Human Factors and Mishap: Fatigue and
Its Effects on The Safety of Flight
Fatigue has long been recognized by the NSTB as a high priority item since the inception of their Most Wanted list in 1990. Several times the NTSB made recommendations to the FAA as well as the NATCA regarding re-evaluation of rest rules and duty time limitations. Even with new rest rules finally around the corner, fatigue is still an issue and self-evaluation is difficult when impaired with fatigue. Examining the Colgan flight 3407 accident, parallels can be drawn between the crewmembers inaction and incorrect stall recovery attempt and their level of fatigue. Countermeasures should include simplification of rest requirement calculations and removal of monetary penalties for crewmembers to remove themselves from duty when sick or fatigued.
Keywords: fatigue, rest rules, duty time limitations, fatigue countermeasures
Human Factors and Mishap: Fatigue and
Its Effects on The Safety of Flight
Of the many human factors and performance topics in existence, fatigue is a top priority for most aviation departments, airlines, flight schools, the Federal Aviation Administration (FAA) and the National Transportation Safety Board (NTSB). In a 2007 letter to the National Air Traffic Controllers Association (NATCA), the NSTB reiterates the concern relating to fatigue and all transportation industries with more than 80 safety recommendations on the topic since 1989 (Rosenker, 2007). In a similar letter to the acting FAA administrator, Rosenker, (2008) points out that “The Board has included safety recommendations related to human fatigue in transport operations on its annual Most Wanted List of Transportation Safety Improvements since its inception in 1990.” While the FAA has since moved forward with new rest and duty time limits, these new regulations are more complicated and confusing than previous ones. Using the 2009 accident of Colgan flight 3407, it will be shown how primary factors in the accident are actually results of underlying fatigue and improper rest.
The New Oxford American Dictionary (Stevenson, 2010) defines fatigue as “extreme tiredness, typically resulting from mental or physical exertion or illness.” Various causes for fatigue rang from sleep loss to poor sleep quality, diet deficiency, and even intentional sleep restriction. According to Reinhart, (2008), fatigue is usually one of two different types: acute and chronic. Acute fatigue can be associated with current events and activities, once the situation is resolved recovery is attained and restful sleep achieved. Chronic fatigue is more serious and attributed to a cumulative effect of sleep loss over several months, which can lead the body to become vulnerable to illness, and increased stress.
Negative Effects on the Safety of Flight
Some of the negative effects are stated by Caldwell (1997) “...biological limits imposed by fatigue will impair the performance of even the most highly skilled and motivated individuals. Thus, the fact that missions are being flown only by the most dedicated ‘high time’ aviators offers no safeguard against the insidious threats posed by sleepiness in the cockpit. The effects of fatigue cannot be overcome by training or experience. In addition, the impact of fatigue cannot be negated by monetary or other incentives. Finally, individual pilots cannot be relied on to accurately judge their own levels of fatigue-induced impairments because judgment capabilities tend to suffer along with performance accuracy in sleepy personnel.”
Additionally, Caldwell (1997) goes on to describe the results of fatigue: “As fatigue levels increase, accuracy and timing degrades, lower standards of performance are unconsciously accepted, the ability to integrate information from individual flight instruments into a meaningful overall pattern is degraded, and a narrowing of attention occurs that leads to forgetting or ignoring important aspects of flight tasks. In addition, the fatigued pilot tends to decrease physical activity, withdraw from social interactions with others, and lose the ability to effectively divide his mental resources among different tasks.”
Fatigue cannot be mitigated directly with training, and a fatigued pilot cannot sufficiently self-diagnose due to cognitive impairments derived from the fatigue itself. This makes the issue of fatigue management primarily education and prevention.
Mishaps involving Fatigue
Rarely is fatigue listed as the primary factor attributed to an accident or incident involving aircraft, yet it has been listed as an attributing factor in several. In a Safety Recommendation letter (Rosenker, 2008), the NTSB stated that “[s]ince 1972, the Board has issued 115 human fatigue-related safety recommendations in all modes of transportation, including 32 recommendations addressing fatigue in the aviation environment and 4 intermodal recommendations.”
Additionally signifying the fatigue as an underlying cause Caldwell (1997) states, “Many of the human errors accounting for well over half of all aviation accidents , are probably the direct result of fatigue-related pilot inattentiveness and failures to respond to critical information in the cockpit. However, fatigue frequently is not cited as a causal factor in air carrier accidents despite evidence pointing to its role in mishaps.”
