And Still, Virtually No Answers
It was a somber
anniversary Monday for both the world of golf and the world of
aviation. Five years ago, golfer Payne Stewart and five others were
killed in a bizarre accident involving a Lear 35. Investigators
believe that the aircraft lost cabin pressure shortly after taking
off from Orlando (FL), headed to Dallas (TX). But,
ultimately, what caused the loss of cabin pressure remains
just as much a mystery as it was five years ago.
The End Of N47BA
The accident aircraft, N47BA, was owned by Sunjet Aviation, an
on-demand air taxi operation based
Instead of landing in Dallas, the Lear 35 continued flying at
altitude for four hours, a ghost ship with no one at the controls.
The aircraft was intercepted twice -- first, by F-16s with the
Oklahoma Air Guard, and then by a pair of Falcons from the North
Dakota Air Guard. Finally, near Aberdeen (SD), the Lear's fuel
supply was exhausted. The Lear lost power and spiraled into the
The NTSB final report on the accident was released November
28th, 2000, more than a year later. In it, investigators listed the
probable cause as "incapacitation of the flight crew members as a
result of their failure to receive supplemental oxygen following a
loss of cabin pressurization, for undetermined reasons."
History Of Pressurization Trouble
N47BA wasn't the first choice for Stewart's last flight. The
42-year old golfer and his three companions were to have taken a
commercial flight from Orlando to Dallas. But fellow golfers Van
Arden and Robert Fraley convinced Stewart that flying an air taxi
was safer. Even though Stewart himself owned a piece of an
aircraft, the tab for this ride was being picked up by a
The aircraft had just come out of the shop, according to
published reports. Pilots on recent flights had reported problems
with the cabin pressurization, saying it sometimes failed to hold
pressure at lower altitudes. A maintenance supervisor at Sunjet
told investigators that, prior to its last flight, N47BA was being
checked for a 'throttle problem.' During a visual inspection of the
left engine, the supervisor spotted a problem with an engine
modulation valve. He said "the spring [was] not functioning." The
valve was replaced the next day.
The repair tag on the old valve read, "Reason removed: ITT
(interstage turbine temperature) split at altitude and cabin
pressurization loss with reduced power setting."
Sunjet executives said the aircraft was flown once before it was
put back into service. However, investigators found that,
during the test flight, the aircraft never flew above
The replacement valve was never officially blamed for the
depressurization that led to the accident. But the NTSB report
noted that it had been the object of scrutiny as early as four
years before the crash.
On April 12, 1995, a prepurchase inspection performed by Learjet
at its Wichita (KS), facility indicated the following:
Cabin pressure follows throttles - 2,000 feet bump both
directions...R/H [right] engine mod...Valve does not shift when
power is brought up...when moving cabin air switch to max flow you
get no increase of air flow...with cabin pressure at 1 pound in
auto, cabin will not up rate when selecting a higher
altitude...should up rate depending on where rate knob is
at...emergency exit seal...coming loose...main cabin door is
smashed at split line area...O2 need serviced.
Investigators did find the valves in the wreckage of N47BA and
noted, "On October 23, 1999, the left engine modulation valve, S/N
P-247, was removed and replaced with one of the modulation valves
that was discovered in the wreckage. The functional test of the
replaced modulation valve revealed that the flow mixing poppet
between the low- and high-pressure stages did not operate (open) at
low bleed air pressures."