Aviation Safety: the Facts and Implications

[Chris Hill]

I am looking at the experimental/amateur built aircraft accident statistics over the last year, and based on what I?ve found, it doesn?t appear that EAB aircraft (or certified aircraft) are significant safety hazards when compared to automobile transportation.

I went to the NTSB website and collected data from the accident query search tool for 1 Jan 2011 through 31 Dec 2011 which I will post here for your review.

With regard to EAB aircraft accidents, I found that there were 71 people killed in 241 accidents. There are approximately 600,000 certified pilots in the U.S. Assuming, perhaps falsely, that they all actively fly at some point during the year, the data shows that .012% of pilots (not counting the passengers which would further reduce the percentage of aviation participants) are killed in EAB accidents. Compare this with automobile deaths, at 42,636 out of approximately 210,000,000 million licensed drivers for a .0203% death rate, and you can see that the EAB accident rate is a little more than half of that.

Now compare total EAB accidents to total automobile accidents (these do not take into account the number of passengers). EAB accidents, 241. Car accidents, 6,420,000. For the same number of licensed participants, EAB has a .0402% accident rate versus auto at 3.05%. Cars have 76 times more accidents per operator than EAB aircraft have!

How about general aviation as a whole though? There were 1380 certified general aviation accidents in the U.S. This is .23% (not 23%) of participating pilots. Cars have 13 times the number of accidents that certified GA aircraft have!

What I learned from this research is that people who dwell on aviation safety and EAB safety are doing more harm than good in the aviation community by accepting responsibility that isn?t ours to accept. Based on what I?ve found, we don?t have a problem here. In fact, we set the example of what safety should be!

Lets step back and see how this fits into the big picture. In economics, there is a term called diminishing returns which states that in all productive processes, adding more of one factor of production will at some point yield lower per-unit returns. Apply this to the cost of safety, and you can see that it might very well cost 10 times more to get an additional unit of safety as it did to get the previous unit. What does this do to aviation? It prices it out of reach for new entrants. For example, the NextGen system, which is coming on line and mandates ADS-B in 2020, will add an additional cost in the name of safety. The irony is that the FAA is imposing this with the idea that air travel will increase by 50% in the next 15-20 years, yet the number of certified pilots in the US is decreasing. I am wondering where all these pilots are going to come from!

 

[Geeman]

Do your statistics account that some pilots may fly a couple of times a month, or less, but drive everyday.

For example, some of us recreational pilots that fly a couple of hours on the weekends may put 8 hours on the hobbs a month....and that is flying alot for me. I have a 30 minute commute to work, so that is 1 hour a day, 20 hours a month, give or take. So I am in my car 2 1/2 times as much as my plane, so therefore more likely to get in a car accident???

My brother is a corporate pilot, and he does not fly all that much. Maybe once a week. I would venture to say he is in his car 2 or 3 times as much as he is flying.

I am not questioning your numbers, because I am definately pro-flying type, and I understand your point. Just wondering if your numbers take that into account.

I always tell people that are afraid of flying that driving your car is much more dangerous, but I couldnt really back that statement up with facts. Maybe I can now.

 

[Wayne Gillispie]

After 25 years of driving...

We feel much safer in our plane! I told my wife in 2007 while driving back North on I-75 from Florida that it would be our last long trip driving in a car. Five years later(June 2012) we did our first long xc to Florida to visit family and friends. 4.5 hrs vs 18 hrs. We never had any instances of "flying rage", no getting lost, no speed traps, no construction, no 80,000 lb tractor trailers to get behind or in front of, no stopping for fuel and no food or restroom stops. We only saw three or four other aircraft while on FF. Now flying out over the ocean while avoiding TS near Jacksonville FL, one might be thinking driving up I-95 would have been safer.

As long as jobs keep leaving this country there will be less money being spent, fewer planes being purchased or built and fewer new private pilots. I expect a decrease in air traffic, especially if fuel prices continue to rise.

 

[Lycosaurus]

...With regard to EAB aircraft accidents, I found that there were 71 people killed in 241 accidents. There are approximately 600,000 certified pilots in the U.S. Assuming, perhaps falsely, that they all actively fly at some point during the year, the data shows that .012% of pilots (not counting the passengers which would further reduce the percentage of aviation participants) are killed in EAB accidents...

I would assume that only a small fraction of the certificated pilot population would be flying an EAB. Would that not change your numbers drastically?

