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Industrial safety research concludes 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.
there was “plenty” of runway remaining for the airplane to land. The witness lost sight of the airplane and did not see the accident because the airport hangars blocked her view.
The wreckage was located about 2,400 feet southeast of the departure end of runway 24. Examination of the accident site indicated that the airplane impacted in a nose-down attitude with a left bank of about 20 degrees. A left turn during departure was consistent with the air- port’s published instrument departure procedures for obstacle avoidance, which required an immediate climbing left turn while proceeding to a navigational beacon located about 7 miles east-northeast of the airport. Examination of the wreckage did not reveal any evidence of preimpact me- chanical malfunctions that would have precluded normal operation.
The pilot had reportedly been awake for about 15 hours and was conducting the departure about the time he normally went to sleep and, therefore, may have been fatigued about the time of the event; however, given the available evidence, it
6 • TWIN & TURBINE / October 2020
was impossible to determine the role of fatigue in this event. Although the circum- stances of the accident are consistent with spatial disorientation, there was insuf- ficient evidence to determine whether it may have played a role in the sequence of events.
NTSB probable cause: The pilot’s fail- ure to maintain clearance from terrain after takeoff during dark night conditions.
Occasionally NTSB reports do identify pilot fatigue as a contrib- uting factor in an accident, such as this example.
The Cessna 414A, flown by an air- line transport pilot, was approaching the destination airport after a cross-country f light in night instrument meteorological conditions. Destination weather about one minute before the accident included an overcast ceiling at 200 feet and half- mile visibility with light rain and fog. The flight received radar vectors to the final approach course for an ILS approach. The airplane’s flight path did not properly intercept and track either the localizer or the glideslope during the instrument approach. The airplane crossed the final approach fix about 360 feet below the glideslope and then maintained a descent profile below the glideslope until it leveled brief ly near the minimum descent alti- tude. The lateral flight path from the final approach fix inbound was one or more dots to the right of the localizer centerline until the airplane was about one nautical
mile from the runway threshold when it turned 90 degrees left. The turn was initi- ated before the airplane had reached the missed approach point; additionally, the left turn was not in accordance with the published missed approach instructions. The airplane made a series of pitch excur- sions as it flew away from the localizer. A simulation study determined that dual engine power was required to match the recorded flight trajectory and ground speeds, which indicated that both engines were operating throughout the approach. The simulation also indicated that the airplane likely encountered an aerody- namic stall during its course deviation. The airplane impacted the ground about 2.2 miles east-northeast of the runway threshold and about 1.75 miles east of the localizer centerline.
The airplane impacted the ground upright and in a nose-low attitude con- sistent with an aerodynamic stall/spin. Wreckage examinations did not reveal any anomalies with the airplane’s flight control systems, engines, or propellers. The glideslope antenna was found discon- nected from its associated cable circuit. Laboratory examination and testing determined that the glideslope antenna cable was likely inadequately connected/ secured during the f light, which resulted in an unusable glideslope signal to the cockpit avionics. There was no history of recent maintenance on the glideslope an- tenna, and the reason for the inadequate connection could not be determined.
Data downloaded from the airplane’s EHSI established that the device was in the ILS mode during the instrument ap- proach phase and that it had achieved a valid localizer state on both naviga- tion channels; however, the device never achieved a valid glideslope state on either channel during the flight. Further, a re- play of the recorded EHSI data confirmed that, during the approach, the device dis- played a large “X” through the glideslope scale and did not display a deviation pointer, both of which were indications of an invalid glideslope state.
There was no evidence of cumulative sleep loss, acute sleep loss, or medical conditions that indicated poor sleep qual- ity for the pilot. However, the accident occurred more than 2 hours after the pilot routinely went to sleep, which suggests that the pilot’s circadian system would