1607

Item 1607

OTHER: Helicopter - Outside - Single (1 seat) - Sikorsky VS-300

The following is just rough preliminary work on using the VS-330 specifications in the Access Momentum and Blade Element calculations for hover.

Sketch of VS-300-C:

Calculations based on The following Limited Information on the Sikorsky VS-300:

Input Values:
Airfoil:	NACA 0012	It looks like a 23012 or 23015 ????
Number of Blades:	3
Rotor Radius:	14 ft
Chord:	1.125 ft	Assumed
Taper:	0.54 in/ft
Twist:	None
Cutout:	0.25 R	Assumed
Gross weight:	1,121 lbs	Avg. of 1,092 lb and 1150 pounds
Engine Power:	65 hp
Blade Pitch:	6.7º	Set to give hover at 1,121 lbs GW.
Rotor Speed:	320 RPM	Tip speed 513 fps. Assumed
Calculated Values:
Momentum Theory	57.5 hp
Blade Element Theory:	42.2 hp

For blade information see Heelicopter by Hunt, page 59

Information Gathered on the Sikorsky VS-300:

VS-300 had a 65 hp Lycoming engine and belt transmission turning a three-bladed main rotor. It flew for the first time on September 14, 1939. By the summer of 1940, the experimental helicopter could stay airborne for 15 minutes at a time.

In 1938, United Aircraft, suffering under the prolonged Depression, had to shut down production at its Sikorsky division. However, in an amazingly far-sighted and generous action, the company allowed Igor Sikorsky to retain a small team and work on a helicopter project on a low-budget basis. Sikorsky was now effectively out of the fixed-wing aircraft business and into the helicopter business full-time. United Aircraft's investment would turn out to be more than they anticipated, but would still pay off handsomely.

The VS-300 was tethered to the ground in its early flights, but Sikorsky kept tweaking it until it could be controlled, and free flights began in the spring of 1940. The VS-300 originally did not have a fuselage or cockpit, being a naked framework with a main rotor, a tail rotor, an exposed pilot's seat, a 65-horsepower Lycoming engine, and the hardware to glue them all together. The machine was reengined with a 90-horsepower Lycoming engine in the summer of 1940.

September 14, 1939 - Igor Sikorsky made first vertical liftoff in his Vought-Sikorsky VS-300; May 6, 1941 - established world helicopter endurance record of 1 hour, 32 minutes, 26 seconds in VS-300; used three-bladed main propeller 28-feet in diameter, stayed in air for 65 minutes and 14.5 seconds.

To the workers at the Sikorsky plant in Connecticut, the machine was known as "Igor's nightmare" and reflected the mechanical complexity of his early prototypes. Sikorsky's first helicopter, the VS-300, was flying by May 1940. A good summary of the technical design is given by Sikorsky (1941, 1942, 1943). His first machine had one main rotor and three auxiliary tail rotors, with longitudinal and lateral control being obtained by means of pitch variations on the two vertically thrusting horizontal tail rotors. Powered only with a 75 hp engine, the machine could hover, fly sidewards and backwards, and perform many other maneuvers. Yet it could not easily fly forward, exhibiting a sudden nose-up pitching characteristic at low forward speeds. This phenomenon was to be traced to the downwash of the main rotor wake, which as airspeed built, blew back onto the two vertically thrusting tail rotors and destroyed their lift. The main lifting rotor of the VS-300 was used in the later VS-300A with a more powerful 90 hp engine, but only the vertical (sideward thrusting) tail rotor was retained out of the original three auxiliary rotors. In this configuration, longitudinal and lateral control was achieved by tilting the main rotor by means of cyclic-pitch inputs; the single tail rotor was used for antitorque and directional control purposes. This configuration was to become the standard for most modern helicopters.

American Helicopter Society

http://www.vtol.org/History.htm#_Toc486998801

In 1938, the design team built a rotor test stand to study lift and torque forces. The following spring, they began the design of a simple test vehicle. The VS-300 (Vought-Sikorsky – helicopter No. 3) was powered by a 65 hp (48 kW) Lycoming engine, driving a 28 ft (9 m) 3-blade main rotor and a single blade, counter-balanced tail rotor. Gross weight was 1,092 lb (495 kg).

VS-300's 1150 pounds ~ The Dragonflies

Igor Sikorsky Timeline with Related Information:

	Date:	Activity:
	1924	S-29-A. It appears that 1 was built
		S-38. A total of 101 aircraft were built.
	1930-1931	S-39. 21 aircraft of this type built
	27 June 1931	Sikorsky files patent for 'Direct Lift Aircraft', Granted on 19 March 1935. It was a single main + tail-rotor configuration.
	Early 1930s	S-40. 3 built.
	1936	The Flettner Fl 185 helicopter was an experimental German helicopter developed in 1936 with support of the German Navy. "main rotor and two auxiliary propellers mounted on outriggers attached to the fuselage. The auxiliary propellers worked in opposition to each other and served to cancel the torque of the main rotor, a function handled by a single, variable-pitch tail rotor on contemporary helicopters."
		S-42. 10 built
		S-43. 53 had been sold.
	13 August 1937	VS-44. Only 3 were produced, Excalibur, Excambian and Exeter. The last fixed wing aircraft built by Sikorsky. US Navy XPBS-1 (Sikorsky S-44) was built in direct competition with the PB2Y from Consolidated Aircraft Corporation. Consolidated was awarded the contract. The contract was for 350 craft but it was cancelled after 50 were built, apparently because of poor rough water performance.. William Hunt says "Had Sikorsky won the contract, the VS-300 experimental helicopter might never have been built" I read somewhere that the proliferation of airports was the demise of large amphibious aircraft.
	1938	Test stand that provided data for VS-300 helicopter
	1942	The initiation of the Spruce Goose. It flew in1947. It was intended to solve a specific wartime transportation problem.

Last Revised: November 28, 2008