Continental Connection flight 3407. In February of 2009 a Colgan Air Bombardier Q400 operating as Continental Connection flight 3407 crashed into a residential neighborhood while on an instrument approach to Buffalo-Niagara airport from Newark, New Jersery.
According to the NTSB ("Loss of control," 2010) prior to reporting for duty for the accident flight, the captain had completed a two-day trip sequence. Living in Seattle, Washington, the First Officer began her commute to Newark the day prior to the accident flight, commuting all night from the West to East coast. Several pilots that saw the first officer during her commute stated she looked responsive and alert. No person that observed either the First Officer or Captain prior to the accident flight described them as drowsy or fatigued.
What the report does show however is that both the Captain and First Officer had habits of sleeping during commutes, or in the crew lounge prior to flight assignments. While not directly prior to the accident flight, the Captain had spent the night in the crew room 4 days prior and the First Officer spent 6 hours sleeping in the crew room the day of the accident flight.
Prior to departing Newark the CVR recorded the First Officer stating “I’m ready to be in the hotel room” and “this is one of those times that if I felt like this when I was at home there’s no way I would have come all the way out here.” Additionally she stated “if I call in sick now I’ve got to put myself in a hotel until I feel better … we’ll see how… it feels flying. If the pressure’s just too much … I could always call in tomorrow at least I’m in a hotel on the company’s buck but we’ll see. I’m pretty tough.” ("Loss of control," 2010).
In addition, during the entire flight, both crewmembers failed to maintain a sterile cockpit, which the NTSB stated as a contributing factor in the accident. The aircraft departed Newark and flew en-route with no remarkable event other than several sounds of yawning from both the Captain and First Officer recorded on the CVR.
On approach to Buffalo-Niagara, the crew noted that the aircraft was accreting significant amounts of ice on the windshield and wings. While configuring for the approach with flaps and gear, the Captain slowed the aircraft to 135 knots with the gear down and flaps selected to 15° while the FDR showed them at 10° moving towards 15°. The Bombardier Q400 AFM indicated that with flaps set to 10°, the approach speed minimum in icing conditions is 144 knots (for the weight that the accident aircraft was at).
Approximately 6 seconds later, the stick shaker activated alerting the crew that a stall was imminent. Providing aural and tactile cues to the pilot flying, the shaker sends vibrations through the control column and deactivates the autopilot. When the autopilot disengaged, the FDR showed the airspeed was 131 knots. The Captain moved the control column aft and advanced the power levers to approximately 10° below the rating detent (not quite full power). It was noted by the NTSB that this initial pitch-up placed the aircraft approximately at a G load of 1.42, further increasing the stall speed of the aircraft, exacerbating the situation.
Throughout the stall, the aircraft oscillated from 45° of roll, left wing down, to 105° roll, right wing down. While passing through wings level the first time, the stick pusher (automated nose-down movement of the control yoke to reduce wing angle-of-attack) activated and the First Officer selected flaps 0° (yet another stall exacerbation). The airspeed was now about 100 knots. The second time the aircraft was rolling through wings level, the stick pusher activated a second time.
The First Officer stated she had retracted the flaps and now asked if she should retract the gear. At this point the aircraft was 100° right wing down and 25° airplane nose down, and the stick pusher activated a third time. Four seconds later the CVR records sounds of impact and the CVR recording ended.
While there were several factors contributing to this specific accident, I believe Caldwell (1997) was correct when he stated “Many of the human errors…are probably the direct result of fatigue-related pilot inattentiveness and failures to respond to critical information in the cockpit.”
At first glance, it’s easy to pinpoint the lack of airmanship from the Captain as the primary causal factor. Listed in the NTSB report were several training deficiencies, failures, remedial training, and unreported events during the Captain’s training and airline career. You can even point to the First Officer and her decision to retract the flaps during the stall event as a primary factor for the continued stall and eventual impact.
I don’t think the crew made these decisions because they felt they were the correct decisions, or the best decisions for the situation. I don’t think the First Officer would have retracted the flaps had she been well rested, healthy and alert. I don’t think the Captain would have used less than full power or inducing accelerated G forces with an excessive pull-up had he been well rested and alert. I think the entire accident flight error chain can be traced to fatigue, lack of restful sleep, and poor sleeping environment.
