The pilot reported for work as scheduled at 2 a.m. for a Part 135 light cargo flight, flying a Piper Lance from Burbank, Calif., to Phoenix, Ariz. He arrived at Phoenix and managed to get about five hours of sleep, waking at about noon local time.
On the next leg of the flight – the return to Burbank – he took off at 20:55 local. Several hours later, while maintaining a constant altitude, heading and airspeed, he collided with a mountain near Palm Springs -about 10 nautical miles south of his usual course. The investigators could find no evidence that indicated that the pilot had attempted to avoid the collision.
Investigators could find no mechanical reasons for the crash. After examining the pilots duty schedule, the NTSB concluded the accident was caused by incapacitation of the pilot due to inadequate sleep.
After most aircraft accidents, the reasons are intertwined, complex and very difficult to sort out. Pieces and parts of the airplane that have failed, actions that the pilot took or didnt take are usually discovered by investigators, but sleep deprivation and excessive fatigue are not easily found as causes.
Fatigue, sleepiness and the upset of individual circadian rhythms have played major roles in aircraft accidents since the earliest days of flight. The over-riding pressures to rise to the challenge and get the job done, get home or complete the flight is stronger, unfortunately, than the survival instinct for many pilots. They are too tired to make it, but they try it anyway.
Pilots who operate commercially feel a lot of pressure to continue a flight when they are really too tired to make it safely. There are very few occupations that combine so many factors that make it almost impossible to be alert while on the job.
For the career pilots: its shift work, long hours with irregular schedules and attempting to get some sleep in different environments at various times of day and night. Jet lag is a bonus effect.
On top of this, commercial pilots are required to make workable decisions and operate extremely complex aircraft – often with the lives of passengers in the balance. Corporate jet schedules rarely take the circadian rhythms of the pilots into consideration. There are trips that cross numerous time zones with the flight crew working from 16 to 18 hours at a time.
The farther down the totem pole you go – commuters, single and multi-engine freight dogs, and Part 135 on demand air taxi pilots – the heavier the pressure is to meet the schedule. There are always people waiting off-stage to jump in and take chances. Job security is extremely shifty for aspiring career commercial pilots.
Air carrier pilots go through an intense screening process that weeds out people who arent strong – physically and mentally. But even that doesnt mean that the pilots who finally make it to the flight deck can successfully resist the fatigue factors caused by circadian desynchron-ization and sleep loss.
Air carrier and corporate pilots live in a world where external time is shifted randomly and rapidly on a day-to-day basis – which is all out of line with their internal clocks. Meals are not at a time that agrees with an internal clock that is running on another time zone.
General aviation pilots, who usually dont earn their living by flying, are subject to the same pressures as their commercial brethren – and sometimes more. Self-imposed stresses are combined with the kinds of pressure only family and close friends can impose. The temptation to go is intense.
Many general aviation pilots tend to feel that using an autopilot during a long day at the controls will help prevent fatigue due to sleep deprivation. The problem, however, is that you can become bored and drowsy during autopilot flight. If you are tired, monitoring the autopilot in a low stimulus environment (worse, when dimly lit) will easily lead to a state of automation complacency at best and a full-scale nap at worst. If you are too tired to fly the trip manually, you are too tired to fly it at all.
A pilot suffering from lack of sleep faces a dramatic increase in reaction time and deteriorated psychomotor skills and vigilance. Its not surprising that sleep deprivation accidents happen; in a way its surprising they dont occur more often.
The Value of Zs
There are three stages of normal sleep. In the first stage the body slows down for about 10 minutes, into a dreaming phase. A deeper sleep follows in the second stage, which lasts from 15 to 30 minutes, when the body rebuilds strength. The mental rest comes during the third stage, lasting about an hour, which is deep sleep. We go through these stages about 4 times during a good nights sleep.
To get quality sleep, having a nightcap wont help at all. You may drop off to sleep more quickly after a few drinks but it doesnt last long. Alcohol interferes with the natural sleep cycle and the net result. You dont get the physical or mental rest that you need.
Without enough sleep, you generate a sleep debt. The average adult between 30 and 50 needs seven to eight hours of sleep per night. While that may not be news, researchers have calculated that 60 years ago adults averaged eight to nine hours per night and the average has been decreasing ever since.
Most adults today are trying to get by on an average of five to six hours of sleep per night. This leads to the sleep debt trap.
Missing sleep has something of an additive effect. Losing an hour or two every night soon leads to serious impairment. Research has shown that pilots or any other equipment operators have shown significantly decreased performance during periods when they are experiencing additive sleep loss.
Researchers have examined actual and potential mishaps filed with the NASA Aviation Safety Reporting System in an effort to understand how many of the errors were the result of pilots not paying attention to what they were doing. This included whether the pilots were able to see what they were supposed to do but didnt do it because of fatigue.
Their findings left little doubt. All of the pilots involved admitted that they routinely had been getting less than six hours of sleep per night. The easy conclusion was that fatigued pilots are more likely to be involved in accidents and incidents because they make more mistakes.