 

[Alan Carroll]

I appreciate that the point here is to present a more accurate picture of homebuilt accident statistics. Another interesting analysis can be found here:

http://www.eaa.org/news/2010/homebuilts_report_wanttaja.pdf

I think however that the numbers presented in the first post need some major adjusting. For example there are about 23,000 EAB registered, which is probably a better reference point than 600,000 pilots. I also think you can't simply ignore hours flown, even if the data are shaky. The average car is driven more hours in a year as the average EAB airplane is flown in its lifetime.

Another way to look at things is to compare the total fatal accidents to the overall size of the fleet. When you do this for RV's the numbers work out to something like 150 fatal accidents for 7800 airplanes. Doing the math, about 1 in every 50 RVs ever produced has been involved in a fatal accident. Personally I find this a little disturbing.

 

[vfrazier]

It's been awhile since I actually did the math, but I believe that your lifetime risk of dying in a car is 1 in 60. About 1 in 3 suffer a permanent injury of some degree from a car accident. These are pretty sobering numbers. I suspect that motorcycles are even worse, but haven't checked.

Somewhere I heard that 1 in 25 RVs or Rockets, will kill someone. Ack. Also very sobering.

However, in all of this, isn't the big question really "Do you really want the government to define what risks are acceptable for YOU?" Now, that's a whole 'nuther discussion.

Fly safely. Don't give the gov't any more ammo against us!

 

[2bolts]

Diminishing returns

Lets step back and see how this fits into the big picture. In economics, there is a term called diminishing returns which states that in all productive processes, adding more of one factor of production will at some point yield lower per-unit returns. Apply this to the cost of safety, and you can see that it might very well cost 10 times more to get an additional unit of safety as it did to get the previous unit. What does this do to aviation? It prices it out of reach for new entrants. For example, the NextGen system, which is coming on line and mandates ADS-B in 2020, will add an additional cost in the name of safety. The irony is that the FAA is imposing this with the idea that air travel will increase by 50% in the next 15-20 years, yet the number of certified pilots in the US is decreasing. I am wondering where all these pilots are going to come from!

However, in all of this, isn't the big question really "Do you really want the government to define what risks are acceptable for YOU?" Now, that's a whole 'nuther discussion.

Ahh, both are examples of the British way of doing things, which is why it's so expensive over there, not just flying, everything.

 

[LettersFromFlyoverCountry]

What I learned from this research is that people who dwell on aviation safety and EAB safety are doing more harm than good in the aviation community by accepting responsibility that isn’t ours to accept.

I really don't know where to begin with a statement like that so I won't bother. John and Martha King did it a few years ago.

But last night I saw a guy land at KSGS. No radio call until he was near the end of a downwind, no call once he announced a base turn, no call to indicate he was doing a touch and go, no call to announce he was making a right departure even though right departures are banned at the airport... and no call to announce he was going to do steep turns at 500 feet over the neighborhood, which is built right up to the airport fence. (and, I should point out, right on the arrival pathway for the downtown Saint Paul airport)

What an idiot! and for the record, I have ZERO problem with anything the government can do to get him out of my airspace. As I said after Mark Giron's session in homebuilt camping during Oshkosh, I'm clearly an outlier in the EAB community on this.

As for statistics, read any and all of Ron Wantaja's work for a complex and scientifically accurate assessment of the risk of homebuilts and flying.

 

[2bolts]

But last night I saw a guy land at KSGS. No radio call until he was near the end of a downwind, no call once he announced a base turn, no call to indicate he was doing a touch and go, no call to announce he was making a right departure even though right departures are banned at the airport... and no call to announce he was doing to do steep turns at 500 feet over the neighborhood, which is built right up to the airport fence.

What an idiot! and for the record, I have ZERO problem with anything the government can do to get him out of my airspace. As I said after Mark Giron's session in homebuilt camping during Oshkosh, I'm clearly an outlier in the EAB community on this.

As for statistics, read any and all of Ron Wantaja's work for a complex and scientifically accurate assessment of the risk of homebuilts and flying.

Agreed the guy was an idiot. He broke several rules.

But I'm sure you took this guy to task and pointed out the error of his ways, and/or, reported him to the FAA. It's up to you to get these people out of your airspace, there are enough rules and regs to enable you to do that surely? I have every problem with a Govt butting into my life, on it's say so.

