Air Force the Official Service Journal - Air Force Historical Studies ...

R.6
I:>:CJ: the AAF
S helicopter, the
accepted
Sikorsky
delivery of its first successful
XR--I-, in the spring of 19-1-),
three new models have been added to our whirligig family.
The most unllSu;l] design among the newcomers is that
of the Plutt-Lcf'agc XR-I, a twin-rotor craft weighing 4,800
pounds. Far from being rcadv to appear in qua ntitv, the
XR-I is just coming out of the experimental stage. Its
couvcntionallv shaped fuselage has tandem scats with sliding
canopies and the bottom of the compartments is of transparent
plastic. The high stnbilizcr and rudder empennage
of the tail arc similar to those of the normal airplane tail
assembly. There arc no elevators,
At each end of the pvlous, which project from the fuselage
like \\'ings. is a three-bladed rotor, each hlacle approximately
15 feet long. These rotors neutralize torque bv
rotating in opposite directions. thcrcbv eliminating the
need for the tail rotor used on the Sikorskv-tvpc helicopters.
A -I-50-hp Pratt and \\'hitnev radial engine powers the
XR-l. /\lthough ordered earlier than the first experimental
R-4, the XR-l was not succcssfullv flight tested until the
summer of 19-1-).
An improved version of the original R--1-helicopter has
been designated the R-b. The "Six" looks like an 0\'('[sized
squash gourd with rotors and wheels. The square
corners of the R--I- h;l\c been eliminated in its successor.
A small nosc-who;-] protects the plexiglas nose of the craft.
Other new materials used in the R-b include a paper-based
cowling that encloses the engine and rotor shaft. The cabin
is constructed of plastic impregnated glass fiber cloth. The
OCTOBER,1944
OUR NEW HELICOPTERS
slender tail cone has a covering of tough magnesiulll skin.
Powered with a 2-1-5-hp Franklin six-cvlindcr horizontullvopposed
engine, the R- ') has a top speed in excess of I rio
mph, a normal useful load capacity of approximutclv half a
ton and can climb to 5.900 feet in less than seven minutes.
E\'aeuation litters can be installed on each side of the
fuselage. Pilots and observer sit sidc-bv-sidc.
The R-,) helicopter is the big brother of the "Six." In
configuration the craft resembles the R-b and R--I- helicopters,
having one main three-bladed rotor and a vertical
tail rotor. The main rotor is the largest ever built. measuring
-1-8feet across the disc. The R-S's nine-evlinder aircooled
Pratt and \\-hitnev engine den-lops -I-50-I;p.
Fuselage of the R-:; measures approximately 40 feet
from nose to tail. It is built in three sections. The center
section. supportiug the eugine. is made of welded steel
tubing, cowlcd with plastic-impregnated molded plywood.
The tail section is a wooden monoeoque cone to snpport
the tail rotor. A long shaft atop the cone's exterior is geared
to the engine for turning the solid wood, seven-foot blades
of the vertical rotor. The nose section is an aluminum .rllov
channel superstructure mounted on an aluminum mOJ1(jcoque
floor. This forward section houses the plexiglas-enclosed
cabi».
The R-,) has a convcnt ional landing gen. The observer
sits in the nose with the pilot directly behind him. Stick
and rudder controls arc dual. Space is available for cameras,
radio accessories and other auxiliarv equipment in cockpits.
Four litters, two on a side, em he carried hy the R-5. * 53
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