Thorp T-18

The T-18 design was originally developed with the Lycoming 0-290G (ground auxiliary power unit) in mind, by John Thorp. Which was easily converted to a Lycoming 0-290D engine producing 125 HP.

The T-18 is an all metal 2 place side-by-side high performance aircraft. Control response is exceptional and control forces are well harmonized. The T-18 is a very capable cross-country airplane. It will carry 2 people, 80 lbs. of baggage, and depending on engine and prop, can cruise around 180 mph. Powerplants range from Lycoming O-235 (115hp) to IO-360 (180).

The T-18 was designed to be built from twelve 4' x 12' sheets of aluminium ranging in thickness from 0.016 to 0.040. Ribs and fuselage frames were designed to be hand formed with a mallet over plywood form blocks. Simple aluminium angle extrusions are used for stringers and longerons. The main wing spar caps are made from 1/4 "U" channel on top and angle on bottom with flat sheet for spar webs.

John Thorp designed the aircraft to be small, yet strong with excellent take-off and climb performance. The landing gear is a simple "A" frame of heavy wall 4130 steel tubing, heat treated to 180,000 lbs./sq. in. and bolted to the firewall with (3) 3/8" bolts. The engine mount is also attached to the "A" frame allowing landing stresses not to be transmitted directly to the fuselage. This landing gear system has proven to be rugged and durable. The T-18 incorporates the "flying tail" which John Thorp held the patent for. This design also incorporates a sliding bubble canopy, like a fighter style.

The T-18 is a very historic aircraft. It was one of the first all metal homebuilts. It was the first homebuilt to use the stabilator or all-flying-tail. The stabilator was designed by John Thorp and was later used by Piper on their line of Cherokee aircraft. Today you can see the extensive use of this design on military aircraft. The T-18 was the first homebuilt aircraft to fly around the world. It was also the first homebuilt airplane to fly to both the geographic and magnetic north poles. The legendary Don Taylor completed all of these feats in the early 1970's. His famous T-18 is now on display in the EAA museum in Oshkosh, Wisconsin. 

T-18 plans are available again through Eklund Engineering. They are also developing a kit version, using laser cut parts and of course John Thorp's matched hole tooling concept. The laser cut parts are beautiful and it promises to be a wonderful kit. For more information contact Eklund Engineering at: or by phone at: (209)727-0318

No other homebuilt has done all the things that have been done by this airplane. It is no doubt one of the best designed aircraft in the world.

T-18 Designations / Models

The original design by John Thorp in about 1963

The original T-18 fuselage design, but incorporating Lu Sunderlands new Convertible or folding wing. Plans were available through John Thorp. The folding wing was a supplement to the original T-18 drawings. The plans were taken off the market in 1984 when John Thorp retired.

Not many of these exist, but is the wide body version of the fuselage as designed by Lu Sunderland, using the standard T-18 wing platform. Plans were available through John Thorp. The wide body modification was a supplement to the T-18 drawings. The plans were taken off the market in 1984 when John Thorp Retired.

This is the predecessor to the S-18. It is the wide body version of the fuselage, and also the Convertible or folding wing as designed by Lu Sunderland. Drawings were available from John Thorp and they contained supplements for the fuselage and wing modifications. The plans were taken off the market in 1984 when John Thorp retired.

This is my own designation for this model and I hope it will be accepted. This model uses both the standard fuselage and the standard wing plan form, but incorporates the LDS airfoil designed by Lu Sunderland and used on the S-18. There are no actual drawings for the "L" version, as builders have taken it upon themselves to make the airfoil change.

This is the redesigned version of the T-18 by Lu Sunderland. A complete new set of drawings were done and offered in 1985. It is basically the T-18CW

wing span
wing area
empty weight
useful load
gross weight
fuel capacity
Lyc. HP Range180/125-180
18.9 ft
5.1 ft
20.8 ft
x940 lb

1500 lb
29 gal
500 n.m


takeoff distance, ground roll
rate of climb
max speed
cruise speed
landing distance, ground roll
service ceiling
1000 ft
1500 fpm
210 mph
201 mph
1800 ft
18,000+ ft

limiting and recommended speeds

design manoeuvring speed (Va)
never exceed speed (Vne)
stall, power off (Vsl)
landing approach speed
60 mph

All specifications are based on manufacturer's calculations