By Hildegaard Verploegen
Tuesday, September 3, 1996
Editor's Note: This is Hildegaard Verploegen's last Kokua Line column. Hilde retired today after 28 years at the Star-Bulletin.
Editor's Note: This is Hildegaard Verploegen's last Kokua Line column. Hilde retired today after 28 years at the Star-Bulletin.
As you probably know, the "black" boxes with the recorders aren't black. They are painted orange or bright yellow and have reflective material applied to make them easier to spot.
The most advanced recorders are solid state recorders that store flight information or cockpit sounds on computer memory chips, said Mary Quick, spokeswoman for Allied Signal, a manufacturing company in Redmond, Wash. Solid state means there are no moveable parts.
Allied uses hardened stainless steel for the outer shell of both boxes. Some manufacturers use titanium.
The boxes must be able to withstand the impact of 3,400 G's, or 3,400 times the force of gravity.
This is equivalent to coming to a complete stop in 18 inches from a speed of 400 mph, Quick said. For this test, company technicians shoot samples from a pneumatic cannon aimed at a barrier.
To test to make sure the boxes cannot be penetrated, a slender hardened steel rod is attached to a 500-pound weight that is dropped from a height of 10 feet and aimed at the weakest point of the box.
Samples are tested for crush resistance by applying 5,000 pounds of force for five minutes.
The boxes must be able to withstand the temperature and length of a jet fuel fire. Samples are tested in flames of 2,000 degrees Fahrenheit for 30 minutes, and in temperatures of at least 500 degrees Fahrenheit for 10 hours to simulate being in smoldering wreckage.
Samples also are tested to make sure the "black" box can survive 30 days in water pressure equal to 20,000 feet below the surface, and survive the corrosive effects of salt water for at least 30 days.
Federal Aviation Administration regulations require that both recorders be attached to the plane's most reliable source of electrical power. This means the recorders stop when the power is stopped during a crash, preventing the recorders from erasing information.
Each box has an attached sonar pinger with a battery that activates when it hits water, and emits a sound every second for 30 days, Quick said. The cockpit voice recorder records the last 30 minutes of sound, such as conversation among flight crew members or their conversations with traffic controllers.
European aviation authorities have started requiring recorders to store the last 120 minutes of sound. The flight data recorder keeps a record of operating data from the aircraft systems for the last 25 hours.
Allied's voice recorders are about 5 by 6 by 13 inches and weigh about 16 pounds. The flight data recorders are about 5 by 6 by 20 inches and weigh about 17 pounds. Allied's flight data recorders cost from $15,000 to $18,000. Its voice recorders cost about $12,000 for the 30-minute length, and about $17,000 for the 120-minute length.
- Retirees and the payroll lag