VS-300A NX 28996 in Forward flight with Igor Sikorsky at the controls
Igor Sikorsky dreamed of building a helicopter from his youth. In 1931, he applied for a patent for a single main rotor helicopter which included nearly every feature that would be incorporated in the VS-300. By 1938, technology had caught up with his dream. When he was summoned to United Aircraft Headquarters in Hartford, Connecticut to be told that the Sikorsky Division which at that time was building fixed-wing aircraft was being shut down due to a lack of business, he requested that he be allowed to keep his design team together to design a helicopter. His request was granted along with an initial $30,000 budget. The VS-300 was America’s first practical helicopter. It was also the first successful helicopter in the world with a single main rotor and a torque compensating tail rotor
Some preliminary helicopter design work had already been done by Igor Sikorsky, who was the Engineering Manager, and his associates “off the clock” and they were ready to start work. The basic VS-300 helicopter looked very similar to the 1930 design.
The VS-300 was designed in the spring of 1939 and built that summer.
VS-300 under construction September 8, 1939
The first flight version of the VS-300 included a 28 foot diameter main rotor and a 75 hp Lycoming engine. A 40” single blade tail rotor and rigid 4 wheel landing gear with a full swiveling nose and tail wheels were installed. The VS-300 featured full cyclic main rotor control (pitch and roll) and a single pedal tail rotor control (yaw). Vertical control was provided by a large wheel to the right of the pilot. The first flight on September 14, 1939 by Igor Sikorsky lasted approximately 10 seconds to a height of a few inches. The helicopter was tethered to a heavy plate by four cables which allowed the helicopter to move in all directions by dragging the plate. A ground crew was always present to stabilize the helicopter if the pilot lost control to prevent a roll over. No helicopter flight training was available, so Igor Sikorsky got “On the Job” training learning with each additional flight. The design team was not familiar with the fact that a spinning rotor had gyroscopic properties (precession) which required an input 90 degrees in rotation before it became effective. The VS-300 therefore rolled left when the cyclic stick was pushed forward. The initial pilots, Igor Sikorsky and Serge Gluhareff, had no idea whether the control problems were caused by the helicopter design or pilot technique.
The VS-300 in a stable hover on November 24, 1939
Changes to the helicopter were made after every flying day by the Night Crew. Obvious changes since the first flight in the above photo are outrigger main landing gear with full swiveling wheels, the tail wheel moved aft, and dampers have been added to the flapping hinge on the main rotor
Flight of the VS-300 continued with each flight a little longer than the last as the pilots adjusted to this unruly machine until December 9, 1939 when a gust of wind tipped over the VS-300 grinding the rotors into the ground and causing major damage to the VS-300. This ended the career of the First Configuration.
The link below, with a commentary in German, shows rare footage of the earliest VS-300 flights.
The VS-300 was completely redesigned and rebuilt. A decision was made to abandon cyclic control of the main rotor and adapt a design suggested by I.A. Sikorsky, a draftsman and mathematician, and Michael Buivid, the Chief Engineer, which locked out cyclic control and replace it with two additional horizontal tail rotors. Collective pitch control for vertical control was left on the main rotor. Prior to flight testing of the second configuration, the helicopter was mounted on a pedestal and operated without the main rotor blades installed. This allowed fine tuning of the new control system and allowed the pilots to become comfortable with the new system before actual flight.
An early version of the VS-300 second configuration
VS-300 Development Timeline
VS-300 First Flight September 14, 1939
VS-300 second configuration with heavy duty outriggers
Igor Sikorsky after setting endurance record with VS-300 Second Configuration
The link below is to a Paramount Newsreel “He Sits on Air” which includes footage of the endurance record.
Les Morris hovers the VS-300A Third Configuration with “Bob Sled” nose.
The link below is to a promotional film from 1943 of Sikorsky Test Pilot Les Morris flying the VS-300A and a helicopter status report by Igor Sikorsky.
