The DarkAero 1 prototype was disassembled in September to begin painting the airframe and to complete outstanding tasks on the control system, fuel system, and electrical system.

Fuel System
The fuel system on the DarkAero 1 requires a shut-off valve for emergencies and for service. Additionally, FAR 23.995 requires there to be a separate and distinct action to place the selector in the OFF position. Fuel shut-off valves are easy to find, but it can be challenging to find one with a handle that prevents it from turning without a secondary action. Off-the-shelf solutions are typically the first choice when it comes to hardware items like valves, but sometimes fabricating hardware in-house is unavoidable. This was the case with the fuel shut-off valve.

The first choice was to use the Andair FS20 valve, an off-the-shelf solution that would work well for the DarkAero 1. However, their lead time was several weeks. To avoid delaying progress, a custom handle was fabricated for a conventional fuel shut-off valve to enable locking it into its ON and OFF positions to prevent accidentally shutting off the fuel flow. The handle design was modeled in Onshape and then CNC machined using drop aluminum that came from a previous project. From there, the handle was combined with a few off-the-shelf components including a knurled handle, spring, and locknut to complete the assembly.

In addition to the new locking handle, the shut-off valve was relocated to a new position between the pilot and co-pilot for easier accessibility. Previously, it was located just upstream of the fuel pumps which are mounted ahead of the co-pilot armrest. The previous fuel shut-off position required an awkward reach for the pilot, which was not ideal in emergency situations. Relocating the fuel shut-off valve required a new center console that was fabricated from a folded composite sandwich panel. The fuel sump was modified to accommodate the new fuel line routing. The locking handle and relocation of the fuel shut off valve improve the functionality and overall safety of the fuel system.

Flap Controls
The DarkAero 1 uses split flaps that extend from the bottom face of the wing to enable slower landing speeds and steeper approach angles. The split flap design was selected for its balanced offering of design simplicity, manufacturability, low drag in cruise flight, and sufficient lift increase for landing. Previously, both manual and electric actuation mechanisms were under consideration for extending the flaps. As both design concepts were explored in parallel, it was eventually decided that a simple manual flap actuation mechanism would be the best choice for the prototype aircraft. The manual mechanism is lighter and simpler than an equivalent linear actuator, and it is more compact. The flap handle will be positioned on the centerline of the airplane between the pilot and copilot seats just below the throttle handle. This location provides equal access from both the left and right seats, allowing the aircraft to be easily landed by either pilot. Fabrication and installation of the system is underway, with the last pieces of hardware for the system scheduled to arrive in early October.

Cabin Work
Covers for the access openings on the armrests were designed and fabricated. Beyond concealing the control system hardware and stick wiring, the headset and microphone jacks were also integrated into the covers. The jacks will be interfaced with 90 degree adapters at the outputs to optimize the cable routing from the jacks to the headsets. Locating the connectors on the covers allows them to be easily changed in the future if a better position is determined, since replacing the covers is easier than repairing a hole in more permanent fuselage structures. Upcoming taxi testing and flight testing will help determine if this location is ideal, with the option available to continue iterating on the design in the future. In addition to the arm rest covers, covers for the main landing gear actuation hardware were installed on the seatback bulkhead.

Exhaust Tunnels
Modification work on the exhaust tunnels was wrapped up in September. Metal flat patterns for the heat shield were received and bent into their 3D geometry to match the tunnel dimensions. These were installed in place along with their respective backing layer of ceramic blanket. The new design is a major improvement over the old, compound curved exhaust tunnels that were challenging to fireproof and adapt to cowling flaps.

Paint
Work continued on refining the process to paint the aircraft. Much of September was spent preparing the air system, measurement tools, cleaning equipment, PPE, lighting, and painting fixtures.  A process was established to paint both the small and large structures of the aircraft using a series of racks on wheels. Paint tests were conducted to determine the best methods for both surface preparation and painting various parts of the aircraft. The results of these tests so far have proved successful, and painting the airframe will proceed in October.

DarkAero Courses
Session 11 of the Aerospace Composites Course was held in September. This course has been running for a full year now, and the course topics and demonstrations have continued to be refined and improved. Exciting updates coming in the next session of the Aerospace Composites Course include the addition of a new module on composite repair as well as a demo with prepreg composite material. The next two sessions will be held October 6-7 and November 4-5. These will be the last two sessions in 2022. Seats can be reserved at the link here:

Aerospace Composites Course Sign Up! 

The Aerospace Composite Course is also available in an online format to reach those who cannot attend in person. It is offered at a reduced rate relative to the in-person course, making it an appealing option for college students or individuals who are just beginning to explore composite materials. The online course can be accessed here:

Online Aerospace Composites Course Sign Up! 

Session 2 of the Mold Making Course was held in September as well. Session 3 of the Mold Making course will be held on November 11-12. The Mold Making Course also continues to be refined and improved. Seats can be reserved at the link here:

Mold Making Course Sign Up!

YouTube
A new YouTube was released, highlighting ground vibration testing work on the DarkAero 1 prototype. This was a technical topic, but it was a fun subject to make a video about. The video can be viewed at the link here:

A livestream was recently held for the DarkAero Mach 2 Community Members. There was much to discuss because it had been a few months since the last livestream. The major milestones over the past few months were highlighted, and some interesting bonus stories were shared. The event was wrapped up with a Q&A session to close out the night. A replay of the livestream can be viewed here:

DarkAero Apparel
It’s officially fall in Wisconsin, and the temperatures are starting to drop. If you are entering fall weather as well and are looking for a way to stay warm, wearing a DarkAero hoodie and beanie is a great way to keep out the cold! Head over to our shop page to get your own! 

DarkAero Apparel Store

Looking Ahead
In October, focus will be placed on completing the flap actuation mechanism, manufacturing the main landing gear actuation and main gear doors, and painting the aircraft in preparation for high speed taxi and flight testing.