PRODUCT
Flight Data Recorders
Built to Survive
B Y T O N Y B A I L E Y
O
K, I know the truth. Most avi- speed, vertical acceleration and time.
onics technicians will never These early devices had very limited
get involved with the inter- recording capabilities. The five ana-
nal workings of a flight data recorder log parameters of heading, altitude,
(FDR) and if they do, it is probably be- airspeed, vertical accelerations and
cause they work for one of the original time were embossed onto a metal foil
equipment manufacturers (OEM) like (Incanol Steel), which was used only
Boeing, Cessna or Gulfstream. So, why once. The foil was believed to be
is the FDR the most recognized piece nearly indestructible; however, crash
of aviation electronics? The FDR, or boxes following an accident. These are survival remained a serious problem.
better known as the “Black Box,” is a especially helpful when a plane lands Original requirements were for a unit
common household term because of the in the water. There are two possible to be able to withstand a 100 G impact
dynamic function it performs and the origins of the term “black box.” Some and be installed in the forward avion-
amount of media attention it receives believe it is because early recorders ics bay with the rest of the avionics
after a catastrophic aircraft failure. were painted black, while others think boxes. After several accidents with
Usually, a statement like this makes it refers to the charring that occurs in aircraft equipped with FDRs, it soon
headlines just after a catastrophic flight post-accident fires. became evident that the 100 G speci-
occurrence: Of course, the adoption of FDRs fication was inadequate. To correct the
“Data from two voice recorders was not without trials and tribulations. situation, the Federal Aviation Admin-
from Air France Flight 358 has been Efforts to require crash-protected flight istration (FAA) in 1965 made a speci-
successfully downloaded, the lead in- recorders date back to the 1940s. The fication change which increased the
vestigator into the accident said Fri- introduction of FDR systems, how- impact requirements to 1,000 Gs and
day. The black boxes, containing the ever, experienced many delays. Thatʼs relocated the recorder to the rear of the
flight data and cockpit voice recorders, because technology could not match aircraft. The reasoning for the change
had been quite damaged in the fire and the design requirements of a unit that was that, following initial impact, the
investigators were concerned whether could survive the forces of an aircraft rear of the aircraft would be moving at
they would be able to retrieve informa- crash and the resulting fire exposure a slower speed, thus, more recorders
tion. ʻSo I think thatʼs a good surprise until 1958, when the world authorities would survive.
and certainly Iʼm very relieved to find approved minimum operating require- With just five parameters, however,
out that data was good quality data,ʼ ments for an FDR. This was about the there was not enough recorded data
Transportation Safety Board investiga- beginning of the so-called “Jet Age,” for a meaningful accident investiga-
tor Réal Levasseur told reporters.” with the introduction of such aircraft tion. Consequently, in 1987, these re-
Although FDRs are called “black as the Boeing 707, Douglas DC-8 and corders became unacceptable to most
boxes,” aviation recorders are actually the Caravelle. government regulatory authorities
painted bright orange. These distinct The initial requirement of these and additional parameters were re-
colors, along with the strips of reflec- newly mandated data recorders was to quired. Although most major airlines
tive tape attached to the recorderʼs exte- record the actual flight conditions of replaced these old-technology record-
rior, help investigators locate the black the aircraft, i.e., heading, altitude, air- ers long before required by law, many
38 AVIONICS NEWS • JANUARY 2006
of these first-generation recorders are crash-protected “tape” unit. In the late the capability of magnetic-tape record-
still flying in older model aircraft. The 1970s and early 1980s the Internation- ers. On July 17, 1997, the FAA issued
remainder of these foil recorders will al Civil Aviation Organization (ICAO) a Code of Federal Regulations that
soon be unusable, since the industry began recommending that digital air- requires the recording of at least 88
supply of the lncanol Steel recording craft record 32 parameters. As the parameters on aircraft manufactured
medium has been depleted. ICAO had no enforcement capabili- after Aug. 19, 2002.
