Monday, February 16, 2009

PST, EST, UTC, GMT, and Zulu

This morning I awoke around 5:30a.m., as I usually do, except that it was 5:30 Pacific Standard Time (PST), in California instead of my home time zone: Eastern Standard Time. That meant it was really 8:30am, or 1330Z (Zulu), or Coordinated Universal Time (UTC) or Greenwich Mean Time (GMT). If I would have awakened this late at home, I would have felt like I had slept most of the day away. I was somewhat comforted by the fact that I was on duty til 11pm PST, which is 0700Z (or UTC or GMT) or 2am EST. Confused yet?

The truth is, my watch is set to EST, though I can press a button and see UTC time. UTC is the time system used in aviation, referred to as Zulu. Weather forecastings, flight plans, air traffic control clearances, and maps all use UTC to avoid confusion about time zones and daylight saving time. The UTC time zone is sometimes denoted by the letter Z – a reference to the equivalent nautical time zone (GMT), which has been denoted by a Z since about 1950. Since the NATO phonetic alphabet and amateur radio word for Z is "Zulu", UTC is sometimes known as Zulu time. This is especially true in aviation, where Zulu is the universal standard. This ensures all pilots regardless of location are using the same 24-hour clock, thus avoiding confusion when flying between time zones.

EST is UTC+5, which is pretty easy math. But then try this delimma: According to my tripsheet, I am expected to take off from Des Moines at 10am, making a 2 1/2 hour flight to Pheonix, but the passenger is 45 minutes late and we won't expect to take off for another 30 minutes by the time we settle the passenger, get the engines started, taxi out and take off. Upon his arrival my passenger asks me what time we will now arrive in the local time so he can have his driver pick him up. I look at my watch and I see 11:45am EST. The time shown on my paperwork is out the window due to the delays. What should I tell him?

So the answer to the above can be a nightmare. If it's 11:45am EST, subtract an hour for CST, but add 30 minutes ground time. Then add 2 1/2 hours for flight time and then adjust it to the new time zone of your destination. We have to convert to Pheonix local time, which is MST. But not always. They don't observe Daylight Saving Time (DST), so, darnit, should I subtract 1, 2, or 3 hours? (Don't forget, the passenger is expecting you to have a ready answer - you destroy your credibility if you can't come up with the answer ASAP!)

Another wrinkle to consider when you're adding and subtracting:

Arizona does not observe Daylight Saving Time (March through November). They do not "spring Forward" in Phoenix -- they always stay on Mountain Standard Time. During Daylight Saving Time (DST) most of Arizona is at the same time as California (Pacific Daylight Time or PDT). On the first Sunday in November, when DST ends, most everyone else in the country "falls back" or sets their clock back one hour. They do not. From that first Sunday in November through the second Sunday in March they are one hour ahead of those states on Pacific Standard Time, like California and Nevada; one hour behind states in the Central Time zone, such as Texas and Illinois; and only two hours behind those states on Eastern Time, such as New York and Florida.

So, depending on the time of year, let's say today, we don't have to worry about AZ not switching to DST, so they are still MST, which means just an hour behind CST. Whew! It is somewhat easier to do all of this math in Zulu time and then just convert at the end. MST is UTC - 7.

Of course there will always be some confusion no matter how big the timezone difference. I was on an Army flight out of England years ago and the passengers waited for the crew for an hour. The General was looking at the Local time in London to determine when to show for his flight. Because they also have daylight savings, Local time was not the same as Zulu time (which determined when we showed for our flight). We briefly tried to explain the difference, and then just decided to say, Yes, sir," and move on.

Anyway, I just find it easier to keep my body clock on Eastern time no matter where I am. The most I am going to be "off" is three hours when I go to the West Coast, which means I get up really early according to their clocks. Staying up late like I had to do the last two nights in a row becomes more of a challenge. Caffeine can be a short term solution, but I don't recommend it for long. One may be awake, but not necessarily alert.

The medical community usually advises people to go to bed and get up at the same time every day.

