On July 26, 2002, Federal Express flight 1478 struck trees on short final to Runway 9 at Tallahassee
Regional Airport in Florida. The captain, first officer and flight engineer were the only occupants. All three survived but were seriously injured. The aircraft was destroyed by the impact and ensuing fire. The accident occurred in benign weather following a botched approach in nighttime VMC. The captain had over 13,000 flight hours and a reputation as a solid pilot. The first officer had 8,000 hours and was viewed as a reliable copilot. The flight engineer had 2,600 hours and was being considered for a check airman position at FedEx. Combined 24,000 flight hours, good reputations, and yet this crew failed to notice a descent profile that shorted the target runway by 3,000 feet. One final (and conspicuous) note: The accident occurred at 0437 CDT.
The first officer was the pilot flying. The captain had initially suggested Runway 27 since it was equipped with an ILS and offered a shorter taxi to parking. Working against 27 were mild tailwinds. Following a somewhat disjointed conversation, the crew settled on the headwind to 9 versus the ILS for 27 (Runway 9 had a PAPI but no ILS). During post-accident interviews, none of the crew recalled being low during the approach. NTSB analysis indicated that three white and one red light on the PAPI (slightly high) would have been observed when the Boeing 727 rolled onto final at 1,700 feet AGL. From this point the aircraft began a steep descent which resulted in four red lights (substantially below glideslope) by 800 feet. The aircraft maintained the steeper than normal approach until 200 feet when it transitioned to a 500 fpm rate of descent. It continued on this profile until it struck trees a little more than a half-mile from the end of the runway.
“Neither skill nor experience provides an effective countermeasure to the debilitating effects of tiredness.”
Eleven years later, UPS flight 1354 crashed short of Runway 18 in Birmingham, Alabama. The accident occurred at 0447 CDT following a localizer approach to Runway 18. The aircraft (an Airbus A300-600) was capable of calculating a constant rate of descent for non-precision approaches (which allows a non-precision to function like an ILS), yet a mistake in programming resulted in the computer-generated glide path being unavailable.
Once he realized the error, the captain elected to utilize the “dive-and-drive” method for the non-precision approach (where the crew selects a rapid descent prior to leveling off at MDA). The aircraft was slightly high crossing the final approach fix. The captain selected a 1,500 fpm rate of descent, which was maintained until the Enhanced Ground Proximity Warning System (EGPWS) provided an aural “sink rate” alert at 300 feet AGL. Following this, the captain adjusted the vertical speed to 600 fpm. Three and a half seconds later, the captain reported “runway in sight” (the aircraft was around 900 feet MSL at this point – 300 feet below the charted MDA). Neither pilot commented on the non-standard approach profile. The initial impact with trees occurred 1.25 miles short of the threshold to Runway 18. Neither pilot survived.
That captain reported 8,600 hours of flight time on his most recent first-class medical. The first officer had approximately 4,700 hours of flight time. Though the captain’s flying skills were described as “average to above-average” by company pilots who had flown with him, he also had a somewhat checkered training background. The first officer had a clean training record and a reputation as a solid crewmember. With better than 13,000 hours between them, the crew flew a perfectly good aircraft into the ground 8,000 feet short of the touchdown zone.
Post-Accident Investigation
The captain of FedEx 1478 told investigators that he had not slept well the two nights before the accident trip. The family dog had deteriorating health, which interrupted his sleep both nights. He could only account for 3.5 hours of “pretty good” sleep prior to the accident flight. The first officer had not anticipated operating the accident flight. He had arrived at Memphis (the departure airport) at 2300 following what he believed to be his last flight of the day. Instead of going home, he received a message that he had been reassigned to the accident flight. He contacted crew schedulers questioning whether the assignment was legal. He was told it was and agreed to accept it, though he told NTSB investigators that he planned to object to it via a union grievance.
Since they were unable to interview the captain and first officer of UPS 1354, the NTSB primarily utilized the crew’s electronic devices in order to determine their sleeping habits. The captain’s “opportunity for sleep” was determined to be generally sufficient for basic rest needs. The first officer’s, however, was pronouncedly inadequate. She arrived for duty two nights prior to the accident having been awake 13 hours; her duty day following arrival was scheduled for 9.5 hours. During a 14.5 hour layover following the first night of her trip, she obtained around 4 hours of sleep. She would get a limited nap before the accident in a UPS sleep room but was clearly carrying a substantial deficit of sleep into the accident flight.
Insidious Fatigue
In 2004 the FAA conducted a study to determine the relationship between flight test failures and enforcement actions. They found a “very low [correlation]…less than one percent.” The general conclusion was that training records can be somewhat meaningless as it relates to predicting the accident record (particularly when a pilot only has a few failures). This is not the case with fatigue. Scientific research has demonstrated that fatigue results in reduced alertness, degraded response time, inaccurate responses to stimuli, the inability to prioritize tasks in a coherent manner, a reduction in leadership skills, and an overall loss of motivation. Fatigue has been shown to contribute to impulsive decisions, fixation on only one aspect of an encountered problem, and slow or non-existent reactions to emerging dangers. In other words, fatigue degrades the skills required to safely operate an aircraft. It is simply not possible to overcome its debilitating effects.
