The following article, written by a pilot, describes the surprising
physics of the turn of a flying aircraft. Strongly-held beliefs
that humans bring to flight sometimes appear to contradict the
physics, but as William Langewiesche explains, we ignore it at our peril.
The text of the article is mirrored from
http://www.theatlantic.com/unbound/langew/turn.htm.
It first appeared in December 1993 issue of The Atlantic monthly.
The Turn
By William Langewiesche
At the very heart of winged flight lies the
banked turn, a procedure that by now seems
so routine and familiar that airline
passengers appreciate neither its elegance
and mystery nor its dangerously delusive
character. The author, a pilot, takes us up
into the subject
People who distrust the sensations of flight,
who balk when an airplane banks and turns, are
on to something big. I was reminded of this
recently while riding in the back of a United
Boeing 737 that was departing from San
Francisco. Directly over the Golden Gate we
rolled suddenly into a steep turn, dropping the
left wing so far below the horizon that it
appeared to pivot around the bridge's nearest
tower. For a moment we exceeded the airline
maximum of a thirty-degree bank, which is
aerodynamically unimportant but is imposed for
passengers' peace of mind. Sightseeing seemed
more important now. Our pilots may have
thought we would enjoy a dramatic view of the
famous bridge and the city beyond. But as the
airplane turned, startled passengers looked
away from the windows. A collective gasp
rippled through the cabin.
The reaction did not surprise me: as an
instructor of beginning pilots, I've heard gasps
and worse from my students. Pilots are merely
trained passengers. They have to be told not to
flinch, whimper, or make audible appeals to the
Savior. They have to be encouraged to ride the
airplane willingly, as they would a horse, to
think as it thinks. And they have to be persuaded
of the strange logic of the turn. At its core lies
the relationship between banking, and the
resulting flight path, and the fact, difficult at
first to accept, that neither can be felt.
Most people -- certainly the ones who were
sitting next to me over San Francisco -- would
insist that they can indeed feel the bank. We
have all had the experience while reading or
dozing on an airliner of feeling a lurch and
looking up to see, as expected, that the airplane
is tilted. The lurch comes when the airplane
dips or raises a wing, starting into a turn or
starting out of one. Sometimes we can even give
a direction to the bank. But if we then close our
eyes, we have no way of telling that we are
sitting at an angle. I know from experience how
difficult it is to convince people of this. When
the bank is visible -- for instance, on a clear
day -- the tilted horizon looks so unusual that
the view overpowers other perceptions. But
during flight on black nights, or in clouds, the
bank is imperceptible, and passengers are
heedless. They may feel the odd lurch, but they
have no way of guessing the airplane's degree
of bank. The inner ear, and with it the sense of
balance, is neutralized by the motion of flight.
The airplane could be momentarily upside
down and passengers would not know.
Of course, none of this matters unless you are
the pilot. But historically pilots have made the
same mistakes as passengers. Having been
given the airplane, they had to learn to use it.
Generations were required. Eventually they
admitted that instinct was unreliable in clouds,
and that they needed special instruments to tell
them what was happening to the plane. Without
the instruments they went into mysterious banks
and dived out of control. Thus was born the
most basic distinction in flying, between
conditions in which the turn is visible and
conditions in which it must be measured. The
ability to fly through weather and in darkness is
more important than speed in the conquest of
distance. The mastery of the turn is the story of
how aviation became practical as a means of
transportation. It is the story of how the world
became small.
Some definitions are in order. The bank is a
condition of tilted wings, and the turn is the
change in direction that results. The connection
between the two is inexorable: the airplane
must bank to turn, and when it is banked, it must
turn. The reason is simple. In flight with level
wings the lifting force of the wings is directed
straight up, and the airplane does not turn; in a
bank the lifting force is tilted to the side, and the
airplane therefore must move to that side. It
cannot slide sideways through the air, because
it has a vertical fin on the tail, which forces the
turn by keeping the tail in line behind the nose.
The result is an elegantly curved flight path,
created as the airplane lifts itself through the
changes in direction.
