SIKORSKY PRODUCT CHARTS:

Please click on any of the coded models listed on the pages below to learn more about its background and why it came into being, its special features, its specifications and its production history. The following lineage charts are organized in groups:


S-48(R-5)

S-48/R-5   Helicopter

S-48-1
Sikorsky S-48/XR-5 Army Serial No. 43-28237


Background

The Sikorsky S-48/VS-327/R-5 model was a follow-on to the successful R-4 helicopter. It was designed to meet a 1942 U.S. Army Air Forces (USAAF) requirement for a larger more capable observation helicopter as well as  a British requirement. The XR-5 helicopters featured a 48 foot 3 bladed fully articulated main rotor and a 3 bladed tail rotor powered by the reliable Pratt and Whitney 450 hp R985-AN-5 radial engine. The S-48 had a 2 place tandem cockpit with the observer in the forward position and the pilot aft.  Four Experimental XR-5 helicopters were initially built with a fifth XR-5A ordered later. The first flight was on August 18, 1943.

The successful testing of the five Experimental XR-5 helicopters resulted in a USAAF order for 26 YR-5A developmental helicopters for service testing in March 1944.  A follow-on production contract from the USAAF for 100 R-5D rescue configured helicopters was received in 1944 but only 34 were actually built.  The end of World War II resulted in the cancellation/curtailment of many contracts.

In 1945, a demonstration of the capabilities of the XR-5 was done by Sikorsky test pilot Les Morris picking up 10 people weighing over 2,000 lbs into a hover with the ladies of Sikorsky cheering them on.  The link below is Paramount New coverage of the event

http://www.youtube.com/watch?v=XTnRmbgbXsc

S-48-2
YR-5A hovering with 10 passengers and 2 crewmen.

The first civilian rescue by a helicopter was accomplished on November 29, 1945 by a YH-5A helicopter flown by Sikorsky chief pilot Jimmy Viner and assisted by U. S. Army Capt. Jack Beighle  The YR-5A rescued a
captain and his crewman from a barge aground in a storm on Penfield Reef, Fairfield Connecticut. Penfield Reef is located just offshore from the Sikorsky Bridgeport Connecticut plant.  The complete story of this historic rescue is told on the Sikorsky Archives website. A link is provided below.
http://www.sikorskyarchives.com/Civilian_Rescue.php

S-48-3
First Civilian Rescue, Penfield Reef, Fairfield, Connecticut

 

S-48/R-5 Development Timeline

  • December 21, 1942.  Cost plus fixed fee contract for five XR-5 helicopters signed.
  • August 18, 1943.  First Flight of the XR-5
  • September 17, 1943.  XR-5 lifted 10 men, plus a crew of 2 for a short hovering flight at a gross weight of 5,576 lbs.(2,529.2 kg)
  • January 9, 1944 XR-5 set unofficial speed record of 115 mph (100 knots) over a 13 mile (21 km) course.
  • January 10,1944  XR-5 set unofficial altitude record of 21,200 ft (6,461,8 m) February 1944  First YR-5A delivered
  • July 1-31, 1946 Operation Mail. In conjunction with the USAAF and the US Post Office, Air Mail Service in the greater Los Angeles area was established using three R-5A and two R-5D helicopters. The Air Mail routes required a total of 13 flying hours and 110 landings per day for the available helicopters.

 

Configuration Features

The Sikorsky XR-5 fuselage was built in 3 sections: an aluminum framed cabin with plexiglass windows and tandem seating for 2; a steel frame center section was covered with plastic impregnated plywood panels, and the tail cone was a wood monocoque design.

S-48-4
YR-5A Army Serial no. 43-46624 with panels removed shows construction details

The YR-5A helicopters were modified to several different configurations during their years of service. The configuration differences are listed below.  Five YR-5A helicopters were modified to the YR-5E configuration with dual flight controls for pilot training.  The R-5D had a wider cabin with the pilot moved forward and a 2 place bench seat in the rear. Provisions for a rescue hoist and an auxiliary fuel tank were added.  In June, 1948, the U.S.Air Force helicopter designations were changed from R to H.  The Air Force Rescue service operated H-5D, H-5F, H-5G, and H-5H helicopters.  The only problem was that the F, G, and H models were S-51 models.  The only S-48 model operated by the Air Force is easily identified by having both a small nose wheel and a tail wheel.  This has caused numerous errors in history write-ups and picture identification. 

S-48-5
R-5D (H-5D) being introduced in Hawaii 1947


The RTAF Museum in Bangkok has H-5A and H-5F helicopters on display side by side which clearly shows the differences between the 2 models.

S-48-6
H-5A and H-5F helicopters on display at the RTAF Museum Bangkok Thailand

 

S-48-7
S-48/R-5 Configuration Differences

 

Main Rotor Assembly
A 3 blade fully articulated main rotor head was installed on the S-48 helicopter. The rotor diameter was 48 feet.