Igor Sikorsky flies the VS-300A for the last time October 7, 1943
Igor Sikorsky in cockpit of VS-300A at completion of last flight
The link below is a short newsreel of the Sikorsky VS-300A Helicopter at the Henry Ford (Edison) Museum (1943)
A Souvenir Postcard carried on last VS-300A flight
Synopsis of VS-300 Configurations
VS-300 Helicopter Design
The VS-300 was designed as a research vehicle which was easily modified based on test results. Although the VS-300 is described as having four configurations it was in fact modified every night after a test flight. A ”Lessons Learned” meeting was held by the design team after each flight and decisions were made on what to try next. By the end of the VS-300 development program only the pilot seat, 2 main landing gear wheels, main transmission box, central fuselage framework, and gas tank remained from the original VS-300. The picture below shows the VS-300 on the day of the first flight. Visible in this picture is the single tail rotor pedal and the Collective control wheel, similar to the trim controls on the flying boats, on the right side of the helicopter. The cables from the top of the main rotor to the blades prevented the blades from drooping too much when the blades were not turning.
VS-300 on the day of the first flight, September 14, 1939
The picture below dated November 13, 1939 shows a much modified main landing gear with swiveling wheels, dual tail rotor pedals, dampers on the main rotor flapping hinge, and a “T” bar to provide a horizon reference are noticeable changes from the first flight configuration.
Cyclic control for a helicopter was an unknown area in 1939. Juan de la Cierva had attempted to use it on the Autogiro but abandoned it after an unexplained accident. After a VS-300 accident in December 1939, cyclic control was abandoned by the Sikorsky design team. It was not returned until the Summer of 1941, when lateral control was returned to the main rotor in the 3rd configuration. The gyroscopic qualities of a spinning rotor were still not understood and acceptable control was obtained by experimentation rather the mathematical calculations. Control inputs to the stationary swashplate were incrementally moved until moving the cyclic stick left rolled the helicopter left. Once lateral control was satisfactory, the 4th configuration was constructed returning full Azimuthal control (pitch and roll control) with the first flight on December 8, 1941. Flights with this configuration encountered a “Wobble” when accelerating. This issue was resolved on December 31, 1941when Igor directed the crew to reinstall dampers, previously used to control blade flapping, in a horizontal position to dampen lead and lag blade movement. This was the “Silver Bullet” and resulted in a smooth flying machine. As a historical note, the XR-4 helicopter with full Azimuthal flight controls made its First Flight on January 14, 1942, two weeks after control problems were solved on the VS-300A.
Power was supplied by a 75 hp (at 3200 rpm) Lycoming O-145-C3 air-cooled four cylinder horizontally opposed engine. The engine was installed with the propeller shaft pointed aft and connected to the main gear box by a series of six V-belts. Tension on the belts was provided by engaging an idler pulley. In July, 1940 the engine was replaced with a 90 hp (at 2,500 rpm) Franklin 4AC-199-E air cooled four cylinder horizontally opposed engine to provide additional power. In April, 1941 an upgraded 4AC-199 engine with 90 hp at 2680 rpm and 100 hp at 3050 rpm was installed.
Franklin 90 hp model 4AC-199-E (O-200-1) engine
The engine was cooled by a “squirrel cage“, V-belt driven, cooling fan in a sheet metal enclosure mounted above the engine which forced cooling air down across the cylinder cooling fins.
Starter and Battery
In order to save weight the battery was removed from the VS-300 after the first flight. Then the starter was also removed. A handle was installed on the starter and it was held in place to start the engine and then removed. Later the engine was started by a rotary shaft attached to the lower pulley on the engine. After engine start, the rotor was spun-up by hand and then the idler pulley was engaged to tension the 6 drive belts. A bungee cord maintained tension on the idler pulley.
The original landing gear consisted of 2 main landing gear with diagonal struts and swiveling front and rear wheels. This was soon replaced by vertical oleo struts with swiveling wheels on the main landing gear and a nose wheel. As development progressed diagonal main landing gear was reinstalled and eventually the nose and tail wheel were removed with only a tail skid remaining on the final version.