The turn, however, comes at a price. As the
bank steepens, the airplane has greater difficulty
holding its altitude. Flown at bank angles
approaching ninety degrees -- in which the
wings point straight up and down -- a normal
airplane cannot keep from descending. In such
"knife-edge" flight the force that once lifted the
wings in a direction perpendicular to the earth's
surface is now directed parallel to it, and
gravity pulls the airplane down. However, if the
pilot controls the airplane carefully and allows
it to keep turning, it will happily roll past the
vertical, onto its back, and finally right side up
again. During such a maneuver San Francisco
Bay would momentarily appear above you, and
the Golden Gate Bridge would seem to hang
from the water. This is fine if you are prepared
for it. Full rolls are the purest expression of
flight. They are normally flown only in fighters
and other acrobatic airplanes, but if you ignore
convention, you can fly them in any airplane,
including a Boeing 737.
None of this would have comforted the man
sitting next to me during that steep turn over the
Golden Gate. He was large, sharp-eyed, and
alert. When the wing dropped, he said, "Hey!"
and grabbed the armrests. Now he rode "above"
me in the bank, leaning into the aisle as if he
feared toppling into my lap. He need not have
worried. If he had dropped his pen, it would
have fallen not "down" in the conventional
sense -- toward me and the earth -- but rather
toward the tilted carpet at his feet. If he had
dangled the pen from a string, it would have
hung at a ninety-degree angle with respect to the
tilted floor.
A dangled pen is a primitive inclinometer, like
a plumb bob or the heel indicator on a sailboat.
On land or at sea it will hang toward the center
of the planet. But in flight it will hang toward
the floor, no matter how steeply the airplane is
banked. A carpenter's level would be equally
fooled. This peculiar phenomenon is a
manifestation of the turn's inherent balance. The
earth's gravity acts on an airplane, and of course
on objects in an airplane, but so do the forces of
inertia, the desire of any mass to keep doing
what it has been doing. The neatness of this
Newtonian package is beautiful to behold. Bob
Hoover, a stunt pilot, mounted a video camera
in his cockpit, set an empty glass on the
instrument panel, and poured himself a soft
drink while flying full rolls. Our United pilots
seemed inclined to fly the same way. If they had
done so, as we passed inverted above the
Golden Gate Bridge and saw it hanging from the
water, my sharp-eyed neighbor could have
watched his pen dangling toward the sky.
During the roll the flight attendants could have
walked upside down. And some passengers, too
busy to look outside, wouldn't even have
noticed.
The human body is another inclinometer.
Undisturbed by the view, it sits quietly,
dangling toward the tilted floor, churning out
memos for the home office. The man next to me
was not about to fall into my lap. He could have
relaxed, lowered the tray in front of him, and
called for a coffee. Unlike a table on a sailboat,
an airplane tray requires no gimbals. Flight
attendants do not develop sea legs. They brew
coffee on a fixed counter, deliver it without
worrying about the bank angle, and fill cups to
their brims. Full cups make people behave
during turns: if they try to hold them level with
the earth, the coffee pours out and scalds their
thighs. If this is hard to believe, imagine the
alternative -- an airplane in which "down" was
always toward the ground. Bedlam would break
loose in the cabin during turns.
As long as its wings are level, an airplane is
well mannered and slow to anger. If you pull its
nose up and then release the controls, it puts its
nose back down; if you push it down, it answers
by rearing up. Like horseback riding, flying
consists mostly of leaving the beast alone. The
problem is that this particular beast does not
stay on the trail unguided, and once it strays, it
develops a strong impulse to self-destruct.
Unguided, any airplane will eventually begin to
bank. That by itself would be fine if you didn't
mind the resulting turn. But as the bank tilts the
lift force of the wings, reducing their vertical
effectiveness, it erodes the equilibrium that
previously countered the pull of the earth. The
airplane responds to the loss by lowering its
nose and accelerating. Sitting in the cockpit
with folded arms and watching it proceed is
like letting a temperamental horse gallop down
a steepening slope: it requires steady nerves
and a morbid curiosity. In flight the slope
steepens because the acceleration tightens the
airplane's turn, which increases its bank angle,
which causes further acceleration. Sooner or
later a sort of aerodynamic lock-in occurs. The
airplane banks to vertical or beyond, and points
its nose straight down.