Studies have shown that someone who has been awake for 17 hours performs at about the same level as a person with a .05 blood-alcohol level. If you have been awake 24 hours, you basically act like youre legally drunk. You may feel that you are alert and capable, but drunks do too.
Concerned about unexplained accidents occurring during the landing phase of flight, the Air Force conducted a series of tests in a flight simulator using pilots who were in serious sleep debt. Of the 100 tested, 22 fell asleep either in the landing phase or from the final approach fix inbound to the runway.
All were victims of micro-sleep that didnt last long – perhaps just a few seconds – but it was enough to lose control or crash.
Micro-sleep can blank out consciousness at exactly the wrong time. The NTSB estimates that perhaps half of accidents where the pilots were found to be responsible were related to pilot fatigue.
Excess fatigue is a function of sleep patterns, and there are some things to consider when determining how good your own sleep patterns are. A few of the circumstances that can lead to sleeplessness and general fatigue include stress, poor nutrition, lack of exercise, heavy workloads and the indiscriminate use of alcohol or drugs.
The Midnight Brunch
Long-range and high speed aircraft are a big part of corporate aviation, and airline delays are leading more pilots to consider light planes for long personal trips as well. Desynchronosis – known to you and me as jet lag – is all too frequently the result.
At one time the airlines solved the problem of reducing crew fatigue by posting flight crews in different cities around the world for extended periods of time. This allowed long-term adaptation to different time zones. It was an excellent solution for the problems caused by long-distance east/west flying, but most airlines discontinued it because of the expense.
Some operators use another strategy to try and beat crew fatigue. They try to return their aircrews to home base as quickly as possible, before their biological clocks start to reset to different time zones. If scheduling doesnt allow it, they provide sleeping quarters that are free of local time distractions to keep the pilots on home-base time as much as possible.
Another strategy is to give routes ratings, based on the amount of sleep disruption they may cause. The direction of travel is taken into account, the number of time zones crossed, and whether its a day or night flight. These ratings are then used to work out how much rest the pilots should need after each flight.
A persons biological clocks will reset themselves at the rate of about one time zone per day. However, sooner or later, almost any pilot will be asked (or required) to fly during his personal circadian low point.
This is the time when the probability of pilot errors is at its peak.
One of the best ways to prevent fatigue-induced errors when youre not at your peak is to use printed checklists. With two crew members, one should read aloud the items and the other pilot should make a clear spoken response. Anything less invites the inevitable error.
The single pilot – fighting a low circadian point and a high error count – needs to read and respond to himself aloud to all checklist items.
The record is stuffed with accidents that could simply have been avoided by such a simple step. Accidents resulting from takeoffs without flaps, unlatched doors, improper go-arounds, gear-up landings and fuel miscalculations can frequently be traced to a tired brain in the left seat.
Some corporate pilots, who never remain at a destination long enough to adapt to local time, carry two watches – one to set on local time and one kept on their home time zone. They try to stay on the home time zone as much as possible – sleeping in the daytime and eating breakfast at night if necessary – but it gets them around jet lag.
One thing that doesnt work is drinking to fall asleep and then using caffeine (or something stronger) to get going again. A circadian low period just cant be brought up by stimulants. Only rest will do.
Sometimes getting rest means catching naps at the FBO while waiting for departure. Even a 15-minute catnap can do wonders for your mental alertness and is better than draining the whole pot of coffee.
Watching a ball game on TV in the pilots lounge, however, doesnt count as rest. Even if its baseball.
If the trip or the delay is a bit longer and you want real sleep, keep a few things in mind. If youre going to sleep longer than a nap, try to keep your sleep cycles whole.
Everyones sleep cycle varies, but for most people it is around 1 hours to two hours.
Thats the time it takes to cycle from light sleep through deep sleep and back to light sleep. If your cycle is 90 minutes, four and a half hours of sleep may leave you feeling better than five and a half hours.
Relax and try to get some light exercise, even if its just walking. Watch what you eat and limit your consumption of coffee and chocolate.
Finally, white noise helps drown out many of the disrupting noises you may find while traveling. Turning the radio on quietly and tuning it between stations helps mask outside noise, as does the air conditioner fan.
Remember that fatigue-related problems are serious. Fatigue slows reaction times and is the cause of many errors due to inattention.
Insufficient rest and the loss of sleep are the most common causes of fatigue. But there are also important and contributing factors – the pressures of business, financial worries and family problems are high on the list. If you are deeply tired, carrying an extra emotional load, and are scheduled to fly – dont.
If you are on a cross-country flight and things havent worked out and you are off to a late start – sit down a minute. Your chances for an accident are building up fast. Cancel your flight plan. Catch a cab to the motel.
Call whoever is waiting for you. After a nights rest, the whole picture will look much better – and the flight will be safer.
During long flights, keep active in the airplane. Make ground checks, do some radio-navigation position plotting, check and recheck your cockpit configuration, fuel consumption and engine instruments.
Keep your mind active and avoid any monotonous or non-essential activities.
Also With This Article
Click here to view “FAA Rules Clarified.”
-by Ray Leis
Ray Leis is an ATP and CFII with more than 23,000 hours under his belt. He was awake for most of them.