[AI] Fwd: Black Boxes...............................?

Rohiet A. Patil patil_rohit at dataone.in
Fri Jun 4 12:08:48 EDT 2010

A very informative article. But is this not a off topic on this list?
----- Original Message ----- 
From: "vinod babu" <vinodbkollam at gmail.com>
To: <accessindia at accessindia.org.in>
Sent: Friday, June 04, 2010 2:17 PM
Subject: [AI] Fwd: Black Boxes...............................?

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From: ravi krishna <ravi.99ks at gmail.com>
Date: Thu, 3 Jun 2010 22:31:17 +0530
Subject: Fwd: Black Boxes...............................?
To: insight_friends at googlegroups.com

          Airliner Black Boxes

                      [image: untitled 2.bmp]

  The "black box" is a generic term for two recording devices carried aboard
commercial airliners. The Flight Data Recorder (FDR) records a variety of
parameters related to the operation and flight characteristics of the plane.
The Cockpit Voice Recorder (CVR) records the voices of the flight crew,
engine noise, and any other sounds in the cockpit. All large commercial
airliners and certain varieties of smaller commercial, corporate, and
private aircraft are required by law to carry one or both of these boxes,
which generally cost between $10,000 and $15,000 apiece. The data these
devices provide is often invaluable to experts investigating the events
leading up to an accident. The recovery of the boxes is one of the highest
priorities in any mishap investigation, second only to locating survivors or
recovering the remains of victims. FDR information is also often used to
study other aviation safety issues, engine performance, and to identify
potential maintenance issues.

[image: cockpit-voice-recorder.jpg]
*Example of a Cockpit Voice Recorder (CVR)*
 Despite the nickname "black box," the FDR and CVR are actually painted a
bright high-visibility orange with white reflecting strips to make them
easier to spot at a crash scene. The meaning of the term black box itself is
somewhat unclear. Some suggest it refers to the black charring that occurs
in a post-crash fire while others believe the color black is a reference to
the deaths often associated with an accident investigation. The design of
modern black boxes is regulated by a group called the International Civil
Aviation Organization (ICAO). The ICAO determines what information the black
boxes must record, over what length of time it is saved, and how survivable
the boxes must be. The ICAO delegates much of this responsibility to the
European Organisation for Civil Aviation Equipment (EUROCAE) that maintains
a document called the Minimum Operational Performance Specification for
Crash Protected Airborne Recorder Systems.
Black boxes first began to appear in the 1950s and became mandatory during
the 1960s. These early devices used magnetic tape for data storage, much
like that used in a tape recorder. As the tape is pulled over an
electromagnetic head, sound or numerical data is recorded on the medium.
Analog black boxes using magnetic tape are still present aboard many planes,
but these recording devices are no longer manufactured. Newer recorders
instead use solid-state memory boards, called a Crash Survivable Memory Unit
(CSMU), that record data in a digital format. Instead of the moving parts
present in older recorders, solid-state devices use stacked arrays of memory
chips similar to a USB memory stick. The lack of moving parts eases
maintenance while reducing the chance of a critical component breaking in a
crash. Solid-state recorders can also save considerably more data than older
magnetic tape devices and are more resistant to shock, vibration, and

[image: fdr-egyptair990.jpg]
*Magnetic tape from within the FDR of EgyptAir 990 that crashed in 1999*
 Whatever the medium used to record the data, the purpose of the black boxes
is to collect information from various sensors aboard an aircraft. The
Cockpit Voice Recorder, for example, saves sounds from microphones located
on the flight deck. An area microphone is typically placed in the overhead
instrument panel between the pilots, and an additional microphone is located
in the headset of each member of the flight crew. These microphones pick up
conversations between the flight crew, engine noises, audible warning
alarms, landing gear sounds, clicks from moving switches, and any other
noises like pops or thuds that might occur in the cockpit. The CVR also
records communications with Air Traffic Control, automated radio weather
briefings, and conversations between the pilots and ground or cabin crew.
These sounds often allow investigators to determine the time of key events
and system failures.
Analog magnetic tape recorders are required to store four audio channels for
at least 30 minutes while digital solid-state devices are required to record
for two hours. Both types use continuous recording such that older
information is written over as new data is collected beyond the maximum time

