Page 20 - Forum-2020-JulyToSeptember

The following article is the Remembering Before the Crash:
final of four essays from the
2019 Kapustin scholarship
winners presented during
ISASI 2019. The number of
scholars selected each year
depends upon the amount of
money ISASI members donate
annually to the scholarship
fund. Details about scholarship
applications and additional
information can be found on
the ISASI website at www.
isasi.org. Application and
essay deadlines are mid-April
of each year.—Editor
Elise Marie Vondra
20 • July-September 2020 ISASI Forum
Nonvolatile Memory Can Change
The Course of an Investigation
By Elise Marie Vondra, University of Southern California
n the last 20 years, investigators have Helios Airways Flight 522
made air travel increasingly safer by Enroute from Larnaca, Cyprus, to Prague,
learning from past accidents. Between Czech Republic, a Helios Airways Boeing
I1990 and 1999, 541 fatalities in 34 com- 737-300 lost contact with air traffic control
mercial aircraft accidents occurred, and (ATC) mid-flight. Loss of cabin pressure
those numbers dropped to 67 fatalities caused both pilots to lose consciousness.
in eight accidents in the years 2007–2017 The aircraft flew until fuel starvation,
(1). Investigators painstakingly find, eventually impacting terrain 33 kilom-
sort, and analyze data from the aircraft eters northwest of Athens, Greece. The
to determine the accident’s cause. In Air Accident Investigation and Safety
the aftermath of an accident, however, Board (AAIASB) of the Hellenic Minis-
news media coverage focuses mainly on try of Transport and Communications
two major types of data, the flight data concluded that the cabin pressurization
recorder (FDR) and cockpit voice re- mode was set to manual control, and both
corder (CVR), publishing articles such as pilots failed to identify any subsequent
“Crashed Lion Air Plane’s Cockpit Voice warnings. The AAIASB supplemented FDR
Recorder Found” (2). and CVR data with data from the NVM of
The FDR and CVR seemingly give two cabin pressure controllers. The No. 2
investigators enough data to work slave controller survived the accident, and
with, yet an increasingly important and investigators sent it to Nord-Micro, the
more-nuanced source of data comes from manufacturer of the sensor. It contained
nonvolatile memory (NVM) sources on more than 301 hours of information from
the aircraft. NVM data are stored within past flights. In comparison, the FDR used
the chip of a component; are utilized in in this aircraft contained the maximum of
avionics such as the GPS, altimeters, and 50 hours of flight data. The extended data
pressure sensors; and survive without a allowed investigators to conclude that the
power source. NVM can record data from pilots’ behavior of selecting manual cabin
more flights than current FDRs and CVRs. pressure was abnormal, as past flights did
Currently, the widely used Honeywell not show a pattern of this selection (4).
Connected Recorder-25 (HCR-25) FDR
and CVR store only the last 25 hours of
flight data (3). In contrast, an NVM chip Turkish Airlines Flight 1951
on a cabin pressure controller, such as The use of NVM to determine patterns
that used on Helios Airways Flight 522, in data was especially useful in Turkish
can store more than 300 hours of data (4). Airlines Flight 1951. The Boeing 737-800
As avionics advance, the use of NVM on crashed just under a mile from Runway
components and their available storage 18R on approach to Schiphol Airport in
will increase. The investigator must adapt Amsterdam, the Netherlands, enroute
to find and utilize this data, not only after from Istanbul, Turkey. At the time of the
an accident occurs, but also in preventa- accident, the first officer was acting as
tive measures. pilot-in-command (PIC). The Boeing
Three accidents, Helios Airways Flight 737-800 has redundant radio altimeter
522 in 2005, Turkish Airlines Flight 1951 systems, which default to using the left-
in 2009, and a general aviation flight in hand altimeter. However, before the crash,
Papua, New Guinea, in 2009, highlight the the left-hand altimeter was incorrectly
importance of NVM and how it can be reading an altitude of -8 feet. Since the PIC
taken advantage of in accident investiga- was looking at the right-hand altimeter,
tions. which was reading accurately, neither the