Thorp T-18 Tiger

The Thorp T-18 Tiger is a two-place, side-by-side, all-metal, low-wing, plans-built homebuilt designed by John Thorp in 1963. It holds two historically significant "firsts" in experimental aviation: it was the first successful all-metal homebuilt aircraft offered to amateur builders, and the first homebuilt to use an all-flying stabilator tail. John Thorp famously argued that metal airplanes could be simpler to build than wood-and-fabric designs, and he proved the point by publishing a serialized construction guide in EAA's Sport Aviation magazine in the mid-1960s.

By 2011, over 1,600 sets of plans had been sold and roughly 400 examples were flying. The T-18 dominated the fast-homebuilt category throughout the 1970s and early 1980s until vans-rv4 and the rest of Richard VanGrunsven's RV kit series eclipsed it on the strength of matched-hole kits and factory support. The T-18's most famous achievement is Don Taylor's N455DT, which in 1976 became the first homebuilt aircraft to circumnavigate the globe (now in the EAA Museum). The type is beloved by builders who value plans-built tradition, rugged aluminum construction, and genuine cross-country speed on modest horsepower.

Performance varies dramatically with engine choice: 125 hp examples cruise around 140 mph, 150 hp at ~160 mph, and 180 hp examples hit 175-200 mph. Most flying T-18s today are O-320 or O-360 powered with the C-wing modification.

Published numbers in this page reflect a typical 180 hp O-360 C-wing example. The T-18 is famously clean for its era — essentially an early RV in spirit — and delivers honest 150-160 KTAS cruise on around 8-9 GPH. It climbs strongly (1,000-1,500+ fpm solo) and accelerates rapidly in a dive. Builders routinely report breaking the 214 mph red-line straight-and-level with higher-horsepower installs, so the T-18 rewards discipline on the throttle in descent.

Stall behavior is honest but the short-coupled airframe and relatively high wing loading (roughly 17 lb/sq ft on the C-wing) yield a landing approach speed of 75-80 mph — faster than contemporaries like the Luscombe or Cessna 140. Density altitude performance is excellent for an experimental of this era, with the service ceiling genuinely usable into the high teens. See cross-country for how the T-18 scores as a distance burner.

With 1,500 lb gross weight and ~900 lb empty weight, the C-wing T-18 has approximately 600 lb useful load.

• Full fuel (29 gal = 174 lb) + pilot + passenger + bags: 600 - 174 = 426 lb for two occupants and baggage. Two 180 lb adults fit with ~65 lb remaining — enough for soft bags but not golf clubs plus weekend gear.
• Two 200 lb pilots + weekend bags (50 lb): 450 lb of people+bags, leaves 150 lb for fuel = 25 gallons useable. At 8.5 GPH, roughly 2.5 hours + reserves or ~350 nm no-wind range.
• Solo with full fuel: Pilot, full tanks, and 250 lb of baggage is realistic — the airplane becomes a genuine 450+ nm cross-country single.

The T-18 is a true two-seat airplane, not a 2+2. Payload-range math favors solo travel and short-hop weekend trips over loaded-up long hauls.

Sources: Wikipedia: Thorp T-18, Aviation History & Technology Center, Thorp T18 Specifications, Plane & Pilot: Thorp T-18, EAA Museum: 1968 Thorp/Taylor T-18 N455DT, Kitplanes: Designer Spotlight John Thorp, T18.net community forum.

• Local fun flying (9): Bubble canopy, responsive controls, genuine sport-airplane feel, and all-metal durability make it a standout for weekend flying. See local-fun-flying.
• Cross-country (7): 150-160 KTAS on 8-9 GPH is excellent economy; 29 gallons gives ~450-500 nm range with reserves. Small cabin and limited baggage cap long-haul comfort. See cross-country.
• Aerobatics (5): Rated +6/-3 G (1,250 lb standard wing, 1,500 lb C-wing). Rolls, loops, and basic positive-G aerobatics are fine, but the airframe is too clean for serious aerobatic work — pilots can blow through Vne in a botched maneuver. See aerobatics.
• Business travel (4): Two seats, limited baggage, no meaningful IFR certification path. Speed is there, utility is not.
• Flight training (3): Narrow gear, high landing speed, and short-coupled taildragger character make it a poor primary trainer. Acceptable for transition training with an experienced CFI.
• Backcountry (2): Low wing, fragile gear, small tires, and fast approach speeds rule out unimproved strips.
• Cargo hauling (2): ~600 lb useful load and a cramped cabin; this is a sport airplane, not a hauler.
• Surveying (4): Speed and economy are good, but low wing, two seats, and experimental category limit commercial/Part 91 mission use.

As an experimental, the T-18 has full access to the non-certified avionics market — one of its biggest cost advantages over legacy certified aircraft.