That's the spiral dive. In its most lethal forms it
is called the graveyard spiral. The airplane
flies in ever-steeper circles and either
disintegrates from excessive speed or hits the
ground in a screaming descent. Most flights
would suffer this end if the pilot (or auto pilot)
did not intervene. In good weather the
intervention is easy. When you see that the
airplane has banked, you unbank it. During turns
you hold the controls more firmly, and keep the
nose from dropping.
The increased loading caused by inertia during
a well flown turn is felt within the cabin as a
peculiar heaviness. Pilots measure it in "Gs," as
a multiple of gravity's normal pull. An airplane
that banks to thirty degrees creates a loading of
1.15 Gs: the airplane, and everything in it,
temporarily weighs 15 percent more than
normal. Fifteen percent is hardly noticeable.
But when the bank grows only a bit steeper, to
forty-five degrees, the load increases to 1.4 Gs:
people feel pressed into their seats, and they
might notice that the wings have flexed upward.
Technically it is not important. Airplanes are
strong. Pilots shrug off two Gs, and may feel
comfortable at twice as much. But passengers
are unaccustomed to the sensation. As we
pivoted over the Golden Gate, I estimated that
my neighbor had gained about eighty pounds.
Had he dangled his pen toward the tilted floor,
it would have pulled on the string with
surprising force. This might not have reassured
him. But the extra heaviness is a measure of the
pilot's success in resisting the spiral dive. If we
had felt "normal" during the turn, it could only
have meant that the nose was dropping fast
toward the water.
No pilot would make such a mistake on a clear
day. The view from the cockpit is dominated by
the horizon, the constantly renewing division
between the sky and the earth. It forms a line
across the windshield, and makes immediate
sense of the airplane's movements. In clouds or
on black nights, when they cannot see outside,
pilots keep their wings level by watching an
artificial horizon on the instrument panel. The
artificial horizon is a gyroscopically steadied
line, which stays level with the earth's surface.
The airplane pitches and banks in relation to
this steady line, which in spatial terms never
moves. Of course, in airplane terms it does
move -- which presents a problem, because
pilots are part of the airplane: they fly it from
within, strapped to their seats. In clear skies
they would never misjudge a bank as the tilting
of the earth, but with their view restricted to the
abstractions of the instrument panel they
sometimes do just that: when the airplane banks,
they perceive the motion as a movement of the
artificial horizon line across the face of the
instrument. This causes them to "fly" the wrong
thing -- the moving horizon line, rather than the
fixed symbolic airplane. For example, as
turbulence tilts the airplane to the left, the
pilots, tilting with it, notice the artificial
horizon line dropping to the right. Reacting
instinctively to the indication of motion, they
sometimes try to raise the line as if it were a
wing. The result of such a reversal in such
cases is murderous. Pilots steer to the left just
when they should steer to the right, and then in
confusion they steer harder. While cruising
calmly inside clouds, I have had student pilots
suddenly try to flip the airplane upside down.
These were perfectly rational people,
confronted by the turn.
Airplanes did not shrink the world
overnight. The Wrights flew straight and level
at Kitty Hawk in December of 1903, and
nobody paid much attention. They went home to
Dayton, rented a cow pasture, and spent the
following year stretching their flights and
learning to turn. The first detailed account of
their flights appeared in Gleanings in Bee
Culture, a journal for beekeepers published in
nearby Medina. The editor, A. I. Root, traveled
to the pasture and on September 20, 1904, saw
Wilbur fly the first full circle. Bees, of course,
are the great specialists in full-circle flying;
they spend their days on round-trip missions,
and construct whole worlds out of their ability
to turn. I do not know if Root was influenced by
these thoughts, but he understood the
significance of the Wrights' achievement. The
U.S. Army was slower to catch on. Five years
later, after much persuading by the Wrights, it
reluctantly took delivery of its first airplane. In
1909 horses still seemed more glorious.
