Aftermath: Asleep at the Wheel

Fatigue proves to be a treacherous companion.

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For nervous passengers who stiffen the moment an airplane begins to move forward and do not relax until the grab-your-carry-ons chime has sounded, it must be hard to imagine that pilots could actually fall asleep while flying. No pilot would like to admit to doing so. Nevertheless, there have been instances of airline crews overshooting their destinations or becoming unresponsive for long periods, creating a strong presumption of somnolence or at least of profound stupor. Of course, they deny it. Some instances of controlled flight into terrain by general aviation aircraft similarly seem to suggest a pilot who has fallen asleep, although it is impossible to know for certain.

In the September issue of Flying, Sam Weigel described an accident that befell a pilot hauling cargo up California's Owens Valley. The pilot's Piper Lance flew straight into a mountaintop in broad daylight. When flying the same route earlier with Weigel himself, this pilot had on two occasions dozed off near the very area where the crash occurred. Circumstantial evidence that the same thing happened again was strong, but the National Transportation Safety Board avoided drawing any firm conclusion.

That was then. Different NTSB report writers will assign different probable causes to similar accidents, but certain broad trends come and go over the years like skirt lengths and tie widths. Blaming the pilot is fashionable at the moment, and so it is not particularly surprising that a recent fatal instance of controlled flight into terrain by a solo pilot in a 172 brought forth the following probable cause:

The pilot’s decision to continue the cross-country flight while fatigued, which resulted in him falling asleep during the initial descent for landing.

The wording is noteworthy, even if you overlook the misuse of “him” for “his.” Whereas the 2004 flight of the autopilot-equipped Lance into a mountain at the very location where the pilot had on two prior occasions been observed to succumb to drowsiness earned only a cautious “failure of the pilot to maintain clearance with mountainous terrain for undetermined reasons,” the unexplained descent of the 172 into the ground at the end of a long day’s flying got not only an unqualified “resulted in him falling asleep” but also “the pilot’s decision.” Not only has the mere likelihood of his having fallen asleep become a certainty, but it is also now viewed not as a piece of bad luck but rather as the pilot’s fault. He didn’t just passively succumb to drowsiness; he actively decided to risk it.

The accident took place in Land O’ Lakes, Florida, in September 2012. The pilot, 48, was a 14,000-hour A330 captain employed by the Swiss charter airline Edelweiss Air. He was delivering the newly purchased 172, of which he was a co-owner, from Boulder, Colorado, to Tampa. He had spent the previous night in Oklahoma and then had stopped at Minden, Louisiana, and Pensacola, Florida. He took off from Pensacola at 9:44 p.m. local time for the 340 nm leg to Tampa Executive and checked in with Tampa Approach at 1:30 a.m. He was then about 40 miles out at 7,500 feet. Approach cleared him to descend VFR, pilot’s discretion, through Tampa Class B airspace.

At 1:49, the Tampa controller observed the 172 descending below 1,000 feet and tried nine times to call the pilot. There was no response. The 172 clipped a tree and crashed into level grassland 17 miles north of the airport.

The NTSB often invokes fatigue among the possible causes of an accident but usually as a factor contributing to some kind of pilot error. In this case, the effect of fatigue was more profound: The pilot was thought to have been unconscious when the airplane crashed.

Eight days before the accident, he had flown a charter from Zurich to the Dominican Republic. From there, he flew commercial the next day to Tampa by way of Miami to visit an old friend whose husband had recently died. There, the friend later reported, the pilot, who she noticed had gained a lot of weight since she last saw him, fell asleep in his chair in the midst of a conversation. He again fell asleep while conversing the next morning, but after waking up, he spent a normal day, went to bed at 11 p.m. and rose at 8 the next morning.

That afternoon, he returned to Santo Domingo and deadheaded from there to Varadero, Cuba, the following morning. That evening, he flew a returning charter to Zurich with a stop at Cancun, Mexico. Four hours after arriving in Zurich, he caught a Swiss International flight to Newark, New Jersey.

At 5:30 the next morning, he took a United flight to Denver. There he met the owner of the 172, who later reported that the pilot appeared “easily winded” when walking on the ramp. They drove together to Boulder and completed the sale, and at 2:00 p.m. the pilot took off in the 172 for Woodward, Oklahoma, 340 nm distant. He arrived five hours later — a surprising time en route, perhaps suggestive of a stop along the way — checked into a motel and had dinner.

He left Woodward for Minden at 8:30 a.m., arriving at 2:40 p.m. after taking more than six hours to cover 350 nm. At Minden, he bought 27 gallons of fuel. Again, he may have stopped along the way; the elapsed time is not consistent with either the distance or the amount of fuel purchased.

He reached Pensacola at 7 p.m., bought 24.3 gallons of fuel, had dinner and texted the former owner that the airplane was flying nicely and that he would be continuing to Tampa that evening.

At about midnight on that final leg, ATC, which was providing flight-following service, queried the pilot about his planned route. In the ensuing conversation, it emerged that the pilot, who reported that his GPS was inoperative and he was using “basic” navigation, believed he was approaching the Seminole VOR when in fact it was already 20 miles behind him. In light of what was soon to happen, his confusion suggests that he could have fallen asleep while tracking inbound on autopilot and not noticed on waking that the to/from flag had flipped. The accident occurred less than two hours later; it was then 7:50 a.m. Zurich time.

While the narrative of the pilot’s last eight days sounds extremely hectic and involves many time-zone changes, he still had ample opportunities to sleep. But the NTSB explains that “multiple and frequent time-zone crossings would result in circadian disruption and would have diminished the pilot’s ability to obtain restorative sleep [and] would have caused the pilot to be in a fatigued state” after an 18-hour day mostly spent flying. Still, he was a long-haul pilot by profession; circadian shifts were part of his working life.

From Woodward to Tampa is about 1,000 nm. A 180 hp 172 cruising at 120 ktas ought to make the trip in eight or nine hours, plus two stops to stretch, refuel and eat. Is that too much for a single day? Many pilots would say no. But throw in the circadian displacement and the fact that the hours of flying had been spread out over an 18-hour day, and perhaps the calculus changes.

The notion that sleep disruption, whether from jet lag or other causes, may harm performance is commonly accepted. Some people are more strongly affected than others. Since there is every reason to suppose that the pilot fell asleep while flying, it is logical to infer that he was “fatigued.” But whether he felt himself to be particularly fatigued before taking off, we cannot know.

The wording of the probable cause implies that the accident was the result not merely of fatigue but of the pilot’s choice to fly despite being fatigued and that it was, therefore, basically his own fault. Airlines limit their pilots’ duty cycles without reference to the pilots’ subjective evaluation of their own fatigue. The NTSB seems to expect private fliers to do the same.

This article is based on the NTSB’s report of the accident and is intended to bring the issues raised to our readers’ attention. It is not intended to judge or to reach any definitive conclusions about the ability or capacity of any person, living or dead, or any aircraft or accessory.

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