Nederlandse Modelbouw en Luchtvaartsite

Dutch Modelling and Aviation

In Memoriam

Klaas Willem Jonker
† April 30, 2018

On Monday 30 April 2018, Wilko Jonker died after a long illness at the age of 58. He leaves behind a wife and two children. The Dutch military aviation and plastic modeling were his hobby and on this website he shared all the knowledge he has collected over the years. His hobby has been able to distract him from the persistent disease in his body until the last week of his life. The contacts with other hobbyists were a major support for him.

This website will be maintained by different people for as long as possible, so that other enthusiasts can continue to benefit from extensive content.

Sikorsky S-51


The Sikorsky R-5, the designation of the S-51 till 1948, was developed as the successor of the Sikorsky R-4. This helicopter was the helicopter to be produced in rather large numbers.
The S.51 was used under several designations and was also built under license by Westland as Westland-Sikorsky WS-51 Dragonfly. Over 300 examples were built.


The purpose of the R-5 was to improve the work load, service ceiling, range and speed of the R-4. The aircraft had an enlarged rotor diameter, larger fuselage and a more powerful Pratt & Whitney Wasp Junior rated 450 hp.

First flight of the R-5 was August 18, 1943 and in March 1944 the USAAF ordered for 26 pre-production machines designated as YR-5. The first of this order was delivered in February 1945.

Soon a second order for 100 R-5As followed, thought just 34 examples of this type were delivered.
Sikorsky soon developed a modified version, the e S-51, with an enlarged rotor, enlarged work load and had a higher weight. The first S-51 flew on 16-02-1946.
The S-51 was, because three passengers could be carried, meant for both the civil as the military market. It was the first helicopter built for commercial, civil purposes.
Eleven examples went to the USAF as R-5F and ninety examples tot the US Navy as HO3S-1.
Westland started in 1946 with the production for the Royal Navy and Royal Air Force. The Westland built aircraft were equipped with an Alvis Leonides engine rated 500 hp. This improved the performance and raised the maximum speed to 166 km/h and the service ceiling to 4300 m. Westland built 133 examples.

Westland also developed an own helicopter type, Westland Widgeon, which never saw production.

Twenty-one Sikorsky R-5As were later modified with a third seat, a hoist, external fuel tank and a nose-wheel. Three of this modified R-5As were evaluated by the US Navy as HO2S-1. Another five examples were modified and equipped with double steering under the designation YR-5E.
In 1948 thirty-nine examples of the H-5Gs, a special rescue version, while later another sixteen aircraft were modified with floats under the designations H-5H.
In 1949 several H-5Hs were modified and equipped with extensions at both sides, in which two stretchers could be carried, see this example


prototype based upon the Sikorsky VS.372. Five examples built; Two seats; tail-wheel; One Wright 450hp R-985-AN-5 engine.
Pre-production version, differed little from the prototypes. 26 built, including two HO2S-1 for the US Navy.
Production-version as rescue helicopter with provisions for two stretchers. 34 examples built. Later designated as H-5A.
  • R-5B: never built, modified R-5A.
  • YR-5C: never built, modified R-5A
  • R-5D: Modified R-5A with nose wheel and hoist. Twenty examples were modified. Later designated as H-5D.
  • YR-5E: Modified YR-5A with double steering; Five examples modified; later designated as YH-5E.
Four-seat, civil version from 1947. Elf examples built. Later designated as H-5F:
Four-seat version designated as H-5F, equipped with rescue equipment. 39 examples built.
As H-5G with updated equipment. 26 examples built.
  • HO3S-2: never built USN version of the H-5H.
US Navy designation of two YR-5As
US Navy designation of the four seat H-5F; 88 examples built.
  • HO3S-1G: nine examples of the HO3S-1, built for the US Coast Guard
One, in 1950 modified HO3S-1 with a new developed main rotor
Civil, four seat version.


Technical information
Length with rotor 12,5 m Rotor diameter: 14,6 m
Height: 3,9 m Tail Rotor diameter: - m
Empty weight: 1920 kg Full weight: 3500 kg
Max. speed: 145 km/hr Cruising speed: 113 km/hr
Range: 451 km Service ceiling: 3000 m
Engine type: One Pratt & Whitney R-985-An-5 Wasp junior rated 450 hp
Crew: Two
Rotor diameter: 14,6 m; Rail rotor diameter: 2,5 m