Sonex / Waiex / Onex / SubSonex

Sonex Aircraft (Oshkosh, Wisconsin) builds the budget hot rod of kit aviation. Founded by John Monnett, the Sonex family delivers sport-plane performance — 150 KTAS on 120HP — in the cheapest all-metal airframe you can build. Kit prices start under $20,000 for the airframe, and total build costs of $30,000-$55,000 make the Sonex one of the most affordable paths to aircraft ownership.

By 2014, over 500 Sonex family aircraft had been completed and were flying. The product line includes the Sonex (conventional tail), Waiex (Y-tail), Xenos (motor glider), Onex (single-seat with folding wings), and the remarkable SubSonex — a single-seat jet powered by a PBS TJ-100 turbojet.

The Sonex-B and Waiex-B (2016) are the current production models with enlarged cockpits, electric flaps, and support for multiple engine options including the Sonex-proprietary AeroVee 2180 (80HP Volkswagen-based), Jabiru 3300 (120HP), Rotax 912 (100HP), and UL Power UL350i (118HP).

In 2024, Sonex approved a gross weight increase to 1,220 lbs for aircraft with 100HP or more, improving useful load and MOSAIC eligibility.

The AeroVee 2180 is Sonex's own engine — a heavily modified Volkswagen Type 1 engine producing 80HP. At approximately $7,500 complete, it's the cheapest new aircraft engine available. The Jabiru 3300 at 120HP is the performance option, adding 20 KTAS to cruise speed. The Rotax 912 at 100HP provides the best balance of power, reliability, and parts support.

Sonex-B with Jabiru 3300 (120HP): 150 KTAS (170 MPH) cruise at 8,000 feet on 5.5 GPH. This is faster than a Cessna 172 on less than two-thirds the fuel. Rate of climb at 1,400 FPM is excellent. The 23,000-foot service ceiling reflects the low weight and adequate power. Range of 350 nm from 16 gallons is limited — the Sonex is a short-legged speedster.

Sonex-B with AeroVee 2180 (80HP): 130 KTAS (150 MPH) cruise on 4 GPH. Still faster than most trainers on a Volkswagen-derived engine costing $7,500. Range extends to approximately 400 nm due to lower fuel burn.

Waiex: Identical performance to the Sonex. The Y-tail provides a distinctive appearance and slightly different pitch characteristics but no meaningful performance difference.

Onex (single-seat, 80HP): 130 KTAS cruise at just 740 lbs gross weight. Folding wings for garage storage. The ultimate single-seat fun machine.

SubSonex JSX-2 (turbojet): A single-seat jet kit aircraft priced at approximately $125,000. Cruises at approximately 200 KTAS on a PBS TJ-100 turbojet producing 240 lbs of thrust. Fuel burn of approximately 30 GPH Jet-A limits endurance to approximately 45 minutes. This is purely a novelty/sport aircraft — the only affordable jet kit.

The 16-gallon fuel capacity is the Sonex's primary limitation. At 5.5 GPH (Jabiru), endurance is about 2.5 hours with reserve — requiring fuel stops on any trip over 300 nm.

Sonex-B (Jabiru 3300, 120HP, 16 gal fuel):

Sonex-B (AeroVee 2180, 80HP, 16 gal fuel):

The Sonex's 600 lbs useful load is generous for a 1,220-lb aircraft — two 180-lb pilots with full fuel still have 144 lbs for baggage. Two 220-lb pilots can fly with full fuel and 64 lbs of bags. The 16-gallon fuel capacity is the constraint: 350 nm range (Jabiru) or 400 nm (AeroVee) limits the Sonex to regional missions. Solo flying with full fuel leaves 304 lbs for pilot and baggage — more than adequate for the single-occupant sport flying mission.

• Flight Training (4): The Sonex's light weight and responsive handling could serve for tailwheel training or sport flying education. The low stall speed (35 KIAS) provides good margin. Not ideal for primary training due to experimental category, limited fuel, and tandem-like shoulder width.
• Backcountry (1): Low wing, fixed nosewheel or tailwheel, and minimal ground clearance. Not a bush plane.
• Business Travel (1): 150 KTAS but only 350 nm range and two seats. Not practical for business.
• Aerobatics (3): The Sonex can perform basic aerobatic maneuvers — loops, rolls, spins. Not competition-capable but the light weight and 120HP make it entertaining for sport aerobatics. G-limits at approximately +6/-3 at aerobatic weight.
• Cross-Country (4): 150 KTAS cruise is excellent, but 350 nm range means frequent fuel stops. Adequate for weekend 200-nm trips. The 16-gallon tank is the constraining factor.
• Cargo Hauling (1): Two seats, minimal baggage area. Not a cargo aircraft.
• Local Fun Flying (9): THE Sonex mission. Fast, light, responsive, and cheap to operate. The Sonex delivers sports-car handling at $30-$45/hour operating cost. The enormous Sonex community provides fly-in culture and builder support. Pure flying pleasure at the lowest cost in aviation.
• Surveying (1): Low wing, limited endurance. Not applicable.