[image: fdr-plots.jpg]
*Sample data recovered from a Flight Data Recorder*
 The Flight Data Recorder collects data from a number of sensors to monitor
information like accelerations, airspeed, altitude, heading, attitudes,
cockpit control positions, thermometers, engine gauges, fuel flow, control
surface positions, autopilot status, switch positions, and a variety of
other parameters. Most parameters are recorded a few times per second but
some FDRs can record bursts of data at higher frequencies when inputs are
changing rapidly.
The data measured by the different sensors is collected by the Flight Data
Acquisition Unit (FDAU). This device is typically located in an equipment
bay at the front of the aircraft beneath the flight deck. The FDAU assembles
the desired information in the proper format and passes it on to the FDR at
the rear of the plane for recording. The Federal Aviation Administration
(FAA) required the FDR to record between 11 and 29 parameters, depending on
aircraft size, up to 2002 but now requires saving a minimum of 88 sets of
data. Analog FDRs can save a maximum of around 100 variables while digital
recorders are often capable of collecting over 1,000 parameters over the
course of 25 hours.

[image: recorder-locations.jpg]
*Diagram of data flow to aircraft black boxes*
 Power for the black boxes is provided by electrical
to the engines. The generators on most large airliners produce a
standard output of 115 volt, 400 hertz AC power while some smaller planes
instead generate 28 volt DC power. Black boxes are typically designed to use
only AC or DC power but not either one. Recorders built for compatibility
with the AC power supplies on larger planes cannot be used on small
DC-powered aircraft. In the event of engine failure, larger aircraft are
also equipped with emergency backup power sources like the auxiliary power
generator and ram air
continue operating the black boxes. In addition, the ICAO is
making a battery mandatory on solid-state recorders to provide an
independent power supply in the event of a complete power failure aboard the
A common misconception states that the black boxes are "indestructible." No
manmade device is indestructible, and no material has ever been developed
that cannot be destroyed under severe enough conditions. The black boxes are
instead designed to be highly survivable in a crash. In many of the worst
aviation accidents, the only devices to survive in working order are the
Crash Survivable Memory Units (CSMUs) in the black boxes. The remainder of
the recorders, including the external case and other internal components,
are often heavily damaged.

[image: black-box-interior.jpg]
*Interior cut-away of a black box design*
 The CSMU, however, is contained within a very compact cylindrical or
rectangular box designed to safeguard the data within against extreme
conditions. The box is composed of three layers to provide different types
of protection to the recording medium. The outermost shell is a case made of
hardened steel or titanium designed to survive intense impact and pressure
damage. The second layer is an insulation box while the third is a thermal
block to protect against severe fire and heat. Together, these three layered
cases allow the FDR and CVR to survive in all but the most extreme crash
Current regulations require the black boxes to survive an impact of 3,400
g's <http://www.aerospaceweb.org/question/instruments/q0040.shtml> for up to
6.5 milliseconds. This rapid deceleration is equivalent to slowing from a
speed of 310 miles per hour (500 km/h) to a complete stop in a distance of
just 18 inches (45 cm). This requirement is tested by firing the CSMU from
an air cannon to demonstrate the device can withstand an impact force at
least 3,400 times its own weight. The black boxes must also survive a
penetration test during which a steel pin dropped from a height of 10 ft (3
m) impacts the CSMU at its most vulnerable point with a force of 500 pounds
(2,225 N). In addition, a static crush test is conducted to demonstrate that
all sides of the CSMU can withstand a pressure of 5,000 pounds per square
inch (350 kg/cm�) for five minutes. The fire resistance of the CSMU is
further tested by exposing it to a temperature of 2,000�F (1,100�C) for
up to an hour. The device is also required to survive after lying in
smoldering wreckage for ten hours at a temperature of 500�F (260�C).

