- And even if we forget the WTC steel, there's the curious
incident of the planes' black boxes - not ONE of the EIGHT black boxes
- two per plane - survived! Not just those of the planes that crashed into
the Twin Towers, but also of the other two planes! Not even of the one
that crashed into the ground in Pennsylvania.
-
- Do you know the kind of crash these black boxes are designed
to withstand? The National Transportation Safety Board (NTSB) web site
gives valuable information regarding these devices.
-
- Regarding the Cockpit Voice Recorder it says:
-
- "The CVR records the flight crew's voices, as well
as other sounds inside the cockpit. The recorder's "cockpit area microphone"
is usually located on the overhead instrument panel between the two pilots.
Sounds of interest to an investigator could be engine noise, stall warnings,
landing gear extension and retraction, and other clicks and pops. From
these sounds, parameters such as engine rpm, system failures, speed, and
the time at which certain events occur can often be determined. Communications
with Air Traffic Control, automated radio weather briefings, and conversation
between the pilots and ground or cabin crew are also recorded." [NTSB
web site]
-
- Regarding the Flight Data Recorder it says:
-
- "The FDR onboard the aircraft records many different
operating conditions of the flight. By regulation, newly manufactured aircraft
must monitor at least twenty eight important parameters such as time, altitude,
airspeed, heading, and aircraft attitude. In addition, some FDRs can record
the status of more than 300 other in-flight characteristics that can aid
in the investigation. The items monitored can be anything from flap position
to auto-pilot mode or even smoke alarms." [NTSB web site]
-
- Thus as we see each plane is equipped with two separate
"Black Box" devices which relay different yet complimentary information.
-
- It goes on to say:
-
- "Both the Flight Data Recorder and the Cockpit Voice
Recorder have proven to be valuable tools in the accident investigation
process. They can provide information that may be difficult to obtain by
other means." [NTSB web site]
-
- They are meant to be the hardy and sure way to get information
regarding the last minutes before the plane went down.
-
- Here are the specifications of these devices including
what they can withstand:
-
- FLIGHT DATA RECORDER
- Time recorded: 25 hour continuous
- Number of parameters: 5 - 300+
- Impact tolerance: 3400Gs /6.5ms
- Fire resistance: 1100 degC/30 min
- Water pressure resistance: submerged 20,000 ft
- Underwater locator beacon: 37.5 KHz
- Battery: 6yr shelf life 30 day operation
-
- COCKPIT VOICE RECORDER
- Time recorded: 30 min continuous, 2 hours for solid state
digital units
- Number of channels: 4
- Impact tolerance: 3400 Gs /6.5ms
- Fire resistance: 1100 deg C /30 min
- Water pressure resistance: submerged 20,000 ft
- Underwater locator beacon: 37.5 KHz
- Battery: 6yr shelf life 30 day operation
-
- These specifications indicate equipment which can survive
just about any conditions and any crash. Indeed, Black Boxes have been
recovered from crashes in swamps, mountains, and oceans.
- ABC News reports:
-
- "Although investigators look for an entire black
box, sometimes the only parts of the device that survive are the recorder's
crash-survivable memory units (CSMU). the csmu is almost indestructible.
It is housed within a stainless-steel shell that contains titanium or aluminum
and a high-temperature insulation of dry silica material." "It
is designed to withstand heat of up to 2,000 degrees fahrenheit for one
hour, salt water for at least 30 days, immersion in a variety of liquids
such as jet fuel and lubricants, and an impact of 3,400 G's. By comparison,
astronauts are typically exposed to up to six Gs during a shuttle takeoff."
[ABCNews]
-
- So the Black Box is designed to withstand an impact of
3,400 G's. So what about the Pennsylvania crash site?
-
- "The voice recorder was said to be heavily damaged,
and the manufacturer was being asked to help with further analysis. The
plane that crashed in Pennsylvania was reported to have hit the ground
in excess of 500 miles per hour." [ABCNews]
-
- The plane hit the ground at 500 mph. Taking the weight
of the plane, its speed of descent, the G's end up much, much lower than
3,400.
-
- Since each plane has two separate Black Boxes which are
designed to be indestructible in the event of a tragedy, that makes a total
of eight black boxes. We are to believe that all the Black Boxes were damaged
beyond use, while a measly paper passport survived!
-
- http://www.themedianews.com/DAGGER/Front%20Page/9-11_black_boxes_.htm
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