S-48--8
S-48 (R-5) Main Rotor Assembly

Main Rotor Control
The main rotor head controls were located around the main gear box.  They consisted of three jackscrews and the chain system to actuate them.  The jack, in turn, actuated the azimuth star (swashplate).  The three jacks when operated in unison through manipulation of the Collective Pitch Control Stick raise the star to increase the pitch of the three rotor blades, lower the star to decrease the pitch.  Fore-and Aft cyclic control was accomplished by the differential motion of the fore-and aft jacks, which tilt the azimuth star forward or backward.  Sideways control was accomplished by raising or lowering the right jackscrew only, which tilted the azimuth laterally to one side or the other.

 

S-48-9
 Control Jackscrews and Chain Installation

  1. Forward Jackscrew
  2. Collective Pitch Sprocket Shaft
  3. Cyclic Pitch Fore-and-Aft Sprocket Shaft
  4. Cyclic Pitch Lateral Sprocket Shaft
  5. Collective Pitch Chain
  6. Cyclic Pitch Fore-and-Aft Chain
  7. Cyclic Pitch Lateral Chain
  8. Right Jackscrew
  9. Rear Jackscrew

 

Engine
A Pratt and Whitney Wasp Jr. 450 hp R-985 AN-5 engine was installed horizontally under the center section of the helicopter with a cooling fan/flywheel above. A centrifugal clutch connected the engine to the transmission. The throttle control was located on the main pitch control lever (Collective) and was synchronized to increase the throttle when pitch was increased and decreased when pitch was decreased.

Main Rotor Blades
The main rotor blades were constructed with wood spars, plywood ribs and leading edge, canvas covered pockets, and a NACA 0012 airfoil.

Tail Rotor
A semi-articulated tail rotor with 3 blades was installed. Blades were constructed of laminated wood.  

General Arrangement Drawing

S-48-10
S-48 (R-5) 3-view Drawing

Mission Systems

The tactical mission of the S-48 helicopter was for observation and assisting the artillery by locating suitable targets and adjusting fire.

Two XR-5A helicopters were provided to the British Air Commission for trials aboard ship to determine if they could assist in combating the submarine menace.

The R-5D helicopter was equipped with a rescue hoist and an auxiliary fuel tank and was the first helicopter assigned to the USAAF/USAF Air Rescue Service.

General Characteristics and Performance S-48 (R-5)

PERFORMANCE
Standard Day, Sea Level


Maximum speed (Vne)

107 kts       198 km/hr.

Range

275 miles       442.6km

Service ceiling

14,800 ft         4,511 m

Rate of Climb

2,000 ft/min   10.1 m/s

Absolute hover ceiling

3,000 ft           914.4 m

WEIGHTS


Maximum takeoff gross weight

 

R-5A

4,900 lbs  2,222.6 kg

R-5D

5,100 lbs  2,313,3 kg

R-5E

4,,985 lbs 2,261.2 kg

Weight empty

3,780 lbs  1,714,6 kg

Maximum fuel load

 

R-5A

100 gal       378.5 ltr

R-5D

71 gal         268.8 ltr

R-5E

64 gal         242.3 ltr

GENERAL DATA

Crew seating capacity

2

Seating capacity (R-5D)

2 passengers


POWERPLANT RATINGS
Standard Day at Sea Level


Pratt and Whitney R985 AN-5

450 hp          335 kw

 

AIRCRAFT DIMENSIONS

Main rotor diameter (blade tip circle)

48’ 0”          14.63 m

Tail rotor diameter (blade tip circle)

8’ 5”"             2.44 m

Fuselage length

41’7.5"           12.5m

Length over-all (including rotors)

57’1"             17.4 m

Height over-all

13’ 1.5”              4 m

Main landing gear tread

12' 0"               3.7 m

 

Production History

S-48 (R-5) production consisted of 65 helicopters:

  • 5 XR-5 models manufactured from August 1944 to November 1944
  • 26 YR-5A  models manufactured from November 1944 to July 1945
  • 14 R-5A and 20 R-5D models manufactured from July 1945 to October 1946.

 

S-48-11 
S-48 XR-5 Army Serial No.43-28237 in flight

 

S-48-12
YR-5E Army Serial No. 43-46611 with dual controls for flight training

 

S-48-13
R-5D Army Serial no. 43-46646 in Nicaragua in May 1947

 


Additional Information:

The S-48 (R-5) was replaced by the more capable S-51 helicopter which addressed many of the lessons learned from the S-48 program.

 

Prepared by Vinny Devine

 

for further resding see NEWSLETTER APRIL 2011 and
NEWSLETTER JULY 2012

 

last update SEPTEMBER 7, 2012