Sunday, December 12, 2010

The hardest part of flying

In the aftermath of the Mangalore crash, the Directorate General of Civil Aviation (DGCA, India) has brought out a number of circulars on aviation safety, even as investigations reveal that the pilot-in-command (PIC) of the ill-fated 737 was suffering from "sleep inertia".

A factor crucial to aviation safety, that could be easily overlooked is the physical and mental state of the pilot(s). In this context, it would be worthwhile making an effort to understand the following:


From the above diagram, the period between 02:00 and 06:00 (from the point of view of the human body) is characterized by low performance, low levels of alertness, low body temperature, and high fatigue. This is called the "window of circadian low". In most cases, the human body clock has conveniently chosen this period (in response to environmental conditions like sunlight, ambient temperature, etc) to "switch-off", as this is absolutely essential for its proper functioning.

Research done at the University of South Australia Sleep Research Center reveals that performance while fatigued is comparable to performance while intoxicated. Volunteers were subjected to judgment, reasoning, vigilance, and hand-eye coordination tests on two different occasions; on one occasion, after making them tired, and, on another occasion, after making them drunk. It was found that after 17 hours of wakefulness, at about 03:00, the effects of fatigue on performance were equal to a 0.05% blood alcohol concentration; and at 08:00 (about 22 hours of wakefulness), a performance impairment equivalent of 0.1% blood alcohol concentration was noted. In many states in the US, a blood alcohol concentration of 0.05% to 0.1% is enough to be arrested for DUI (driving under influence).


When was the last time you "dozed off" in the middle of doing something ? That feeling of heaviness in the eyelids; that feeling of just letting go of things and surrendering to sleep, that nothing is more important in those few moments than getting your forty winks..........and at the same time, the feeling that you are still mindful of your job and everything seems to be looking good..........until suddenly, someone comes by and says that you have been nodding off, or your newspaper drops to the floor, or you fall off the chair !

The above mentioned "feelings" are cues/warning signs that you might soon experience bouts of microsleep, which are brief unintended episodes of loss of attention associated with events such as blank stares, head snapping, prolonged eye closure which may occur when a person is fatigued but trying to stay awake to perform a monotonous task. A microsleep is an episode of sleep that can last anywhere from a fraction of a second to several seconds and is often the result of sleep deprivation and mental fatigue. Microsleep is extremely dangerous in situations that demand constant alertness, primarily because people who experience microsleep usually remain unaware of them, and instead believe that they are indeed awake and have only just temporarily lost focus.


This is also something that could go unnoticed until it really begins to matter. We need about 8 hours of sleep per day, on average; now let's say that due to "commercial pressures", a pilot gets only 6 hours on Monday. On Tuesday, he again manages to squeeze in 6 hours, and on Wednesday, he gets only 5 hours. I have dared to assume that it is only a busy work schedule that has cost our pilot his sleep - NOT taking into account non-professional factors like staying up all night (for various reasons.....). By Thursday, he has lost almost a night's worth of sleep, and this is bound to show by way of degraded performance and physical fatigue, not to mention tendencies for microsleeps to occur.

An easy way in which sleep debt can build, is during flight operations on the back side of the clock, to which, particularly cargo pilots might be very susceptible. The human body is naturally programmed to sleep during certain hours (as mentioned earlier, the "window of circadian low" occurs between 02:00 and 06:00). When we try to override this, there are two consequences:

1. We are trying to stay awake, when the body wants to be sleeping.
2. We are trying to sleep, when the body wants to stay awake.

(2.) has the effect that even when we have the time to sleep (albeit during the day, when off-duty), we find it difficult to catch up on sleep, and even if we do, it is often inadequate. Frequent and extended occurrences of this sort would eventually result in cumulative sleep debt.


A proper night's sleep fully recharges your batteries, but as soon as you wake, energy slowly drains out as the day progresses. So it is equally important for a pilot to be aware of "time since awakening", and take care that it does not lead to cumulative sleep debt.


It seems to have happened to the pilots involved in the recent air crash (Air India Express Flight IX 812, Boeing 737NG) at Mangalore. Sleep inertia is a physiological state immediately following a sudden awakening (from sleep) and is characterized by a decline in motor dexterity, accompanied by feelings of lethargy and grogginess, and a tendency to want to return to sleeping. Sleep inertia can be more severe when a person is awoken from deep sleep due to fatigue/sleep debt.


AWARENESS - Know how much sleep you ideally need to be able to perform well. Also know how long you can keep up the good work before performance begins to degrade and you need to take rest.

PLANNING - The earlier you know your fixtures for the week (or month), the better you can plan how you are going to distribute your sleep during those periods. It would also help to plan for changes in sleep patterns early on, instead of at the last minute.