However, flight data containing five ties, each country continued to follow Since the solid state memory does
parameters alone could not provide all its own existing regulations; however, not require scheduled maintenance or
the accident information needed by the their goals were to eventually meet the overhaul, there are potential cost sav-
investigators. A new “tape” technol- ICAO recommendations. ings to the operator. Additionally, the
ogy (recording data in a digital format) In the United States, the FAA re- data is easier to retrieve, and is read-
was expanded to the FDR. This sec- quires that commercial airlines record ily available to assist in monitoring the
ond-generation FDR allowed a manu- a minimum of 11 to 29 parameters, performance of the aircraft, or during
facturer to build products that would depending on the size of the aircraft. scheduled maintenance inspections.
record many additional flight param- Magnetic-tape recorders have the po- Using technology of the third-genera-
eters while meeting higher crash and tential to record up to 100 parameters. tion recorders, operators can extract
fire protection requirements. In the late The Solid State Flight Data Re- stored data in a matter of minutes. This
1960s and early 1970s, the introduc- corder (SSFDR) became commer- data can show how the aircraft has
tion of sophisticated aircraft such as cially practical in 1990. “Solid State” performed in flight, or if a monitored
the B-747, DC-10, L-1011 and A300 refers to storage of data in semicon- device needs maintenance. Now, the
required new recorders that could re- ductor memories or integrated circuits, operators of newer generation aircraft
tain information about the engines, rather than using the older technology can fly with greater safety and reliabil-
flight controls, flaps, etc., that fully as- of electromechanical methods of data ity.
sist accident investigators. retention. SSFDRs can record more Of course, the data is only good if it
In the late 1960s, Englandʼs Civil than 700 parameters or seven times is protected. The search for this seem-
Aviation Authority required that ad- ingly indestructible box amidst the de-
ditional parameters be recorded. Sev- bris of the wreckage is akin to the quest
Terms and Definitions
eral versions of FDRs were available for the Holy Grail. But in the absence
with multiple metal styli that allowed CSMU Crash Survivable Memory Units of any survivors or eyewitnesses, it is
marking on both sides of the foil. This FDAU Data Acquisition Unit within these steel walls of the box that
allowed for the recording of pitch, roll ECAM Electronic Centralized the digital recordings of the last few
and flaps. While this provided addition- Aircraft Monitor minutes of flight are stored, thus the
al information for the accident inves- best prospect for clues to the disaster.
tigator, it generated much more work EFIS Electronic Flight Instrument But there is no guarantee that even if
for the shops and resulted in lower re- System found, the FDR will have the answers.
liability of the unit. Moreover, this ad- FAA Federal Aviation Administration So, after many years of operation,
ditional information was very difficult FDAU Flight Data Acquisition Unit the FAA increased the durability re-
to read and even harder to interpret. quirements on the recorders and their
FDR Flight Data Recorder
By installing a Flight Data Acquisition casings to survive severe impact and
Unit (FDAU), these analog aircraft HSI Horizontal Situation Indicator fire. All aircraft capable of carrying
could provide much more data. The ICAO International Civil Aviation 10 or more passengers for scheduled
new specification required a new digi- Organization commercial use are required to have
tal type recorder that would record 64 voice and data recorders connected to
OEM Original Equipment
12-bit words each second for 25 hours, the electrical power generators of the
Manufacturers
which represented the round-trip time aircraftʼs main engines.
between New York City and Japan or PFD Primary Flight Display The storage medium of each record-
between Los Angeles and Europe. PSI Pounds per Square-inch er is located in a protective capsule,
The FDAU would take in all of the which must be able to withstand an im-
SSFDR Solid State Flight Data Recorder
analog signals, convert them, and then pact of 3,400 Gs (3,400 times the force
send a single digital data stream to the ULB Underwater Locator Beacon
Continued on following page
AVIONICS NEWS • JANUARY 2006 39
FLIGHT DATA RECORDERS At 3,400 Gs, the CSMU hits an alu- fire test, the memory interface cable
Continued from page 39 minum, honeycomb target at a force that attaches the memory boards to
equal to 3,400 times its weight. This the circuit board is burned away. After
impact force is equal to or in excess the unit cools down, researchers take
of what a recorder might experience in it apart and pull the memory module
an actual crash. out. They re-stack the memory boards,
• Pin drop—To test the unitʼs pen- install a new memory interface cable
etration resistance, researchers drop and attach the unit to a readout system
a 500 pound (227 kg) weight with a to verify that all of the preloaded data
0.25 inch steel pin protruding from the is accounted for.