 

[pvalovich]

Homebuilt Safety

In comparing aircraft accidents to automobile accidentsI think you have completely missed the point. It is an undeniable fact that within the aviation data set, the experimental accident rate is much higher than the spam can accident rate. The ongoing question is why.

I don't expect the two numbers ever to be equal, but the challenge is the steps we as homebuilders can do to reduce the delta.

I don't have firm data, but it appears that within the homebuilt community the "Life is harder when you're stupid" accidents occur more frequently than in the certified community.

What can we do to help fix that?

 

[Ron Lee]

For example, the NextGen system, which is coming on line and mandates ADS-B in 2020, will add an additional cost in the name of safety.

ADS-B as far as the mandate does ZERO for safety. It only mandates ADS-B Out systems for aircraft that fly above 10,000' MSL and in certain other airspaces (basically that now require a transponder).

So unless you can receive all ADS-B position info, it does nada for you.

It does allow the FAA to reduce their radar costs at YOUR expense.

 

[RV8R999]

ADS-B as far as the mandate does ZERO for safety. It only mandates ADS-B Out systems for aircraft that fly above 10,000' MSL and in certain other airspaces (basically that now require a transponder).

So unless you can receive all ADS-B position info, it does nada for you.

It does allow the FAA to reduce their radar costs at YOUR expense.

Cmon...right now, today, ahead of the 2020 mandate folks are receiving ADSB weather and traffic. I can personally attest to the safety benefit of having access to additional traffic info readily available in the cockpit as can many, many others. To say there is ZERO safety improvement is off.

 

[LettersFromFlyoverCountry]

Agreed the guy was an idiot. He broke several rules.

But I'm sure you took this guy to task and pointed out the error of his ways, and/or, reported him to the FAA. It's up to you to get these people out of your airspace, there are enough rules and regs to enable you to do that surely? I have every problem with a Govt butting into my life, on it's say so.

Well, that's why they made Texas.

I was pretty busy at the time -- flying and all -- so didn't grab his N-number. I don't have flame wars on the radio, so I made sure to call my friend on the ground and say, "do you see this guy?", knowing that the pilot heard my calls when I pointed out what he was doing (and I think it's safe to say he pretty much knew what he was doing).

So, yeah, I'm sure he's a much safer pilot now.

But seriously, I'm pleased to see you pointed out there are "enough rules and regs" to get the guy out of the air, at least conceding they have a role to play in this endeavor.

I don't have a problem if he ends up killing himself -- God has a pretty good way of thinning the herd in that regard. But I wonder how many pancake breakfasts and Young Eagles flights just went for naught in the neighborhood because of one jerk in the sky who probably talks incessantly about his freedom to fly the way he wants. I can solve that once I get those guns mounted on the 7A.

 

[Ron Lee]

Cmon...right now, today, ahead of the 2020 mandate folks are receiving ADSB weather and traffic. I can personally attest to the safety benefit of having access to additional traffic info readily available in the cockpit as can many, many others. To say there is ZERO safety improvement is off.

My statement is correct. You only benefit if you install ADS-B In which is not in the 2020 mandate.

 

[LettersFromFlyoverCountry]

My statement is correct. You only benefit if you install ADS-B In which is not in the 2020 mandate.

If follow the mandate , am I showing up on the panel of those who have installed ADS-B?

 

[Ron Lee]

Bob, my understanding is that people who get ADS-B In traffic info will also get position info on Mode S/C (?) transponder only equipped aircraft...but verify.

The problem will be that if the FAA removes radars, then you get coverage holes for current day transponders.

 

[2bolts]

Well, that's why they made Texas.

I was pretty busy at the time -- flying and all -- so didn't grab his N-number. I don't have flame wars on the radio, so I made sure to call my friend on the ground and say, "do you see this guy?", knowing that the pilot heard my calls when I pointed out what he was doing (and I think it's safe to say he pretty much knew what he was doing).

So, yeah, I'm sure he's a much safer pilot now.

But seriously, I'm pleased to see you pointed out there are "enough rules and regs" to get the guy out of the air, at least conceding they have a role to play in this endeavor.

I don't have a problem if he ends up killing himself -- God has a pretty good way of thinning the herd in that regard. But I wonder how many pancake breakfasts and Young Eagles flights just went for naught in the neighborhood because of one jerk in the sky who probably talks incessantly about his freedom to fly the way he wants. I can solve that once I get those guns mounted on the 7A.

