Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-09-07

$ TeUOEUEng around central point.
TN spite Of the fact that large rotating wings
seem awkward and clumsy, they have been
found the only solution to the problem of how
to rise vertically, DR.. Dryden explains The
first machines attempted were built years ago
and used one or more small propelers which
turned as fast as those that drive airplanes
today. These ships were entirely unsuccessful
AS propeller speed Is increased, the power re-
quired rises much faster than the force pulling
upward. Expressed by the aerodynanic law
power is proportional to the cube, of the speed.
and thrust. or upward driving force to the
square of the speed.
The rotating surfaces must be large because
they take the place of wings of the usual air.
plane. Their linear speed must compare with
airplane speed and yet is limited by the fast-in-
creasing power required
"A verticaiiy-rising machine is after all
an airplane with rotating WINGS" DR.. Dryden
sums up. I'm fact, an engineer once designed
one which consisted Of two airplaneS attached
to opposite ends of beam and facing in OPP
poSite directions. The affair was supposed to
rise by revolving about the middle of the beam.
and once in the air the two machines were 10
face in the same direction and travel like Ordi-
nary airplanes. Though never heard OF am
actual trial, this arrangement well illustrates
the principle Of vertically rising aircraft"
Some OF the first helic0pterS, whose failure
helped to flnd aerodynamic laws applying to
them, were curious craft One early machinu
represented a combination between bicycle
ana parachute, and was to be operated, by
man-pOwer. Safety in descent after the opera--
tor got tired pedaling was apparently upper
most In the mind of its inventor. =
Twenty propellerS were used to operate am
other, which was built in 1903 and 1909 by
Wilbur r. Kimball OF the Aeronautic Society Of
New York.
AS the gasoline motor was improved and
more power was concentrated into less space,
and as inventors learned that they must use q
few large slow-rotating surfaces rather than
many faSt-turning propelleFss their problem
CHANGED, or rather it was half solved. They
found that it was comparatively easy to rise
up in the air; but, once ups they could not
control their machine and bring it slowly and
safely back to earth. Many helicopterS had
tendency to soar upward swing over in O. greaG
arc and come diving back to the ground head
first.
PROBABLY the first successful vertically.
rising flying machine was the Petroczy.
KaEmau helicOpter developed In Austria during
the World War. But it could rise straigft un
and do nothing else. IT was tethered to the
ground by three cables and as long as these
cables We're kept taut it could not tip over. It
could not be controlled well enough to permit
1t to sink to earth gradually under a leSsening
OF its own power, but it had to be pulled in
by the cables. During one test it was ntted
with an electric motor and operated success
fully for few minutes on current supplied
from the ground
The French have sought stability in the
Oehmichen heiicopter by swinging the whole
craft beneath a small balloon. The balloon is
by no means large enough to lift the entire
weight but its buoyancy helps to keep the craft
right side up
Compressed air was tried by the Leinweber
Brothers OF Chicago as the stabilizing agent
for their machine. The craft was designed so
that the least tilt out OF balance would swing
a pendulum to set in motion a. compressed air
motor. This In turn was to open valve which
would allow air to enter the motor and right
the machine instantly.
It was humnling bird that, by its we'll
controlled flight, first directed the attention
Of the father Of the Leinweber Brothers to-
ward building helicopter. After the fathers
death, his sons continued the experimental
work. They devised new type propeller, .
motor that has immense horsepower for 1ts
weight and the system OF fitting motors 10
any angle by means OF compressed a1e.