This is a blog that’s documenting a Sonex A-model plans build.
NOTE
I’m still fabricating the Zenith. Just wanted to start a more cross-country centric project as my primary focus. Instead, the Zenith CH750 Cruzer will probably take on a more specialized role. Maybe as a float plane :)
ANOTHER
Okay, look. I get the whiplash. If you take a look at the Vans RV-7 overview, you’ll see the reason why I cancelled that build for now. The Sonex build is meant to be a replacement for that project and will fufill a very similar mission profile.
Mission Profile
The mission that this build is looking to fill is a fast two-seat cross country tourer with light aerobatic capabilities. It’s primary purpose is to cruise at a high enough airspeed that it doesn’t take forever to get places, even with a slight head wind. Secondary purpose is to be a recreational aerobatic plane to have fun in the local pattern areas.
As a list:
- Two-seats
- I only ever take my partner. That’s true for basically 100% of my flying.
- The second seat would be handy for cross-country baggage if flying solo.
- 20+ lbs of baggage at full tanks
- It’s not nearly as much as an RV-7, but room for some light baggage would be perfect. The Sonex holds 40lbs.
- Push 200mph true air speed
- This is important in fighting head winds. The Rans only really cruises around 136mph and is heavily affected by wind. From Phoenix, AZ to Hammonton, NJ (KDVT - N81), we’re talking 16+ hours with a slight headwind!
- The Sonex has a Vne of 198 mph, and a Jabiru 3300 config gets up in that range.
- 10k+ feet cruising altitude
- Need enough engine to get up high and have options around weather and terrain. The default AeroVee Turbo doesn’t quite breach 10k from what I’ve been reading, but there are alternatives if I can afford them.
- Stable enough for IFR work
- Enough engine and slippery airframe for high density altitude days.
- I live in mountains, so climb rate is crucial!
- Fun in the local area
- Many light sports are spritely and responsive. I’d love for this plane to be able to do some light aerobatics as well to challenge myself!
- Not wildly expensive
- It’s a scratch build, so will definitely save a decent chunk.
- Widely supported plans
- Many people have plans-built a Sonex over the years. Chatting with one of the folks there, the factory is absolutely happy to field questions.
- All Metal
- Found all metal construction easy to work with.
Not many two-seat plans-builds really meet these requirements. Mostly it’s the speed aspect that’s challenging. As far as I can tell, in terms of metal aircraft, the Sonex A-model fits that bill.
Factory Specifications (A-Model)
General Specifications
| Specification | Value |
|---|---|
| Length | 18’ 1” |
| Wing Span | 22’ |
| Wing Area | 98.0 sq. ft. |
| Tail Configuration | Conventional |
| Tail Height (Std Gear) | 56” |
| Tail Height (Tri-Gear) | 74” |
| Tail Width (with tail tips) | 92” (interior width required for enclosed trailer) |
| Main Gear Width | 71” (with wheel pants) |
| Air Foil | 64-415 |
| Primary Structure | 6061 aluminum |
| Cockpit Width | 40 in. |
| Fuel Capacity | 16 US Gal. |
| Stall Speed (full flaps) | 40 mph [64 km/h] |
| Stall Speed (clean) | 46 mph [74 km/h] |
| Max Flap Extended Speed (Vfe) | 100 mph [161 km/h] |
| Maneuvering Speed | 125 mph [201 km/h] |
| Never Exceed Speed (Vne) | 197 mph [317 km/h] |
Performance
| Performance | 80 hp 2180 AeroVee | 80 hp Jabiru | 120 hp Jabiru |
|---|---|---|---|
| Empty Weight | 620 lbs | 620 lbs | 620 lbs |
| Range | 550 miles | 550 miles | 400 miles |
| Cruise Speed @ Sea Level* | 130 mph | 130 mph | 135 mph |
| Cruise Speed @ 8000 ft (TAS) | 150 mph | 150 mph | 170 mph |
| Power Loading (GW/HP) | 13.125 | 13.125 | 9.583 |
| T.O. Distance | 400 ft | 400 ft | 250 ft |
| Landing Distance | 500 ft | 500 ft | 500 ft |
| Service Ceiling (calculated) | 16,000 ft | 16,000 ft | 23,000 ft |
Utility Category
| Utility Category | 80 hp 2180 AeroVee | 80 hp Jabiru | 120 hp Jabiru |
|---|---|---|---|
| Gross Weight | 1100 lbs | 1100 lbs | 1150 lbs |
| Baggage (Max) | 40 lbs | 40 lbs | 40 lbs |
| Useful Load | 480 lbs | 480 lbs | 530 lbs |
| Rate of Climb | 500-900 fpm | 500-900 fpm | 1000-1400 fpm |
| Positive Load Factor | +4.4 Gs | +4.4 Gs | +4.4 Gs |
| Negative Load Factor | -2.2 Gs | -2.2 Gs | -2.2 Gs |
| L/D | 11:1 | 11:1 | 11:1 |
| CG Limits | 20-32% Wing Chord | 20-32% Wing Chord | 20-32% Wing Chord |
Aerobatic Category
| Aerobatic Category | 80 hp 2180 AeroVee | 80 hp Jabiru | 120 hp Jabiru |
|---|---|---|---|
| Gross Weight - Aerobatic | 950 lbs | 950 lbs | 950 lbs |
| Baggage (Max) | 10 lbs | 10 lbs | 10 lbs |
| Rate of Climb | 800-1100 fpm | 800-1100 fpm | 1500-2000 fpm |
| Positive Load Factor | +6.0 Gs | +6.0 Gs | +6.0 Gs |
| Negative Load Factor | -3.0 Gs | -3.0 Gs | -3.0 Gs |
| CG Limits | 23-29% Wing Chord | 23-29% Wing Chord | 23-29% Wing Chord |
Note: All models meet FAA Sport Pilot Regulations at maximum continuous power at sea level, as required.