The war in Europe changed that. Unsullied by
the carnage in the trenches, pilots chased across
the sky, turning hard on each other's tails. The
war taught them to fly with confidence, and
encouraged the myth of instinct. Those who
survived made the dangerous discovery that
they could feel at home in the sky. They learned
to accept the strangeness of a steep bank -- the G
load and the tilted horizon -- and the magic of a
full roll. Nonetheless, they still believed in
instinctive balance: when they ducked through
small clouds and emerged with their wings
slightly tilted, they did not appreciate the
significance of this small clue -- did not suspect
the importance of the unfelt bank. Although
scientific thinkers on both sides of the Atlantic
had, by the end of the war, come to understand
the intricacies of the banked turn, pilots,
trapped by vanity, paid little heed. And because
pilots at the time rarely flew in bad weather or
on black nights, they did not expose themselves
to the conditions that would have fostered
deeper insight.
At the end of the war regular airmail service
started in Europe and the United States. It made
airplanes useful to the public for the first time,
gave birth to the airlines, and placed pressure
on the pilots to operate on schedules. They
followed rivers and railroads in open-cockpit
biplanes, flying under the weather, sometimes at
extremely low altitude, dodging steeples and oil
derricks. Many pilots were killed.
In December of 1925 a young Army pilot named
Carl Crane got caught in the clouds at 8,000 feet
directly over Detroit while trying to fly a
congressman's son to Washington, D.C., in a
biplane. Crane later became a famous master of
the turn. Recalling this particular flight, he said,
"In a short time I was losing altitude,
completely out of control. I could not fly the
airplane at all -- it had gotten into a spiral dive.
Halfway down I looked around at my boy in the
back, and he was enjoying the flight no end. He
was shaking his hands and grinning, and I was
slowly dying because I knew we were going to
crash."
The boy in the rear cockpit was just unaware.
Crane had an altimeter and an airspeed
indicator. He thought he was dying "slowly"
only because of the way experience is
compressed when an airplane goes wild.
People's minds can work extraordinarily fast.
Pilots tend to think not about God or their lives
but about solutions. Crane searched his training
and remembered only vague admonitions to stay
out of bad weather. Of course, he was in it now,
and couldn't see a thing. He knew he was
turning but could make no sense of the compass.
It is a notorious problem: because the earth's
magnetic field does not lie parallel to the
globe's surface but dips down toward the
magnetic poles, the compass responds to banks
by spinning erratically, jamming, and sometimes
showing turns in reverse. Crane did not know
which wing was down, let alone by how much.
If he tried to level the wings, he was just as
likely to roll upside down as right side up. If he
tried to raise the nose, the effect would be
exactly the opposite: the turn would quicken,
steepening the descent. For a pilot these are the
central issues of the spiral dive. Crane
understood none of it at the time, but he sensed
that his situation was hopeless.
In modern times air-traffic control recorded the
radio transmissions of an unskilled pilot who,
with his family on board, tried to descend
through overcast. After he lost control, he began
to sob into the microphone, begging the radar
controllers to tell him which side was up. But
radar shows air traffic as wingless blips on a
map, and is incapable of distinguishing banks.
Controllers are in the business of keeping
airplanes from colliding. Pilots are in the
business of flight control. This one had
instruments on board by which he could have
kept his wings level, but in the milkiness of the
clouds he became confused. The controllers
listened helplessly to his panic and, in the
background, to the screams of his children. The
transmissions ended when the airplane broke
apart.
Crane's biplane was stronger. "Finally it got
down to under a thousand feet, and I said, 'Well,
here we go. I'm going to look at my boy once
more.' And as I turned around to look at him, a
sign went by my wing. It said 'Statler Hotel.' I
had just missed the top of the Statler Hotel. In
all the mist and rain, I could see the buildings
and the streets. I flew down the street and got
over the Detroit River, and flew about ten feet
high all the way to Toledo, shaking all the
way."