I came here from a country where the government, of each flavour felt it had the right if not the duty to interfere in every aspect of your life. Once they start they do not stop. Take my word for it. That’s all I’ll say about that, so this thread doesn’t get killed.

I agree with you about flame-wars on the radio, they’re pointless. It really is a shame that neither you, nor your friend couldn’t get the ‘N’ number, because these people always mess up other people’s airspace/airfield environments not their own. Maybe if he heard your radio call, it might ward him off and he’ll stay away. I’m sure, as are you that he won’t be any safer either.

But the FAA will 99 times out of 100 never ‘be there’, we will. We should talk to these people, politely, and point out what they’re doing wrong. If they do it again report them, with a photo if possible, if they become abusive report them anyway. Just stay polite. If they’re breaking local circuit procedures, I’m not sure what you can do. I don’t know what action the FAA might take for the lack of radio procedure, if he had a radio.

We need to police ourselves more effectively, DR had a good idea, similar to above (I’m not saying mine is better)

I agree with you, if the guy wants to kill himself, let him fly to the middle of nowhere and do it, Darwin strikes again.

These people are a right pain, but initially we need to deal with these people, by either taking to them or reporting them, so the FAA can carry it forward.

Re the accident rate with homebuilds, am I under the impression this is a pilot problem as against an airframe problem?

Again what do to? Training costs money, and we’ve reasonably well established that it’s the cost of flying stopping people from flying in the fist place.

With freedom comes responsibility, we need to hold these people responsible.

Would your 7 lift 2x.50’s and the whole nine yards for each?

That would be a sight to see, 1 each side of the cockpit.

I sympathise, but I don't think giving the FAA more power would have solved this problem.

I'm not anti FAA, the people I've met have been very friendly and helpful, but, there is a limit to what we can expect these people to do. And indeed, what we should expect them to do. It isn't our job to prosecute idiots like your intruder, it's theirs, but unless we talk to the idiots, or report them, the FAA doesn't see a problem, And as you conceed he'd already broken enough rules.

 

[2bolts]

ADS-B

I think I agree I see the main aim of ADS-B is a transfer of costs nothing more. and selling us weather and traffic as a benefit

I agree being able to see other traffic and weather will help pilots, but I think this will lead to more head in the cockpit time, instead of eyeballs out, especially when looking for traffic, this stuff should really announce traffic, e.g. 'Warning traffic 9 o'clock, 2 miles, decending heading....' Then you wouldn't have to look in just look for the traffic.

 

[DSmith]

The problem with Next Gen is all the data is based on GPS being available and something our gov't and the military doesn't seem to realize that there are alot of countries who don't wish us well. What will happen when some enemy disrupts our GPS net? Or figure a way to pirate control like our new high tech drone in Iran? Or maybe some natural space disturbance?

Maybe I worry too much but I just think our airspace control is too dependant on GPS.

 

[2bolts]

The problem with Next Gen is all the data is based on GPS being available and something our gov't and the military doesn't seem to realize that there are alot of countries who don't wish us well. What will happen when some enemy disrupts our GPS net? Or figure a way to pirate control like our new high tech drone in Iran? Or maybe some natural space disturbance?

Maybe I worry too much but I just think our airspace control is too dependant on GPS.

We'll all have to go back to map reading and using MK1 eyeball navigation, maybe using VOR's etc as backup

 

[RV8R999]

My statement is correct. You only benefit if you install ADS-B In which is not in the 2020 mandate.

well no kidding, any system expected to enhance safety will require pilots to do something. In this case that "something" will be to install ADSB-in and hopefully -out as well.

The current system required pilots to purchase and install xpdrs and radios and actually use them...

What safety system would you propose which requires no action on your part?

 

[Alex Caldwell]

I appreciate that the point here is to present a more accurate picture of homebuilt accident statistics. Another interesting analysis can be found here:

http://www.eaa.org/news/2010/homebuilts_report_wanttaja.pdf

I think however that the numbers presented in the first post need some major adjusting. For example there are about 23,000 EAB registered, which is probably a better reference point than 600,000 pilots. I also think you can't simply ignore hours flown, even if the data are shaky. The average car is driven more hours in a year as the average EAB airplane is flown in its lifetime.

