FORT RUCKER, Ala. -- The advent of the rotor-wing technology aircraft changed the world and became an invaluable asset in the Aviation community, but it all had to start somewhere, and that somewhere is on display at the U.S. Army Aviation Museum.

The Sikorsky R-4 helicopter was the first production helicopter and the brainchild of Igor Sikorsky, a pioneer in both fixed-wing and rotor-wing Aviation, and according to Robert Mitchell, U.S. Army Aviation Museum curator, the world of rotor-wing Aviation wouldn't be the same without his game-changing innovation.

"We can't tell the story of the R-4 without telling the story of Sikorsky. He was a very prolific manufacturer of airplanes, mostly seaplanes, but always in the back of his mind he was fascinated by vertical flight," said the curator. "He kept working on the idea, and many had tried and failed."

A problem that plagued early designers and engineers of vertical-lift aircraft was the problem of the rotor wings causing the aircraft to spin uncontrollably, but Sikorsky figured out a solution to the problem, Mitchell said.
"He finally figured out that if you put an anti-torqueing rotor on the long arm of the tail boom and make it pitch changeable when controlled with the pedals, then as you increase power in the aircraft, you could bring the nose back," he said.

When Sikorsky solved that issue, he produced what was called the VS-300, which was the prototype aircraft. After much experimentation, and trial and error, he was able to put one into production in 1942 and dubbed it the R-4, and subsequently offered it to the military. The R-4B was the first production model and consisted of a two-level and two-pedal control design, which would become the standard for rotor-wing aircraft, said Mitchell, and was made of an aluminum frame with some fabric casing the top and rear of the aircraft.

The military, including the Army, bought several of the new R-4 helicopters to be used for general utility and observation, and the aircraft were deployed in the Pacific Theater and the China-Burma-India Theater during World War II, the curator added.

The versatile capabilities of the helicopter were showcased during an incident that occurred in 1944 when an L1 airplane went down behind Japanese lines in heavy jungle, said Mitchell.

"They were able to maintain contact with the pilots of the aircraft through radio, and then a commander approached a lieutenant and told him to take the helicopter to go and pick up the pilots of the L1," he said. "Helicopters don't generally perform very well in high altitude, high humidity and heat, and this was the first aircraft of its kind, so it had some power problems, so this was a pretty tall order."

The lieutenant proceeded to rescue the downed crewmembers, which took about a week to complete since the helicopter only had two seats for the pilot and co-pilot, Mitchell said. In order to complete his mission, the pilot had to fly with a fuel can on the seat, pick up one crewmember, put the fuel in the aircraft, throw the fuel canister away and fly back. Then he had to land, drop off the crewmember, refuel, restock, and fly back out and repeat the process until all of the crewmembers were rescued.

"This is what set the wheels in motion for the Army to develop the modern-day helicopter and for the entire world to benefit from the modern-day helicopter," he added.

The technology for the helicopter rapidly developed in just a few, short years, and before the war had ended, the helicopter had advanced from the first production model to the R-5 then R-6.

"You go from R-4 to the R-5, which is like a quantum leap in technology," said the curator. "The two aircraft were developed only a few years apart."

The R-4 that currently sits in the museum is one of only two in the collection, and the R-5 that sits across from it is the only surviving model left in the world, according to Mitchell.

The R-4 used a radial engine that was repurposed from airplane engines, which were eventually phased out for turbine engines, which drastically reduced vibrations in the aircraft, and paved the way for the modern-day helicopter, he said.