Shocked by the way intuition had abandoned
him, Crane began to ask questions. For years he
got no intelligent answers. Veterans of the
military and the airmail service still insisted
they could fly "by the seat of the pants," and
they thought less of those who could not. Their
self-deception now seems all the more profound
because the solution to the problem of flying in
clouds and darkness -- a gyroscope adapted to
flying -- was already widely available.
The gyroscope is a spinning wheel, like a
child's top, mounted in gimbals that allow it
freedom of movement. It has two important
traits: left alone, it maintains a fixed orientation
in space (in relation to the stars); and when
tilted, it reacts in an odd but predictable way.
Elmer Sperry, the great American inventor,
started playing with these traits in the early
1900s. As a curiosity, he designed a
gyrostabilized "trained wheelbarrow," and he
tried, without success, to interest a circus in it.
Undiscouraged, Sperry turned to the U.S. Navy
instead, and interested it in gyro-compasses and
ship stabilizers. Competitors in Europe
developed similar devices, and during the
buildup to war interested their countries'
navies, too.
Airplanes were an intriguing sideline. Sperry
built a gyroscopic auto pilot in 1910, not to
enable blind flight but to stabilize the otherwise
unruly early flying machines. In 1915 he began
to ponder instrumentation, and with prescient
insight into the problems of flight was able after
three years to produce the first gyroscopic turn
indicator, an instrument still in use today. Its
face consisted of a vertical pointer, which
indicated turns to the left or right. (Necessarily,
it also included a ball like the one in a
carpenter's level, an inclinometer that showed
not bank but "skid" or "slip" -- conditions of
imbalance.) Sperry called the instrument a
"crutch for the compass." In his patent
application he described it as an instrument that
would allow pilots to fly indefinitely through
clouds, implying that without it they could not.
One of the earliest cloud flights with a turn
indicator was made by William Ocker, an Army
pilot, in 1918. Though he, too, spiraled out of
overcast, he concluded correctly that his
mistake had been to favor sensation over the
instrument's indications. During the 1920s a few
Post Office pilots began to fly by instruments.
When Charles Lindbergh crossed the Atlantic,
in 1927, a turn indicator kept him from spiraling
into the sea when he met fog. Two years later
Jimmy Doolittle made a "blind" landing, after
flying a complete circuit around an airport in a
special biplane modified with a domed cockpit
from which he could not see outside. The
landing itself was a technical dead end. Once
Doolittle was over the field, he reduced the
power and waited until the biplane plunked into
the grass -- a technique that would not be
practical for the airlines. More significant were
the special devices that made the precisely
flown circuit possible. The airplane was
equipped with navigational radios, an airspeed
indicator, an improved altimeter, a turn
indicator, and two new gyroscopic instruments
from Elmer Sperry -- a gyroscopic compass and
an artificial horizon. This combination was so
effective that it still forms the core of instrument
panels today. Doolittle compared the artificial
horizon to cutting a porthole through the fog to
look at the real horizon. Devising technology
was the easy part. The more stubborn problem
of belief remained. As late as 1930 one of the
airlines wrote to Sperry complaining about a
mysterious problem: the instruments worked
fine in clear air, but as soon as they were taken
into clouds, they began to indicate turns.
Still worried about his near collision with the
Statler Hotel, Carl Crane read with fascination
the descriptions of Doolittle's flight. He was
now, in 1929, an Army instructor at a training
base in Texas. Though his superior officers
disapproved of instrument flying, Crane was
convinced of the need for gyroscopes. He
finally got permission to cover over a cockpit
and turn one of the biplanes into an instrument
trainer. While he was at work on this, William
Ocker wandered into the hangar. Ocker didn't
look like much of a pilot, with his bifocals and
his mournful, puritan face, but he had a
powerful mind and the restless soul of a
missionary. The truth about instrument flying
had come to him in 1926, during a routine
medical examination in San Francisco. To
demonstrate that the senses could be fooled, a
doctor had asked Ocker to close his eyes while
being spun in a chair. Ocker felt the chair begin
to turn, and guessed the direction correctly --
but when the chair slowed, he felt it had
stopped, and when the chair stopped, he felt it
was now turning in the opposite direction. For
the doctor, it was a trick on the inner ear, an
amusing exercise in vertigo. For Ocker, it was a
stunning revelation: the sense of accelerating
into a turn is the same as that of decelerating
from the opposite turn. The chair induced the
same false sensations that led pilots to mistrust
their turn indicators. Even those who accepted
their inability to feel the bank were losing
control. Ocker now knew why. He had found
here in the spinning chair the proof that instinct
is worse than useless in the clouds.
