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NTSB Weighs Call For Recorder Backups

JAMES T. McKENNA/WASHINGTON

U.S. accident investigators may soon urge National Transportation Safety Board members to recommend transports be retrofitted with backup power supplies that would enable cockpit voice and flight data recorders to capture pilots' conversations and performance indications after an aircraft's main power is lost.

Senior safety board officials said the prospective recommendation stems from a string of investigations that were hampered by premature cutoffs of the recorders.

The most recent was the Sept. 2, 1998, crash of a Swissair MD-11 off Nova Scotia. The NTSB is assisting Canada's Transportation Safety Board (TSB) in searching for the cause of the crash, as are investigators from Switzerland's accident-investigation agency.

Bound from New York to Geneva, Flight 111 crashed after its pilots diverted to Halifax and reported smoke in the cockpit. All 229 on board were killed. Investigators have been stymied in their search for the crash's causes by the lack of data from the CVR and FDR, both of which stopped working 6 min. before impact.

The staff of the Canadian TSB is weighing a similar recommendation, according to officials familiar with the investigation.

Other hampered investigations include an Indonesian-run probe that remains unable to determine the cause of a December 1997 SilkAir 737 crash, in large part because its recorders stopped before the aircraft rolled over and plunged 35,000 ft. into a Sumatran river.

Trans World Airlines Flight 800's recorders cut off as the 747-100 disintegrated off Long Island, N.Y., on July 17, 1996, but the aircraft did not impact the Atlantic for 40-50 sec. ValuJet Airlines Flight 592's recorders stopped 40-50 sec.before that DC-9-32 crashed near Miami on May 11, 1996.

Most FDRs capture at least 25 hr. of data, erasing the oldest and replacing its with the newest. CVRs generally record the 20-30 min. of most recent cockpit sounds.

In addition to weighing a call for back-up power supplies, NTSB staffers are debating the merits of a recommendation for a second set of recorders to be installed in the nose oftransports to supplement thosetraditionally installed in the tail section.

Some safety board officials acknowledge that the FAA and airlines are likely to reject a recommendation for backup power as well as for redundant recorders. Agency officials and airline executives have argued in the past that such retrofits would be extremely costly but benefit only investigators after major crashes, which although spectacular, are extremely rare based on the number of hours flown.

In a related development, Canadian investigators dismissed as inaccurate a Jan. 21 report in The Wall Street Journal that Flight 111's pilots were disagreeing with each other over emergency procedures and the speed with which they should have landed their aircraft once smoke was detected in the cockpit.

The investigator in charge for the TSB, Vic Gerden, said the report mixed information from a summary of CVR, FDR and other data with interpretations of the crew's actions that were "not only misleading, but inaccurate and unfair."

Other officials familiar with the investigation and the CVR summary from Flight 111 said the pilots' conversation was not unusual or strained, given the high workload of the emergency situation and their struggle to fly the aircraft, communicate with air traffic control, and identify and deal with the source of the smoke.

© February 1, 1999, The McGraw-Hill Companies Inc.