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Chelton as a Flight Data Recorder: Post Accident Analysis
Jeff,
The Log files that are downloadable via the ground
access menu are most likely where Brent got the data. Most all the values
are there, but only on 1 second intervals. perhaps more data is stored
somewhere internally, I'm not sure.
However the format for this log file is public
information and is available in the installation
documentation.
I created a perl script over a year ago to use with the
Reno racers and to allow the data to be plotted on Google maps. I recently
cobbled together a webpage, where you can send your logs and get a CSV (comma
delimited file) back. This can then be given to www.gpsvisualizer.com to do the mapping
or you can just use the raw data and plot away in excel.
Here's the link that I posted on the CheltonEfisPilots
forums about it.
Have fun, if there is a data element that I've not
pulled over, just let me know, I don't decode all of the, but to do so is very
easy.
Alan
Our Chelton units are durable flight data recorders that frequently retain
their data after a catastropic accident. I recall in May 2003 when the
Chelton unit was pulled from the wreakage of my frined's Lancair IVP (N29ME) and
given to Brent Regan for analysis, there were some graphic descriptions of the
VSI shifts and G forces and roll angles and pitch changes that not only
impressed me what happens inside a TStorm, but scared me to think that's what
awaits us inside that IMC. For example, Brent described one moment 5,328
fpm UP and the next moment 10,208 fpm DOWN with extremes in bank angle.
Here's the NTSB report:
http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20030520X00696&ntsbno=ATL03LA094&akey=1
The damaged Sierra Flight
Systems navigation systems were forwarded to the Seattle Flight Standards
District Office for further analysis by Regan Designs, Coeur-D"Alene, Idaho. The
data cards were removed and the systems were downloaded after replacing damaged
components. Review of information downloaded from the Sierra Flight Systems
navigation system revealed the airplane was at 11,676 feet at 1755:31. The
airplane climbed up to 12, 236 feet at 1755:46, and entered a left spiraling
dive. The last data point at 1756:01 shows a tightening left hand spiral dive
with a true airspeed of 253, and a positive 3.75 G's.
I also recall that his description was later suppressed in an apology and
an expression of regret that the Chelton data retreived was disclosed to us
outside the NTSB process, conceiveably a "no no" by the bureaucracy.
http://mail.lancaironline.net/Lists/lml/Message/19072.html
And so we get very little descriptive information in the NTSB reports about
the sheer terror of the forces acting on the plane at the time of the accident
event. I think this is a missed opportunity, and would like to ask if
others would also be interested in these details. The NTSB excerpt above
contains some of these Chelton details, but does not invoke the timeline and in
the way that Brent Regan did many years ago.
The recent N101BX accident had a Chelton unit, as have many others.
Perhaps there is a way to have this raw Chelton data available outside the NTSB,
or have the more detailed interpretation of this data shared with us, so we can
benefit from the recorded events.
I think there is a need for this type of detail beyond the NTSB summary
report. Does anyone agree, and does anyone know how to gain access to
it?
As a footnote, I'm sure many ListServ members appreciate Brent Regan's
contributions everytime he weighs in.
Jeff Liegner
LIVP
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