Cirrus down, Chapel Hill NC

On Jul 15, 12:28*am, Ron Wanttaja wrote:
Mxsmanic wrote:
a writes:

It may be selective memory on my part, but it seems these airplanes
have been over represented among GA accidents lately.

They are indeed over-represented.

No. *Their accident rate is less than that of Cessna 172s manufactured
over the same time period.

In 2009, there were 23 Cirrus accidents, vs. 3699 aircraft registered as
of January 2010. *There were 3003 Cessna 172s on the registry that had
been manufactured since production restarted in the '90s. *The NTSB
accident listing for 2009 shows 23 Cessna 172S models and four 172R models.

Cirrus: *23/3699 = *0.62%

New-Production 172s: *27/3003 = 0.89%

Ron Wanttaja

That you compared aircraft and accident rates manufactured in the same
interval -- S model 172s -- very nicely compares apples with apples
in my view. Nice data, nice logic.

a wrote:
On Jul 15, 12:28Â*am, Ron Wanttaja wrote:
Mxsmanic wrote:
a writes:

It may be selective memory on my part, but it seems these airplanes
have been over represented among GA accidents lately.

They are indeed over-represented.

No. Â*Their accident rate is less than that of Cessna 172s manufactured
over the same time period.

In 2009, there were 23 Cirrus accidents, vs. 3699 aircraft registered as
of January 2010. Â*There were 3003 Cessna 172s on the registry that had
been manufactured since production restarted in the '90s. Â*The NTSB
accident listing for 2009 shows 23 Cessna 172S models and four 172R models.

Cirrus: Â*23/3699 = Â*0.62%

New-Production 172s: Â*27/3003 = 0.89%

Ron Wanttaja

That you compared aircraft and accident rates manufactured in the same
interval -- S model 172s -- very nicely compares apples with apples
in my view. Nice data, nice logic.

Yeah and with rates that low you can not establish any "blame" on the
manufacturer, you are down into the realm of random, stupid pet tricks.


--
Jim Pennino

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Ron Wanttaja wrote:
Mxsmanic wrote:
a writes:

It may be selective memory on my part, but it seems these airplanes
have been over represented among GA accidents lately.

They are indeed over-represented.

No. Their accident rate is less than that of Cessna 172s manufactured
over the same time period.

In 2009, there were 23 Cirrus accidents, vs. 3699 aircraft registered
as of January 2010. There were 3003 Cessna 172s on the registry that
had been manufactured since production restarted in the '90s. The
NTSB accident listing for 2009 shows 23 Cessna 172S models and four
172R models.

Cirrus: 23/3699 = 0.62%

New-Production 172s: 27/3003 = 0.89%

Having between 0.5% and 1% of an aircraft fleet (or subset) involved in
accidents per year always seemed a high attrition rate to me. But I can't
say I ever bothered to check before what the equivalent number was with
respect to automobiles. A quick check of approximate number of autos in the
U.S.[1] and accidents per year in the U.S.[2] seems to yield:

Autos: 6,000,000/250,000,000 = 2.4%

On the other hand, the auto accidents probably include many fender benders
which would probably be more equivalent to "Incidents" rather than
"Accidents" as those terms are defined by the FAA (or NTSB?), so the two
ratios aren't directly comparable. For fatal automobile accidents[3] the
numbers appear to be (roughly):

Fatal Auto Accidents: 40,000/250,000,000 = 0.016%

And idea how many of those Cirrus and Cessna 172 accidents involved
fatalities?

[1] http://en.wikipedia.org/wiki/Passeng..._United_States
[2] http://www.car-accidents.com/pages/stats.html
[3] http://www.car-accidents.com/pages/f...tatistics.html

Jim Logajan writes:

And idea how many of those Cirrus and Cessna 172 accidents involved
fatalities?

A quick look at the NTSB database reveals 85 fatalities for Cessna 172s since
January 1, 2008, and 48 fatalities for Cirrus SR-22s since that same date.

There are 26,163 Cessna 172s registered currently, and 3,746 Cirrus SR-22s.

The fatality rate during this period on a per-aircraft basis is therefore
0.00324 for Cessna 172s and 0.01281 for Cirrus SR-22s. The rate for the SR-22s
is thus nearly four times higher than that for Cessna 172s.

Now, if you are convinced that 23,000 Cessna 172s are idle and only 3000 or so
are flying, and/or that all Ciruss SR-22s are flying, you're going to have to
show data to support this--otherwise it is pure and misleading speculation.
Just glancing at aircraft at the local airport won't do.

Mxsmanic wrote:
Jim Logajan writes:

And idea how many of those Cirrus and Cessna 172 accidents involved
fatalities?

A quick look at the NTSB database reveals 85 fatalities for Cessna 172s since
January 1, 2008, and 48 fatalities for Cirrus SR-22s since that same date.

There are 26,163 Cessna 172s registered currently, and 3,746 Cirrus SR-22s.

The fatality rate during this period on a per-aircraft basis is therefore
0.00324 for Cessna 172s and 0.01281 for Cirrus SR-22s. The rate for the SR-22s
is thus nearly four times higher than that for Cessna 172s.

How does that compare to the rate for a Chevrolet Corvair?



--
Jim Pennino

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"Mxsmanic" wrote in message
...
Jim Logajan writes:

And idea how many of those Cirrus and Cessna 172 accidents involved
fatalities?

