Sleep deprivation, often trivialized or ignored by pilots, nearly brought down two of the most famous aircraft in the world: The Spirit of St. Louis (1927) and Voyager (1986). The thoroughness of the flight planning seemed almost obsessional; to reduce weight and extend range, Lindbergh trimmed the edges from his charts and one of the Voyager pilots, Jeana Yeager, clipped off her long tresses. But although these pilots previously experienced the devastating effects of sleeplessness, they put the countermeasures originally planned on the back burner, and they paid dearly for the omission.
The effects of sleep deprivation on Lindbergh and the Voyager crew were dramatic – so much so they may not seem to pertain to contemporary commercial or general aviation. Nevertheless, understanding these difficulties and the reasons they happened will help today’s pilots develop countermeasures.
New York to Paris in NYP
Try to imagine embarking on one of the most difficult flights ever attempted after not sleeping for 23 hours and then enduring another day-and-a-half of sleeplessness. It was “the most difficult and dangerous factor” of Lindbergh’s New York to Paris odyssey.
Lindbergh was no stranger to physical or psychological challenges and, as he planned the flight, he knew what he might encounter. As a mail pilot, he had often flown at night with little or no sleep during a previous day or two. But en route Paris he flew an unstable aircraft, navigated by dead reckoning, and flew some 15 hours on instruments through a well developed weather front with but needle, ball and airspeed. Then too, he contended with icing conditions in cockpit temperatures as low as - 23 degrees Fahrenheit, his six-foot, four-inch frame sandwiched into NYP’s tiny cockpit, his face barely two feet from the instrument panel that blocked his forward vision. Yet none of these or many other challenges, taken alone or together, compared with his sleeplessness, which prompted him to say: “There comes a point when the body’s demand for sleep is harder to endure than any other pain I have encountered.”
Only recently have scientists focused on the implications of sleep deprivation for contemporary civilian and military aviation, even space flight. Professor David Dinges at the University of Pennsylvania Medical Center, who runs one of only two sleep deprivation labs in the World, is a leader in the field.
As Dr. Dinges says, “I became interested in the Lindbergh experience because, for the past 20 years, my laboratory has done research for various federal agencies: NIH, NASA and DOD, as well as the Naval Research Labs, and the Air Force Office for Scientific Research. We have a long-standing interest in sustained operations and, in particular, how people stay awake and alert in airplanes over a long period of time.
One of Professor Dinges’ graduate students counted the number of words in The Spirit of St. Louis that deal with Lindbergh’s perceived need to sleep and tallied them. A numerical scale was constructed to quantify the severity. So many words scored 4, fewer was 3, fewer still was 2 and no mention at all was 1. These were plotted across the flight, and compared with 16 test subjects who were kept awake 88 hours. The curve perfectly matches Lindbergh’s circadian profile (see fig. 1), and closely correlates with those of the test subjects.
“Lindbergh is a natural experiment,”says professor Dinges. “But my primary interest was not so much in the flight per se, but rather the detailed analysis of his sleep prior to the flight, and his behavior and performance during the flight – his own sense of what was happening to him. So the primary focus of our investigation was what did he actually do during the flight, how sleepy did he become, and how did he resist the sleepiness. For example, it’s extraordinary to me that people don’t entirely understand that one of the things he did out of desperation was to fly so low he could get ocean spray in his face through the side windows. He wouldn’t eat food for fear that it would further contribute to his falling asleep. There are segments of his log book with no entries which means he very likely was in full blown reverie – stage one reverie, which is a period right between awake and asleep.”
During the reverie, Lindbergh hallucinated. He thought he was visited by ghost-like apparitions that appeared throughout his cockpit and even gave him directions. And yet, he was nearly as alert when he landed after not sleeping 56 hours as he was at takeoff, although he almost lost it in between! As the chart illustrates, he became sleepier and sleepier until he started a new biological day!
One of the main reasons for Lindbergh’s fatigue was the “sleep debt” with which he started his flight. This is the difference between the amount of sleep a person needs and the amount he or she gets. As Dr. Melissa Mallis, Principal Investigator of the Fatigue Countermeasures Program at NASA Ames Research Center, puts it: “Sleep loss can be additive and can result in a sleep debt. A sleep debt can occur during erratic flight operations when the person's biological timing for sleep does not coincide with the actual time allowed for sleep.”
Around the World in Voyager
“Edwards tower, this is Voyager One. We’re ready to go.”
“Roger, Voyager One. You’re cleared for take off. ATC clears Voyager One from Edwards Air Force Base to Edwards Air Force Base via flight plan route. Maintain 8,000. Godspeed.”
And so, with 26,366 miles to go, Voyager began its epochal flight around the World. With pilot Dick Rutan at the controls and co-pilot Jeana Yeager reading off airspeeds, Voyager started down Edwards’ main runway – at 15,000 feet, the longest in the World. The take off roll was 14,200 feet.
To understand fatigue problems on the flight, one has to know a bit about the flight crew, the ground crew, and this most unusual, single mission aircraft. There never has been and never will be another like it.
Dick is a former Air Force navigator and fighter pilot. He volunteered for three tours in Viet Nam where he flew 325 combat missions in F-100s, the last 105 in the high-risk MISTY program. He escaped from North Viet Nam after being shot down on his last mission. After completing his Air Force career, he joined his brother Burt as the Chief Experimental Test Pilot for Rutan Aircraft Factory where he set many World speed and distance records in Vari EZ and Long EZ aircraft.
Jeana is a World class pilot with numerous World speed and distance records. Perhaps most importantly, she provided much of the motivation and leadership that kept the Voyager volunteers together during the agonizing five years from the conception of the idea to lift off. This was especially important because the entire program was conducted without government funding.
