercially or carry passengers for hire. That's what the "C" stood for in the old N-number: "Commercial."

But anybody was welcome to build their own airplane, and they didn't need to register them with the CAA. The mayhem continues. Then states got involved, banning flight by aircraft that WEREN'T registered. By WWII, if your plane didn't bear an "NC" registration (or NR, or the NX that was assigned to company test aircraft) you weren't allowed to fly in 47 states.

Part 23 and its predecessors have had one benefit that most people forget: It standardized how airplanes handle. It might take training to operate the systems, but with a few minutes' familiarization just about anyone with a pilot's certificate can fly any Part 23-certified airplane. They all fly similarly, some with lighter control forces, some with heavier, but with predictable, standard reaction to pilot input and about the same behavior when stalled.

Personally, I think this is partially the reason for the higher accident rates in homebuilts: Many planes don't fly the way people are used to. Controls aren't balanced, stall behavior is different, the stick-force-per-G is sometimes odd, the planes aren't stable. Sure, "hot pilots" can handle them, but too often, the new owners of homebuilts are just ordinary people.

For instance, my homebuilt doesn't have a cockpit-adjustable trim tab. Doesn't need one. This tends to stun some pilots; managing trim is one of the skills they have developed, and can't imagine NOT having one. I flew a homebuilt demonstrator once where I was glad the demo pilot didn't turn the controls over until we reached altitude. Never SEEN an airplane with that much adverse yaw. And, don't forget the ultralight/homebuilt in the early '80s where the ailerons were connected to the pedals, and moving the stick left and right activated the rudder.

I don't argue with the notion that Part 23 can and *should* be simplified. But it has served a critical role in GA in America. As long as the Experimental Amateur-Built category exists, the way to experimentation is open.

Ron Wanttaja
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
15,281
Location
Port Townsend WA
Ron, you fly a single seat airplane. I don't think any single seat airplane* has ever been certified in my lifetime.
When the burden is such that no small business can comply, then it is effectively a ban on single seat low powered airplanes. I don't see how this effective banning of light airplanes and leaving homebuilts as the only option serves any purpose since homebuilts don't meet the standards.
Frank was a wealthy businessman that could afford to pay the cost (much less decades ago) for an old style design that hardly differed much from the 40's Cub.
It isn't that easy to get anything approved now. What is needed is relaxed burdens for one and two seat airplanes.

*I am talking affordable here, not Extra 300
 
Top