OK, Luke, Here's More Numbers for You

" wrote:

Are you talking about your 172RG? Do they really cruise at 155 MPH?
I thought they cruised around 145 MPH. Is yours modified?

It will actually do a bit more, just like the one I used to rent. It's
not modified.

I'm asking because I'm looking to buy one.

I'm about to put mine up for sale -- it's a great airplane but I need
more room. I'll be looking for a C-210.
--
Dan
C172RG at BFM

I used to flight plan 140-145 knots when my flying club had one.
With two on board and the gear up, they have a tremendous glide!

wrote:
Are you talking about your 172RG? Do they really cruise at 155 MPH? I
thought they cruised around 145 MPH. Is yours modified?

On 31 Dec 2004 11:38:32 -0800, "Jim Rosinski" wrote:

Ron Wanttaja wrote:

We'll probably never really know the true answers, until somebody
makes a long term comprehensive study of hours flown and types of
flying versus accidents across the whole fleet.

Ahem. KITPLANES magazine, October 2004.

How about a brief summary for those of us who don't subscribe? One
wouldn't expect a magazine of that title to be completely unbiased
about such a subject, but even biased information can be useful.

A brief summary is tough, when we're talking a 3000+ word article with a bunch
of graphs (I was the author of the article).

The biggest problem with a summary is that it's tough to include all the
cautions and caveats about the input data used. I can't guarantee the results
the article show are accurate, except within the framework of the data and
assumptions used. I've had several email exchanges with folks who didn't agree
with some of the assumptions I used. That's fine...*that's* why I explained my
processes in the article.

But on a summary... it's tough to make it clear where errors could have been
introduced. Given a couple of days, I can probably get the entire article
online. But let me give what summary I can, now.

The study was based on homebuilt aircraft accidents from 1998 to 2000,
inclusive. I downloaded the full NTSB accident summaries for each of those
years. For each accident involving a homebuilt, I studied the narrative and
made my *own* assessment of the cause of the accident. I did the same for
Cessna 172 and 210 accidents (to provide a baseline of comparison of causes). I
referred to these as "Accident Initiators," leaving the phase "Probable Cause"
to the NTSB.

In addition, I already possessed the FAA Registration databases for July 1997
and January 2001. I determined the average "fleet size" for homebuilts and for
the total US registered aircraft for the 1998-2000 time period.

This leads to one problem with the input data. Each registry entry includes a
field for an Airworthiness Classification code. This code will be "1" for a
Standard Category aircraft, "2" for Limited category, "3" for restricted, "4"
for Experimental, and so forth.

Supposedly, this code is assigned when the airplane receives an airworthiness
certificate. Unfortunately, this doesn't always happen with homebuilts...I've
found a number of operational aircraft that have a blank in this field. I've
also found a number of aircraft still under construction that *do* have an
entry.

A while back, I did a step-by-step analysis of the FAA registration database,
and found about 4000 aircraft with "homebuilt-like" names, that have
airworthiness column blank. How many of these airplanes are currently flying?
No one knows. But the FAA and EAA *only* count aircraft that are positively
indicated as Experimental, and have the appropriate code in another column that
indicates that they are Experimental Amateur-Built aircraft. These are also the
only planes *I* counted in my analysis...basically because there was no reliable
way to tally the unmarked aircraft.

With that said: My analysis showed an average annual fleet accident rate of
1.05% for homebuilt aircraft, and 0.68% for all US-registered aircraft. The
Cessna-alone rate was probably more indicative of the GA rate, that was 0.72%.

If homebuilt aircraft during their first 40 hours of flight are eliminated from
the homebuilt accidents, the overall homebuilt rate drops to 0.85%.

Of more interest was determining the accident rate on a per-hour basis. There
are no real figures available. I attempted to approximate this, using the NTSB
accident reports. They include the model year of the accident aircraft, the
date of the accident, and the total time at the time of the accident. I used
these figures to determine the average hourly rate for various types of
aircraft.

Of importance was not, so much, the actual magnitude of the figures, but the
*relative* magnitude, between the two types of aircraft.

But this method had problems as well. It's easy to figure what "1972" in the
model year column means for a Cessna 150...but what does it mean for a
homebuilt? Was it the first year it was registered (which might be ten years
before the first flight), or the predicted completion date, or the actual date
the airplane made its first flight?

But I ran the figures. I came up with an average annual utilization rate for
homebuilts of around 55 hours. For single-engine, fixed-wing, non-agricultural
aircraft, the rate was about 155 hours per year. It results in homebuilts having
a accident rate per 100,000 flight hours about five times higher than the GA
average.

I'm personally skeptical of this figure. I think if one could extract the
*equivalent* operations from the production-aircraft accidents...e.g, only
aircraft that were personally owned and operated (homebuilt can't be rented,
etc.), I think the comparative figures would be closer to the fleet rate.

I'm skeptical of the five times higher rate... but that's the way my numbers
came out, that's what I put in the article, and that's what KITPLANES magazine
printed.

I'll probably do some work and get the whole article online in a bit.

Ron Wanttaja

Ron Wanttaja wrote:
On 31 Dec 2004 11:38:32 -0800, "Jim Rosinski" wrote:


Ron Wanttaja wrote:


We'll probably never really know the true answers, until somebody
makes a long term comprehensive study of hours flown and types of
flying versus accidents across the whole fleet.