• Budget ($3k-8k): Steam-gauge legacy panel (vintage KX-155 or narco + mechanical gyros), uAvionix tailBeaconX for ADS-B, iFly or ForeFlight tablet for nav.
• Mid ($10k-20k): Garmin G5 or two, GTR 200B comm, GTX 335 ADS-B out, autopilot optional (Trio or Trutrak-style).
• Premium ($25k-45k): Dual Dynon SkyView HDX or Garmin G3X Touch, GTN 650Xi (if the owner wants VFR GPS/com integration), Dynon or Garmin autopilot servos, engine monitor. A well-panel'd T-18 can have better avionics than a 1980s certified four-seater for half the money.

See avionics-pricing for experimental vs. certified unit pricing.

Experimental aircraft don't use STCs, but the T-18 community has produced a well-documented catalog of builder modifications:

• Sunderland "C-wing" (folding wing): Raised gross weight to 1,500 lb, added folding-wing capability for trailering/hangar sharing. Standard on most modern builds.
• Engine upgrades: O-290G to O-320 to O-360 progression; each step yields meaningful cruise and climb gains. O-360 is the sweet spot.
• Constant-speed prop: Adds ~$6-10k but dramatically improves climb and takeoff performance. Common on 180 hp installs.
• Nosewheel (S-18) conversion: Dick Cavin / Eklund offered the tri-gear S-18 variant; reduces ground-handling risk at the cost of some weight and drag.
• Larger canopy / wider fuselage stretches: Some builders widened the cabin by 2-3 inches for comfort.
• Vortex generators and aileron gap seals: Lower stall speed and improve low-speed handling.

As an experimental amateur-built, the original builder (or subsequent owner with a repairman certificate) can perform unlimited maintenance and inspections. Condition inspections annually must be signed off by an A&P or the original builder.

• Parts availability: Good. Thorp Aircraft (thorpaircraft.com) and the T-18 Mutual Aid Society support the community with drawings, hardware, and technical help. Airframe is largely standard 2024-T3 aluminum and AN hardware — nothing exotic.
• Mechanic familiarity: Common among A&Ps willing to work on experimentals; the Lycoming O-320/O-360 powerplant is universally serviceable.
• Annual cost range: $4,500-8,500 for a condition inspection plus typical consumables (oil, filters, tires, brake pads). Reserves for engine overhaul at $28k / 2,000 hr TBO = $14/hr.
• Expensive items: Canopy replacement ($2-3k), prop overhaul ($1.5-3k fixed pitch, $4-6k constant speed), O-360 top overhaul ($10-14k).

See maintenance-ecosystem for broader parts and labor context.

T-18 pricing is tightly correlated with (1) build quality and builder reputation, (2) engine time since overhaul, (3) avionics modernity, and (4) whether it has the C-wing modification. See valuation-methodology for the engine/avionics/airframe adjustment framework.

• Project / run-out engine: $15k-22k
• Flying, steam gauges, mid-time O-320: $25k-35k
• Well-built, O-360, modern EFIS, recent paint: $40k-55k
• Rare "showpiece" builds: $55k+ (uncommon — the market caps lower than for comparable RVs)

Premium for C-wing over standard wing: roughly $5k. Constant-speed prop: $4-6k value add. Good paint/interior: $5-8k. The T-18 consistently trades at a discount to equivalent Van's RV-3/RV-4s because of smaller builder community and parts support.

As an experimental amateur-built, the T-18 is not subject to FAA Airworthiness Directives on the airframe. However, the Lycoming engine carries the full Lycoming AD list (crankshaft, oil pump gear, magneto, etc. — see maintenance-ecosystem).

Pre-buy red flags specific to the T-18:

• Wing spar rivet workmanship: Many early builders used solid rivets in structural joints; quality varies widely builder-to-builder. Inspect carefully.
• Tailwheel steering linkage wear: Short-coupled geometry amplifies any slop.
• Canopy cracks: Large bubble canopies crack around attach points and at the rear lip; replacements are available but not cheap ($1,500-3,000).
• Fuel tank sealant degradation: Integral wing tanks in some builds; look for blue staining.
• Ground loop history: The T-18's taildragger reputation means a large fraction of airframes have had a gear/wingtip incident at some point. Verify repair quality.
• Build quality variation: The single biggest risk factor. A T-18 built by an experienced metal-working A&P is a different airplane than one built by a first-time amateur.

See insurance-underwriting for the experimental taildragger category. Typical annual premiums for an owned T-18:

• Hull only ($30-40k stated value), 500+ hr pilot with tailwheel endorsement and 25+ hr make/model: $1,400-2,000/yr
• Low-time pilot (<200 hr TT) or no tailwheel time: Very difficult to place; insurers often require 5-10 hr of dual-received instruction in type before binding, and some will decline outright.
• Liability only: $600-900/yr
• Aerobatic endorsement: Adds ~15-25% and may require documented aerobatic training.

The T-18's ground-loop statistics and experimental category combine to produce higher rates than a comparable-value certified Cessna 150. Nosewheel S-18 variants insure for roughly 25% less.