The biggest problem with the various early helicopter
designs produced by Louis and Jacques Bréguet,
Igor Sikorsky, Juan de la
Cierva, and others was that although
they could lift off the ground, they could not be controlled in flight.
Inventors did not understand the aeronautical forces facing the helicopter
and did not know how to design mechanical devices to address these forces.
To control a helicopter, inventors had to devise a means
of directing the downward thrust of the rotors slightly off-centre so the
craft would move in the opposite direction. They also had to find a way to
overcome the twisting motion, or torque, induced by the heavy turning
By the early 1930s, Louis Bréguet, one of the pioneers
of helicopter development, began to think about helicopters again,
establishing the Syndicate for Gyroplane Studies and hiring a young
engineer named Rene Dorand. Bréguet took a far more cautious approach than
he had more than a decade before. He oversaw the building of a helicopter
that attempted to solve the problems of stability and control. He
cautiously named this aircraft the Gyroplane-Laboratoire, clearly
identifying it as an experimental aircraft.
To make the most of a limited budget, Dorand built the
craft as much as possible from available bits and pieces. He used a
Bréguet 19 airplane fuselage for the craft's body and a surplus aircraft
engine to power it. The craft consisted of a thin metallic frame with a
tail and three wheels—one on either side mounted on outriggers and a
smaller one at the front of the aircraft. The engine was located forward,
and the pilot sat behind it in an open cage. Two
twin-bladed rotors, each nearly 54 feet
(16.5 meters) long, were stacked coaxially on top of each other, rotating
in opposite directions and thereby cancelling out their torque. The rotor
blades were attached to the shaft with a hinge mechanism (they were "articulated"),
and the pitch of the rotor could be
increased or decreased on each revolution (cyclic pitch control), thereby
controlling lift. If the propellers were
angled so they pushed the air down more, lift would increase, and the
craft would rise.
Bréguet had confidence in his machine despite warnings
from his mechanics that the controls were not yet perfected. In November
1933, he scheduled a demonstration flight for his investors. A former
French Army pilot named Maurice Claisse reluctantly agreed to make the
test. He climbed into the craft and started the engine as three men stood
by on the ground to hold the machine. The rotors turned and the craft
immediately tilted to the right. As bystanders—including the
ground-handlers—ran for cover, the rotor blades hit the ground and
shattered. Fortunately, no one was hurt, but the aircraft was badly
damaged, postponing any further tests.
Throughout 1934 and 1935, Bréguet extensively modified
his craft and performed ground tests. His most important addition was a
new system for controlling the direction of flight. By tilting the axle on
which the rotors turned, pitching the rotor disk, the helicopter could be
made to move forward, sideways, or even backward. He added a system for
controlling the yaw of the helicopter
(turning the helicopter to the left or right) by allowing the two rotors
to each have a different pitch (differential collective pitch).
On June 26, 1935, test pilot Maurice Claisse hopped in
the craft again. This time he was able to lift it off the ground without
crashing. He then made several flights at speeds of 18 to 30 miles per
hour (29 to 48 kilometres per hour). The French Air Ministry was so
impressed it gave Bréguet a contract that covered the cost of flight
trials and provided a million-franc-bonus if all performance goals were
By December 1935, Bréguet began the series of test
flights. He then proceeded to push his aircraft far beyond the limits of
any previous rotary aircraft. He was not always successful. Occasionally
the rotors collided with each other (a problem that still exists today on
helicopters with a similar design) upon landing or the rivets popped out.
But Bréguet repaired the craft in time for each new test flight. The craft
achieved a record speed of 75 miles per hour (121 kilometres per hour) and
climbed to a record altitude of 518 feet (158 meters), remaining in the
air for more than an hour. It stayed in a hover over one spot for ten
minutes—also a record. Bréguet completed his initial tests in late 1936
and received the one-million-franc bonus.
Bréguet received another Air Ministry contract for
further development but made little progress over the next several years.
One big concern about helicopters was what would happen if the engine
failed in flight. An airplane could glide to the ground, but a helicopter
needed to descend while "autorotating," essentially using the rotor as a
parachute. Bréguet's aircraft was badly damaged during an autorotation
test in 1939. With war imminent, Bréguet put his craft in storage and
turned his attention to the full-scale production of bombers. His
helicopter was ultimately destroyed in 1943 during the Allied bombing of
the Villacoublay Airfield.