Ahem. KITPLANES magazine, October 2004.

How about a brief summary for those of us who don't subscribe? One
wouldn't expect a magazine of that title to be completely unbiased
about such a subject, but even biased information can be useful.


A brief summary is tough, when we're talking a 3000+ word article with a bunch
of graphs (I was the author of the article).

Uh, Ron, I think your summary was longer than the original article... :-)


Matt

"Dan Luke" wrote in message
...

" jls" wrote:
http://www.seqair.com/FlightTest/Kil...lYourself.html

From the article:
"Overall the safety record of homebuilt aircraft is not greatly
different from production aircraft."

The author provides no evidence. Where are the numbers?

Some people want to fly faster than that 130 mph Cessna of yours

That's a 155 mph Cessna, son.

Still slow, Danny Boy, for all the fuel you're burnin'. Somebody in FAST
GLASS taxi by you smirking? Fast glass drivers laugh up their sleeves
while climbing out by your spamcan hanging there in a sort of a hover,
humiliating you, Danny?


Now you got all the numbers you need. Winnow them for yourself, or be
considered lazy like that 172.

" jls" wrote:
Now you got all the numbers you need. Winnow them for yourself, or be
considered lazy like that 172.

Being called lazy by someone who failed to answer the original question,
or who failed to respond to any of the numbers he asked for doesn't
carry much sting.

....and BTW, the idea you've got that I don't like homebuilts is
something you made up in your head.
--
Dan
C172RG at BFM

"Dan Luke" wrote in message
...

" jls" wrote:
Now you got all the numbers you need. Winnow them for yourself, or be
considered lazy like that 172.

Being called lazy by someone who failed to answer the original question,
or who failed to respond to any of the numbers he asked for doesn't
carry much sting.

...and BTW, the idea you've got that I don't like homebuilts is
something you made up in your head.
--
Dan
C172RG at BFM

Ah, no, Danny, I figured maybe you're just an envious wannabe owner of an
experimental when you associated experimentals with wacko Evel Knievel.

The point you ignore is the numbers are there, if you will but glean them.
And you (well, not YOU, but someone capable of *thinking* about it) should
consider that many experimental aircraft accidents are attributable, as the
writer who explained the solution to so many Grumman Cheetah accidents, to
lack of experience in the aircraft --- not the aircraft itself.

The predecessors of New Gasair can furnish anecdotal details: Until
somebody had a brilliant idea that pilots of 4-place Gasairs should get
instruction from an experienced pilot before flying them for the first time,
they were regularly dropping out of the sky.

Same for all the other experimental aircraft with performance which humbles
that 172 of yours. Same for ANY experimental aircraft which because of its
uniqueness klunky-footed 172 drivers are not usually equipped to handle it.

Bye, now.

Ron Wanttaja wrote:

A brief summary is tough, when we're talking a 3000+ word article
with a bunch
of graphs (I was the author of the article).

Thanks very much for the detailed summary! That would be great if you
can get the entire article on-line. I realize there may be legal issues
involved with putting a magazine article on the web that anyone can
read for free.

Have to say that since the bottom line from your summary was that
homebuilts are involved in *more* accidents than their factory-built
counterparts, the credibility of the analysis goes up a few notches in
my book. And the reasoning you presented for many of the necessary
assumptions was sound, I think.

Jim Rosinski

" jls" wrote:
The point you ignore is the numbers are there, if you will but glean
them.

By "gleaning" I presume you mean "ignoring the ones jls can't face."
The fact remains that experimentals are 10.4% of the fleet and have 17%
of the fatal accidents, a statistic you have tried to weasel out of
confronting.

In case you have forgotten, you said experimentals have an "enviable"
safety record; I asked you by whom. Ever going to get around to
answering that question?

And you (well, not YOU, but someone capable of *thinking* about it)
should
consider that many experimental aircraft accidents are attributable,
as the
writer who explained the solution to so many Grumman Cheetah
accidents, to
lack of experience in the aircraft --- not the aircraft itself.

Same thing goes for certified aircraft.

The predecessors of New Gasair can furnish anecdotal details: Until
somebody had a brilliant idea that pilots of 4-place Gasairs should
get
instruction from an experienced pilot before flying them for the first
time,
they were regularly dropping out of the sky.

Same thing goes for Cirrus Designs. So what?

Same for all the other experimental aircraft with performance which
humbles
that 172 of yours. Same for ANY experimental aircraft which because
of its
uniqueness klunky-footed 172 drivers are not usually equipped to
handle it.

You know as little about me as you do about examining accident
statistics; that is to say, virtually nothing.

Bye, now.

AMF

jls wrote:

Still slow, Danny Boy, for all the fuel you're burnin'. Somebody in
FAST GLASS taxi by you smirking? Fast glass drivers laugh up their
sleeves while climbing out by your spamcan hanging there in a sort of
a hover, humiliating you, Danny?

I'd say "Danny Boy" has pretty well humiliated *you* in the ongoing war
of words between you two in this thread, hotshot. Evidently you need to
compensate--for something.

Jim Rosinski