A quick look at the NTSB database reveals 85 fatalities for Cessna 172s
since
January 1, 2008, and 48 fatalities for Cirrus SR-22s since that same date.

There are 26,163 Cessna 172s registered currently, and 3,746 Cirrus
SR-22s.

The fatality rate during this period on a per-aircraft basis is therefore
0.00324 for Cessna 172s and 0.01281 for Cirrus SR-22s. The rate for the
SR-22s
is thus nearly four times higher than that for Cessna 172s.

Now, if you are convinced that 23,000 Cessna 172s are idle and only 3000
or so
are flying, and/or that all Ciruss SR-22s are flying, you're going to have
to
show data to support this--otherwise it is pure and misleading
speculation.
Just glancing at aircraft at the local airport won't do.

Using your figures, fatal accidents are lower for the Cirrus SR22 than for
automobiles.

As to accidents involving "substantial damage" to automobiles, for which I
have never seen a seperate statistic, the point probably is that there is no
point!

Mxsmanic wrote:
Jim Logajan writes:

And idea how many of those Cirrus and Cessna 172 accidents involved
fatalities?

A quick look at the NTSB database reveals 85 fatalities for Cessna
172s since January 1, 2008, and 48 fatalities for Cirrus SR-22s since
that same date.

I was asking Ron for the number of accidents in his count that yielded
fatalities, not the number of fatalities for your subset.

There are 26,163 Cessna 172s registered currently, and 3,746 Cirrus
SR-22s.

As has been already pointed out to you, the registration count for
Cessna 172s does not provide any idea how many are actually in use for
any measurement period. Here is what the FAA says about their
registration records with respect to this issue:

"Of the more than 343,000 aircraft registered, an estimated 104,000, or
about one-third, are possibly no longer eligible for registration."
From:
http://rgl.faa.gov/Regulatory_and_Gu... ndSection=-5

Now, if you are convinced that 23,000 Cessna 172s are idle and only
3000 or so are flying, and/or that all Ciruss SR-22s are flying,

Unfortunately you continue to use data sets that have already been
pointed out as unreliable basis for normalization.

Mxsmanic wrote:
Jim Logajan writes:

And idea how many of those Cirrus and Cessna 172 accidents involved
fatalities?

A quick look at the NTSB database reveals 85 fatalities for Cessna 172s since
January 1, 2008, and 48 fatalities for Cirrus SR-22s since that same date.

There are 26,163 Cessna 172s registered currently, and 3,746 Cirrus SR-22s.

The fatality rate during this period on a per-aircraft basis is therefore
0.00324 for Cessna 172s and 0.01281 for Cirrus SR-22s. The rate for the SR-22s
is thus nearly four times higher than that for Cessna 172s.

I've been looking at fatality rates in regards to homebuilt aircraft.
There's a strong correlation between the cruise speed of an aircraft
with its fatality rate. This is obvious...twice the speed at impact
means the occupants are subjected to four times the energy. The Cirrus
is faster than the 172, hence passengers will be subjected to more
energy in a crash.

Planes don't all CRASH at cruise speed, of course. But generally
speaking, faster airplanes have faster approach speeds and hence there's
more energy to be absorbed at impact.

For instance, compare the fatality ratio for the Lancair IV vs. the
Zenith CH 701. The Lancair's rate is about seven times higher.

The other factor is that Cessna 172s are commonly used as trainers, and
training accidents are usually more in the "fender bender" line. For
example, there were 155 Cessna 172 accidents in 2007. In over half the
cases (81), the NTSB report says the purpose of the flight was
instruction. Of those, only four resulted in fatalities.

Ron Wanttaja

On Jul 13, 7:47*am, a wrote:
It may be selective memory on my part, but it seems these airplanes
have been over represented among GA accidents lately.

The story of this crash can be found here (and elsewhere)

http://www.heraldsun.com/view/full_s...e-Plane-crashe...

A little more about this crash.

It appears the airplane landed, bounced along the runway, and 600 feet
from touchdown went off the runway, hit a tree, and the impact
deployed the rescue parachute.

At first blush, an accident on landing. The NTSB report will be
instructive, it's not often I've read of GA airplanes at that stage of
landing being in a fatality.

http://www.newsobserver.com/2010/07/...ay-veered.html

On Jul 13, 7:47*am, a wrote:
It may be selective memory on my part, but it seems these airplanes
have been over represented among GA accidents lately.

The story of this crash can be found here (and elsewhere)

http://www.heraldsun.com/view/full_s...e-Plane-crashe...

The NTSB preliminary report has been issued.

http://www.ntsb.gov/ntsb/GenPDF.asp?id=ERA10FA356&rpt=p

There are several items embedded in the report that were
'inconsistent' with my guesses as to what might have contributed to
this accident. Note that the pilot had a significant number of hours
-- over a hundred -- as PIC in this airplane, and a reasonable amount
of total time -- 400 plus. A hundred hours in the Cirrus, probably 70
landings. The PIC could have been any medium time pilot among us. If
it was VFR those numbers would have given me enough confidence to sit
in the back seat!

What is the lesson we who fly can learn from this-- be careful to
control airspeed on final? Control attitude on go-round? Pay
attention to the basics?

It was a flight for a sad purpose with an even sadder ending. May all
somehow find peace.