Progress continued on the DarkAero 1 prototype in July, with efforts focused on molding structures that will be incorporated into the center section of the wing. Additional manufacturing equipment was acquired, and the DarkAero team attended the annual EAA AirVenture airshow in Oshkosh, WI.

Testing
While the DarkAero 1 has been shown taxiing and undergoing system tests, it is important to note that portions of the aircraft are still under development and are not yet flight-ready. Much of the work happening now involves validation testing of structures and systems, and reworking any hardware that does not meet prototype flight test ready acceptance criteria during testing. The pace of development reflects both the ambitious goals of the project and the reality that only a small portion of the full team has been working full-time on the aircraft. Future updates will include clearer distinctions between systems that are experimental, in review, or nearing flight readiness, to better reflect where the aircraft actually stands in its development.

The pi joint molds that were manufactured in June were put to use in July. The molds incorporated multiple segments to form the geometry found in the multi-pi joints that were specifically developed for the DarkAero 1 wing. A quick test was initially performed by building a mini mold and pi joint to more accurately quantify the thermal expansion of the additively manufactured mold segments. The thermal expansion of the mold segments controls the dimensions of the pi joints, which ultimately dictates adhesive thickness during assembly when installing the center shear webs. Therefore, characterizing the expansion was essential to understand prior to manufacturing the larger components. 

The pi joints consist of a base laminate co-cured with an overlaminate to achieve the highest out-of-plane strength in the highest stressed areas of the joint. The delta-fillet areas of each joint are filled with prepreg unidirectional “noodles” to create a small fillet for the twill-weave-overlaminate to conform to without wrinkles. The resulting layup is structured to prevent wrinkles at small radii and thermal expansion of the mold segments results in easy mold removal.

Traditional pi joints are typically built as individual pi preforms to join skin and bulkhead structures at a right angle. The pi joints used in the DarkAero 1 prototype are built as a unified assembly of five pi junctions to interface with the five center section shear webs in the wing. While this approach is slightly more involved from a part manufacturing perspective, it was chosen to provide the most controlled geometry and ease of assembly when interfacing with the existing wing structures. 

Although the molds functioned as designed, some material deficiencies were discovered in the additively manufactured mold segments, which lead to one of the pi joint segments being scrapped. These mold segments were reprinted and manufacturing will proceed into August.

As part of the wing center spar update mentioned in the previous monthly update, a new flap actuation system mounting design will be implemented in the wing. This design features hard points recessed into the center shear web honeycomb panels to provide a strong, lightweight interface for the flap system. While pi joint manufacturing was underway, the flap mount hard points were machined in parallel to keep the assembly process moving. Advancing multiple processes at once requires a team that can shift between disciplines fluidly, and having versatile team members has been critical to maintaining momentum during this phase of the build.

AirVenture 2025
The annual EAA AirVenture airshow was held at the end of July in Oshkosh, WI. The DarkAero team attended on July 24th to meet with customers, suppliers, and the broader aviation community. The UL Power Aero Engines booth served as a central location for DarkAero enthusiasts to meet up. It was fun to connect with others who share a passion for aviation, and attending AirVenture always provides a valuable boost to the DarkAero project. Thank you to UL Power, and to everyone who stopped by!

Manufacturing Equipment
As part of an ongoing effort to expand in-house manufacturing capability, DarkAero recently integrated a Vision Miner 22 IDEX v3 3D printer into its prototyping and tooling operations. This machine is capable of running high-temperature, engineering-grade materials like PEI, PEEK, and carbon fiber-filled nylon, making it a useful addition for producing heat-resistant structural parts. It includes dual independent extruders, allowing for mirrored part production and clean support removal using dissolvable materials. While much of the hardware manufactured by DarkAero is still composite assemblies and machined components, the new printer enables faster turnaround on jigs, mold inserts, airflow duct prototypes, and other development hardware. The new machine was immediately put to use creating additional mold segments for use in forming pi joints for the DarkAero 1 wing. 

Courses
Session 26 of the DarkAero Aerospace Composites Course will be held on October 2-3. The course material has been continuously refined over the past three years, and covers both the theoretical and hands-on aspects of Aerospace Composites. Demos of wet layup, vacuum bagging, infusion, and prepreg allow students to gain experience in a broad range of manufacturing processes so the right process can be selected for their application. Fiber reinforcements including carbon, glass, aramid, and boron fibers are discussed, as well as approachable methods for selecting fabric weave types. Reserve your spot in the next session using the link below:

Sign up for the DarkAero Aerospace Composites Course!

DarkAero Careers
The DarkAero team is continuing to grow! Several new positions were recently added to the DarkAero Careers page, including Test Engineer, Propulsion Engineer, Operations Specialist, Quality Assurance Technician, Welder, and Machinist. Candidates with a strong work ethic, hands-on skills, and a desire to work on challenging projects are an ideal fit for the team. Visit darkaero.com/careers to apply!

Looking Ahead
Pi joint manufacturing and installation will continue in August, along with the testing of landing gear actuation system modifications that are underway. Additionally, two new team members will be joining the manufacturing team.