Page 9 - 213934_October20T

not have been promoting alertness dur- ing the flight. Further, at the time of the accident, the pilot likely had been awake for 18 hours. Thus, the time at which the accident occurred and the extended hours of continuous wakefulness likely led to the development of fatigue.
The presence of low cloud ceilings and the lack of glideslope guidance would have been stresses to the pilot during a critical phase of f light. This would have increased the pilot’s workload and situational stress as he flew the localizer approach, a pro- cedure that he likely did not anticipate or plan to conduct. In addition, weight and balance calculations indicated that the airplane’s center of gravity (CG) was aft of the allowable limit, and the series of pitch excursions that began shortly after the airplane turned left and flew away from the localizer suggests that the pilot had difficulty controlling airplane pitch. This difficulty was likely due to the adverse handling characteristics associated with the aft CG. These adverse handling char- acteristics would have further increased the pilot’s workload and provided another distraction from maintaining control of the airplane. Therefore, it is likely that the higher workload caused by the pilot’s attempt to f ly an unanticipated localizer approach at night in low ceilings and his difficulty maintaining pitch control of the airplane with an aft CG contributed to his degraded task performance in the minutes preceding the accident.
NTSB probable cause: The pilot’s fail- ure to maintain control of the airplane during the instrument approach in night instrument meteorological conditions, which resulted in the airplane exceed- ing its critical angle of attack and an aerodynamic stall/spin. Contributing to the accident were pilot fatigue, the pilot’s increased workload during the instru- ment approach resulting from the lack of glideslope guidance due to an inad- equately connected/secured glideslope antenna cable, and the airplane being loaded aft of its balance limit.
The Federal Aviation Administration publishes rules for flight, duty day and rest regulations applicable to air carrier operations. According to the FAA, “Fatigue threatens aviation safety because it increases the risk of pilot error that could lead to an accident. The rule recognizes the
universality of factors that lead to fa- tigue in most individuals and regulates these factors to ensure that f light crew members in passenger operations do not accumulate dangerous amounts of fatigue.”
The FAA does not, however, publish fatigue-mitigation regulations for most Part 91 operations. The only fatigue rule for non-91K fractional ownership aircraft that applies to light aircraft is the prohibition against f light in- structors conducting more than eight hours of “dual given” in any 24-hour period. The rest of us are on our own to determine whether we’re alert enough to fly.
Pilot fatigue is a virtually unre- searched and potentially major factor in general aviation accidents as well. Common symptoms of fatigue include: • Measurable reduction in speed and
accuracy of performance
• Lapses in attention and vigilance • Delayed reactions
• Impaired logical reasoning and de-
cision-making, including a reduced ability to assess risk or appreciate the consequences of actions
• Reduced situational awareness
• Low motivation to perform op-
tional activities
The symptoms of fatigue are exactly
the same as those of alcohol impair- ment. Industrial safety research con- cludes that after a restful, eight-hour
sleep, being awake for 18 hours results in performance equivalent to that of someone with a blood alcohol content of 0.05. After being awake 23 hours, performance is the equivalent of a blood alcohol content of 0.12. Many states define “legally drunk” as a blood alcohol content of 0.08. Of course, there is no blood alcohol level permissible to serve as pilot-in-command.
It’s not enough to get a good rest the night before a challenging trip. “Sleep debt,” the negative cumulative effect of getting less than eight full hours of sleep, applies not only the night before a flight but for several nights prior to that as well. According to research cited by the FAA, “The average per- son requires in excess of nine hours of sleep [in a single] night to recover from a sleep debt.”
Sleep debt and the effect of fatigue on pilot performance are likely huge as unidentified factors in aircraft ac- cidents. Add long f lights and dark conditions, and a pilot who took off in a reasonably well-rested state may not have what it takes to safely complete a f light when presented with adverse or unusual circumstances. Many owner-pilots tend to make trips after the end of a full workday, sometimes at the end of a long work week – expos- ing themselves, their passengers and the people they fly over to heightened risk from fatigue.
Pilot fatigue is a virtually unresearched and potentially major factor in general aviation accidents.
PHOTO COURTESY OF SAM SCHOOLFIELD
October 2020 / TWIN & TURBINE • 7