• Typical Sonex panel: Minimal VFR — basic flight instruments, engine monitor, single comm radio. Many Sonex builders keep panels ultra-simple to save weight and cost. $2,000-$5,000 for a basic panel.
• Upgraded panel: Dynon D10A or Garmin G5, GPS, ADS-B transponder. $8,000-$15,000.
• The Sonex philosophy is simplicity. Heavy glass panels defeat the purpose of a 620-lb aircraft. Most builders optimize for lightweight flying, not avionics capability.

Experimental amateur-built — no STCs required.

• Engine choice is the primary builder decision: AeroVee 2180 ($7,500, 80HP), Jabiru 3300 ($15,000, 120HP), Rotax 912ULS ($20,000, 100HP), UL Power UL350i ($18,000, 118HP), or CAMit 3300 ($12,000, 120HP).
• Tailwheel or nosewheel: Builder's choice. Tailwheel is lighter; nosewheel is easier.
• Auxiliary fuel tank: Some builders add a small header tank or auxiliary tank to extend the 16-gallon standard capacity.
• Electronic ignition: Common modification for VW-based AeroVee engines.

• Condition inspection: $400-$800/year. Simple all-metal construction.
• Engine overhaul: AeroVee: $3,000-$5,000 at 1,000-hour TBO (builder-maintained). Jabiru 3300: $8,000 at 2,000 hours. Rotax 912: $12,500 at 2,000 hours.
• Parts availability: Good. Sonex Aircraft in Oshkosh maintains strong factory support. All-metal construction means raw aluminum is available anywhere.
• Mechanic familiarity: Common. Simple construction. AeroVee engine maintenance can be done by any VW-experienced mechanic.
• Annual all-in cost: $3,500-$7,000 at 100 hours/year. Among the lowest in all of aviation.
• Operating cost: $30-$50/hour all-in. The AeroVee on auto fuel achieves $15-$20/hour fuel cost. The Sonex may be the cheapest aircraft per hour to fly.

• Sonex/Waiex (original, AeroVee 80HP): $20,000-$45,000. Budget builds at the low end.
• Sonex/Waiex (Jabiru 120HP): $35,000-$70,000. Performance builds.
• Sonex-B/Waiex-B (2016+, various engines): $40,000-$100,000. Current production; best examples.
• Onex (single-seat, 80HP): $20,000-$40,000.
• SubSonex (jet): $80,000-$125,000. Niche market.
• New kit (airframe): ~$16,000. Complete with AeroVee engine: ~$30,000. Complete with Jabiru: ~$45,000. Complete with Rotax: ~$55,000.

Per valuation-methodology: Engine choice is THE primary value driver. AeroVee at $7,500 vs Jabiru at $15,000 vs Rotax at $20,000 creates significant value tiers. Build quality matters as with all homebuilts. The Sonex market is price-sensitive — buyers are typically looking for maximum value. Low total time and excellent build quality command premium.

No ADs (experimental category).

Common Problems:

• AeroVee engine reliability: The VW-based AeroVee is affordable but requires careful builder attention. Head stud failures, oil cooling issues, and carburetor icing have been reported. The Jabiru and Rotax engines are more reliable but cost 2-3x more.
• Jabiru 3300 cylinder concerns: Some Jabiru 3300 engines have experienced through-bolt failures and cylinder cracking. The issue has been addressed in newer production but is a concern on used aircraft.
• Fuel capacity: 16 gallons limits mission flexibility. No headwind tolerance on longer trips.
• Cockpit width: The Sonex cockpit is narrow. Two larger pilots (shoulder width 18"+) will be uncomfortable. The B-model improved this somewhat.
• Build quality: Standard homebuilt caveat. Pop-rivet construction is accessible but quality varies.
• Landing gear: Fixed spring aluminum gear can develop fatigue cracks.

Per insurance-underwriting:

• Hull + liability: $1,000-$2,500/year for typical hull values ($25K-$60K).
• Liability only: $300-$500/year.
• Tailwheel vs nosewheel: Tailwheel versions cost 10-20% more to insure.
• Low hull values keep insurance affordable. The Sonex's modest value and good safety record help.