Our recent focus on the DarkAero 1 prototype has centered on getting the airplane on the landing gear so we can fire up the engine for the first time. This past month we made progress towards that goal with a number of tasks completed on the main landing gear, firewall forward electrical system, and fuel system. AirVenture 2021 also marked an important event for the team this past month.

AirVenture
We attended AirVenture as a team but did not bring the prototype aircraft to display. This was a tough decision, but we felt it was important to reduce impacts to the development schedule and ultimately bring the prototype to completion sooner. With this in mind, we attended the show for only one day, but it was still action packed. We spent much of our time at the UL Power booth and got to meet with a number of our customers as well as other aviation enthusiasts. We are looking forward to AirVenture 2022 when we plan to have the airworthy DarkAero 1 on display. 

Main Landing Gear
After we redesigned the retract mechanism for the nose gear, several design improvements were identified that we wanted to incorporate into the main gear. We made progress on the CAD work for these changes that included new drag links, retract mechanism, locking mechanism, and mounting structure.

The architecture of the main landing gear is similar to the nose gear and uses an electrically-driven, geared retract mechanism. The gear struts are constrained in the down, locked position by CNC machined drag links. We ordered stock for the new drag links and drag link brackets and are looking forward to machining these components once the stock arrives.

We also made progress assembling the gear struts by creating some of the smaller carbon fiber sections used to unite the gear strut halves. The gear struts are made from carbon fiber and are assembled in two halves because there are internal structures in the struts which need to be installed before they are closed out. 

Electrical System
Work continued on wiring the firewall forward area as we pushed to get the panel fit up into the aircraft and powered on. With the positions of the firewall bulkhead electrical connectors finalized, we spent some time laying out the wiring to come up with the shortest and most secure paths. Once we had an arrangement we liked, the connectors on the firewall side were wired, allowing us to fire up the panel. Next month we’ll turn our attention to improving the fit of each interface running from the firewall to the panel. Additionally we’ll be moving onto the installation of the harness moving backwards from the cockpit. This work will include installing mounting hardware, safely navigating the wiring through space constrained areas, installing bulkhead through-holes, and powering on the aft electronics plate for further harness debugging. 

Fuel System
This past month we worked on final installation of the fuel system into the aircraft. This included plumbing the sump tank into the rest of the fuel system, installing sight gauges, and purchasing the remaining firewall forward fuel hoses.

The fuel system on the prototype DarkAero 1 will use both a sight glass and a pressure gauge for measuring fuel level in the tank. The sight glass will provide visual indication of fuel levels when filling the tanks, preflight inspecting the airplane, and in level flight. The pressure gauge will provide a secondary piece of fuel level data that can be fed into the EFIS on the instrument panel. We are also considering some alternate means of fuel level measurement including capacitive fuel probes and float-style gauges for future iterations. 

Wing Skin Reinforcement
One long outstanding task that we completed this month included the addition of foam core reinforcement to the top wing skin above the flaps. This non-structural section of the wing requires a small amount of reinforcement to achieve adequate stiffness, but we had not finalized the technique that would be used to reinforce it when the wing was originally assembled. We settled on using a process similar to what was done to stiffen the flaps, rudders, and sections of the fuselage, which was to nest a layer of foam under several layers of carbon fiber. We used wet layup to add this in the prototype, but in production this foam layer would be embedded during the infusion process of the top wing skin. 

Kitplanes Article Part Two
Kitplanes Magazine released part two of the two-part article series they wrote about DarkAero. In part two, Eric Stewart did a Q&A with each of us to get more one-on-one insight into our project. Thank you again to Eric Stewart and Kitplanes Magazine for the excellent write ups! We feel both honored and excited to be featured in Kitplanes! The article can be viewed here:

Shining a Light on DarkAero

YouTube
We released four new YouTube videos highlighting progress on the DarkAero 1 prototype as well as other aspects of the engineering and manufacturing challenges we work through. You can view these videos by clicking the links below:

How to Manage Complex Designs

When to Outsource a Part

The first retract! | DarkAero Shop Vlog | July 10th, 2021

Primitive Carbon Fiber Technologies | DarkAero Shop Vlog | July 27, 2021

Looking Ahead
In August we plan to continue work on the main gear manufacturing and installation. We’ll also continue installing the fuel system and finalizing installation of the electrical system from the panel to the engine bay. These three areas make up the critical path to getting the airplane on the landing gear before firing up the engine, which we are pushing to reach by the end of September.