Sonex Onex

The Onex is a single-seat aerobatic homebuilt with folding wings that costs $43,812 as a complete kit, and the folding wings are the point. Wings folded it is 94 inches wide and under 8 feet tall, which fits a domestic garage — so it is one of the very few airplanes a person can own without renting hangar space.

It is the small one in the Sonex line. Where the two-seat Sonex and Waiex share an airframe, the Onex is its own design: 16 ft 5 in long, a 20-foot span (or 18 ft 9 in as an option), 84.4 square feet of wing, and a 27-inch cockpit that Sonex describes as enlarged "to accommodate more pilots than ever before".

On the published figures: 135 KTAS at 8,000 feet on about 3.8 gph, a 400-foot take-off, a 43-knot clean stall, +6/−3 g, and 465 nm of still-air range on 15 gallons. The power comes from an AeroVee 2180 — an 80 hp Volkswagen conversion built by Sonex's own AeroConversions division — with AeroVee Turbo, Jabiru, UL Power and Rotax options offered.

Why this page exists. Until 2026-10-12 the Onex was a row in the variants table of sonex-waiex, a page storing seats: 2. The Onex has one seat. The protocol is explicit that different seat counts never share a page, and a buyer filtering for a single-seater could not find this airplane. The same page also listed the SubSonex, a single-seat turbojet, under engine_type: piston_single — that one is discussed on the parent page and could not be split out, for reasons given there.

Two options change the airframe rather than the engine: an 18 ft 9 in wing (78.0 sq ft instead of 84.4), which lowers the folded height to under 7 feet, and tricycle gear for $1,200 in place of the standard taildragger.

Siblings: the two-seat Sonex and Waiex, and the Xenos motorglider, remain on sonex-waiex; the SubSonex jet is discussed there too.

One correction to Sonex's own engine list. It reads "Jabiru 2200 120hp". The Jabiru 2200 is a four-cylinder of about 85 hp — the 120 hp engine is the six-cylinder 3300, and our own jabiru-j-series page records the 2200 at 85 hp. The error is in the source and no figure from that line is carried here.

Everything Sonex publishes is in mph and statute miles, and every stored figure is converted — Vne 216 mph is 188 knots, and the 535-mile range is 465 nm. Storing 535 as nautical would have overstated it by 15%.

The fuel burn is derivable rather than invented, and that distinction matters. Sonex publishes no gallons per hour. What it publishes is the method: "Conservative, low altitude calculation: 135 mph TAS @ 35.5 mpg." That gives 135 ÷ 35.5 = 3.8 gph, which is consistent with an 80 hp VW conversion and is arithmetic on the manufacturer's own stated figures rather than a guess. At 8,000 feet Sonex claims 155 mph TAS at 44.25 mpg — 3.5 gph — so the stored figure is the conservative one.

Two cruise figures, and the stored one is the higher. 135 mph at sea level and 155 mph TAS at 8,000 feet, which converts to the stored 135 KTAS with cruise_altitude_ft: 8000 recorded alongside it so the condition travels with the number.

The take-off and landing figures are read as ground rolls. Sonex labels them "T.O. Distance 400 ft" and "Landing Distance 500 ft" without saying whether either clears a 50-foot obstacle. 400 feet is implausibly short for an obstacle distance and entirely plausible as a ground roll, so they are stored as rolls and no obstacle figure is invented.

The glide is published as a ratio, not a speed: L/D 10:1. From 3,000 feet AGL that is about five nautical miles. No best-glide speed is given.

The gross weight is the aerobatic one and there is no other. Sonex's table says "Gross Weight - Aerobatic | 950 lbs" with no separate normal-category figure, so 950 lb at +6/−3 g is what the airplane has.

350 lb of useful load, 90 lb of fuel if filled, one seat:

A single-seat airplane with 350 lb of useful load is not payload-limited by any normal standard — the tank runs out long before the scales do. 15 gallons at 3.8 gph is just under four hours, which at 135 knots is the 465 nm range Sonex publishes with nothing held back. Plan a reserve out of that.