Another way to look at things is to compare the total fatal accidents to the overall size of the fleet. When you do this for RV's the numbers work out to something like 150 fatal accidents for 7800 airplanes. Doing the math, about 1 in every 50 RVs ever produced has been involved in a fatal accident. Personally I find this a little disturbing.

I was just checking the actuarial tables the Social Security Administration
uses.

http://www.ssa.gov/oact/STATS/table4c6.html

I'm a male age 64. I have a 1.5 % chance of dying in the next year of
all causes. I guess they lump in people who crash in their airplanes in calculating
the overall death rates. I have almost a 100% chance of
dying of something in the next 17.9 years (my life expectancy) as far as they are concerned.
In fact, they're betting on it in making their calculations as to how much
they'll have to pay out. I find this rather disturbing.

I had a friend who died of multiple myeloma and systemic amyloidosis at age 65 last year. He always
wanted to try flying, but never got around to it and then it was too late. You
have to weigh the risk of flying vs. the regret of never trying flying until
you're too old and feeble to try it. But it seems to make
a 1:50 chance of crashing over the number of years I've got left flying not
really seem all that bad. I guess if you're only 21, you might have to look
at it differently, since your chances of dying of other causes, especially
natural causes, in the next year are so much lower. It's also not to say that
trying to reduce that 1:50 rate of RV destruction as low as possible isn't worth the effort.

Alex Caldwell
RV-3A
Tulare, CA

 

[Chris Hill]

Do your statistics account that some pilots may fly a couple of times a month, or less, but drive everyday.

Agreed, some people drive more than they fly. Who can accurately measure that though? I suppose that may not make it right for me to ignore it...but an attempt to use awful data is more of a lie than explicitly excluding in my opinon.

I would assume that only a small fraction of the certificated pilot population would be flying an EAB. Would that not change your numbers drastically?

Perhaps not...for example, I fly professionally. I also fly recreationally in certified aircraft and EAB aircraft. If I crash in any one of these, in what category will I be placed? Most certainly the one that most closely matches the airframe in which I am flying at the time.

I think however that the numbers presented in the first post need some major adjusting. For example there are about 23,000 EAB registered, which is probably a better reference point than 600,000 pilots. I also think you can't simply ignore hours flown, even if the data are shaky. The average car is driven more hours in a year as the average EAB airplane is flown in its lifetime.

Agreed, hours flown would be a much better way to categorize safety in most any activity. BUT I would submit that the data available for such a statistic is completely unuseable. The only people I know who track every single hour to the minute are the military and airlines. Everyone else...has a lapse at somepoint, if they log at all...There is also no public record keeping for GA flight hours (which I would say is a good thing).

Another way to look at things is to compare the total fatal accidents to the overall size of the fleet. When you do this for RV's the numbers work out to something like 150 fatal accidents for 7800 airplanes. Doing the math, about 1 in every 50 RVs ever produced has been involved in a fatal accident. Personally I find this a little disturbing.

That?s a decent way to look at it I guess. My only problem with taking a specific airframe is that now you are starting get into usage instead of averaging it across the entire EAB community. Though in 2011, there were 10 fatal RV accidents out of 70-80 fatal EAB accidents (I'm getting slightly different results depending on how I query the NTSB database). Of those, at least 3 of them appear to be suicide. Like they say, you can build stats to paint whatever picture you want to paint...

I really don't know where to begin with a statement like that so I won't bother.

My point was this: If you say, youre right, we could increase safety by 3.58%, then someone (usually an all knowing government agent) will force you to do it. How much is that 3.58% going to cost you? How much is it going to cost me?? If you don?t provide pushback, you will get run over every single time. Make sure that before you agree to someone else?s stats, you find better ones that help your case!

In comparing aircraft accidents to automobile accidentsI think you have completely missed the point. It is an undeniable fact that within the aviation data set, the experimental accident rate is much higher than the spam can accident rate.

I don't have firm data, but it appears that within the homebuilt community the "Life is harder when you're stupid" accidents occur more frequently than in the certified community.

Can you see why I'm having a hard time following you here? What is your rate based upon? Hours flown? Number of pilots? number of aircraft?

It's also not to say that trying to reduce that 1:50 rate of RV destruction as low as possible isn't worth the effort.

Alex Caldwell
RV-3A
Tulare, CA

Alex, this is exactly my point though. It may not be worth the effort right now if we want to see general aviation reverse its decline.

