Thorp T 18

Design and development

The T-18 was designed to be easily constructed from sheets of aluminum, and use the modified Lycoming O-290G powerplant. It was originally designed with an open cockpit and with the cylinder heads protruding through the engine cowling 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 and a bubble canopy. These modifications allow a T-18 with 125 hp (93 kW) to cruise at 160 mph (257 km/h) and higher-powered examples to cruise in excess of 200 mph (322 km/h). Some aircraft have been constructed with retractable landing gear.

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 125 hp (93 kW) 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, Lycoming O-340, Lycoming O-360 and the Lycoming IO-360.

T-18 plans are currently available to builders from Eklund Engineering, which is also developing a laser-cut kit version and as of 2009 had aileron, flap and empennage kits. Classic Sport Aircraft at one time supplied plans, parts, and kits for the S-18 and the S-18T tricycle gear version, but is no longer in business as of 2014. Thorp Central acquired the assets of Classic Sport Aircraft and now provides these services.

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 in 1976. This was the first successful circumnavigation 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.

S-18T

Tricycle landing gear version

Specifications (S-18 with Lycoming O-360)

Data from Eklund & Classic Sport Aircraft

General characteristics

Crew: one

Capacity: one passenger

Length: 18 ft 10 in (5.77 m)

Wingspan: 20 ft 10 in (6.35 m)

Height: 5 ft 1 in (1.55)

Wing area: 86 ft² (8 m²)

Empty weight: 1000 lbs (454 kg)

Useful load: 600 lbs (271 kg)

Loaded weight: 1600 lbs (725 kg)

Powerplant: × Lycoming O-360, 180 hp (135 kW) each

Propellers: constant speed propeller, 1 per engine

Propeller diameter: 72 in (1.83 m)

Performance

Maximum speed: 200 mph (320 km/h)

Cruise speed: 180 mph (292 km/h)

Range: 540 sm (875 km) , 900 sm (1458 km) with optional wing tanks

Rate of climb: 1500 fpm (7.6 m/s)

Wing loading: 18.6 lb/ft² (90 kg/m²)

Power/mass: 8.9 lb/hp (0.19 kW/kg)

Related content

Related development:

Thorp T-211

Comparable aircraft:

Jeffair Barracuda

Mustang Aeronautics Mustang II

Smyth Sidewinder

Stoddard-Hamilton Glasair II

Van's Aircraft RV-6