Refining the control system on the DarkAero 1 prototype was the main focus in September. Seals were added in the engine compartment to reduce potential cooling air leaks, the landing gear lock toggle mechanism was implemented, and two additional team members were brought on to help accelerate progress on the prototype, prepare for production, and help support DarkAero Services. 

Control System 
The DarkAero 1 prototype was fully assembled last month, and all of its primary flight controls were installed and tested. Although the control system had been designed and built up in different stages much earlier in the project, it had not yet been installed as a fully functioning system. Bringing the controls to an airworthy state could really only be accomplished with the entire system installed and connected in the airframe. The control system is flight critical, and extra attention was given towards its function.

With the control system built up, basic functional metrics like the control surface movement and total travel were confirmed first, but then focus shifted towards refining the system. One aspect of this involved reducing friction and free play in all of the linkages and hardware between the pilot controls and the control surfaces. It is important to eliminate free play or backlash to achieve tight control response and to reduce the potential for flutter in the control surfaces. A small amount of backlash was discovered in the elevator controls, and it was traced back to where the pilot and co-pilot controls are connected through a torque tube. This torque tube pivoted on a series of AN bolts, but these were introducing too much free play. This will be corrected by replacing the AN bolts with pins. The fix will also make the elevator torque tube easier to install. 

As the control system was assembled and tested, a handful of other minor issues were uncovered that required modifications. An example of one of these issues related to the ease of assembly and serviceability. It was confirmed that an aileron pushrod in the fuselage could no longer be installed after the main landing gear was installed. This was an anticipated problem, and one of the potential solutions was to add an extra access opening on the fuselage side. Instead of cutting a hole though, the pushrod was segmented in the middle and a connecting coupler was added, allowing it to be installed as two shorter pieces and assembled in place.

Remaining work on the control system will include further reduction of free play and friction, dialing in the balance of the control surfaces, and refining the secondary flight controls. The secondary flight controls include the flaps and trim system. An internal spring system was originally planned for the trim, but an external trim tab was selected for the prototype to reduce the amount of iteration required to achieve a workable trim system. 

Firewall Heat Shield Extension and Cowling Seals
A cutout in the firewall allows the nose gear to retract through the firewall and into the nose gear wheel well, but this cutout also creates a gap in the heat shield that could allow flames to reach the unprotected walls of the wheel well. The cutout can also interfere with the engine cooling when the nose gear is extended as air passes through the nose gear wheel well instead of through the exhaust tunnels as intended. 

An extra portion of heat shield was added to enclose the nose gear and prevent fire from reaching the wheel well. This heat shield extension was designed and prototyped in August, and then converted to a final titanium version in September. Flexible seals were also added around the nose gear cutout in the lower cowling to prevent cooling air from passing through this opening. Installing the additional heat shielding and seals will provide more flexibility in flight testing, since it will make the engine cooling performance independent of whether or not the landing gear is up or down. 

Nose Gear Lock Toggle Solenoid
When the nose landing gear actuation has been showcased in the past, the mechanism to disengage the gear lock has been absent. The gear lock keeps the nose gear strut from folding backwards, and it holds the gear in the retracted position while the airplane is in flight. The lock is toggled with a linear solenoid, and several different solenoids were recently tested to identify the right match. Given the limited space available in the nose gear wheel well, the solenoid needed to be as small as possible while maintaining enough force to overcome the lock mechanism even in worst case loading scenarios. A solenoid was identified that met these constraints and it was integrated into the retract system along with its associated wiring. 

Team Expansion 
Two additional team members were added in September to help accelerate progress on the DarkAero 1 prototype, prepare for kit production, and support DarkAero Services. As production activities and DarkAero Services continue to ramp up, more trained composite technicians with hands-on skills and attention to detail will be needed. If you, or someone you know would like to apply to work at DarkAero for these roles, please reach out at careers@darkaero.com. 

YouTube
The DarkAero 1 is engineered to fly fast while maintaining high efficiency. It has long been theorized that a pusher propeller arrangement would be best for this mission, so questions have often been raised about the logic behind the tractor propeller configuration of the DarkAero 1.

A new DarkAero YouTube video released in September discusses pusher vs tractor propeller arrangements to assess their performance impact on an aircraft like the DarkAero 1 as well as the pros and cons around each option. This evaluation complements the recent progress on the cooling system refinement work in the engine bay. Check out the video at the link below: 

A second YouTube video was released covering the recent work on the control system. An early release of this video is available to YouTube community members, and the public release will be available later this week! 

Community members can watch an early release of the video at the link below:

All DarkAero YouTube videos are released early for paid tier members of DarkAero YouTube Community. Bonus pictures and behind-the-scenes design discussion are shared to the YouTube community throughout the month as well, allowing for more frequent updates in between video releases. To see the very latest updates on the project, become a channel member at the link below:

Become a DarkAero YouTube Community Member!

DarkAero Courses
Session 19 of the DarkAero Aerospace Composites Course was held in September. Each session brings a new group of students with unique and exciting projects ranging from race cars to spacecraft, but the latest group was mainly focused on aviation related composite applications. A composite wing design example was used throughout the course to make the course material as relevant as possible for these students. 

The September session marked two years that the course has been run. During that time, the curriculum and demos have continued to be refined based on student feedback. A new module on boron fiber reinforcement will be included in the next session, since this material is seeing renewed interest in specialty applications in the realm of UAVs, military aircraft, and spacecraft. Boron fiber can be added to a composite laminate to improve compressive strength beyond what can be achieved with carbon fiber alone so it is an appealing option in high strength applications. The new boron fiber module will also be added to the online version of the course, and students who have already completed the course will still be able to access the new material. 

Limited spots are available for the next in-person session on November 10th-11th, and prices will be increasing for all sessions starting January 2024. Sign up for the course using the link below: 

Sign up for the Aerospace Composites Course!

For those embarking on creating their first composite part, it is also important to have knowledge and skills in mold making. The DarkAero Aerospace Mold Making Course was developed to give both hobbyists and professionals the knowledge and hands-on skills required to design and build high-quality molds that can make high-quality composite parts!

There are a few spots remaining for the October 13th - 14th DarkAero Aerospace Mold Making Course, and prices will be increasing for all sessions starting January 2024. Enhance your knowledge and skills by registering for the course at the link below:

Sign up for the DarkAero Aerospace Mold Making Course!
 

Looking Ahead
In October, the team will work on final refinement of the primary flight controls, installation and refinement of secondary flight controls, completing the canopy latch mechanism, and finalizing the fuel system testing.