Investigators still no closer to solving crash mystery
A valve in the cabin-pressurization system was replaced two days before golfer Payne Stewart's Learjet slammed into a South Dakota pasture, but the system worked fine during a short flight after the replacement, the chief government investigator said today.
Government officials have said one possible explanation for the crash is that the jet lost cabin pressure soon after taking off from Florida, causing everyone aboard to die or lose consciousness.
For four hours on Monday, the jet flew 1,400 miles across the country, apparently on autopilot, before running out of fuel and spiraling nose-first into a soggy field.
Bob Benzon of the National Transportation Safety Board said investigators learned that a device called the left-hand modulator valve, which takes heated air from the engine and runs it through the air-conditioning system to pressurize the cabin, was changed on the plane Saturday.
If the left-hand valve failed, the one on the right engine should have fed sufficient air into the cabin, he said.
Benzon said the valve was replaced Saturday to balance engine thrust on the plane -- not because of any prior problem with cabin pressure. After the valve was replaced, the plane pressure-regulation system worked fine during a short flight on Saturday, he said.
Benzon said he does not know whether such a valve has ever been a factor in a crash.
"The fact it was changed doesn't really mean anything right now, but it's something we're looking into," he said, speaking at the crash site.
Investigators today had removed about a quarter of the jet from the 10-foot crater, and found human remains, engines, golf clubs and oxygen masks for the passengers.
They found the cockpit voice recorder just before sundown, Benzon said.
Though the Learjet had no flight data recorder that could provide mechanical information, the cockpit voice recorder has a 30-minute loop that usually records over itself. Officials do not expect to hear anything about what happened when radio contact was lost and the plan veered off course because that happened hours before the crash.
But the voice recorder could have picked up sounds at the end of the flight that could tell a lot about what was happening in the plane, Benzon said. The recorder was soaked in fuel and the cassette was cracked, but information from the tape might be available as early as Friday, he said.
"We're still confident we can get some good information off that tape," Benzon said.
Investigators also want to determine whether oxygen masks had dropped from the ceiling as they are designed to do during a loss of cabin pressure, he said. The pilots' oxygen masks had not been found.
Stewart, 42, was one of the world's most recognized golfers, known for wearing knickers and a tam-o'-shanter hat. Also killed were Stewart's agents, the two pilots, and Bruce Borland, one of Jack Nicklaus' golf course designers.
Benzon said investigators hope to finish recovering wreckage and human remains by Friday, when the investigation will shift to a detailed examination of the parts in a hangar in nearby Aberdeen.
Planes that fly above 12,000 feet are pressurized because the air does not contain enough oxygen for people to breathe comfortably. If a plane loses pressure at high altitude, those aboard could gradually lose consciousness or, in the case of a broken door or window seal, die in seconds from lack of oxygen.
Air traffic controllers could not reach anyone on the plane by radio soon after it took off Monday from Orlando, Fla. Fighter pilots who chased it reported that its windows were frosted over, indicating the temperature inside was well below freezing. That has raised suspicions that the plane suddenly lost pressure.
Tissue samples from the victims will be tested. But a pathologist said toxicology tests may be unable to establish whether the victims suffered a sudden deprivation of oxygen.