Hypoxia, poor planning a deadly combination
Hypoxia, poor planning a deadly combination
Hypoxia—a state of oxygen deficiency sufficient to impair functions of the brain and other organs—can affect pilots flying above 12,000 feet msl in unpressurized aircraft without supplemental oxygen. Hypoxia causes lapses in judgment, memory, and coordination, signs that are often masked by a euphoric sense of well being. These effects alone are a serious threat to safe piloting. Combine them with inexperience and poor preflight planning, and you’ve got a recipe for disaster.
On the night of Jan. 23, 2003, a PA-28R was destroyed when it struck terrain and burned during a forced landing attempt near La Sal, Utah. The 140-hour, noninstrument-rated private pilot and her three passengers were killed.
The VFR flight departed Longmont, Colo. for Las Vegas at 4:57 p.m., about 10 minutes before sunset. Visual meteorological conditions prevailed for the westbound flight, during which the pilot flew above 12,500 feet msl for 2 hours, 17 minutes; above 14,000 feet msl for 1 hour, 49 minutes; and at approximately 16,000 feet msl for an estimated 45 minutes. The unpressurized aircraft was not equipped with a supplemental oxygen system, and the pilot did not bring a portable oxygen unit.
While flying above 14,000 feet msl, the pilot received numerous heading corrections from ATC—some of them as large as 70 degrees. At one point, the pilot reported that she was over Montrose, Colo. The controller informed her that she was actually over Telluride, about 35 nautical miles south of Montrose. The pilot responded, “Roger that, I appreciate it. Can’t see a darn thing out here.” (Hypoxia can cause rapid deterioration of night vision, even at altitudes as low as 5,000 feet msl.)
As time passed, radio communication between the pilot and ATC became increasingly difficult and erratic. At 8:30 p.m., the airplane began to descend from 14,800 feet msl. The rate of descent increased to more than 1,000 feet per minute. At 8:35 p.m., the pilot transmitted the following: “Denver radio, mayday, mayday. I’ve got myself in (unintelligible).” Two minutes later, another aircraft in the area reported picking up a strong but brief ELT signal. The wreckage was discovered a day and a half later by a rancher investigating a column of smoke on his land.
The aircraft was found upright on sloping, tree-covered terrain at an elevation of approximately 7,100 feet msl. The landing gear was in the down position. The NTSB determined that the pilot likely was attempting an emergency landing after losing power due to fuel starvation. Ironically, an estimated 10 to 15 gallons of fuel remained in the unselected tank of the low-wing aircraft—fuel that fed the post-impact fire that consumed the cabin and fuselage.
The pilot’s hypoxic impairment was cited as a contributing factor in her failure to follow proper fuel-management procedures. According to FAR Part 91.211, pilots must use supplemental oxygen when the cabin pressure altitude is above 12,500 feet msl for longer than 30 minutes. It must be used continuously when flying above 14,000 feet msl. At cabin pressure altitudes above 15,000 feet msl, each occupant of the aircraft must be provided with supplemental oxygen. None of this occurred during the accident flight.
But there’s more to this story than just hypoxia. The NTSB further determined that the pilot had not received the required logbook endorsement to operate a complex airplane like the PA-28R. She had logged just a few hours in the aircraft, and her instructor reported that she “was a little behind the airplane.”
Moreover, the pilot’s logic and judgment were questionable during preflight planning—long before she reached hypoxic altitudes. The pilot filed a VFR flight plan with a cruising altitude of 15,500 feet msl, a 140-knot airspeed, four hours time en route, and eight hours of fuel on board. The chosen altitude exceeded the airplane’s service ceiling of 15,000 feet. In addition, the altitude was inappropriate for a westbound VFR flight, which should be flown at even thousands plus 500 feet.
Of greater concern was the fuel planning. With full tanks, the accident aircraft actually was capable of no more than five hours of flight (not eight, as filed). Even without wind, the pilot’s intended route of flight would have taken nearly five and a half hours to complete (not four), and winds aloft data for 15,500 feet on the night of the accident indicated a direct headwind of about 30 knots.
In short, the planned flight was impossible to accomplish. When the brain-dulling effects of hypoxia were added, the fate of this pilot—and her three passengers—was tragically sealed.
November 11, 2009