What's Classified As Error Could Be Avoidable Fatigue

By ANN Contributor Steven Lund

• Read Part One

Following a Congressional request in 1980, the NASA Ames Research Center created an on-going program to examine whether "there is a safety problem of uncertain magnitude, due to transmeridian flying and a potential problem due to fatigue in association with various factors found in air transport operations." Such as:  flying across numerous time zones. 

Reporting in a Hearing on pilot fatigue, before the Aviation Subcommittee of the US House of Representatives' Committee on Transportation and Infrastructure in the summer of 1999 NASA's Deputy Associate Administrator, Office of Aero-Space Technology said "The NASA Ames Fatigue/Jet Lag Program (now the Fatigue Countermeasures Program)… was created to collect systematic, scientific information on fatigue, sleep, performance in flight operations, and circadian rhythms-the biological "time clock" that regulates the body's daily sleep-wake patterns  NASA established three program goals, which continue to guide research efforts to:

• Determine the extent of fatigue, sleep loss and circadian disruption in flight operations.
• Determine the impact of these factors on flight crew performance. 
• Develop and evaluate countermeasures to mitigate the adverse effects of these factors and maximize flight crew performance and alertness."

The NASA Program gathered data regarding the existence and extent of fatigue in aviation from several realistic sources, including actual flying, laboratory studies, high fidelity simulations, and surveys.  These data have been consistent in showing that fatigue is an issue with complex, diverse causes and potentially critical consequences. Field studies specific to different aviation environments and using a range of measures (e.g., performance, physiology, and behavior) have revealed a number of factors related to fatigue. For example, in long-haul operations, the non-24-hr duty/rest cycles, the circadian desynchronization associated with transmeridian flights, and the sleep loss accompanying night-time flying are all associated with fatigue. 

It has been evident, throughout this research program, that pilot fatigue is a significant safety issue in aviation. Rather than simply being a mental state that can be willed away or overcome through motivation or discipline, fatigue is rooted in physiological mechanisms related to sleep, sleep loss, and circadian rhythms. These mechanisms are at work in flight crews no less than others who need to remain vigilant despite long duty days, transmeridian travel, and working at night when the body is programmed for sleep.

A dramatic example of fatigue in U.S. aviation operations showed up when NASA researchers collaborated with NTSB investigators in assessing whether fatigue was present in the 1993 crash of a U.S. DC-8 freighter in Guantanamo Bay, Cuba [Mentioned in Tuesday's article].

NASA concluded that fatigue is a problem with diverse causes, requiring a multi-faceted and comprehensive yet integrated approach. Based on current research, such an approach should have at least the following components:

• education and training
• hours of service
• sound scheduling practices
• effective countermeasures
• incorporation of appropriate design and technologies
• research

A NASA/FAA countermeasure study empirically demonstrated the effectiveness of a planned cockpit rest period in improving performance and alertness in long-haul flight operations.  Flight crews who were provided a planned 40-minute nap opportunity (resulting in an average of 26 minutes of sleep) subsequently exhibited improved physiological alertness and performance compared to flight crews not receiving the nap opportunity.

The crewmembers napped one-at-a-time in a three-person cockpit with minimal disruption to normal flight operations and no reported or identified concerns regarding safety. The benefits of the nap were observed throughout the critical descent, approach and landing phases of flight. The planned nap appeared to provide effective and acute relief from significant sleepiness experienced by crews in three-person flight operations

Technology continues to evolve rapidly, but humans have not changed their need for sleep, their rate of adjustment after circadian desynchronization, or the relationship between fatigue and performance. Good system design incorporates information about human physiology, its limitations and strengths, early in the process. Technological approaches that use this information can take many forms, including flight crew scheduling algorithms (i.e., the methodology of choosing flight crews) and alertness monitoring/management systems. Fatigue Program work in this area includes a project examining on-board crew rest facilities to determine the quantity and quality of sleep obtained and the factors that promote or reduce good sleep in the bunk.  Onboard bunks are used in operations with extra (augmented) flight crewmembers onboard so that crews can rotate through flight deck positions and non-flying crew can obtain sleep during long flights.

A current NASA study is examining the feasibility of a video-based, automated, online system for drowsiness detection on the flight deck. Because we tend to underestimate our own degree of sleepiness, these systems have the potential to play a valuable role in detecting dangerous levels of fatigue and alerting crewmembers to their presence. 

However, once crews are alerted to the presence of fatigue, the next problem is what can be done to ameliorate it?  Does the industry mandate that a fatigued pilot immediately enter into a regiment of "power naps" -- designed to provide restful sleep, without negative post nap effects such as grogginess, disorientation, or headaches?  Or, should airlines be required to constantly provide backup crew members to replace ones with detected levels of fatigue?  Both of which would be required if modern flight decks were fitted with drowsiness detection devices.  Clearly not an incentive for the industry to mandate such devices:  Why measure a condition for which there is no established mitigating procedure if the Pilot's "Drowsiness Hi" light comes ON at the top of descent? 

The most viable solution would be that the industry require pilots be adequately rested before the flight operations they are scheduled to work; giving due consideration to the quality of rest obtained, including their rate of adjustment after circadian desynchronization in addition to the current Federal Air Regulations (FARs) concerning crew duty cycles! 

Considerable progress has been made during the last half of the 20th Century regarding knowledge about sleep, sleep need, the effects of sleep loss on performance, and related issues. Even more recently, major advances have occurred in human circadian rhythms research, leading to an improved understanding of these daily rhythms and their control by the human circadian pacemaker in the brain .  However, the NASA studies concluded that more research is needed to fully understand the capabilities and limitations of the human sleep and circadian systems. An additional challenge is the appropriate application of this research to operational environments such as aviation. Given the recent development of technologies claiming to be able to detect fatigue, focused research is needed to ascertain the sensitivity, reliability, and validity of these devices. 

According to NASA, research also needs to continue to address regulatory, scheduling and countermeasure questions. The area of fatigue is plagued by misconceptions about its causes and characteristics. There is no substitute for valid empirical data to guide decision making and policy.

Accident Investigation Strategies

If there is any question about "Pilot Performance" being an issue in the chain of events leading to an accident, the Human Factors Group should attempt to document the quality of the Crew rest experienced by the Pilots in addition to determining adherence to the appropriate flight and duty time regulations.  For instance, did the pilot experience any sleep disorders, such as Insomnia or sleep apnea [caused by relaxation of the muscles of the tongue and the soft palate at the base of the throat, allows the breathing passage to collapse in individuals with a narrow airway. Although chest movements may continue, no air flows into the lungs and oxygen levels in the blood decrease. When blood oxygen levels fall too low, the person briefly wakes to take a breath.

This cycle of sleeping, then, the repeating cycle of airway collapsing, waking, and sleeping, often occurs hundreds of times in a night. Individuals with this common sleep apnea might not remember these brief awakenings and believe they slept through the night.  However, the interrupted sleep leaves the individual exhausted in the morning and sleepy throughout the day].  Even something as innocuous as trying to rest in a noisy hotel room replete with interruptions to the normal sleep cycle should be documented.

(Steven R. Lund is the retired director of flight safety investigations in flight operations for the Douglas Products Division of the Boeing Commercial Airplane Group in Long Beach, California. He has spent over 36 years in the U.S. aerospace industry, the last 32 of which have been at the Douglas Aircraft Company (now Boeing). His entire career at Douglas/Boeing has been devoted to flight test, flight safety, and commercial jet transport incident and accident investigation. -- ed.)

FMI: www.faa.gov