EXTENDED OPS FACTORS
Choices are many and prices are high—and with ranges that cover the planet, body clocks take time to recover.
By Mike Venables
Dassault Falcon 7X is an example of the growing category of bizjets with 5000-nm-plus range. Flight durations can exceed 12 hrs, causing significant disruption to circadian rhythms.
Scaled Composites' GlobalFlyer was a very long-range aircraft indeed with its distance record of 22,390 nm. The record was claimed in 2006 following a flight that started at Kennedy Space Center in Florida and ended at BOH (Bournemouth, England) after circling the globe and crossing the Atlantic twice.
GlobalFlyer was not designed to be fast—the flight averaged a groundspeed of 291 kts including tailwinds—although the endurance of both the aircraft and the pilot, Steve Fossett, at 76 hrs 45 min, was impressive. However, the payload capacity (other than fuel) was meager and creature comforts were nonexistent. The flight landed with 200 lbs of fuel remaining. Hardly NBAA reserves!
While it is a challenge to create an ultralong-range aircraft, it is an even greater challenge to create a long-range aircraft that will fly a long distance at a reasonable speed with an acceptable payload. A number of long-range business jets are on the market and more are coming.
Establishing an arbitrary minimum range of 5000 nm, a recent survey of business aircraft revealed the qualifiers shown in the table on this page. As can be seen, while the speeds and payloads are acceptable, the durations start at slightly less than 12 hrs and top out at over 16!
As difficult as it is to design and build these aircraft, it is far more difficult (read "impossible") to design and create a long-range pilot. Despite the public perception of the steely-eyed jet pilot, we are all subject to fatigue and the influence of our circadian rhythms.
A circadian rhythm is an internally driven cycle, of roughly 24 hrs, in biochemical, physiological or behavioral processes. Circadian rhythms have been widely observed in plants, animals, fungi and some bacteria.
Although circadian rhythms are built-in and self-sustained, they are adjusted to the environment by external cues called zeitgebers (from the German for "time giver" or "synchronizer"), of which the primary one is daylight. Other zeitgebers are temperature, social interactions, exercise and eating/drinking patterns.
According to Bombardier Chief Pilot (Widebody Aircraft) Yann Lemason, his demo flight department policy requires a 3rd pilot if the duty day exceeds 16 hrs (about a 12-hr flight).
Let's assume that such a flight stayed in the same time zone (say from Atlantic Canada to Chile).
If we refer to the figure on this page, we can see that secretion of melatonin (the sleep-inducing compound) stops at 7:30 am, making an 8:30 am departure reasonable. This results in an arrival at 8:30 pm—also reasonable. The problem is that, if the flight extends beyond 9:00 pm, melatonin secretion starts again.
The crew will be starting the approach as their bodies are getting ready for sleep. Hence the logic to adding the 3rd pilot on longer flights. The pilots can take a rest in rotation so that at least 2 of the 3 pilots are rested—or should be—for the final phase of the flight.
Unfortunately, most flights do not stay in a single time zone, nor do they leave at 8:30 am for an evening arrival (a daytime flight). An 8:00 pm departure from New York results in an 11:00 pm arrival in Taipei, Taiwan (15 hrs at Mach 0.85). Maintaining crew alertness throughout the very long night flight means minimizing the impact of the normal circadian rhythm.
Crew self-help actions
Pilots can do some things to help themselves when it comes to minimizing the effects of these rapid time zone crossings. These include eating lightly and keeping hydrated throughout the flight. On shorter flights, catnaps of 20–40 min—a "NASA snooze"—can revitalize a fatigued brain. Getting out of the cockpit for a walk helps to reinvigorate blood circulation, key to restoring clear thinking—one of the zeitgebers.
Yann reports that Bombardier Demo Flight Ops also has a policy of running continuous system reviews and examining "what if?" scenarios to keep the pilots engaged and alert. Electronic flight bags—both Class 2 types and iPads—provide easy access to documentation for these reviews. Prior to flight, a variety of software tools are also available to aid scheduling to reduce fatigue.
Crew rest area
As most, if not all, of these long-range aircraft have custom interiors, owners can contribute significantly to reduction of fatigue effects by adding a crew rest compartment. It must be isolated from the rest of the cabin so that the resting crewmember can sleep soundly.
This means that it must be soundproof or remote from high-activity areas. It should allow the occupant to eliminate light (100% effective windowshades and no cracks around the door) and to control the temperature independently of the rest of the aircraft, as cooler temperatures are required for deep sleep—another zeitgeber. Needless to say, it must have a lie-flat bed.
While an appropriate crew rest area takes away from space that would otherwise be available to the owner and his/her fellow passengers, these features create an environment that leads to a more refreshed crew and should therefore be seen as safety features.
As mentioned above, good hydration is vital. Therefore, a lavatory that the crew can access without disturbing the passengers is also a godsend as it allows free access at any time, regardless of what the passengers are doing.
Placing the flight attendant station and galley close to the flightdeck further enhances fatigue-busting interaction.
Cockpit design features
Aircraft manufacturers themselves play the biggest part in creating an environment that battles fatigue. To start with, the flightdeck should be roomy and easy to enter and exit, since cramped quarters stimulate the release of body chemicals that only exacerbate fatigue. Yann notes that careful design can assist by creating the illusion of even more room.
To the greatest extent possible the flightdeck should be isolated from noise and vibration, since even the most comfortable headset becomes a source of irritation on very long flights. There should be good circulation to keep the air fresh without drafts and hot or cold spots.