That original gyro compass, though bulky, slow to assume
Transcript of That original gyro compass, though bulky, slow to assume
I
MAGINE a world without a compass, a wold of uncertain
poles, depending entirely on the sun and the stars for
guidance in commerce or even in the everyday of human
relations. Imagine such a world, and you are thinking of
things as they were centuries before the birth of Christ ― by
any standards a world of primitive living, of laborious travel
with limitations which for generations now have been
nonexistent.
Vastly helping to bridge the gap between those tightly
circumscribed Old World centuries and the sprawling
civilization of today was the compass ― the common little
magnetized pole-seeking needle which has meant as much to
mankind as any other invention ever created.
The arrow that quivered, settled in man's early compasses,
was pointing to more than just the direction of north or
south.
It was pointing the way to progress and expansion and
men followed, until today an ocean is spanned, a continent is
crossed in a matter of hours, when weeks and months were
consumed before. The mosaic of progress would doubtless
have been there, but its framework might never have taken
the shape of things today had it not been for that little
swinging arrow.
Utilization of the compass in the past quarter century in
aerial navigation has contributed heavily to its earlier value
as exemplified in terrestrial navigation. Today, when men
and machines are locked in combat in uncharted skies, its
value finds an added, accentuated meaning. Warfare itself,
whether in the air or on the ground, is fundamentally a thing
of direction and of maps, which are based upon the north-
pointing compass needle.
This has always probably been true, for it was in
connection with warfare that the compass first made the pages
of history. Records show that the earliest mention of such a
device was in a battle communique issued in the sixty-fourth
year of the reign of a Chinese emperor named Ho-Ang-Ti,
about 2634 BCE.
When Ho-Ang-Ti found his troops frustrated in an attack on
Tchi-Yeou in the plains of Tchou-Lou by what may have been
the earliest smoke screen, he had built a tchi-nan, or compass
chariot, consisting of a figure on a magnetized base mounted
on a cart. Natural magnetic forces caused the hand of the
figure to point south. Having thus oriented himself, Ho-Ang-
Ti presumably went on to triumph. From primitive beginnings
of this sort, the compass changed little through the years until
American ingenuity created the first basically new device of
this kind for general use. The gyro compass, based on the
gyroscope invented by the French physicist, Foucault, was
developed in the middle of the Nineteenth Century.
That original gyro compass, though bulky, slow to assume
initial stability, did provide a meridian- seeking shipboard
compass, unaffected by rolling, turns or magnetic variations.
From it came the aircraft gyro compass, which offers stability
during rough air and turns for a brief period but which
requires initial setting from the magnetic compass and
frequent resetting in flight, especially when the going is rough
or erratic in direction.
It thus has been considered a compass aid, rather than a
primary navigation instrument.
Seven years ago necessity again proved the mother of
invention. W A Reichal, director of engineering at Eclipse-
Pioneer Division of the Bendix Aviation Corporation, started
working on a new compass.
Today that answer has materialized in the Gyro Flux Gate
Compass, a revolutionary type which enables Allied airmen to
fly straight to their target under virtually any conditions,
return just as unerringly to their bases after showering
destruction on enemy objectives.
Charles Marcus, vice president in charge of engineering,
calls the new device "as great an advance over the
conventional magnetic compass as that compass was over the
lodestone." It incorporates a new principle, for the sluggish
and frequently wavering needle is replaced by a fixed coil
system in which actuating currents combine with energy
generated by the earth's magnetic field to turn the compass
indicator.
Technically, the compass is called a remote indicating earth
inductor system, consisting of a gyro stabilized flux gate
transmitter, an amplifier, a master indicator and from one to
six Magnesyn remote indicating repeaters. It is designed
to provide an accurate indication of the magnetic
direction of an aircraft under all possible flight conditions
up to an angle of sixty-five degrees with the horizon.
The flux gate, or magnetic azimuth sensitive element
of the system (magnetic azimuth is direction with relation
to magnetic north) is fully electrical and is maintained at
the horizontal by an electrically driven horizon gyro.
Because of this arrangement, the compass system's
indications are not appreciably affected by the sudden
maneuvers in flight. A stable compass proves its worth to
airmen who dive, turn their planes at 300-400 mph.