Ocker became so obsessed with the spinning
chair that he was hospitalized twice for sanity
tests and later banished by the Army to Texas.
His preaching had become tiresome.
Nonetheless, he had discovered the most
disturbing limitation of human flight -- the
feelings that cause people to sway dizzily from
wings-level flight into spiral dives. Having
gyroscopes is not enough. Pilots must learn to
believe them, even though their bodies may
have invented phantom turns. And fiction can be
compelling. I have seen students break into a
sweat in the effort not to submit.
Ocker and Crane began a systematic exploration
of flying inside clouds. In 1932 they published
Blind Flight in Theory and Practice, the first
clear analysis of instrument flying. The book
had an enormous influence. The authors tried to
lay to rest the old faith in flying by instinct.
They described the physics of the turn and the
confusion experienced by the inner ear, but their
most dramatic argument grew out of an
experiment with pigeons. From everything
pilots had learned, it seemed evident that birds,
too, must be unable to fly without a visible
horizon. Ocker and Crane blind folded pigeons,
took them up in biplanes, and threw them out.
Sure enough, the birds dropped into fluttering
emergency descents -- they panicked and went
down like feathered parachutes. It is possible,
of course, that they did not like the blindfolds,
which were made of Bull Durham tobacco
pouches. But anyway, the experiment was the
kind pilots understood. If God had meant birds
to fly in the clouds, He would have given them
gyroscopes.
Birds are not the perfect flyers that you might
expect. They cannot fly through heavy rain.
They get sucked up by thunderstorms, frozen by
altitude, and burned by lightning. They crash
into obstacles, wander offshore, run out of fuel,
and die by the millions. They would rather not
migrate in bad weather, and usually don't.
Nonetheless, it now appears that Ocker and
Crane may have been wrong: there is evidence
that some birds do occasionally fly inside
clouds. This is big news. Word of it appeared
in 1972, in the proceedings of a NASA
symposium on animal navigation. Hidden
among reports like "When the Beachhopper
Looks at the Moon" and "Anemomenotactic
Orientation in Beetles and Scorpions" (that is,
"When a Bug Feels the Wind") was a paper
titled "Nocturnal Bird Migration in Opaque
Clouds." It was written by Donald Griffin, the
Harvard zoologist who discovered the use of
sonar by bats. Griffin reported that he had
bought a military surplus radar and on overcast
nights in New York had tracked birds that
seemed to be flying inside clouds. There were
only a few, and Griffin was able to track them
only for a couple of miles, but they appeared to
be flying straight. Griffin's biggest problem was
uncertainty over the flight conditions at the
birds' altitude. Were the clouds really as thick
as they looked from below? Were the birds
really flying blind? Griffin had good reason to
believe so, but as a scientist he had to be
cautious. His final report, in 1973, reinforced
the earlier findings but was more cautiously
titled "Oriented Bird Migration in or Between
Opaque Cloud Layers." Ornithologists still cite
it from memory. To those interested in bird
navigation, the difference between "in" and
"between" is just a detail; the point is, the birds
seemed to know their way without reference to
the stars or to the ground. But to birds, whose
first job is keeping their wings level and
controlling their turns, the distinction might be
crucial. Griffin, a former pilot, understands its
importance. I recently mentioned to him my
impression that some ornithologists seem stuck
on the ground, and he laughed. "I keep telling
them, 'Gee, birds fly!'"
