DECOMPRESSION ACCIDENT REVIEW


Recent high profile accidents have put many of the “issues” of decompression emergency in the forefront of our minds. It’s not hard to remember these accidents.


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Operator: Sunjet Aviation Aircraft & Registration: Learjet 35, N47BA Location: Aberdeen, South Dakota Date: October 25, 1999


WHEN A LEAR JET 35 AIRCRAFT operated by Sun Jet Aviation crashed on October 25, 1999, in a grassy field near Aberdeen in South Dakota, America watched in horror. On board were six people, including professional golfer, Payne Stewart. All were killed. But it wasn’t just its famous passenger which saw this flight make headlines – the Lear had just spent nearly four hours crossing the US on autopilot with an incapacitated crew.


The aircraft had departed Orlando, Florida with its four passengers and two pilot crew at around 9:19 am enroute for Dallas, Texas. The planned flight time was two hours, but the aircraft carried four hours and 45 minutes worth of fuel. Less than 30 minutes later, the aircraft was northwest of Gainesville, Florida. It had been cleared to 39,000 ft and was passing through 37,000 ft when radio contact with air traffic control was lost. Radar plots showed the aircraft continuing on a northwesterly heading.


Five military aircraft (F-16 fighters) were sent to intercept the Lear Jet at an altitude of approximately 45,000 feet, following the aircraft until it crashed due to fuel exhaustion, after crossing half a dozen US states and traveling almost 2,500 kilometers. The fighter pilots were unable to find any sign of structural damage to the aircraft, but they reported that the windows of the Lear were misted over, and they couldn’t discern any signs of life inside.


The military pilots observed the airplane depart controlled flight and spiral to the ground, impacting an open field. All occupants on board the airplane (the captain, first officer, and four passengers) were killed, and the airplane was destroyed.


The cockpit voice recorder recovered from the accident site contains no voices, but there are sounds which the NTSB feel are consistent with various alarms such as cabin altitude warnings and stall warnings.


PROBABLE CAUSE


The National Transportation Safety Board determines the probable cause of this accident was incapacitation of the flight crewmembers as a result of their failure to receive supplemental oxygen following a loss of cabin pressurization, for undetermined reasons.


One possible explanation considered was that the flight crew’s ability to think and act decisively was impaired because of hypoxia before they could don their oxygen masks. No definitive evidence exists that indicates the rate at which the accident flight lost its cabin pressure therefore, the Safety Board evaluated conditions of both rapid and gradual depressurization.


F-16 fighters were sent to intercept Payne Stewart’s LearJet at an altitude of 45,000 ft. They followed the aircraft until it crashed due to fuel exhaustion, after crossing half a dozen US states and traveling almost 2,500km.


3 High Altitude Awareness Training


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