Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-12-01
AVIATION
BY JOSEPH S. EDGERTON.

by these attachments with thu
fuSelage. Reduction of interference
or the cleaning up" Of airplant
design is necessary to speed anc
efficiency.
While the results of the 2O-foot
tunnel have been of the most far
reaching Importance, the commit
tee now is engaged in the con
tStruction of a tunnel nearly three
times as large, in which full-sizec
airplaneS may be mounted anc
studied.
At Langley Field the committee
also is constructing a Seaplane
testing channel, which will be tC
the Seaplane float and the flying
boat hull what the wind-tunne.
has been to the airplane. Models OF
floats and hullS may be lowed al
various speeds along the 2,50O-foci
channel, the results being record
ed with the greatest scientific
, nicely.
Wind velocities up to 800 miles
per hour, or greater than the
speed of sound, are created in a
high velocity wind-tunnel at
Langley Field. In this tunnel 1t
is possible to study the effects of
air pressure upon airplane pro-
peller tips, which travel at ire
mendouS speeds. In this tunnel it
has been learned that the entire
aspect of wind preSSureS is
changed at great velocity and that
the most efficient airplane wing
loses all its beneficial character
istics at speeds above 600 miles
per hour.
Much Work Still Remains.
Experimental work with fuel
oil engines Of the Diesel type is
being conducted at Langley Field
and there are a score of other
projects under way, each of great
Importance in its own field.
There is a great deal Of work
still to be done before even the
preSent-day airplane design is
brought to a point Of efficiency.
and there Is by no means any GER
tainty that the present airplane
type Will be the type in use with
in few years.
The placing of motors and pro-
pellerS forms one of the important
problems to be solved. Exterior
mounting of motors is aerody-
namically inefficient. A propeller
In front of fuSelage may be
blanketed by fuSelage air interfer-
ence; In front Of wing the pro-
peller interfereS with the lift Of
the wing. If puSher propellers are
to be used it may become neces-
Sary to change the present meth
DDS OF controlling the plane.
There are aviation engineers
who hope to do away with multi
pie propellers, while retaining the
desirable features of multiple mo-
tors. This calls for the gearing
OF two or more engines to a single
propeller shaft and opens the field
for new type of research. The
gearing of several motors to one
propeller would make desirable
the use Of an adjustable pitch pro-
peller. Such a propeller appears
to be necessity even though sin
gle motors continue to be used ex-
cluSively.
Plans have been announced by
a Connecticut company for the
construction Of giant .monoplanes
in which eight motors will be used
In groups Of four, geared to two
propellers. Such construction in
wolves problems which, so far as is
known, never have been worked
out in practice.
There also is growing tendency
to mount engines in tandem, one
behind the other, driving puSher
and tractor propellerS. Just how
much loss in efficiency results
from the operation of one pro-
peller in the SlipStream Of the
other has not been determined
accurately, though it is agreed
among engineers that there must
be quite a considerable loss. This
type of tandem mounting was used
in the new Fokker F-32 four.en-
gined plane, which was DESTROYED
in a crash this week, and in the
giant Dornier Do-X,. which is
powered with IL radiaI air-cooled
engines mounted in tandems
above the wing.
Prop" Efficiency Decreased.
Another new German plane, the
Junkers J-38, which today is the
largest landplane in the world,
has its motors housed within the
monoplane wing, driving tractor
propellerS. This arrangement per-
mitS the engine to be Streamlined
beautifully into the wing and en-
ableS mechanics to get to it in
flight. The drawback to this ar
rangement, it is said, is that the
SlipStream Of the propellerS ruins
the lift of the wing for their en-
tire diameter. Not only do the
propellerS interfere with the wing,
but the interference caused by the
leading edge of the wing also de-
creaSeS the efficiency of the pro-
peller. Whether these losses in
efficiency are counterbalanced by
the gain in aerodynamic efficiency
realized by inclosing the motors
within the wing as a Streamlined
unit is another matter to be de-
termined by use Of the wind-tun-
mel.
These are but a few Of the many
problems which call for thorough
research and which guarantee
that for the immediate future, at
any rate, the laboratory will con-
tinue to play an all-important
part in the development Of avia-
ton.
AMPHIBIANS POPULAR.