The original forward fuselage structure framework was constructed almost entirely of 4130 chrome-molybdenum steel thin wall tubing with the aft fuselage an aluminum box structure. In the second configuration the aft structure.was changed to steel thin wall tubing for strength and easy modification.
VS-300A Main Rotor Head
A Dural Pulley was attached to the propeller shaft on the Franklin 90 hp engine which was connected to a larger Dural Pulley by 6 V-belts (Gates Vulcco Ropes) for the first rpm reduction of 1.76:1. Shafting from the upper pulley went forward to the main gearbox which contained spiral bevel gears from the rear end (differential) of a Mack truck. This was the second rpm reduction of 5.9:1 to obtain the correct main rotor rpm. A rear shaft ran aft and powered the anti-torque tail rotor and the horizontal rotors on earlier versions by V-belt drive. The upper pulley also contained a free-wheeling unit to allow autorotation in the event of engine failure (No autorotations were attempted with the VS-300).
NOTE: RPMs Presented are Nominal for Illustration Purposes.
VS-300 Second Configuration Drive Train Schematic
The Gates Vulco Ropes identified in the illustration were a Gates proprietary design V-belt with concave sides. When the belt was under tension the torque flattened the belt for full contact with the pulley.
Main Rotor Blades
The main rotor blade had a spruce wooden spar extending from root to tip. The leading edge consisted of lamination of spruce, balsa, and mahogany. A high speed (since rotor tip speeds are over 254 mph (374 ft./sec) symmetrical NACA 0012 airfoil was used. This airfoil had a stable center of pressure and the feathering axis and chordwise center of gravity were collocated making it ideal for a rotating wing.
VS-300 Main Rotor Blade before covering – First Flight design
Later design with wire trailing edge
Tail Rotor Blades
The tail rotor blades were all wood. The spar was made of maple, with poplar ribs and birch veneer pockets
VS-300A Tail Rotor Blades
VS-300 Flight Simulator
In 1938 Michael Buivid and Bob Labensky designed and fabricated the first helicopter simulator. The configuration of the simulator changed daily and proved to be a valuable tool in predicting pilot’s ergonomic requirements and reactions to tilting fore and aft and laterally, and rotation for directional control.
Michael Buivid, Igor Sikorsky, Bob Labensky, and Michael Gluharefff with the VS-300 Simulator
Rotor Blade Test Unit
The rotor blade test rig was built to measure the lift and torque required to drive various blade designs.
1939 Single Blade Rotor Lift and Torque Test Rig
General Arrangement Drawing
VS-300A 3-view Drawing
The VS-300 utilized a wicker basket to carry various items to demonstrate the controllability of the helicopter.
On the VS-300A a converted metal bicycle basket replaced the wicker basket.
The VS-300 was originally equipped with 2 Hot Dog floats, a tail float, and a basketball for a nose bumper.
VS-300 with short pneumatic rubber floats
Further along in the program the VS-300A was equipped with longer Hot Dog floats which eliminated the need for the tail float and nose bumper.
VS-300A with long floats picking up a suitcase
General Characteristics and Performance VS-300A
Standard Day, Sea Level
Standard Day at Sea Level
Only one VS-300 was built. Although the configuration changed constantly during development the only change to the designation was to reidentify it to the VS-300A in the 3rd and 4th configurations.
The link below is to a video: Recollections of a Pioneer, narrated by Igor Sikorsky’s son Sergei, which contains excellent vintage movies of the VS-300 and also some famous words from Igor.
September 1999 Sikorsky Archives News “60 Years Ago A Vision Flew”
Anything A Horse Can Do. The Story of the Helicopter
H. F. Gregory (1944) ISBN-10: 1430497505
The Story of the VS-300. The Aircraft that Launched an Industry
Harry Pember Igor I. Sikorsky Historical Archives
Pioneerinng the Helicopter
Charles Lester. “Les” Morris (1945
NOTE: Links in this document to websites outside the Archives site are provided to supplement the information provided. A reference to these sites does not constitute an endorsement nor a confirmation of the historical accuracy of the information by the Igor I. Sikorsky Historical Archives, Inc.
Prepared by Vinny Devine
last update MARCH 4, 2014
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