"Sleep is a homeostatic process [a system where our bodies regulate automatically based on our daily patterns]," says Sonia Ancoli-Israel, Ph.D., a professor of psychiatry at the University of California at San Diego and a spokesperson for the National Sleep Foundation. "If you sleep in, it might affect your ability to fall asleep the next night, since you have to be awake for a certain amount of time before you'll be sleepy enough to go to sleep again."

This is not always possible on the road. For example, I woke up at 3am EST to start this tour, because I had an early morning airline flight to go to pick up my airplane. We immediately started flying west, which means each day we were getting progressively later "start times." Later in the sense that a 7am flight on the west coast is, according to my body clock, a 10am flight. Since we pilots can work a 14 hr duty day, a 7am PST start means theoretically we could be working until midnight (EST). I'm not usually up this late.

But today we are flying back to the east coast, which means there is a chance that I may have to get up early for a flight EST. But like I said, today I "slept in" til 6:30am PST. If tomorrow morning I have to wake up at 6:30am EST, that is virtually 3:30am PST, which is what I've been working off of the last 3 mornings and so will be an adjustment. Is this all making sense?

The result of this, as you may know, is commonly referred to as jetlag. Add to this a disjointed work/eat/sleep schedule, in unfamiliar beds in noisy hotels, and fatigue becomes a factor pretty quickly. An article on Pilot Fatigue written by Dr Samuel Strauss.

“Circadian rhythms” are physiological and behavioral processes, such as sleep/wake, digestion, hormone secretion, and activity, that oscillate on a 25 hour basis. Each rhythm has a peak and a low point during every day/night cycle. Time cues, called “zeitgebers,” keep the circadian “clock” set to the appropriate time of day. Common zeitgebers include daylight, meals and work/rest schedules. If the circadian clock is moved to a different schedule, for example when crossing time zones or changing from a day work shift to a night shift, the resulting “sleep phase shift” requires a certain amount of time to adjust to the new schedule. This amount of time depends on the number of hours the schedule is shifted, and the direction of the shift. During this transition, the circadian rhythm disruption or “jet lag” can produce effects similar to those of sleep loss.

Transmeridian flights in excess of three time zones can result in significant circadian rhythm disruption. When flying in a westerly direction the pilot’s day is lengthened. When flying east, against the direction of the sun, the pilot’s day is shortened. Thus the physiological time and local time can vary by several hours. Symptoms of jet lag are usually worse when flying from west to east as the day is artificially shortened. It takes about one day for every time zone crossed to recover from jet lag. When circadian disruption and sleep loss occur together, the adverse effects of each are compounded (3).

I blogged about this previously in 10 hour turns, in which I discussed a flight crew that had fallen asleep and overshot their destination. According to Dr. Strauss, "many of the unique characteristics of the flight deck environment make pilots particularly susceptible to fatigue."

Contributing aircraft environmental factors include movement restriction, variable airflow, low barometric pressure and humidity, noise, and vibration. In commercial aircraft, hands on flying has been mostly replaced by greater demands on the flight crew to perform vigilant monitoring of multiple flight systems. Research has demonstrated that monotonous vigilance tasks decreased alertness by 80% in one hour (4). This phenomenon is often referred to as “boredom fatigue.”

So what can we do? We can't always stay in our own time zone. The company won't make a profit if they don't get the crews to fly for more than a couple of hours a day, causing pilots to lose their jobs and end up moving back in with their parents. Tragic. So Dr. Strauss lists some countermeasures:

Research has shown that several countermeasures for fatigue are effective in improving alertness and performance. Long naps, 3-4 hours, can significantly restore alertness for 12-15 hours. Short or “power” naps of 10-30 minutes can help restore alertness for 3-4 hours. Allow 15-20 minutes after awakening to become fully alert before assuming aircrew duties (7,12,17).

Other countermeasures include:

Eat high protein meals (avoid high fat and high carbohydrate foods)
Drink plenty of fluids especially water
Caffeine can help counteract noticeable fatigue symptoms if awake for 18 hours or less
Rotate flight tasks and converse with other crewmembers and keep the flight deck temperature cool
Move / stretch in the seat, and periodically get up to walk around the aircraft if possible
Gradually shift times for sleep, meals, and exercise to adjust to a new time zone (19)

On that note, I think I'll go down to the hotel restaurant for lunch. Oops, what time is it? I mean breakfast.

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