Factory Specifications (B-Model)
While I don’t have the plans yet, I’m including the B-Model since it seems like both models have similar engine support. I’m not planning on doing the B-Model conversion, but might as well have both here.
The main thing is that the 100hp AeroVee Turbo is listed, which is a very possible engine choice for the A-Model. While it has high maintenance requirements, the kit itself isn’t that expensive.
Specifications (Sonex-B)
| Specification | Value |
|---|---|
| Seats | 2 |
| Length | 18’ 1” |
| Wing Span | 22’ |
| Wing Area | 98.0 sq. ft. |
| Tail Configuration | Conventional |
| Tail Height (Std Gear) | 56” |
| Tail Height (Tri-Gear) | 74” |
| Tail Width (with tail tips) | 92” |
| Main Gear Width | 71” (with wheel pants) |
| Air Foil | 64-415 |
| Primary Structure | 6061-T6 aluminum |
| Cockpit Width (entire cockpit) | 40” |
| Fuel Capacity | 20 US Gal. |
| Stall Speed (full flaps) | 40-43 mph [64-69 km/h] |
| Stall Speed (clean) | 46-50 mph [74-80 km/h] |
| Max Flap Extended Speed (Vfe) | 100 mph [161 km/h] |
| Maneuvering Speed | 125 mph [201 km/h] |
| Never Exceed Speed (Vne) | 197 mph [317 km/h] |
Performance
| Performance | AeroVee 80hp | AeroVee Turbo 100hp | Jabiru 120hp |
|---|---|---|---|
| Basic Empty Weight | 680 lbs | 700 lbs | 700 lbs |
| Range (1) | 515-634 miles | 450-525 miles | 445-540 miles |
| Cruise Speed @ Sea Level* | 130 mph | 135 mph | 135 mph |
| Cruise Speed @ 8000 ft (TAS) | 150 mph | 165 mph | 170 mph |
| T.O. Distance | 400 ft | 300 ft | 250 ft |
| Landing Distance | 500 ft | 500 ft | 500 ft |
| Service Ceiling (calculated) | 16,000 ft | 23,000 ft | 23,000 ft |
Utility Category
| Utility Category | AeroVee 80hp | AeroVee Turbo 100hp | Jabiru 120hp |
|---|---|---|---|
| Max. Gross Weight | 1100 lbs | 1220 lbs | 1220 lbs |
| Baggage (Max) | 40 lbs | 40 lbs | 40 lbs |
| Useful Load | 480 lbs | 530 lbs | 530 lbs |
| Power Loading (GW/HP) | 13.75 lbs/hp | 12.2 lbs/hp | 10.16 lbs/hp |
| Rate of Climb | 500-900 fpm | 700-1000 fpm | 1000-1400 fpm |
| Stall Speed (full flaps) | 40 mph | 43 mph | 43 mph |
| Stall Speed (clean) | 46 mph | 50 mph | 50 mph |
| Positive Load Factor | +4.4 Gs | +4.4 Gs | +4.4 Gs |
| Negative Load Factor | -2.2 Gs | -2.2 Gs | -2.2 Gs |
| L/D | 11:1 | 11:1 | 11:1 |
| CG Limits | 20-32% Wing Chord | 20-32% Wing Chord | 20-32% Wing Chord |
Aerobatic Category
| Aerobatic Category | AeroVee 80hp | AeroVee Turbo 100hp | Jabiru 120hp |
|---|---|---|---|
| Gross Weight - Aerobatic | 950 lbs | 950 lbs | 950 lbs |
| Baggage (Max) | 10 lbs | 10 lbs | 10 lbs |
| Power Loading (GW/HP) | 11.875 lbs/hp | 9.5 lbs/hp | 7.9 lbs/hp |
| Rate of Climb | 800-1100 fpm | 1000-1500 fpm | 1500-2000 fpm |
| Positive Load Factor | +6.0 Gs | +6.0 Gs | +6.0 Gs |
| Negative Load Factor | -3.0 Gs | -3.0 Gs | -3.0 Gs |
| CG Limits | 23-29% Wing Chord | 23-29% Wing Chord | 23-29% Wing Chord |
Note: All models meet FAA Sport Pilot Regulations at maximum continuous power at sea level, as required.
(1) Range of various power settings and altitudes based on 15 gallons used for cruise flight and 5 gallons used for takeoff, climb, and 30 minutes reserve. At 8,000’ AeroVee-powered Sonex/Waiex can achieve 150 mph TAS @ 3.5 gph. Jabiru 3300-powered Sonex/Waiex can achieve 170 mph TAS @ 4.9 gph at 8,000’.
(2) Gross Weight of 1220 lbs approved for all engines producing 100 hp or greater.