The damaged flight data recorder from bottom onto the CSMU from a height • Deep-sea submersion—The
EgyptAir Flight 990. of 10 feet (3 m). This pin, with 500 CSMU is placed into a pressurized
pounds behind it, impacts the CSMU tank of salt water for 24 hours.
of gravity). Additionally, each must cylinderʼs most vulnerable axis. • Salt-water submersion—The
also survive flames at 2,000 degrees • Static crush—For five minutes, CSMU must survive in a salt water
Fahrenheit for up to 30 minutes, and researchers apply 5,000 pounds per tank for 30 days.
submersion in 20,000 feet of saltwater square-inch (psi) of crush force to each • Fluid immersion— Various
for 30 days. Most flight data record- of the unitʼs six major axis points. CSMU components are placed into a
ers are constructed with an aluminum • Fire test—Researchers place the variety of aviation fluids, including jet
sheet metal chassis, with a protective unit into a propane-source fireball, fuel, lubricants and fire-extinguisher
capsule constructed of heat-treated cooking it using three burners. The chemicals.
stainless steel or titanium. Because unit sits inside the fire at 2,000 degrees While recorders are placed in the tail
new solid-state digital recorders have Fahrenheit (1,100 C) for one hour. The of an aircraft to increase survivability,
no moving parts and are smaller than FAA requires that all solid-state re- the distance from the parameters re-
their predecessors, they are lighter corders be able to survive at least one corded requires long cables running
than analog tape devices, and use less hour at this temperature. During the the length of the plane. If the plane be-
power. In many accidents, the only
devices that survive are the Crash Sur-
vivable Memory Units (CSMU) of the
flight data recorders and cockpit voice
recorders. Typically, the rest of the re-
cordersʼ chassis and inner components
are mangled. The CSMU is a large cyl-
inder that bolts onto the flat portion of
the recorder. This device is engineered
to withstand extreme heat, violent
crashes and tons of pressure. In older
magnetic-tape recorders, the CSMU is
inside a rectangular box.
To ensure the quality and surviv-
ability of black boxes, manufacturers
thoroughly test the CSMUs. Remem-
ber, only the CSMU has to survive a
crash—if accident investigators have
that, they can retrieve the information
they need.
There are several tests that make up
the crash-survival sequence:
• Crash impact—Researchers
shoot the CSMU through an air can-
non to create an impact of 3,400 Gs. Internal Design of a Typical FDR
40 AVIONICS NEWS • JANUARY 2006
gins to break up or power is otherwise as deep as 14,000 feet (4,267 m). Once
severed prior to a crash, recorded data the beacon begins “pinging,” it pings
can be lost. once per second for 30 days. This bea-
In March 1999, the NTSB made con is powered by a battery that has a
several recommendations to the FAA shelf life of six years. In rare instances,
concerning black boxes. The board the beacon may get snapped off during
suggested that the FAA require a ret- a high-impact collision.
rofit program after Jan. 1, 2005. In this Once the design stability of FDRs
retrofit, all aircraft carrying analog tape had been satisfactorily achieved, the
recorders would be furnished with sol- next step was the integration of three-
id-state digital units, which also would dimensional animation technology for Aircraft animation snapshot with instrument
feature an independent power source accident investigation purposes. With panel and terrain elevation data.
able to support 10 minutes of operating the data retrieved from the FDR, the pitch attitude, heading (true or mag-
time and engage automatically when Safety Board can generate a computer netic), glideslope deviation, localizer
aircraft power ceases. To improve data animated video reconstruction of the deviation, magnetic variation, wind
retrieval, the NTSB has also recom- flight. The investigator can then visu- speed, wind direction, temperature and
mended that all aircraft built after Jan. alize the airplaneʼs attitude, instrument station pressure.