The device will not go off its reading when the plane
dives or climbs suddenly, and as Reichel describes it,
"will not lag or overshoot during a turn and will not
oscillate or 'hunt' back and forth in rough weather."
One of the compass problems arising from use of
aircraft equipped with armament, armor plate and laden
with bombs has been solved with the remote indicating
phase of the system. The magnetic azimuth sensitive
element, or transmitter, is placed where interference will
be at a minimum ― that is, at a point remote from
current carrying conductors or causes of local magnetic
deviations such as armament, which would impair the
accuracy of the standard compass.
Through this arrangement, the indications of the
transmitter in its out-of-the-way place are registered on
the master indicator. Further, other indicators are linked
to the compass through the Magnesyn system, which makes
possible remote readings of measurements received from a
master source. Pilot, co-pilot navigator and bombardier have
their own dials, and compass readings are transmitted to
them or to as many as six different points about the aircraft.
In the ordinary compass, deflection must be considered,
and for this purpose a correction card is used. The pilot,
navigator have to refer to this card, correct the deviation. In
combat mistakes are inevitable. In the gyro flux gate system
provision has been made for compensating the compass,
with the result that fully corrected readings are immediately
available, and the possibility of human error in moments of
stress is eliminated.
This compensating mechanism takes care of both
variation, which is the work of natural forces, varying in
different parts of the world, and deviation, which is caused
by local magnetic influences like the armament mentioned
previously.
Variation correction is applied by rotating a knurled knob
on the face of the indicator. This knob offsets the dial either
East or West until the desired variation is indicated on the
lower part of the dial.
Compensation for deviation is applied by adjustment of
screws arranged around the periphery of the dial, which
control the contour of a cam plate. As all compensation
takes place at the main indicator, there is a mechanism for
duplicating the corrections at the other dials in the aircraft.
Position of the master indicator pointer is relayed to the
repeater indicators by a transmitting Magnesyn unit. This
unit is connected through a gear train to the main indicator
mechanism. When the automatic correction takes place on
the master dial, immediate transmission is recorded on the
repeater indicator indicators. To see uncorrected reading,
there is a cut-out at the top of the main dial which records
original indication.
Those seven years of research in the Bendix division's
laboratories have filled the need for fast, undisturbed and
accurate azimuth indication in flight, and through the
repeater arrangement has placed this information at the
fingertips of all key men in the aerial fighting team.
The Gyro Flux Gate Compass is now in production at the
Philadelphia Division of the Bendix Aviation, reputedly the
world's, largest aircraft instrument plant. This plant's
September production of scientific instruments which turn
the blazing guns of victory on the Axis, hit the staggering
total of 175,000 units ― enough to equip more than 100,000
planes with twenty-one instruments each in a year's time.
In order for the instrument to function perfectly, each one
of the 120 parts involved must be matched precisely. Even a
pin-point of perspiration would ruin the amazing accuracy
of the compass. All assembly on the gyro flux gate is done
in air conditioned, dust-free rooms. Once assembled, sealed
under exacting conditions, the compass can operate in any
climate, at any altitude.
One major problem was developing new test equipment
capable of measuring the accuracy, stability of the compass.
Test equipment had to represent flying speeds of 300-400
mph, extreme temperatures, and violent movement.
More aircraft instruments are shipped from this one plant
in six hours than were produced by the entire aviation
industry in one month before 1940, and it will ship more
instruments this year than were turned out in the world in all
the years before 1940.
That the flux. gate compass is, at this moment,
contributing to the rising crescendo of the all-out United
Nations effort to crush our enemies is indicated in the fact
that one or more of them have fallen into Axis hands ―
hence the revelation of its existence.
But possession of such a sample of American progress
will give the big and little Hitlers small comfort. Engineers
agree that there is no possibility that the enemy can catch up
with us, because it will be impossible for him to duplicate
the performance of this compass, much less put it into
volume production during the war.
This article was originally published in the March, 1944,
issue of Air News magazine, vol 6, no 2, pp 39-41.
The original printing was on 9½ by 12¾ paper. The pages
have been reduced here to print on letter-size paper.
Photos credited to Bendix.