Recorder Will Help Swissair Probe
Sep. 08, 1998
WASHINGTON (AP) _ Even though the flight-data recorder aboard Swissair Flight 111 shut down six minutes before the plane crashed, its modern design and the data it gathered after problems were first reported should yield far more information than investigators often obtain.
The recorder aboard the flight was a new digital unit that stored more than 100 types of information on a computer memory chip _ everything from engine speed to whether the smoke alarms were sounding.
By contrast, the recorder aboard TWA Flight 800, which exploded two years ago over Long Island Sound, harvested only 17 types of information and stopped recording the instant the Boeing 747 exploded.
The information recorded in the 10 minutes after the Swissair pilots first reported smoke in the cockpit of their MD-11 _ and before the final 6-minute blackout occurred _ should give a fairly clear picture of what was going wrong aboard the jumbo jet. The plane plunged into the waters off Peggy's Cove, Nova Scotia, killing all 229 aboard.
``Sure, you'd like to know what the crew was doing in those final six minutes, but they should have a pretty good idea what was going wrong from the indicators beforehand,'' said Greg Francois, director of recorders for AlliedSignal in Redmond, Wash. The company is a leading manufacturer of cockpit voice recorders and flight data recorders, including those aboard TWA Flight 800.
AlliedSignal also made the older, magnetic-tape recorder that came with the ill-fated MD-11 when it was delivered to Swissair in August 1991. Afterward, Swissair replaced it with a digital F1000 model made by L-3 Communications Corp. of Sarasota, Fla., L-3 spokesman Bill Hardman said.
Hardman would provide no other information, citing the ongoing investigation.
The Federal Aviation Administration requires flight-data recorders and cockpit voice recorders on all planes capable of carrying 10 or more passengers in scheduled service.
The cockpit voice recorders capture conversations between the pilots as well as their conversations with air traffic controllers and their comments to the passenger cabin. They work on a 30-minute loop, recording the last half-hour of conversations. The Canadian Navy believes it has located the Swissair voice recorder, although bad weather delayed a recovery operation until Wednesday.
Flight-data recorders must capture a minimum of 11 to 29 types of information, depending on the size of the aircraft. The basics include airspeed, altitude and compass heading. The FAA has set rigid design requirements for both the flight-data recorder and the cockpit voice recorder.
Both units, for example, must be able to withstand impacts of 3,400 times the forceof gravity. The normal person blacks out around nine times the force of gravity. The recorders also have to withstand a 2,000-degree fire for 30 minutes, as well as submersion in 20,000 feet of water for up to 30 days.
The units are powered by an aircraft's engines or its auxiliary power units.
Francois, the AlliedSignal executive, said the power loss in the Swissair plane occurred either in the recorder or in a data collection unit that feeds the recorder. Either way, he said it was inconsequential, because if those units lost power, most likely the instruments feeding them data also lost power.
He said there has been an industry debate about installing batteries to the cockpit voice recorder, since conversations could continue even after an aircraft's instruments lost power. The Federal Aviation Administration has not required battery backups.
Francois also addressed a question that is often asked by the flying public: If a black box can survive a crash, why can't the airplane carrying it?
While planes are made of lightweight aluminum, flight-data and cockpit voice recorders are encased in hardened steel or titanium. They can weigh as much as 10 pounds, even though they aren't much bigger than a loaf of bread.
``If you multiple that out in an airplane, the thing would never get off the ground,'' Francois said. ``It would be too heavy.''