[image: locator-beacon.jpg]
*Underwater Locator Beacon on a black box*
 Other requirements specify survivability limits when immersed in liquids.
The CSMU must endure the water pressure found at an ocean depth of 20,000 ft
(6,100 m), and a deep-sea submersion test is conducted for 24 hours. Another
saltwater submersion test lasting 30 days demonstrates both the
survivability of the CSMU and the function of an Underwater Locator Beacon
(ULB), or "pinger," that emits an ultrasonic signal once a second when
immersed in water. These signals can be transmitted as deep 14,000 ft (4,270
m) and are detectable by sonar to help locate the recorders. A final series
of tests includes submerging the CSMU in various fluids like jet fuel and
fire extinguishing chemicals to verify the device can withstand the
corrosive effects of such liquids.
Upon completion of the testing, the black boxes are disassembled and the
CSMU boards are extracted. The boards are then reassembled in a new case and
attached to a readout system to verify that the pre-recorded data written to
the device can still be read and processed.
Another factor important to the survivability of the black boxes is their
installation in the tail of the aircraft. The exact location often varies
depending on the plane, but the FDR and CVR are usually placed near the
galley, in the aft cargo hold, or in the tail cone. The recorders are stored
in the tail since this is usually the last part of the aircraft to impact in
an accident. The entire front portion of the plane acts like a crush zone
that helps to decelerate the tail more slowly. This effect reduces the shock
experienced by the recorders and helps to cushion the devices to improve
their chances of surviving the crash.

[image: fdr-united93.jpg]
*Flight Data Recorder recovered from United Airlines 93 in 2001*
 Once the black boxes have been located following an accident, they are
typically taken into custody by an aviation safety agency for analysis. In
the United States, responsibility for investigating most air accidents
belongs to the National Transportation Safety Board (NTSB). Many countries
lacking the capability to analyze black boxes also send their recorders to
the computer labs of the NTSB or some of the better-equipped investigative
organizations in Western nations. Care must be taken in recovering and
transporting the recorders so that no further damage is done to the devices
that might prevent important data from being extracted.
Upon receipt of the recorders, the NTSB uses a series of computer and audio
equipment to process and analyze any information that can be recovered. The
data is translated into formats readily usable by investigators and is
usually critical in identifying the probable cause(s) of the accident. This
process may take many weeks or months depending on the condition of the
black boxes and the level of processing required to make sense of the data.
Outside experts are also often consulted to help analyze and interpret the

[image: american587-animation.jpg]
*Animation image created using FDR data from American Airlines 587 that
crashed in 2001*
 Flight Data Recorder information is typically presented in the form of
graphs or animations used to understand instrument readings, flight
characteristics, and the performance of the aircraft during its final
moments. Cockpit Voice Recorder information is usually more sensitive and
laws strictly regulate how it is handled. A committee including
representatives of the NTSB, FAA, the airline, the manufacturers of the
aircraft and engines, and the pilots union is responsible for preparing a
transcript of the CVR's contents. This transcript is painstakingly created
using air traffic control logs and sound spectrum analysis software to
provide exact timing. Although the transcript can be released to the public,
only select and pertinent portions of the actual audio recording are made
public due to privacy concerns.
Flight recorder design has improved considerably since the devices were
first introduced in the 1950s. However, no recording device is perfect.
Black boxes are sometimes never found or too badly damaged to recover some
or all of the data from a crash. To reduce the likelihood of damage or loss,
some more recent designs are self-ejecting and use the energy of impact to
separate themselves from the aircraft. Loss of electrical power is also a
common event in aviation accicents, such as Swissair Flight 111 when the
black boxes were inoperative for the last six minutes of flight due to
aircraft power failure. Several safety organizations have recommended
providing the recorders with a backup battery to operate the devices for up
to ten minutes if power is interrupted.

[image: cvr-united93.jpg]
*Cockpit Voice Recorder recovered from United Airlines 93 in 2001*
 Another recommendation is to add a second independent set of recorders on a
separate electrical bus to insure redundancy in the event of a system
failure. The additional recorders would be located as close to the cockpit
as possible while the existing black boxes remain in the tail to reduce the
likelihood of a single failure incapacitating both sets. Accident
investigators have also argued for the installation of a third black box to
record cockpit video. Though pilots have so far resisted the move because of
privacy issues, video data would be useful to better understand pilot
actions in the moments leading up to an accident.
[image: black-box-location.jpg]

[image: Black_box_aeroplane.jpg]


Madhu Vee Vee
k a v a l a y o o r


Vinod. B.

mobile 9809664484

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