Assuming they fly in the clouds, the question is
how? Ornithologists have no answer, and they
shy away from speculation. It is known that
birds navigate by watching the ground and the
positions of the sun, the moon, and the stars --
none of which would help them in clouds. But
they may also use a host of nonvisual clues, and
may use mental "maps" based on sound, smell,
air currents, variations in gravitational pull, and
other factors. Experiments have shown that
some species are extremely sensitive to
magnetic forces. In their heads they have
magnetite crystals surrounded by nerves, which
may give them intuitive knowledge of their
direction (and location) in the earth's magnetic
field.
Another possibility is that birds have internal
gyroscopes of a primitive sort. This is less
farfetched than it seems: the rhythmic flapping
of wings could have the effect of Foucault's
pendulum, allowing a bird to sense turns
without any external cue. A pendulum is more
than a hanging weight -- it is a hanging weight
that has been pushed and is swinging freely.
Swinging gives a pendulum its special ability to
maintain spatial orientation. Leon Foucault was
the French physicist who first used one, in
1851, to demonstrate the rotation of the earth:
though the pendulum appeared to change
direction as it swung, in fact the plane of its
swing remained constant, and the apparent
change was caused by the turning of the earth
underneath it. If birds rely on the pendulum
effect, they are not alone. Flies and mosquitoes
(along with more than 85,000 other species of
Diptera) use specially adapted vibrating rods to
maintain spatial orientation in flight. Not only
can they turn sharply, roll upside down, and
land on the underside of leaves, but they can do
it in fog.
Pilots, too, have relied on pendulums. It is said
that an airliner inbound to New York in the
1950s lost all its gyroscopes in heavy weather
over Block Island. The captain was a wise old
man who had risen with the airlines from the
earliest airmail days and was approaching
retirement. A lesser pilot might have fallen for
the trap of intuition. But the captain simply took
out his pocket watch, dangled it from its chain,
and began to swing it toward the instrument
panel. Flying by the pendulum and the compass,
he proceeded the length of Long Island in the
clouds. After breaking into the clear near the
airport, he landed and wished his passengers a
good day.
The story is not impossible. I had it in mind one
night when I flew out over the Pacific Ocean in
a small airplane. High clouds darkened the sky.
The light of a fishing boat drifted close by the
coast. Flying a mile above the water, I headed
beyond it, into complete blackness.
Nowhere can a person find greater solitude than
alone in flight. At night in clouds and over
water, the cockpit becomes a world of its own,
and the instrument panel another world within
it. The instruments glow in a warm light, telling
the strange story of the airplane's motion.
Enjoying this isolation, I flew on until, behind
me, the fishing boat was a distant glimmer. The
gyroscopes functioned perfectly. The radios
were blissfully silent. I hooked a metal pen to a
fishing line and dangled it from a knob on the
ceiling. Flying by the artificial horizon, I made
a steep turn and watched the pen dangle toward
the tilted floor. Then I straightened out, pushed
the pen toward the instrument panel, and
released it. It swung for almost a minute before
requiring another push. Each renewal would, of
course, erase the pendulum's spatial memory.
Nonetheless, I thought the device might work.
After turning parallel to the coast, I covered the
gyroscopes with slips of paper.
The night air was smooth. The pen swung
rhythmically toward the panel and back. When
eventually the airplane banked and therefore
turned, the swinging pen, though it continued to
swing through a point perpendicular to the
floor, maintained a memory of the airplane's
original heading, and seemed to have redirected
itself to the left. This could only mean that the
airplane had banked to the right. I steered left
gingerly, hoping to raise the right wing just
enough to return to straight flight. The pen
seemed to stabilize in its new direction. I
renewed the swing, shoving the pen again
directly toward the panel. It soon confirmed that
the airplane had indeed leveled its wings. After
the compass settled, it showed that I had turned
twenty degrees to the right. Lowering the left
wing cautiously, watching the pen swing to the
right, I crept back to my original heading. Later,
when I tried to make a large turn, I spiraled and
had to peek at the gyroscopes. But with the
wings level again I flew on for miles, learning
to work with the swinging pen. Trust comes
slowly in the indication of turns. It is a peculiar
faith that makes the world so small.
Copyright © 1993 by William Langewiesche. All rights reserved.
The Atlantic Monthly; December 1993; The Turn; Volume 272, No. 6;
pages 115-122.
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