The Nelson H-63, known in the US military designation system as the YO-65, is an American dual ignition, four-cylinder,

horizontally opposed A flat engine is a piston engine where the cylinders are located on either side of a central crankshaft. Flat engines are also known as horizontally opposed engines, however this is distinct from the less common opposed-piston engine design, wh ...

two-stroke A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...

aircraft engine that was developed by the Nelson Engine Company for use in

helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attribu ...

s and

light aircraft A light aircraft is an aircraft that has a maximum gross takeoff weight of or less.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 308. Aviation Supplies & Academics, 1997. Light aircraft are used as utility aircraft co ...

. The engine designation means ''horizontally opposed 63 cubic inch displacement''.

Design and development

The H-63 was designed in the late 1950s specifically to power the sort of very light single-man helicopters that the

US Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...

was investigating at the time. Application for

certification Certification is the provision by an independent body of written assurance (a certificate) that the product, service or system in question meets specific requirements. It is the formal attestation or confirmation of certain characteristics of a ...

was made on 15 March 1958 and the engine was certified under the CAR 13 standard on 8 February 1960. Engines were produced for Nelson by the

Franklin Engine Company The Franklin Engine Company was an American manufacturer of aircraft engines. Its designs were used primarily in the civilian market, both in fixed wing and helicopter designs. It was briefly directed towards automobile engines as part of the Tuck ...

Syracuse, New York Syracuse ( ) is a city in and the county seat of Onondaga County, New York, United States. It is the fifth-most populous city in the state of New York following New York City, Buffalo, Yonkers, and Rochester. At the 2020 census, the city' ...

under a production certificate. Originally the type certificate was held by the Nelson Specialty Corporation of

San Leandro, California San Leandro ( Spanish for " St. Leander") is a city in Alameda County, California, United States. It is located in the East Bay of the San Francisco Bay Area; between Oakland to the northwest, and Ashland, Castro Valley, and Hayward to the s ...

, but it was transferred to Nelson Aircraft of Irwin, Pennsylvania on 15 July 1966. Ownership of the type certificate was transferred to the present owner, Charles R. Rhoades of

Naples, Florida Naples is a city in Collier County, Florida, United States. As of the 2020 census, the population of the historical city (i.e. in the immediate vicinity of downtown Naples) was 19,115. Naples is a principal city of the Naples-Marco Island, Flori ...

, on 14 February 1996. The four-cylinder engine runs on a 16:1 mixture of 80/87 avgas and SAE 30 outboard motor oil. It is equipped with a single Nelson E-500

carburetor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...

Variants

;H-63A: 42 hp @ 4000 rpm ;H-63C :Vertically mounted version for use in helicopters, producing at 4000 rpm. ;H-63CP :Horizontally mounted version for use in light aircraft, producing at 4400 rpm for take-off. ;YO-65-2: Military designation for H-63 fitted to the Hiller XROE-1 Rotorcycle

Applications

;H-63C * Hiller YROE ;H-63CP * Lobet/Shafor Ganagobie

Engines on display

EAA AirVenture Museum The EAA Aviation Museum, formerly the EAA AirVenture Museum (or Air Adventure Museum), is a museum dedicated to the preservation and display of historic and experimental aircraft as well as antiques, classics, and warbirds. The museum is lo ...

Specifications (H-63C)

References