The Thorp T-18 is an American, two-place, all-metal, plans-built,

homebuilt aircraft Homebuilt aircraft, also known as amateur-built aircraft or kit planes, are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch", from plans, or from assembly kits.Armstrong, Kenn ...

designed in 1963 by

John Thorp John Willard Thorp (June 20, 1912 – April 18, 1992) was an American aeronautical engineer who made significant contributions to aircraft design throughout his life. Born in French Camp, California, John Thorp grew up from age four in the ...

.Bayerl, Robby; Martin Berkemeier; et al: ''World Directory of Leisure Aviation 2011–12'', page 98. WDLA UK, Lancaster UK, 2011. Tacke, Willi; Marino Boric; et al: ''World Directory of Light Aviation 2015–16'', page 105. Flying Pages Europe SARL, 2015. The aircraft was originally designed as an open cockpit aircraft, powered by a military surplus Lycoming O-290G ground power unit engine, but evolved into a fully bubble canopied aircraft powered by engines of up to .

Design and development

The T-18 was designed to be easily constructed from sheets of

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

, and use the modified Lycoming O-290G powerplant. It was originally designed with an open cockpit and with the

cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...

s protruding through the engine

cowling A cowling is the removable covering of a vehicle's engine, most often found on automobiles, motorcycles, airplanes, and on outboard boat motors. On airplanes, cowlings are used to reduce drag and to cool the engine. On boats, cowlings are a cove ...

in the interest of simplicity. Even as originally designed, the cruising speed was quite high. The design showed great potential for higher performance and so modifications were created to install larger, cowled

Lycoming engines Lycoming Engines is a major American manufacturer of aircraft engines. With a factory in Williamsport, Pennsylvania, Lycoming produces a line of horizontally opposed, air-cooled, four, six and eight-cylinder engines including the only FAA-certi ...

and a bubble canopy. These modifications allow a T-18 with to cruise at and higher-powered examples to cruise in excess of . Some aircraft have been constructed with retractable landing gear.Bowers, Peter M. ''Guide to Homebuilts – 9th Edition'', pages 124–127. Tab Books, 1984. Plane and Pilot: ''1978 Aircraft Directory'', page 157. Werner & Werner Corp, Santa Monica CA, 1977. These performance improvements made the T-18 one of the most popular homebuilt designs of the 1970s and early 1980s until the Van's Aircraft RV kitplane series came on the market. The T-18 was designed to use the Lycoming O-290G Ground Power Unit. At the time the T-18 was developed these engines were inexpensive and widely available as military surplus generator motors. When converted for aircraft use they are virtually identical to the O-290D or O-290D2 aircraft engines. Other Lycoming engines can be used, including the

Lycoming O-320 The Lycoming O-320 is a large family of naturally aspirated, air-cooled, four-cylinder, direct-drive engines produced by Lycoming Engines. They are commonly used on light aircraft such as the Cessna 172 and Piper Cherokee. Different variants ...

Lycoming O-340 The Lycoming O-340 is a family of four-cylinder Flat engine, horizontally opposed, carburetor-equipped aircraft engines, that was manufactured by Lycoming Engines in the mid-1950s. Design and development The O-340 was designed by Lycoming specif ...

Lycoming O-360 The Lycoming O-360 is a family of four-cylinder, direct-drive, horizontally opposed, air-cooled, piston aircraft engines. Engines in the O-360 series produce between 145 and 225 horsepower (109 to 168 kW), with the basic O-360 produc ...

and the

Lycoming IO-360 The Lycoming O-360 is a family of four-cylinder, direct-drive, horizontally opposed, air-cooled, piston aircraft engines. Engines in the O-360 series produce between 145 and 225 horsepower (109 to 168 kW), with the basic O-360 producing ...

. T-18 plans were available to builders from

Eklund Engineering Eklund is a Swedish surname. Geographical distribution As of 2014, 57.3% of all known bearers of the surname ''Eklund'' were residents of Sweden (frequency 1:641), 22.2% of the United States (1:60,735), 13.1% of Finland (1:1,564), 1.9% of Norway ...

, which was also developing a laser-cut kit version and as of 2009 had

aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

flap Flap may refer to: Arts, entertainment, and media * ''Flap'' (film), a 1970 American film * Flap, a boss character in the arcade game ''Gaiapolis'' * Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland'' Biology and he ...

and

empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third ed ...

kits.

Classic Sport Aircraft A classic is an outstanding example of a particular style; something of lasting worth or with a timeless quality; of the first or highest quality, class, or rank – something that exemplifies its class. The word can be an adjective (a ''c ...

at one time supplied plans, parts, and kits for the S-18 and the S-18T tricycle gear version, but went out of business in 2014.

Thorp Central ''Thorp'' is a Middle English word for a hamlet or small village. Etymology The name can either come from Old Norse ''þorp'' (also ''thorp''), or from Old English (Anglo-Saxon) ''þrop''. There are many place names in England with the suffi ...

acquired the assets of Classic Sport Aircraft and now provides S-18 plans and parts. By 2011 over 1600 sets of plans had been sold and 400 examples were flying.

Operational history

One T-18, N455DT, was built by Donald Taylor of California and flown around the world from

Oshkosh, Wisconsin Oshkosh is a city in Winnebago County, Wisconsin, of which it is the county seat. The city had a population of 66,816 in 2020, making it the ninth-largest city in Wisconsin. It is also adjacent to the Town of Oshkosh. History Oshkosh was ...

, in 1976. This was the first successful

circumnavigation Circumnavigation is the complete navigation around an entire island, continent, or astronomical object, astronomical body (e.g. a planet or natural satellite, moon). This article focuses on the circumnavigation of Earth. The first recorded circ ...

of the world by a homebuilt aircraft. Taylor subsequently flew N455DT to the geographical North Pole, using a Sperry hybrid inertial navigation system. Clive Canning flew another T-18 from Australia to England earlier the same year.

Variants

;T-18 :Original model ;T-18W :Modified T-18, with changes designed by Lou Sunderland to provide a 2" (5 cm) wider fuselage. ;T-18C :Modified T-18, with changes designed by Lou Sunderland to provide a "convertible" wing that rotates back against the fuselage for trailering or storage. ;T-18CW :T-18 with wider fuselage and folding wing. ;S-18 :Similar to T-18CW, with modified airfoil and other minor changes. The Sunderland changes were made in collaboration with Thorp.Vandermeullen, Richard: ''2012 Kit Aircraft Buyer's Guide'', Kitplanes, Volume 28, Number 12, December 2011, page 48. Belvoir Publications. ThorpS18T

;S-18T :

Tricycle landing gear Tricycle gear is a type of aircraft undercarriage, or ''landing gear'', arranged in a tricycle fashion. The tricycle arrangement has a single nose wheel in the front, and two or more main wheels slightly aft of the center of gravity. Tricycle g ...

version

Specifications (S-18 with Lycoming O-360)

References

{{commons category, Thorp T-18 Homebuilt aircraft 1960s United States civil utility aircraft Low-wing aircraft Single-engined tractor aircraft Aircraft first flown in 1963

Design and development

Operational history

Variants

Specifications (S-18 with Lycoming O-360)

See also

References