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Too tired to thinkToo tired to think


By David Kenny

Occasionally pilots fall asleep in flight, and some even live to tell the tale. But fatigue can also ruin a flight in less obvious ways—by degrading the pilot’s skills, or slowing thought processes until it’s impossible to stay ahead of the aircraft. Most insidiously, fatigue impairs perception and judgment, including the ability to evaluate one’s own condition. When you’re really tired, you may not realize how tired you really are.

At about 11 p.m. Pacific time on March 1, 2009, a Diamond DA40 slammed into the Pacific Ocean off the northern California coast. The airplane was inbound on the Area Navigation (RNAV)/GPS approach to Runway 14 of the Arcata/Eureka Airport in rainy, turbulent weather. The 30-year-old commercial pilot and his passenger were killed; over the next two weeks, about a dozen small pieces of the airframe washed up along 10 miles of beach. Based on their distribution, known ocean currents, and radar-track data, the NTSB estimated that the airplane hit the water just outside the final approach fix, where the minimum crossing altitude is 2,100 msl.

The accident came at the end of a tough three-and-a-half hour leg, departing Bakersfield after dark and flying northwest through light to moderate precipitation and at least moderate turbulence. At one point the pilot blamed turbulence for a 700-foot altitude deviation. His day had started before 5 a.m. Pacific time, but he and his passenger hadn’t just had one long day in the cockpit; they’d had two. The previous day they’d flown seven and a half hours from Plant City, Fla., to Huntsville, Texas—after spending several hours searching for an airplane they could rent for a long cross-country and an hour and a half checking out in the DA40. They arrived in Huntsville about 7:20 p.m. Central time, and the lineman who topped their tanks said they’d initially planned to keep going. Only while refueling did they recognize how tired they both were and decide to stay the night. They checked into a hotel at about 8 p.m. The first employee to arrive at the Huntsville airport the next morning found them already there, preflighting.

They were off the ground by 7:15 a.m. Central time. That afternoon, they refueled in Sedona, Arizona, where the pilot filed two IFR flight plans by CSC DUATS. There is no record that he got a weather briefing. They bypassed their next destination of Palmdale, Calif., for Bakersfield, another 65 nm northwest, and stayed there for just under an hour before launching for Arcata. The NTSB estimated that by the time the pilot received his approach clearance (shortly before 11 p.m. Pacific time), the pilot had crossed four time zones, flown almost 23 hours of the preceding 42, and been “on duty” for more than 30.

The strain had begun to show. After some indecision about which approach to request, the pilot had difficulty copying the name of the initial approach fix, misspelling it after the controller read it to him phonetically. He descended through an assigned altitude, corrected, and then copied the next altitude restriction as “at or below” rather than “at or above.” After he completed the course reversal, the controller terminated radar service and cleared him to the Arcata CTAF frequency. At that point the airplane was established on the final approach course, inbound to the initial approach fix, descending through 3,600 msl.

It kept on descending until it disappeared from radar at 300 msl. The controller made ten unsuccessful attempts to contact it after noticing that it was 700 feet low outside the final approach fix.

We don’t know what happened in the cockpit those last few minutes. But the first link in the accident chain was the pilot’s decision to fly one more leg—at night—on a day he’d already logged 11 hours. He had told the Diamond’s owner that the purpose of the trip was “to build time,” and it seems he wanted to do it as quickly as possible. His decision to press on after dark, perhaps without even checking the weather ahead, suggests that fatigue had impaired his judgment so deeply that he didn’t realize his judgment was impaired.