Music May Have Compounded Confusion on Doomed Flight

Music or voices broadcast by a commercial radio station might have affected instrument landing equipment and compounded confusion in the cockpit of Korean Air Flight 801 in the moments before last summer’s fatal crash during an attempted landing on Guam, an expert testified here Thursday.

Cockpit voice recordings recovered from the shattered, burned-out wreckage of the Boeing 747 illustrate the crew’s uncertainty about a component of the system called the glide slope. It’s a radio beam that tells pilots whether they are descending at the correct angle for a landing.

Although the crew had been told repeatedly that the glide slope was inoperable, they continued to ask one another whether it was still working as the plane sank dangerously below the safe approach path to the airport at Agana.

“No flags,” the captain, Yong-Chul Park, told his crew mates, apparently noting that none of his instruments--including the glide slope indicator--displayed the small red flag that flips up when a system is not operating normally.

However, Nelson Spohnheimer, a navigation systems expert at the Federal Aviation Administration, told a National Transportation Safety Board hearing panel Thursday that the lack of a flag may have falsely indicated--albeit only momentarily--that the glide slope system was functioning properly.

“Spurious signals” from other sources, such as commercial radio stations, have been known to cause glide slope indicators in cockpits to give false readings, Spohnheimer said. “It’s fairly common.”

The FAA engineer said the source of signals that apparently caused the glide slope indicator flag to vanish may never be found. He said that antennas and other broadcast equipment were damaged in a recent typhoon, and even subtle changes may make it impossible to duplicate the conditions that existed at the time.

Uncertainties about the glide slope were only part of the disarray in the cockpit of Flight 801. An on-board radar device barked out repeated warnings that the plane was dangerous low, but the crew apparently ignored them, continuing to run through a routine pre-landing check.

At 1:42 a.m., Flight 801 crashed into a hillside, killing 228 people.