Local flying is a 9 and that is what this airplane is for. Cheap to build, cheap to run at under four gallons an hour, +6/−3 g, and it lives in a garage.

Aerobatics is a 6, the highest in the Sonex line here. +6/−3 g at 950 lb with a 131-knot maneuvering speed is a genuine sport-aerobatic capability. It scores 6 rather than higher because it is a VW-powered 80 hp airplane with a 10:1 glide, not a competition mount — a Pitts or an Extra is a different class of machine, and this one has no inverted fuel or oil system published.

Cross-country is a 4. 135 knots and 465 nm is real reach for the money, and 20 pounds of baggage, one seat and no IFR capability is what caps it.

Flight training is a 1 — structurally, not as a judgment. It has one seat. No instructor can sit in it.

Back-country 2, cargo 1, business travel 1. Low wing, small tires, 350 lb of useful load, 20 lb of baggage.

Parts: good. Mechanics: specialist. Sonex Aircraft of Oshkosh, Wisconsin sells the kit, the engine and the parts, publishes builder documentation, and is one of the better-supported kit companies in the US. Crucially the engine is made by the same company — AeroConversions is a Sonex division — so the airframe and powerplant come from and are supported by one source.

The AeroVee is a Volkswagen conversion, and that is the whole maintenance story. Cheap parts, simple architecture, an owner-builder can overhaul it on a bench, and no FAA-certificated shop is required or even relevant on an experimental airplane. Against that: it is not a Lycoming, so a typical field A&P has no familiarity with it, and the owner-builder community is the support network.

There is no TBO and no overhaul price, and that has a consequence this page states rather than hides. Sonex publishes no time between overhauls and reference/engine-overhaul-pricing.md has no AeroVee row, so the cost model charges no engine reserve at all and the stored annual figure of $6,200 is a floor. A VW conversion's real overhaul interval is a usage-and-build question; budget something rather than nothing.

Prebuy specifics for any amateur-built airplane, and this one in particular: the builder's log; a current weight and balance, because Sonex's 600 lb empty weight is a target and builders miss it; the folding-wing mechanism, its pins and its inspection history, since that is a moving primary structure the other Sonex models do not have; and engine provenance — who assembled the AeroVee and to what standard.

No used figures are stored — few exist and they trade privately. What is sourced is the kit: $43,812 complete, broken down by Sonex as a $25,450 airframe kit, a $12,500 AeroVee, $1,105 of engine options, $554 of firewall- forward and miscellaneous, $2,200 of instruments, a $1,528 propeller and $475 of upholstery. Add $1,200 for tricycle gear or $4,500 for the AeroVee Turbo.

That number is the valuation anchor and the thing that makes this airplane interesting: a complete, new, aerobatic airplane for under $45,000 in parts, before the builder's own thousand-odd hours.

What drives a completed example's value: builder quality above all, engine provenance and hours, panel, and whether it has the folding-wing option set up and working.

An amateur-built Onex holds an experimental airworthiness certificate and the FAA issues no airworthiness directives against experimental aircraft. There is no S-LSA version, so there is no manufacturer safety-directive regime either — compliance with any Sonex service information is the owner's choice, which cuts both ways.

Sonex publishes service information and runs an active builder community. Check for it at prebuy and ask the builder directly, because nothing compels a previous owner to have acted on it.

With production from 2011 in small numbers, there is no fleet large enough to have established pattern faults. The folding wing is the component with no analogue elsewhere in the catalog and the one to inspect hardest.

$1,400 is extrapolated from the light-sport band in reference/insurance-costs.md and set at the low end. No Sonex binder is on file.

It should be among the cheapest airplanes in the catalog to insure: a hull value in the tens of thousands, one seat so no passenger liability, and a 43-knot clean stall. Against that, underwriters price amateur-built airframes cautiously and some decline them outright for a pilot with no time in type, and aerobatic use is usually excluded unless specifically bought — if the +6 g capability is the reason for the purchase, say so when quoting.

Go to an agency that writes experimental aircraft specifically.