HEALTHY LIFESTYLE - A healthy lifestyle with lots of exercise and eating nutritious food will go a long way in regulating how much sleep the body needs. It is needless to mention the ways in which exercise and a good diet are invaluable to health. The human body clock seems to suggest that the best time for exercise would be late in the evening.


CAFFEINE - A hot cup of coffee is the perfect stimulant to stay awake. Take note though, that caffeine takes about half an hour to kick into action, and its effect can last for about 3-4 hours.

For non-coffee drinkers, energy drinks can be a good alternative. However, the amount of caffeine in energy drinks is much less than that in coffee, so more amounts of energy drinks will have to be consumed.

Caffeine fights sleep, so any over-consumption of caffeine will also prevent a well deserved rest after a long flight. It would a good idea to be well-stocked with high-caffeine drinks on every flight, just to play it safe.

MELATONIN - Melatonin is a chemical produced by the pineal gland in the brain, and it has a function in regulating the human biological clock (circadian rhythm). Today, while it is available as a prescription-free, over-the-counter medication in the US, it is also illegal in many countries.

It would be wise to refrain from using this medication as much as possible, even though studies have shown that there are no side-effects due to to the short-term use of this drug. It is a drug, which is used to treat sleeping disorders, and should not be used as a preventive measure, especially without consulting a doctor. Studies have also shown that Melatonin can cause drowsiness, so it must be treated with extreme caution.

BEFORE A FLIGHT - Always be sensitive and aware of your "charge status". In most cases, people are not accurate when they "think they are doing okay" (which is why there are limitations on flight duty time); cues to watch out for are easy irritability and degradation in performance even for simple tasks, mood changes, slower reaction time, weaning concentration, judgmental errors, etc. It is more important (and harder) not to brush away these things. It is good to have an I'M SAFE checklist, if not a better personal checklist.

I - Illness, M - Medication, S - Stress, A - Alcohol, F - Fatigue, E - Emotion (I'M SAFE)

UNEXPECTED DELAYS - It would be wise to anticipate your sleep situation when a prolonged delay occurs, as your situation in the cockpit would be well different from what it would have been a number of hours earlier. A complete assessment from the point of view of safety during the approach and landing phases should be made - commercial pressures can force a fatigued pilot to make a decision which he probably wouldn't make under normal (well-rested) circumstances. Bear in mind that you might be most vulnerable to "get-home-itis" at this stage. As always, keep that shot of caffeine handy.

POST FLIGHT - If a situation arises where you are just unable fall asleep (because you are not yet used to sleeping during that part of the day/night), it is better to try and do some sleep inducing activity (like reading a boring book) and get just a few hours of sleep, rather than struggle in bed for a whole eight hours. Exercise, if done within a couple of hours before sleep, will only disrupt it, as does a heavy meal.

The more complicated a task (let alone multi-tasking), the more fatigued the body gets in trying to deal with it.
I hope the observations made here help the hardest part of flying a little bit easier. Take care and fly safe !

For a further reading on pilot performance in relation to sleep, refer to the article below:;col1

To read more about the FAA's new rules proposed to fight pilot fatigue, refer to the following article:

Wednesday, December 8, 2010

Survival of the leanest (and meanest ?).


The Boeing 737-100 entered service in 1968 and was the smallest variant of the 737 series. The 737-200 was an extended-fuselage replacement for the 737-100. There are no 737-100s in service today. The 737-200s are also being phased out due to poor fuel efficieny, high noise emissions, and high maintenance and operating costs, but quite a few are still used in "second tier" and cargo operations. Later versions of the 737 (300/400/500/600/700/800/900) with better performance and fuel efficiencies are still  with the airlines, making the 737 a huge commercial success for Boeing.

Boeing 737-100
Dassault Mercure-100. Note the Pratt & Whitney JT8D powerplant, also used on the 737-100/200.
The Dassault Mercure was touted as a replacement for the Boeing 737 and McDonnell Douglas DC-9. It was, in fact, the worst failure of a commercial airliner in terms of number of aircraft sold, mainly due to its low operating range. Extremely modern tools for the time were used for the development of the Mercure. The Mercure was larger and faster than the 737, and was certified for CAT3A all-weather automatic landing. Air Inter, a French domestic air carrier, was the only airline that purchased these aircraft (about 10). An attempt to develop a Mercure-200 with better performance was abandoned due to lack of financing. All Mercures were retired from service in 1995, with an impressive 360,000 flight hours, 44 million passengers carried in 440,000 flights, no accidents, and a 98% in-service reliability.