Alarms but No Voices on Stewart Jet’s Cockpit Recorder

The cockpit voice recorder recovered from the crash of golfer Payne Stewart’s jet contains no voices, but federal investigators said Tuesday that alarms, including one signaling cabin pressure problems, sounded before the Learjet went nose down in a South Dakota cow pasture.

The National Transportation Safety Board said tape noises are consistent with alarms on the Learjet 35 that warn pilots when the cabin altitude exceeds normal levels or when the plane is flying at a speed or angle that cannot sustain flight.

“Analysis of the aircraft’s cockpit voice recorder continues,” the NTSB said in a statement. “The tape contains no voices, but there are sounds consistent with various alarms” related to cabin altitude and low pressure and stall warnings.

The NTSB has not determined why the plane crashed Oct. 25 near Aberdeen, S.D., killing Stewart and five others on board. But some aviation analysts have speculated that Stewart’s plane depressurized, incapacitating those on board.

The human body has a limited ability to function above 10,000 feet because there is less oxygen in the air and there is less pressure to force that oxygen through the lungs and into the bloodstream. Airplanes are pressurized so that the atmosphere inside never feels higher than about 8,000 feet, even if the aircraft is flying much higher.

Federal Aviation Administration officials said the plane climbed as high as 51,000 feet during its wayward flight across the nation’s heartland. The jet took off from Orlando, Fla., for Dallas and flew four hours--about 1,400 miles--before running out of fuel and crashing. Controllers last talked to the pilots when they confirmed an instruction to climb to 39,000 feet.

Dave Franson, a spokesman for Learjet based in Wichita, Kan., said a cabin altitude horn in the Learjet 35 automatically sounds when cabin pressure altitude reaches 10,000 feet. It’s not a soft beeping noise but a loud horn to alert the crew to the problem, he said. Under normal conditions when the alarm sounds, pilots correct the problem by manually activating an emergency pressurization system, donning oxygen masks and initiating a descent, Franson said.

NTSB investigators said various fragments of the aircraft, including parts of the pressurization and oxygen systems, have been taken to several manufacturers to be examined. The airplane’s engines, which were severely damaged in the crash, were taken to the manufacturer for inspection, the NTSB said.

Investigators have completed their work at the accident site and have stored the bulk of the wreckage at Aberdeen Regional Airport.