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S-50 Helicopter

 

 
 

S50 1
S-50 full scale wood mockup


Background

The Sikorsky S-50 helicopter was a 1943 company funded design study for a small single engine helicopter based on the S-49 (XR-6) helicopter.  The S-50 design gross weight was 1,450 lbs. vs. 2,590 lbs for the XR-6 helicopter, a 56% reduction in weight.  It was unofficially marketed to the U.S. Army Air Corps. as a single pilot observation helicopter.  The S-50 helicopter program never progressed beyond the full scale mockup stage.

Configuration Features

The Sikorsky S-50 original design strategy was to use the S-49 dynamic components with the 38 foot main rotor diameter reduced to 32 foot by shortening the S-49 main rotor blades.  Weight calculations dictated that a new lighter weight hub and lighter weight blades would be required to meet the design goals.

 

S50 2
S-50 full scale mockup rear view

To save weight the traditional oleo strut tail landing gear was replaced by a tail landing skid with 3 rubber doughnuts to absorb landing loads.

 

S50 3
S-50 tail landing skid with rubber doughnut shock absorber

Main Rotor Assembly
A 3 bladed fully articulated main rotor head was planned for the S-50 helicopter with a 32 foot rotor diameter which was later reduced to 30 foot to save weight.

Tail Rotor Assembly
A 3 bladed 8’ 4’ diameter tail rotor (later reduced to 7 foot) with laminated wood blades was planned for the S-50 helicopter.

Engine
A Franklin 6ACV-298, 150 hp, 6 cylinder horizontally opposed engine was to be installed vertically under the center section of the helicopter with a cooling fan/flywheel above. 

Main Rotor Blades
The main rotor blades were constructed with metal spars, plywood ribs, and plywood pockets with the entire blade covered with 2 layers of fabric. A NACA 0012 airfoil was used.

 

S50 4
S-50 Main Rotor Blade engineering sketch

S-50 Mockup of mechanical parts including flight controls.

 

S50 5
S-50 mockup including flight controls installation

General Arrangement Drawing

S50 6
S-50 3-view drawing

General Characteristics and Performance S-50

PERFORMANCE
Standard Day, Sea Level


Maximum speed (Vne)

103.4 kts  191.5 km/hr

Range

250 miles      402.3 km

Absolute ceiling

16,000 ft         4,877 m

Rate of Climb

1,400 ft/min     7.1 m/s

WEIGHTS

Maximum takeoff gross weight

1,450 lbs    657.1 kg

Weight empty

1,050 lbs     476.3kg

Maximum fuel load

21 gal           79.5 ltr

Useful Load

400 lbs       181.4 kg

GENERAL DATA

Crew seating capacity

1

Seating capacity

1 passenger

POWERPLANT RATINGS
Standard Day at Sea Level


Franklin 6ACV-298   (150 hp@ 3200 rpm)

150 hp       110.3 kw

AIRCRAFT DIMENSIONS

Main rotor diameter (blade tip circle)

30’ 0”              9.1 m

Tail rotor diameter (blade tip circle)

7’ 0”                2.1 m

Fuselage length

23’ 4”              7.1 m

Length over-all (including rotors)

40’ 3”            12.3 m

Main landing gear tread

9’ 0”                2.7 m

 

 

Prepared by Vinny Devine
October 2013

 

 

LAST UPDATED OCTOBER 8, 2013

 
 
   
 
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