**I was not saying or implying that people should seek to be unsafe in their building or flying of any airplane certified or EAB. I am saying, however, that the cost associated with attempting to increase safety is pricing aviation out of reach for new entrants.

 

[Ron Lee]

A huge improvement in safety can occur with ZERO FAA involvement and effectively at ZERO cost to the pilot/builder. Go to RVFlightSafety.org and see where the problems are and note that almost all are solvable by pilots who care to not do grossly stupid things.

 

[2bolts]

My point was this: If you say, youre right, we could increase safety by 3.58%, then someone (usually an all knowing government agent) will force you to do it. How much is that 3.58% going to cost you? How much is it going to cost me?? If you don’t provide pushback, you will get run over every single time.

Agreed. How much are you willing to spend to improve safety say 0.001%? $10's? $1,000? $10,000? when does it become too much? Being that it will be our cheque books, or credit cards which will be hit for this. If what is being enforced might be of dubious safety value anyway. Just because the 'powers that be' say it is so, doesn't make it so in the real world.

 

[Alan Carroll]

It's been awhile since I actually did the math, but I believe that your lifetime risk of dying in a car is 1 in 60.

Vince,

Interesting comparison, I hadn't heard that statistic before but it makes sense. I guess I'm not going to quit driving or flying my homebuilt, but looks like both activities demand some respect.

 

[plehrke]

I don't have flame wars on the radio, so I made sure to call my friend on the ground and say, "do you see this guy?", knowing that the pilot heard my calls when I pointed out what he was doing (and I think it's safe to say he pretty much knew what he was doing).

Next time say on the radio "Did you see all the regs broken by that white and blue Cessna NXXXX did?" Now he knows you have enough info to bust him and it may put a little fear in him that people are watching and actually paying ennough attention to his lack of rule following.

 

[tjo]

By the way, the biggest risk of death is life. Just sayin'...

Back on the original topic, however, my biggest problem with all of the current discussions regarding experimental safety is the classifications. What I mean is, somehow it is a forgone conclusion that the correct categories within which to investigate is EAB vs. Certified. I don't agree with this base assumption.

I don't have the data in front of me, but if we look at two main categories to start with, it would be machine vs. pilot problems. I believe the biggest problems come from the pilot, not the machine, whether we are talking EAB, Certified, Commercial, Military, whatever.

Second, I think the biggest problem associated with pilots is lack of experience in type. So how many of us learned to fly in an RV, much less any other EAB? Not very many. How many learned on 150's? 172's? Cherokee's? What are the most prolific airplanes out there?

With all of this info, it would seem a slam dunk that certifieds would have lower accident rates because you have eliminated the biggest cause of accidents for the largest possible population of certified aircraft, meaning most of us have flown 150's, 172's and Cherokee's, they are the most prolifc airplanes out there, they are certified, and most of us don't have accidents in them. Duh. If the data showed anything different we should be shocked.

The problem with singling out EAB or E-LSA, in my opinion, is that the base assumptions for looking at them as a group is wrong because the cause-effect assumptions are all wrong. As a result, the conclusions have little hope of being correct. They may help safety, but they will not be correct.

All that said, I think we have a lot of opportunity to make flying much safer than it is today. But, I think we should be focusing on GA flying, not EAB flying.

My opinion anyway,

Tim

 

[jrs14855]

Accidents

I am finishing up a detailed study of EAB accident reports from 2008. 08 is the latest year for which final reports are available for all accidents.
RV Accidents 2008:
total 28
10 loss of control on takeoff or landing
13 loss of control other than takeoff or landing, three of these were continued VFR in IFR conditions
13 fatal
5 maintenence related
Perhaps the most shocking events were two fatal accidents with a CFI onboard. One was a BFR. The CFI had conducted two previous BFR's with the same pilot in the same airplane. The other was a loss of control early in the takeoff, the airplane hit trees alongside the runway and burned.
Maintenence:
Rudder pedal failure
Failure of both magnetos in cruise
Failure of gearbox on alternative engine.
Gov line welded, weld failed(fatal)
Bad spark plugs(fatal)

All of the maintenence caused accidents are obviously preventable.
All of the loss of control accidents are preventable. The loss of control accidents on takeoff and landing demonstrate incredibly poor basic pilot skills. It appears that nearly half of the pilots in this sample deperately needed remedial training.