1, 2003, be equipped with two combi- readings, power settings and other Technology has made these ani-
nation voice and data recording sys- characteristics of the flight. This ani- mation programs incredibly accurate
tems. Both systems should continue mation enables the investigating team and detailed. The graphical display of
to record all mandatory parameters, to visualize the last moments of the data-driven instrumentation is a means
but one set should be located close to flight before the accident. of relaying the recorded flight data in a
the cockpit and feature an independent Aircraft animations with synchro- manner similar to what the pilot may
power supply, while the other should nized cockpit instrumentation are an have observed in the cockpit. Some
be mounted in the tail section. effective means of presenting results, examples of cockpit instrumentation
Redundancy, independent power and drawing cause-effect relationships include: control stick, control wheel,
sources, and longer voice recordings from recorded flight data. tachometer, altimeter, horizontal situ-
are big steps in making sure data is The animation of an event encom- ation indicator (HSI), airspeed indica-
reliable, detailed, and clear which is a passes the aircraftʼs flight profile, tor, electronic flight instrument system
key factor in accident investigations. cockpit instrumentation, terrain and (EFIS), primary flight display (PFD)
What people often donʼt know is scenario data. With an ever increasing and electronic centralized aircraft
that in addition to the paint and reflec- number of parameters being recorded Monitor (ECAM).
tive tape, FDRs are equipped with an on aircraft, a method of relaying the While FDRs are successful in air-
Underwater Locator Beacon (ULB). If large amounts of available information craft, new demands and needs have
you look at a picture of an FDR, you in a meaningful manner is needed. 3D spread out into the non-aviation world.
will almost always see a small, cylin- animations are one such method to ef- Black boxes arenʼt just taking flight—
drical object attached to one end of the fectively recreate flight information to theyʼre being grounded as well. Sev-
device. While it doubles as a handle for determine what the aircraft was doing eral automobile manufacturers are
carrying the black box, this cylinder is at any given moment. utilizing black box technology in their
actually a beacon to help locate the box Flight reconstruction consists of uti- Continued on page 47
after a water crash. If a plane crashes lizing recorded flight data to derive the
into the water, this beacon sends out an aircraftʼs instantaneous position and
ultrasonic pulse that cannot be heard orientation relative to an orthogonal,
by human ears but is readily detectable right-handed Cartesian frame of ref-
by sonar and acoustical locating equip- erence that is fixed to the Earth. Sev-
ment. There is a submergence sensor eral algorithms exist for calculating
on the side of the beacon that looks an aircraftʼs flight path, which require
like a bullʼs-eye. When water touches different sets of input parameters. The
this sensor, it activates the beacon. total set of parameters includes air-
The beacon sends out pulses at 37.5 speed, pressure altitude, radio altitude,
kilohertz (kHz) and can transmit sound ground speed, drift angle, roll attitude, Glideslope animation based on FDR data.
AVIONICS NEWS • JANUARY 2006 41
FLIGHT DATA RECORDERS
Continued from page 41
automobiles and a few have been do-
ing so for quite some time. According
to an article titled “Black boxes in
GM cars increasingly help police after
accidents,” General Motors has been
using black box technology for over
a decade. The manufacturer has been
installing a Sensing and Diagnostic
Module on thousands of its cars, in-
cluding the Corvette. Furthermore,
this article reports that “industry in-
siders say as many as a dozen other
manufacturers install similar technol-
ogy under different labels.”
So, black box technology has moved
from airplanes to automobiles—where
is it headed next? It could be on you.
Right now itʼs just a prototype, but
soon the SenseCam could provide you
with an incredible amount of informa-
tion about—well, you!
Letʼs say you attended the recent
AEA convention. Because you forgot
your PDA, you were forced to scribble
dozens of phone numbers and emails
down on random business cards, nap-
kins, and note pads. You made plans
with several colleagues, but much like
the random napkins in the washing
machine at home, your memory just
didnʼt hold up. But, all would not be
lost—if you were wearing a Sense-
Cam. According to its manufacturer,
this badge-sized wearable camera re-
portedly captures up to 2000 VGA im-
ages within a 12-hour day and stores
it in a 128Mbyte flash memory. So,
most every scribbled note and every
promised meeting would be recorded
for you to look at later.
So there you have it. The device
that not only survives crashes, but
time as well. ❑
AVIONICS NEWS • JANUARY 2006 47
