Friday, August 1, 2003
Tired technicians? When people get tired, they lose initiative, self-discipline, and attention to detail. Work degradation from fatigue is well documented. Fatigue may have played a role in the step-skipping the night the elevator control cables were tightened on the Air Midwest Beech 1900D that crashed in Charlotte, North Carolina. From the time sheets examined by National Transportation Safety Board (NTSB) investigators, it is evident that long hours were being logged at the Raytheon Aerospace maintenance facility in Huntington, West Virginia. Technician Brian Zias, who was most involved in adjusting the cable tension, worked 14 hours the night the accident airplane was in the hangar. Quality assurance inspector George States, who was training Zias and approved his work on that task, was working even longer hours. Foreman Rick Tucker also worked a long shift the night the airplane was in for work. A snapshot of three nights suggests that long shifts were being worked at the undermanned facility.
Struck by the hours being worked at this facility, maintenance expert Bart Crotty said, "All ‘Good Practices’ or management work control efforts should have the following underpinning principles:
- Minimize the build up of fatigue over periods of work.
- Maximize the dissipation of fatigue over periods of rest.
- Minimize sleep problems and circadian disruptions."
Crotty said no more than 60 hours should be worked, including overtime, during a seven-day week period. Zias was well on the way to exceeding Crotty's suggested total in four days.
Crotty said, "A span of successive night shifts involving 12 or more hours of work should be limited to six shifts of up to eight hours long, four shifts of 8.1 to 10 hours, and two shifts of 10.1 hours or longer.
"These limits should not be exceeded by overtime," he admonished. For the source of these guidelines, he pointed to a recent paper by the U.K.'s Civil Aviation Authority, "Work Hours of Aircraft Maintenance Workers," which provides the latest word on the subject. The paper suggests a 13-hour limit on the total period of work. On the night the Midwest Airlines aircraft was in for maintenance, all three of the individuals most directly involved worked more than 13 hours.
From: "Work Hours of Aircraft Maintenance Personnel:"
"The aviation maintenance system is heavily dependent upon people being able to perform their jobs reliably and efficiently. Whilst U.K. maintenance-related accident and incident data do not show fatigue as a frequent contributing or causal factor, it is a continual threat to the safety system.
"Confidential reports submitted to the Confidential Human Incident Reporting Programme (CHIRP) have on a number of occasions indicated those excessive working hours and certain shift patterns being worked are a potential safety hazard.
"There have been limitations on the work hours of pilots for some considerable time, and more recently the work hours of Air Traffic Control Officers have also been limited. However, no such limits or recommendations presently exist for the work hours of aircraft maintenance personnel despite their obvious involvement in the overall safety of air transport operations."
A few selected observations from the report:
"It is not surprising that people who try to work at night and sleep during the day often report they cannot do either very well."
"There is a fairly consistent tendency for the relative risk of accidents to be highest on the night shift."
"The increased day sleep durations of permanent night workers relative to that of rotating shiftworkers does not necessarily imply greater adjustment of the circadian system. Rather, it could simply reflect a greater ‘pressure’ for sleep due to the typically greater span of successive night shifts."
Source: UK/CAA Paper 2002/06, "Work Hours of Aircraft Maintenance Workers," March 2003. For the full report, see http://www.caa.co.uk/ docs/33/Paper2002_6.pdf
(What the people involved had to say in post-accident interviews with investigators. Note: people are not good judges of their state of fatigue):
Q: What is your normal sleep schedule?
A: Normally, I get off at 6:30 in the morning, so go home and shower up, out (asleep) by 8:00 and up around 4:00 or 5:00.
Q: How was your sleep in the days before Jan. 6?
A: Okay, as far as I know.
Q: Do you recall what time you woke up on the 6th?
Q: When do you normally -
A: Normally, I get off my shift and I go to sleep ... but sometimes I have errands to run or whatever, I will extend my - instead of going to bed like you would at 11:00, I'll go to bed at 1:00 or whatever.
Q: How do you handle fatigue management on a personal basis?
A: If I feel tired, I go home.
Q: That's your normal sleep/wake cycle. Do you normally go to bed -
A: I normally get up an hour or two before I've got to come to work. When I go to sleep, it all depends on what was going on that night on that shift. Sometimes it's as soon as I get back to the room and sometimes I'm up for a little while.