A companion study by the NTSB found that while only 1 percent of professional aircrews schedules exceeded 13 hours of duty, those schedules produced 5 percent of accidents. In nominal parlance, flying after a 13-hour workday increases the risks of an accident by 500 percent. Flying after a long day represents one of the most significant risks that pilots encounter, every bit as ominous as thunderstorms or volcanic ash. Yet, in aviation, the answer is not as simple as drawing a hard line on hours of service. Like it or not, aviation is a 24-hour business. Fatigue is simply another peril that pilots must mitigate.
Countermeasures can take a variety of forms. For short bursts of energy, coffee or naps are effective in countering the loss of alertness that insufficient sleep produces. A nap (even as short as 15 minutes) increases alertness and mental functioning for a couple hours. Coffee has a similar impact. Naps and caffeine are to fatigue what aspirin is to a headache – you have not cured the underlying illness; you have only reduced the symptoms. The only cure for fatigue is sleep.
There are three types of fatigue: transient, cumulative and circadian. Transient fatigue is brought on by a night of insufficient sleep (it also occurs after being awake for an excessive period of time). Cumulative fatigue occurs when insufficient sleep occurs multiple nights in a row. Circadian fatigue is also known as jet lag. It occurs when the quality of sleep is disrupted by rapidly changing sleep cycles.
Transient fatigue is easily resolved: get extra sleep. The average person requires around eight hours per night (the exact number is inversely related to age). Six hours of sleep will produce two hours of sleep deficit. If you sleep 10 hours the next night, you will be properly rested. If you get six hours of sleep five nights in a row (cumulative fatigue), your sleep deficit is 10 hours. You obviously cannot catch up on this in one night. Two (or more) nights of excess sleep may be required to fully eliminate cumulative fatigue.
Circadian fatigue is a bit more complex. The human body is optimized for regular sleep cycles. A normal person (who is awake during the day) experiences maximum sleepiness from 0200-0600 (which is also the most effective time to be asleep). Conversely, the greatest alertness occurs between 0900-1100 (the least effective time to sleep). The body will (to some degree) adapt to different sleep cycles, but in general, it is only capable of adjusting by around an hour per day. If you change your wakeup call from 0900 to 0500, your body requires four days to produce fully restorative sleep on the new schedule.
It is little surprise to find fatigue related accidents are the bane of cargo operators. It is an industry that often operates on the backside of the geographical clock. The NTSB is quick to reference “insufficient management of off-duty sleep” in accident reports. The view of the NTSB is that pilots are responsible for maintaining a sleep pattern that will facilitate their next duty cycle, regardless of how this impacts off-duty time. This can produce difficult dynamics at home as families inevitably live on diurnal schedules (awake during the day, asleep at night). Given the extended period of time required to adapt to new sleep cycles, a pilot at home for a few days has little hope of fully adapting from family activities to the routine of the graveyard shift.
Fatigue is not the isolated province of check haulers. Passenger red-eyes are routine for eastbound flights. Likewise, mid-sequence schedule changes represent a ubiquitous theme in all forms of flying. Aviation is often more about optimizing operational needs than dodging fatigue. A 6 a.m. departure on Tuesday followed by a 10 p.m. touchdown on Thursday will inevitably involve some degree of fatigue.
Many sleeping aides are approved for pilots (primarily when used to adapt to different sleep cycles. If used to treat an underlying sleep disorder, a special issuance medical is required). Yet most medications require the time between the last dose and flight duty to exceed “five times the half-life” of the drug (the recommended time interval between doses generally equates to the half-life. An antihistamine with instructions to “take every 12 hours,” for example, would require 60 hours between use and flight). Dietary supplements offer more flexibility, though they are not without controversy. Melatonin and tryptophan are two substances found naturally in food that are also produced as sleep aids (both as OTC and as food supplements).
The FAA lists melatonin as “generally safe to fly” (the FAA does not actually approve any drug for use by pilots; it only lists some – such as aspirin – as “generally safe to fly”). Studies have demonstrated that melatonin facilitates a more rapid adjustment to a new sleep cycle when used properly (taken immediately before going to bed). It represents an imperfect solution, but it may be an effective method to counter circadian fatigue for individuals who require a rapid shift from one sleep cycle to another. Note that some countries and certain military branches require flyers to observe a specified interval between the last dose of melatonin and operating a flight.
Fatigue is the indisputable champion. Neither skill nor experience provides an effective countermeasure to the debilitating effects of tiredness. The only way to overcome fatigue is to throw in the towel and find a bed. Resignation is the path to victory in this case. Fatigue diminishes every advantage that an aviator has: mental alertness, experience, training and ingenuity. It is an exam that you can only pass by sleeping through it.