Sonex’s Mark Schaible helmed a presentation on the company’s High Wing prototype during EAA Homebuilders’ Week seminars today. He offered examples of progress since the prototype was displayed, sans engine and wings, at AirVenture 2024 and offered his thoughts on when it will finally fly. (Short answer: March or April 2025.)
A few of the updates he mentioned include a gross weight increase to 1500 pounds, which required a few changes to structure. The current estimates are for the empty weight with the full-span wings (in other words with the extended wingtips fitted) to be around 820 pounds. This helps work with a max baggage capacity of 80 pounds.
Fuel capacity remains 30 gallons, from a 20-gallon header tank and two 5-gallon tanks in the inboard section of the wing, yet still outside the cabin. Sonex has tried to pick up as many systems and pieces from its existing low-wing airplanes as possible.
Currently, Sonex intends to support four engines, including its own AeroVee four-cylinder engines, ULPower 260iS, Rotax 912 series and the Jabiru 3300 six-cylinder. Schaible noted that while someone is likely to try fitting the 160-hp Rotax 916, “That’s way more power than the airframe needs.” The prototype will have the ULPower engine, which makes 107 hp. He said that the company will conduct flight testing with a Sensenich fixed-pitch prop to estimate climb performance with an 80-hp engine. But that the engines in the 100-hp range are likely to be the sweet spot.
Schaible revealed some details of the doors, which will have simple strap-type hinges and open conventionally, with the trailing edge swinging out under the wing. One trick that speaks to Sonex’s desire to have the High Wing aerobatic capable is that the door hinges pivot inside the cabin, so a simple cable system will enable the pivot pins to be pulled and the doors jettisoned in flight if necessary. 
Staying inside, the High Wing will be offered with either side-stick (one in the middle) or center-stick (one at each seat) controls. The under-seat mechanism will be the same, with the builder choosing which of the stick sockets are populated. To ensure the center-only option works, twin throttles will be placed at the outboard edges of the instrument panel. Presumably a builder who only wants to have the twin-stick arrangement could mount a single throttle in the center.
One of the slides showed the High Wing with a metal windshield mockup and Schaible confirmed that the company will be making its own curved windshield. 
Schaible revealed a few details on the control system, which has pushrods and torque tubes in the pitch and roll channels. The only cables in the system are for the rudder. The sticks are tied together under the occupants’ knees, with fore-and-aft movement driving a two-piece pushrod arrangement to the tail. For roll, the sticks translate left and right motion into a rotary motion via a torque tube down the center of the airplane. Behind the seats, a bellcrank sends the motion straight up, where it meets with another torque tube that translates the motion forward into the wing. As that torque tube rotates left and right, it drives the ailerons, which are connected together at the center. (The ailerons themselves have another set of bellcranks to translate the left-right motion to movement of the control surface.) Sonex acknowledges this is a lot of moving parts and is making every effort to keep friction and slop out of the system. For now, the flaps are intended to be electric only.
Staying with the flight-control system for a bit longer, Sonex will change from its normal practice of placing the rudder cables at the outside of the cabin walls and, instead, running them down the center with a crossover. Low-friction guides will help maintain feel. But the biggest news was that Sonex is going to use toe brakes on the High Wing, a first for the company. Not only that, it’ll employ a simple cable connection from the copilot to pilot pedal set so that you can have dual brakes with only one set of master cylinders.
Schaible wrapped up by showing progress of the prototype, which has the ULPower engine hung and some work done locating firewall items such as the fuel pumps, battery and ignition coils. (The ULPower electronic ignition and fuel injection; this iteration will have the MOSAIC-pleasing dual ECUs.)
The out wing spars were complete—note that these are conventionally riveted units that will be completed by the factory in the regular kits—and the crew was beginning to build up the rest of the wing structure. The tail is in place and Schaible described how 3D printing the molds for the fiberglass end caps resulted in some of the best-fitting parts he’d seen. There’s more use of 3D printing elsewhere in the prototype.
Next up is to begin the avionics installation, which will be a pair of Dynon HDX screens and a remote-mounted com and transponder units. While it’s unlikely that the prototype will be fitted with an autopilot, there are plans for one as the kit develops.
Schaible did announce that the company is taking $500 reservations and that, again, the prototype was on track for first flight in March or April. If all goes well, kits could be available later in 2025.
Download the presentation slides.
