Evening star., 1928-12-23
ALT|METER AIDS
PLANE LANDINGS
instrument Designed to Make
Flying Safer Is Perfected
by Young Physicist.
BY the Associated Press.

By the Associated Press.
An instrument to take much of the
guesswork out of landing an airplane
has now been perfected.
It is the Gum altimeter, that meas
ures instantly and accurately true altl-
tude up to 100 feet, and does 1t regard
less of weather conditions or the speed
at which a plane may be rising or de-
scending. The inventor, DR.. Ross Gum
a young physicist, has been at work on
the device tor four years.
The altimeter tells the pilot when he is
within 100 feet of the ground by means
of dial which indicates every foot OF
descent below this level. The instrument
becomes more sensitive the closer it ap-
proaches earth. SO that below Is feet,
where a mistake in judging height is
likely to smash plane landing at SpeedS
of 40 miles an hour or more, it is pos
sible to read the altitude to within few
inches.
Radio Principle Is Employed.
The invisible measuring rod which
this altimeter uses is the earth'S electrl-
cal capacity" Those who tune radios
are familiar with capacity" effects.
whereby occasional squeals are heard,
the tone of which varies with the posi-
blOn Oh IklS Up6LdbOI 11oAAA NhASAA
brought near the radio set.
In DR.. Gums instrument the flying
airplane is the hand" and the earth IS
the radio set, but instead of squeal
Gunn gets the altitude. Actually two
hands" are used in the ship. the plane
itself being one and the other wire or
plate mounted on the under side. The
closer the ship comes to the ground the
greater the capacity between these two
hands" It remains only to indicate
this change of capacity on an altimeter
of some sort which can be calibrated
in feet.
The problem has been made extraor-
dinarily difficult by the fact that the
changes at higher altitude are extreme
" small compared to inherent capaci-
ties on the plane. 1t is just like put
ting a 150-pound man on the scales and
trying to weigh accurately a penny
handed him by noting the increase in
his weight.
The change is SO infnitesimal as COM
pared to the high capacity of the hook
up itself that for years the solution
has generally been regarded as impos-
sible. The entire apparatus in its pres
ent state weighs but IL pounds,
Tested by Army and Navy.
Both the Army and the Navy have
purchased one or more Gum altineters
and their flyers have thoroughly tested
them.
DR.. Gum was the first to demonstrate
the feasibility of such device when he
personally conducted series of flight
tests on his invention at McCook Field
In July, 1925.
He is 81 years old, and lived in Ober-
lin, Ohio, where as boy he was one OF
the States pioneer amateur radio oper-
ators. He was graduated from the Uni
verSity of Michigan as an electrical en-
gineer and served there as an instruc-
tor Later he was radio research en-
gineel for the United States Army Air
Service at McCook Field. In 1928 he
went to Yale, where he received the de-
gree of doctor of philosophy and was
placed in charge of the high frequency
laboratory and graduate courses in radio.
The development of the altimeter was
undertaken at Yale and occupied large
" his spare time for four years. DR..
Gum is now assistant superintendent
of the heat, light and aircraft division
of the Naval Research Laboratory.