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Chelton as a Flight Data Recorder: Post Accident
Analysis
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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