February was a shorter month but we kept busy making more progress on the DarkAero 1 prototype and started on some new and exciting aspects of the project!

Horizontal Stabilizer and Vertical Stabilizer Installation 
Early on in the month of February we made some significant visual progress on the DarkAero 1 prototype by permanently bonding the horizontal stabilizer (HS) and vertical stabilizer (VS) to the fuselage. These assembly steps are builder tasks so we made sure to take our time and document the process. The two subassemblies are installed in sequence with the HS going on first. Installation involved leveling the fuselage in pitch and roll and then confirming the HS alignment matched with the fuselage. Alignment was straightforward but we identified a few positioning features we want to add in production to make the fit up even easier. With the alignment confirmed, we proceeded to bonding the horizontal stabilizer in place. Next, we fitted up the vertical stabilizer and confirmed its alignment. The VS self aligns with the fuselage so the positioning went faster than with the HS. Both the horizontal and vertical stabilizers receive segments of carbon angle reinforcements or “tapes” to further unite them with the fuselage. The permanent installation of the HS and VS allowed us to proceed with a few more tasks on the rudder controls.
 

Rudder System
One of the outstanding items on the rudder controls was the rudder return springs. The rudder return springs provide a positive force that holds the rudders in neutral position and also pulls the rudders back to neutral position when they are deflected.  With the vertical stabilizer permanently attached, we were able to fully install the rudder bellcrank mechanism with the rudder cables and complete the rudder return springs. The final solution for the springs was to use Mil. Spec. extension springs. After installing the springs we finished up the rudder cables and connected the rudder pedals to the rudders for the first time. A couple small adjustments remain to get the feedback just right but overall the system works as designed.

Firewall Corner Brackets
The loads from the engine mount are transferred through the firewall into longitudinal bulkheads behind the firewall and then into the fuselage skins. Part of what enables this load transfer are four structures called the firewall corner brackets. The firewall corner brackets remained an incomplete task for a long time because we had not finalized a method to manufacture them efficiently. They are a small component with many layers of carbon fiber which makes them not well suited for a molding process. We came up with a solution to make them from an assembly of segments of carbon fiber angle, which allows the four brackets to be built up from a single molded piece of angle. The assembly and installation of the firewall corner brackets will be a builder task. 

Wind Tunnel Testing
The upgrades to the UW-Madison College of Engineering’s wind tunnel were completed, which allowed us to start some of our wind tunnel testing. This work is intended to further build upon our CFD simulations and provide a more thorough prediction of flight characteristics of the DarkAero 1. We were able to mount the model in the tunnel and run a few preliminary tests measuring aerodynamic forces and looking at flow visualization. We identified a few improvements we want to make to our mounting structure on the model that will allow us to run the model at higher speeds and use the full speed envelope of the wind tunnel. Further wind tunnel testing is planned for March. 

EAA Chapter 640 & Chapter 93 Talks
In February we gave two public talks about DarkAero. The first was with Learn Build Fly / EAA Chapter 640 in Wausau, WI and the second was with the local EAA Chapter 93 in Madison, WI. We always find significant value in speaking about DarkAero since it allows us to increase our reach as well as make more friends in the aviation community and the general public. We also get asked lots of good questions, which helps us to learn how to better communicate information about DarkAero. Thank you to Dennis Seitz and Learn Build Fly as well as Derek Smidler and EAA Chapter 93 for inviting us to speak! We would love to have the opportunity to come back in the future! 

Avionics
Assembly of the forward bulkhead of the instrument panel is now complete. This involved folding our previously machined instrument panel around four honeycomb sandwich bulkheads. The next major step to finish the instrument panel structure will be construction of its center tunnel, which will also serve as the hinge for the rest of the canopy. In parallel with the instrument panel assembly, we have begun installing the mounting hardware for our avionics. We are primarily using Click Bond studs to interface our hardware with the airframe. As this is a builder task, we are developing simple and accurate techniques for aligning these studs like 1:1 scale paper templates that can be printed out.  Pictured above is one of our ECU’s for the UL Power engine sitting on four installed mount points inside our center tunnel avionics box. This box will sit between the two forward baggage compartments.

Canopy Forming Progress
We made good progress on improving the optical clarity of our polycarbonate canopy. We conducted some more test forms this month with increased emphasis placed on controlling two key environmental factors: dust and moisture. The result of the latest test was our best form to date. The lessons we learned from this test have influenced us to further tighten our process controls to mitigate these environmental contamination factors as we move forward with our next forms in March. 

Nose Gear Components
We completed the machining of the nose gear fork in February. With the amount of complicated geometry and setups for this part, we were pleased with how well it turned out from our 3-axis mill. We have received a few questions regarding how production will work for these components and if we have any concerns for the amount of cycle time. It’s worth noting that the setups and machining rate used for the prototype will not match what will be done for production. The setups we are using now are good for making a few parts without having to purchase or produce any permanent work holding system. For production, we will transition to a more production oriented work holding that is better suited for quick operation changes. Additionally, as we continue to get more comfortable with the capabilities of the machine, we will continue to increase the cutting speed. Currently, we have been running the mill at about a quarter of what it is capable of.  

In addition to the nose gear fork, we also began machining on the nose fork castering link shown above. This component connects the nose fork to the main tube of the nose gear strut and allows the front wheel to caster. 

Popular Mechanics 
We were surprised to learn that we received a shoutout in the latest issue of Popular Mechanics! This was exciting for us since we have been reading the magazine from a young age. 

DarkAero Apparel 
We recently expanded our apparel offering to include hooded sweatshirts and baseball caps! In addition to the new apparel, we also updated our storefront page to make the checkout process easier. You can now create an order with multiple items before checking out. Stay tuned as we plan on adding new designs in the future! If you would like to check out the new items, visit www.darkaero.com/shop! 

YouTube Channel
We made some more YouTube videos in February showing more of the build process and parts manufacturing. If you have not seen the latest videos yet, we recommend heading over to our YouTube channel to check them out. We also recommend subscribing to our channel to stay up to date on the latest content we release. We have some interesting YouTube videos we are planning to release in March that you will not want to miss!

DarkAero YouTube Channel: https://www.youtube.com/darkaeroinc

March and Beyond
March will be a busy month for us as we plan on more landing gear machining, avionics installation, firewall forward work, and more systems installation.