The volunteer contingent grew to 98 and included several experts at the top of their field – flight aerodynamicists, meteorologists, flight surgeons, engineers, and utility hitters without whom the program would have collapsed.
Dick’s brother, World-renowned aircraft designer Burt Rutan, was Mr. indispensable. The flight was his idea and he designed the airplane from composite material half as heavy as steel but five times as strong. It has a canard and twin booms replete with 16 fuel tanks that fed into a single main tank. The system held 7,011 pounds of fuel that powered two Continental-Teledyne engines in tandem: a 4 cylinder, air cooled, 130 H.P. 0-240 in front, and a 4 cylinder, liquid- cooled, 110 H.P. 10L-200 in the rear.
Voyager’s “cabin” and cockpit were telephone booth size – about 3 ½ by 8 feet, and the flight characteristics were, well, peculiar. The wings flapped up and down a disconcerting 30 feet, the pilots knew their plane would disintegrate if they hit even moderate turbulence, and, worst of all, above 83 knots, the flapping wings sometimes oscillated, doubling in amplitude with each cycle. Whether or not the autopilot was engaged, the extremely tricky recovery maneuver from this “pitch porpoise” had to be made within 20 seconds. Jeana never had the time to learn to recover and Dick never had the patience, or he says “the guts”to teach her.
While flying a Long EZ during a closed-circuit record distance flight between Bishop and Mojave in 1979, Dick encountered gremlins just as Lindbergh had. He had a huge sleep debt going into the flight, and was shaken by the experience. “I had no idea what was happening...little green people told me I had already died. They described what happened – you know the fiery wreck. ‘You are actually dead, so come with us. Just come with us and we’ll handle it, we know you’re tired.’ I had gone into a different realm I was not even aware of. Needing sleep so desperately and trying to go to sleep a little bit and then going fully to sleep when you can’t do anything about it.” As a result of this experience, Dick and Jeana visited scientists at the NASA Ames Research Center. They learned Dick’s hallucinogenic experiences were not patholological, but rather a predictable result of sleep deprivation, and they learned about the insidious subtleties of sleeplessness and fatigue. Most importantly, they learned about countermeasures – things pilots can do to prevent or mitigate the effects of sleeplessness.
Following the visit to NASA Ames, Dick secured another distance record flying from Anchorage to the British West Indies. The flight lasted almost 30 hours and his new insights served him well: “...I got myself set with my circadian rhythms. Most people would go out to diner and a show, but I would go to sleep at 6 o’clock so I would be fully rested and adjust my circadian rhythms so when 0300 rolled around, that had become my regular get up time. I spent 10 days up there getting on that circadian rhythm. I also exercised and ate right. And to combat sensory deprivation – to make sure I just didn’t sit there with nothing to do – I took along Saturday night radio mystery hours tapes – little melodramas like “The Shadow Knows.” So every time I wasn’t talking to Air Traffic Control or just sitting there droning away, I’d pop one of those tapes in and, before I knew it, 20 minutes had gone by.”
Dick and Jeana flew Voyager on a record breaking 4 ½ day closed circuit course to “warm up.” But, as Jeana says: “We weren’t able to adjust our circadian rhythms as we should have – there was just too much to be done.” Dick stayed in the pilot’s seat for three full days, making do with ten minute cat naps. Then, to the delight of the ground crew, he finally relinquished the pilot’s seat to Jeana and slept five hours. It was the first time he had truly slept aboard Voyager.
On the World flight, Dick once again stayed glued to the pilot’s seat for three days until the pitch-porpoise problem was behind them. He says his 10 minute naps were effective, but that “it was difficult to be drawn out of that sleep to be functional, and it would take maybe 30 or 40 seconds.”
Throughout the nine day flight, constant weather problems and emergencies meant Dick averaged but two to three hours sleep and he eventually “hit the wall” – he suddenly thought he saw the instruments bulging out at him, and it took Jeana a solid hour to quiet him down and get him to sleep. Then when weather forced them to 20,000, Jeana’s head cold, extreme fatigue and hypoxia caused her to pass out and stop breathing. As she says, “Except when I was oxygen deprived, I never did sleep solidly; I just took cat naps. Instead of 9 days, it seemed like just one long day; I didn’t really look at a clock to get the time – it was more a data point.”
The closest call of the flight was when the oil pressure dropped suddenly and air was introduced to the rear engine. There was some question as to whether Jeana had neglected to monitor the system or Dick had turned the oil replenishment crank in the wrong direction. Either way, it was undoubtedly because of the pilot’s extreme fatigue.
After 9 days, 3 minutes 44 seconds, Voyager landed at Edwards, having achieved what many agree was the last significant milestone in atmospheric flight. As Technical Director Jack Norris said: “I’ve always seen Voyager as a mini-home-grown moon program.”
Lindbergh and the Voyager crew anticipated constant, unrelenting sleeplessness and fatigue, but general aviation pilots usually don’t face such severe problems. Still, we live in a culture that attaches less and less importance to sleep because of our frenetic life styles. As Dick Rutan says, “There is a big, often fatigue-related problem among GA pilots, myself included. We often feel compelled to get where we need to go or we get a case of ‘get homeitis.’ Either of these things can result in bad decisions, especially when fatigue is in play.”
“All too often there are critical meetings to attend at our destination or back home that can lead us to press minimums when we shouldn’t – the kind of decision you are more apt to make when you’re tired. But I’ve learned. I recently had a court appearance in a distant city that could have altered my entire future. The weather at my destination was down to minimums and forecast to deteriorate further as a weather system moved in. So I left a day early, stopped 150 miles short of my destination, and drove the rest of the way in a rented car. If I hadn’t done this, I would have been out fighting the ice, trying to get into some at-minimums airport.”