The NSTB noted contributing factors to this accident in “Losing Control” 2010, as “(1) the flight crew’s failure to monitor airspeed in relation to the rising position of the lowspeed cue, (2) the flight crew’s failure to adhere to sterile cockpit procedures, (3) the captain’s failure to effectively manage the flight, and (4) Colgan Air’s inadequate procedures for airspeed selection and management during approaches in icing conditions.” Subsequently, listed as focus areas were “flight crew monitoring failures, pilot professionalism, fatigue, remedial training, pilot training records, airspeed selection procedures, stall training, Federal Aviation Administration (FAA) oversight, flight operational quality assurance programs, use of personal portable electronic devices on the flight deck, the FAA’s use of safety alerts for operators to transmit safety-critical information, and weather information provided to pilots.”
It is my belief that of the contributing factors that the NSTB listed, three of them are directly related to the fatigue level of the crew.
I think the rest rules the FAA has plans to implement will both improve fatigue mitigation and complicate rest requirement calculations. Currently there are several different ways to determine rest required, compensatory rest, minimum rest and reduced rest limitations. New regulations will be based on time “behind the door” of the hotel room instead of aircraft block in (which never accounted for post-flight duties, debrief, nor transportation time to hotel), which is a significant improvement. Additionally the new rest requirements will take into account the crewmember acclimated time zone, start of duty day, and legs flown. This will help reduce circadian trough fatigue and will provide more protection than previous regulations allowed.
It will however, significantly complicate the determination of required rest and calculation of maximum duty day.
I think the new regulations should be simplified to provide the additional rest and more restrictive duty days with fewer scenarios for variation. While I agree that duty day should be calculated on acclimated start time and legs flown, I don’t think it should be an algebraic formula to determine.
I believe the accident described in detail could have been avoided if the First Officer had confidence that calling out sick would not have cost her pay or an expensive hotel room. Currently most airlines provide hotel rooms for cancellations or sick calls only when out of domicile. They expect you to return home when you call out sick, yet they are fully aware that many pilots commute. I think providing a hotel room for a commuting pilot when sick or fatigued while in domicile is an inexpensive way to encourage pilots to not fly while sick or fatigued. This First Officer either could not afford the hotel, or could not afford the loss in pay. Neither of those consequences are more severe than the resulting accident.
I think flight crews should be disallowed from sleeping in crew rooms overnight. They are often noisy, uncomfortable, and they fail to provide a quality sleep environment or restful sleep. This gives the crewmember a false sense of well-being. They perceive that they acquired restful sleep and are now mentally convinced that they’re no longer fatigued. We know that a fatigued crewmember cannot self-diagnose signs of fatigue and now there is a false sense of security with rest that wasn’t sufficient.
Fatigue is a monster in disguise. When it finally rears its ugly head it might be too late to mitigate or even recognize. Fatigue mitigation must be accomplished through crewmember education and prevention. Once fatigued, a crewmember is no longer capable of sufficiently recognizing their level of impairment. While the FAA is moving forward with new rest rules and duty limits, the regulations should be simplified to prevent confusion and to promote sufficient rest. Monetary penalties should be removed by requiring airlines to provide crewmembers that are either sick or fatigued with hotel accommodations no matter where they call out from work. In addition, crewmembers should not be allowed to fool themselves into thinking they’ve received restful sleep by spending the night in a crew lounge.
Caldwell, J. A. (1997). Fatigue In The Aviation Environment: An Overview Of The Causes And Effects As Well As Recommended Countermeasures. Aviation, Space, and Environmental Medicine, 68(10), 932-938.
National Transportation Safety Board, (2010). Loss Of Control On Approach, Colgan Air, Inc., Operating As Continental Connection Flight 3407, Bombardier Dhc-8-400, N200wq, Clarence Center, New York, February 12, 2009 (NTSB/AAR-10/01)
Reinhart, R. O. (2008). Basic Flight Physiology. (3rd ed.). New York: McGraw-Hill Professional.
Rosenker, M. National Transportation Safety Board, (2007). Safety Recommendation (A-07-30 through -32)
Rosenker, M. National Transportation Safety Board, (2008). Safety Recommendation (A-08-44 and -45)
Stevenson, A. (2010). New Oxford American Dictionary. (3rd ed.). Lindberg, C.A.: Oxford University Press, USA.