Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-11-29
NAVIGATION FEAT
|. REQUIRED OF BYRD
Time Changes Swiftly and
Compass Varies Suddenly
on Polar Flight.
BY RUSSELL OWEN.

! BY Radio to The Star and New York Times.
LITTLE AMERICA, Antarctica, No
vember 10.-Navigating an airplane in
: the polar regions is a difficult task
because of the speed of the plane,
the swift changes in local time, the
rapid changes in compass variations
and the problem of obtaining the DRIFT
over q surface on which there are no
| landmarks and elevations are unknown.
1t Is hard enough to navigate from
one landmarked point to another
| where compass variations are known,
and infinitely more hard to navigate
| from a known point to an unknown
or imaginary unmarked point and back
again.
The flight from Little America to
the South Pole means flying to point
where all meridians Of time and lines
| of compass variation converge, to u
| point which, when it has been reached,
! has no sign post saying: This Is the
! South Pole"
There is only a broad, fairly level
plateau, where 800 flgurative railroad
tracks Of different longitudes and times
converge and all these tracks are ill
visible.
Even If one managed to ny accurate
",
/ and necessary crossings OF Few OF
these time meridians, to the Pole, how
would one know at this imaginary
point where tracks radiate in every
direction and every direction Is north,
which one OF them to choose to retracc
the course?
Problems Worked Out by Byrd.
That, crudely and simply put is the
! problem of this polar flight, and 1t
| was to meet all those conditions that
Comdr. Byrd worked on navigational
! problems so much this Winter, even
| devising instruments to simplify his
! work. There is no time to get ratified
| on such a flight, one must think quick
| ly and accurately and retain up to
certain point q chronological record OF
what has been done.
| II the Polar Plateau were not in the
way, the flight would be simpler. 1t Is
! because of the plateau that the flight
| is SO much more complicated than the
| North Polar fight. Flying at an eleVa-
ton fixed with relation to sea level
| there is a chance to check speed and
by means of the known altitude, deter
mine the drift Of the plane, or the re-
! tardation or acceleration of the plane
speed due to the wind.
But where the altitude changes con-
! tinually and can be determined only APP
proximately, with a possibility Of inn
portant error ' e the air speed inol-
! Gator rea'''' ny not only with the
varying It. of the plane but also with
the altitude, due to the varying density
OF the air, plotting drift anywhere near
accurately is, indeed, a problem.
These two componentS, speed and al
titude, are absolutely essential to de-
! termination Of the rate Of drift.
Time changes rapidly as the Pole Is
approached, so that within 20 miles OF
the Pole there may be a change OF "a
hours in 20 minutes II one were to ny IN
a circle at q speed of 100 miles an hour.
Sun Compass and Time Element.
! The sun compass, which is one OF
Comdr. Byrds most important naviga-
Jtional instruments, depends for its &C
Hcuracy upon being set on a meridian
Of time and q deviation from that me-
| ridian necessarily affects its accuracy
Meridians of longitude may be conceived
of as meridians OF time on this night
because OF the change In the relation
ship Of the sun to the course.
Consequently, II drift is not calculated
with some degree Of accuracy and the
plane swings from the time meridian or
which the sun compass is set to another
the navigator will find himself flying on
I u
he started and one which would take
him not ~ the converging point, the
Pole. but to one side Of it.
| The reason for this Is that the sun Ii
at such an infinite distance that he
/ would fy at an angle to the sun along
a line on the esrth's surface rather
than on another meridian which would
inevitably carry him to the Pole. the
compass being set for the meridian or
| w q
two importa It and easily distorted COM
ponentS Of navigation linked together
drift and the direction of night as in
dicated by the sun compass.
Sextant in Figuring Position.
On the flight observations are being
taken with the SeXatnt, which will give
longitudinal lines of position, cutting
the course at various angles. A posi-
ton line is arrived at by calculation
and Is line which, for ordinary pur-
poses, may be thought of as a line
across the course at a right angle to Z
line from the sun.
If the distance between these points
Of intersection with the course check;
with the dead reckoning, the navigator
may be fairly certain that he is on hi,
course. But II the dead reckoning fall:
short OF such point of intersection II
will indicate that the plane Is on the
side of the line Of night where the DO.
Sition line forms an acute angle, and Il
dead reckoning shows a greater dis.
lance it will indicate that the plane !.
on the other side of the course.
The navigator then halves the dis.
lance between the plotted course anS
the indicated p, Sition Of the plane anC
changes his course to bring him bacI
to the halfway point. Such change:
are not to be variable and in q Ions
flight tend to correct themselves anI
also give check upon the sun com.
pass.
Variation Of Time and Compass.
Another problem on this flight is
necessary change of direction at tn,
mountains in order to get through them
This necessitates cutting across meridi
ans or lines of time, which complicate
navigation tremendously. How much 1
affects the result may be indicated b.
the speed with which time and othe
factors change.
For instance, In so miles of fiyinl
along the eighty-sixth degree of latitude
either east or west, at right angles Il
line Of longitude on which the fiigh
had been made up to that point, tim
: changes so minutes, the compass Varia
: ton changes 20 degrees and the direc
S ton of the South Pole changes Is de
5 grees.
: These are approximate figures an,
t the changes depend also to q large ex
tent upon wind conditions with thei
? resulting calculations.
Checking Proximity TO the Pole.
> If all these conditions of polar navi
5 cation are met successfully and the Pol
? is reached, another problem arises i'm
: mediately, two problems, in fact--hoN
to make sure Of coming within a rea
sonable distance of the Pole and how t
&C. home.
1t must be remembered that to deter
mine the position of the earth's Poles